1Department of Radiology, Oncology and Pathology, Sapienza University of Rome, Rome 00161, Italy.
2IBPM-CNR, Institute of Molecular Biology and Pathology, Italian National Research Council, Rome 00185, Italy.
3Department of Biochemical Sciences, Sapienza University of Rome, Rome 00185, Italy.
4Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland.
5Department of Anatomical, Histological, Forensic Medicine & Orthopedic Sciences, Sapienza University of Rome, laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Rome 00161, Italy.
Correspondence Address: Dr. Andrea Ilari, IBPM-CNR, Institute of Molecular Biology and Pathology, Italian National Research Council, Rome 00185, Italy. E-mail: firstname.lastname@example.org ; Dr. Gianni Colotti, IBPM-CNR, Institute of Molecular Biology and Pathology, Italian National Research Council, Rome 00185, Italy. E-mail: email@example.com
© The Author(s) 2018. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Soluble resistance-related calcium binding protein (Sorcin) is a protein initially labelled “resistance-related”, since it is co-amplified with ABCB1 in multidrug (MD)-resistant cells. While for years Sorcin overproduction was believed to be a by-product of the co-amplification of its gene with the P-glycoprotein gene, many recent studies view Sorcin as an oncoprotein, playing an important role in MD resistance (MDR). Sorcin is one of the most highly expressed calcium-binding proteins, which is overexpressed in many human tumors and MD resistant cancers, and represents a novel MDR marker. Sorcin expression in tumors inversely correlates with patients’ response to chemotherapies and overall prognosis. Sorcin is highly expressed in MDR cell lines over their parent cells. Sorcin overexpression by gene transfection increases drug resistance to a variety of chemotherapeutic drugs in many cancer lines. On the other hand, Sorcin silencing leads to reversal of drug resistance in many cell lines. This review describes: (1) the roles of Sorcin in the cell; (2) the studies showing Sorcin overexpression in tumors and cancer cells; (3) the studies showing the effects of Sorcin overexpression and silencing; (4) the molecular effects of Sorcin overexpression; and (5) the structural and genetic bases of Sorcin-dependent MDR.
Sorcin, calcium, cancer, multidrug resistance in cancer, doxorubicin, endoplasmic reticulum, heart, brain, ryanodine receptors, ER stress
Soluble resistance-related calcium binding protein (Sorcin) was named “resistance-related” since it was found to be co-amplified with ABCB1 in multidrug (MD)-resistant cells. The gene coding for Sorcin (SRI) is located in the chromosome region 7q21 and is about 21.9 kb-long. At least four alternative Sorcin isoforms are transcribed, i.e., isoforms A (a transcript of 15 kb with eight exons and seven introns, translated into a 198-residues long, 22-kDa Sorcin), B, C and D, translated into shorter 19-kDa isoforms, where part of the N-terminal domain and/or of the last aminoacids of the C-terminal domain are missing. Most literature refers to isoform A, although a few studies deal about 19-kDa form of Sorcin. The pseudogene Sorcin-like (SRIL) is in the chromosomal region 4q12.
Sorcin is present in vertebrates, and more generally in metazoans. Its sequence is highly conserved among species: protein sequences of mouse and human Sorcin show only eight differences, concentrated in the second half of the protein, and six of them regard possibly phosphorylatable serine and threonine residues, indicating that species-specific phosphorylation-dependent regulation of Sorcin may occur.
Usually calcium-binding proteins contain an even number of EF-hands, paired both structurally and functionally. Sorcin belongs to the small penta-EF-hand (PEF) family, containing an odd (5) number of EF-hands. Sorcin is a homodimer, although heterodimerization with another PEF protein, grancalcin, has been observed[3,4]. Sorcin monomers are formed by two domains, i.e., a rather short, flexible, glycine- and proline-rich N-terminal domain and a C-terminal domain Sorcin calcium-binding domain (SCBD), globular and composed by eight alpha-helices, which form five EF-hands (EF1-5) [Figure 1].
Figure 1. X-ray crystal structure of human sorcin in the apo (blue) and calcium-bound (magenta) forms
EF-hands couple through short β-sheets: EF1 pairs with EF2; EF3 pairs with EF4; the odd EF5 pairs with another EF5, belonging to the other monomer, forming part of the dimeric interface. The dimer contains five EF pairs and can be considered the structural unit of Sorcin. The long and rigid D- and G-helices connect different EF-hands pairs, with the D-helix belonging to both EF2 and EF3, and the G-helix connecting EF4 and EF5. The SCBD can be divided in two subdomains: the EF1-3 subdomain (residues 33-134) is composed by the three EF-hands that bind calcium with high affinity, while the EF4-5 subdomain (residues 135-198) mediates dimerization, contains many potential phosphorylation sites, but does not bind Ca2+ with high affinity. Calcium binding to EF hands determines the transition from a “closed” structure to an “open” structure[5,6]. Binding of calcium to EF3, the highest-affinity calcium-binding motif, EF2 and EF1 sites activate Sorcin: Ca2+ binding to EF3 alters the conformation of the loop containing Glu124, and this change is transmitted to EF2 via a movement of the long D-helix connecting EF3 with EF2. Overall, calcium binding to the EF1-3 hands promotes a large conformational change in Sorcin structure, involving a movement of the long D-helix and the opening of EF1, with the two subdomains moving away of 21° [Figure 1]. This movement determines the exposure to solvent of hydrophobic residues of the D-helix, of the EF loop and of the G-helix, with a consequent dramatic decrease of solubility, thus allowing Sorcin to translocate from cytosol to membranes, and to bind and regulate a series of target proteins[6-9]. The hydrophobic pocket can accommodate in Ca2+-bound Sorcin a portion of the N-terminal domain displaying the consensus binding motif identified by phage display experiments [Figure 2].
Sorcin is one of the most expressed human calcium binding proteins; it is expressed in most human tissues, at high levels in bone, heart, brain, B- and T-lymphocytes, monocytes, kidney, breast and skin (sources: MOPED, PaxDb and MaxQB databases). In addition, Sorcin is overexpressed in many cancer types, and especially in MD-resistant cells (see below). Cell localization of Sorcin is dynamic. During interphase Sorcin is localized in the nucleus, in the cytosol, in the plasma membranes, at the endoplasmic reticulum (ER) and in ER-derived vesicles along the microtubules, containing ryanodine receptors (RyRs), ER Ca2+ ATPase (SERCA), calreticulin and Rab10. The shorter 19-kDa Sorcin variant was found localized at the mitochondrion. During mitosis, Sorcin localizes in the cleavage furrow during late telophase, and at the midbody before cytokinesis.
In the cytosol, Ca2+ concentration is maintained below 100 nm since on one side it is actively pumped from the cytosol to the extracellular space, into ER and into mitochondria, and on the other many proteins bind Ca2+, contributing to calcium buffering. Sorcin participates in the regulation of Ca2+ homeostasis by many mechanisms. Sorcin is able to bind Ca2+ in the micromolar range, thereby participating in cation buffering. More importantly, Ca2+-bound Sorcin can interact with RyR and ER Ca2+ ATPase (SERCA), located in the ER, with the L-type calcium channel Cav1 and Na+-Ca2+ exchangers (NCX), located in the plasma membrane, and regulates them: Sorcin increases ER Ca2+ storage by activating SERCA and by inhibiting RyR [Figure 3], increases size and Ca2+ load of ER-derived vesicles, and increases mitochondrial Ca2+ concentration[7,8,10,11,13-19].
Figure 3. Sorcin inhibits the ryanodine receptor and up-regulates ER Ca2+ ATPase (SERCA) and Na+-Ca2+ exchangers (NCX), increasing Ca2+ load of the endoplasmic reticulum (ER) (and possibly of mitochondria) and decreasing ER stress
High Sorcin expression increases ER Ca2+ concentration, can prevent ER stress and the unfolded protein response, and increases escape from apoptosis. Sorcin is necessary for normal glucose tolerance and protects against lipotoxicity in vivo, is able to induce ATP-evoked Ca2+ release from intracellular stores and induces glucose-stimulated insulin secretion[20,21]. Sorcin represses the glucose-6-phosphatase catalytic subunit-2 promoter activity through NFAT activation, activates ATF6 transcriptional activity while repressing ER stress markers as CHOP and Grp78/BiP. Conversely, Sorcin silencing activates apoptotic proteases as caspase-3 and caspase-12, Grp78/BiP, Bcl-2, Bax, c-jun, c-fos and release of cytochrome c, results in major mitosis and cytokinesis defects, blocks cell cycle progression in mitosis, increases the formation of rounded, polynuclear cells and induces apoptosis[10,18,22]. Sorcin increases basal and caffeine-stimulated mitochondrial Ca2+ concentration; the folding and expression of the mitochondrial 19-kDa Sorcin isoform is regulated by TRAP1.
Sorcin contains several potential phosphorylation sites, and also interacts in a Ca2+-dependent fashion with many serine-threonine kinases, which participate in the regulation of mitosis progression, such as Akt2, Csnk2A1, Csnk2A2, polo-like kinase 1 (Plk1), Aurora A and Aurora B. Sorcin is phosphorylated by Plk1, induces Plk1 autophosphorylation, and participates in Plk1 regulation; Ca2+-calmodulin dependent kinase II (CaMKII) and cAMP-dependent protein kinase (PKA) phosphorylate Sorcin, thereby regulating Sorcin binding to RyRs and SERCA and Ca2+ homeostasis[6,23].
Sorcin has been identified in other types of vesicles, other than the ER-dependent ones. Sorcin is present in nanovesicles released in a Ca2+-dependent fashion from the erythrocytes and containing Annexin A7; Sorcin was found to interact with Annexins A7 and A11[7,8,10,15,25], Ca2+-dependent phospholipid-binding proteins, the latter being required for midbody formation and completion of the terminal phase of cytokinesis.
Sorcin has been identified in many types of exosomes from different sources, such as B-cells, mesenchymal stem cells, human urine, platelets and from many types of tumor cells, as colorectal cancer, ovarian cancer, prostate cancer cells, squamous carcinoma and neuroblastoma[27-35].
The microRNA miR-1 targets Sorcin specifically and non-redundantly; miR-1 decreases Sorcin levels, while the antagomiR-1 increases Sorcin expression; treatment with miR-1 determines Ca2+ signaling dysregulation, especially at cardiac level.
Sorcin contributes to regulate Ca2+ homeostasis and cardiac excitation-contraction-relaxation processes. Excitation-contraction-relaxation is a fast (800 ms) process, started by the electrical excitation of cardiomyocytes by a wave of depolarization that opens voltage-dependent Na+ channels located in the T-tubules, determining a rapid membrane depolarization and Ca2+ influx via voltage-operated Ca2+ channels (mainly Cav1 L-type channels). Cav1 channels (with four subunits Cav1.1, Cav1.2, Cav1.3, Cav1.4) are juxtaposed to ryanodine receptors (RyRs), i.e., sarcoplasmic reticulum (SR) or ER Ca2+ release channels. Ca2+ entry via Cav1 increases Ca2+ concentration near RyRs, triggering Ca2+ release from the SR. This flux further raises the free intracellular Ca2+ concentration [Ca2+]I of the cardiomyocyte: Ca2+ binds to troponin C and triggers contraction. For relaxation to take place, RyR is closed and Ca2+ is pumped out of the cytosol, mainly via the SR Ca2+-ATPase (SERCA), which pumps Ca2+ back into the SR, and the sarcolemmal (and mitochondrial) Na+/Ca2+exchanger (NCX): [Ca2+]i decreases rapidly and Ca2+ dissociation from the myofilaments can occur.
Sorcin is able to interact with all the channels, exchangers and pumps responsible for Ca2+ fluxes during the excitation-contraction-relaxation process, and to regulate them. Sorcin modulates Cav1, by interacting with its Cav1.2 (CACNA1C) subunit with its C-terminal domain, slowing its Ca2+-dependent inactivation and stimulating voltage-dependent inactivation of Cav1-dependent Ca2+ currents[13,14].
Sorcin also Ca2+-dependently interacts with RyR2, the most expressed cardiac RyR, and strongly inhibits it, thereby reducing Ca2+ efflux from SR/ER by decreasing RyR mean open time and frequency of open event[8,15,17]. Sorcin is also able to interact with SERCA and to activate it, and to activate NCX via Ca2+-dependent interaction of the respective C-terminal, calcium binding domains; Sorcin overexpression in cardiomyocytes has also been associated with increased NCX activity[19,38]. Fast rates of association and of dissociation between Sorcin and NCX allows NCX regulation on a “beat to beat” basis.
Overall, Sorcin regulates the excitation-contraction-relaxation processes in the heart and muscle: Sorcin terminates the excitation-contraction processes, by inhibiting Ca2+-induced Ca2+ release by the SR, helps [Ca2+] decreasing and induces relaxation by inhibiting RyR2-dependent calcium release from the SR, by activating SERCA2-dependent calcium pumping from cytosol to the SR and by increasing NCX-dependent Ca2+ efflux through the sarcolemma (and possibly into the mitochondrion) [Figure 3].
Sorcin phosphorylation alters its Ca2+-dependent activation, its translocation to the SR and the ability to regulate RyR2 activity. Sorcin is hyperphosphorylated in the failing heart; this increases Sorcin translocation to the SR membrane and the SR Ca2+ content and possibly results in the reduction of SR stress, in the reduction of basal [Ca2+]i and in improvement of cardiac relaxation[16,23,39].
The mutation F112L, located in the EF3 hand and associated with a familiar form of hypertrophic cardiomyopathy and hypertension, as other mutations in the EF3 and/or in the D-helix of Sorcin decreases the capacity of Sorcin to interact with RyR and to modulate SR Ca2+ release, and determines complex cardiac alterations[15,40]. In failing heart, levels of SERCA2a and of RyR2 are often decreased, and consequent altered cytosolic Ca2+ transients lead to abnormal contraction. Sorcin overexpression in mice increases cardiac contractility in the normal heart and determines a rescue of the abnormal contractile function of the diabetic heart, possibly due to improved Ca2+ transients[40-43], while Sorcin KO mice present ventricular arrhythmia and sudden death when challenged by acute stress.
Sorcin has a very high expression level in the brain, 5-10 times higher than in the heart. Sorcin is one of the most expressed Ca2+ binding proteins in the prefrontal cortex, in the amygdala, in the hypothalamus and in many brain tumors (GeneAtlas). The extent of Sorcin expression and its ability to regulate Ca2+ homeostasis make Sorcin a potentially important protein in brain function and dysfunction. According to the so-called “Calcium Hypothesis”, deregulation of Ca2+-mediated signaling, perturbed ER Ca2+ homeostasis and ER stress are at the basis of the abnormal accumulation and aggregation of specific proteins, which are deposited in intracellular inclusions or extracellular aggregates during brain aging and in many neurodegenerative diseases, as Alzheimer's disease (AD) and Parkinson’s disease (PD). PD is characterized by progressively distributed Lewy pathology and neurodegeneration, linked to the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Ca2+ entry through Cav1 channels, mitochondrial oxidant stress and PD pathogenesis are strictly linked. Alterations in RyR expression and function are observed in cells bearing familial mutations in the genes of the β-amyloid precursor protein (βAPP) and of presenilins (the catalytic core of γ-secretase complexes that cleave the βAPP to generate amyloid β-peptides), in the brain of transgenic AD mice models and in AD-affected human brains. RyR participates in the control of βAPP processing and of Aβ peptide production: RyR alteration or mysfunction alters neuronal death, synaptic function and memory and learning abilities, and its regulation by Sorcin can be important in maintaining ER Ca2+ load in ER and possibly decreasing ER stress and unfolded protein production in the brain. Further, Sorcin is able to directly interact as a function of Ca2+ concentration (in vitro, in cultured cells and in human brain) with alpha-synuclein (AS) and presenilin 2 (PS2), important in PD and AD pathogenesis, respectively[48,49]. Sorcin binds to the C-terminal part of PS2 that forms low-conductance Ca2+ channels in planar lipid bilayers, interacts with RyR in a Ca2+-dependent fashion, and regulates Ca2+ homeostasis. Sequestration of Sorcin by aberrant forms of tau compromises its function, impairing calcium homeostasis and cellular resistance by ER stress, and contributing to the progression of AD. Sorcin is overexpressed in a PD cell model induced by 1-methyl-4-phenylpyridinium ion (MPP+) in SH-SY5Y cells, which is one of the most differentially expressed proteins in PD vs. normal human substantia nigra and in PD vs. human brain samples, and is overexpressed in AD brain samples[56-58], in particular in sporadic AD and in AD brains with severe cerebral amyloid angiopathy, as well as in frontal cortical tissues from postmortem cases of frontotemporal dementia. Further, Sorcin is overexpressed in 7 different Huntington’s disease human and mice models, where it has been associated with the unfolded protein response. Sorcin also interacts with the ionotropic glutamate receptor NMDAR1 Ca2+ channel, important in several cascade pathways and in synaptic plasticity, in caudate-putamen nucleus, and with annexins A7 and A11, involved in Ca2+ homeostasis in astrocytes.
Sorcin was isolated in 1981 as a soluble protein expressed in hamster lung tumor cells resistant to vincristine, and named according to its main characteristics as soluble, resistance-related, calcium binding protein (Sorcin). Sorcin is overexpressed in different tumors, from many tissues, mostly with an ABCB1-dependent MD-resistant phenotype. The SRI gene resides in the same amplicon of ABCB1, in chromosome 7q21.12, and was identified as a resistance-related gene because often its gene is co-amplified with ABCB1 in MD-resistant cancer cells. For two decades, Sorcin overexpression was believed to be an accidental by-product of this genomic co-amplification process; in the last 15 years many studies have defined Sorcin as an oncoprotein, characterized both as a marker and a cause of MD resistance (MDR).
Sorcin is overexpressed in many human cancers, including adenocarcinoma, breast cancer, colorectal cancer, gastric cancer, lung cancer, nasopharyngeal cancer, hepatocellular carcinoma and ovarian cancer, lymphoma, leukemia and myeloma, and particularly in cancers with ABCB1-dependent MD-resistant phenotype[67-81]. The level of expression of Sorcin is one of the main markers of poor outcome in embryonal tumors of central nervous system; Sorcin is a histological marker for malignant glioma, and is overexpressed in anaplastic astrocytoma, glioblastoma and oligodendroglioma[83-86].
Sorcin is an oncoprotein with multifaceted activity in both tumorigenesis and the onset of a MD-resistant phenotype [Figure 4]. Sorcin, by loading calcium in ER and mitochondria, prevents ER stress and possibly the unfolded protein response, and increases cell escape from apoptosis[10,11,78]: in MD-resistant tumor cells overexpressing Sorcin, the equilibrium between cell life and death is shifted towards proliferation.
Figure 4. Multidrug-resistance (MDR) depends on a series of factors, including absorption, distribution, metabolism, elimination (ADME), drug influx and efflux, drug activation/inactivation, drug target alteration, DNA damage repair, cell death inhibition, epigenetic alteration and epithelial-to-mesenchymal transition (EMT). Sorcin contributions to the onset of a MD-resistant phenotype are indicated in red (see text)
In doxorubicin-resistant leukemia cell lines, Sorcin is overexpressed with respect to the drug-sensitive parental cell line. In leukemia patients, Sorcin expression level correlates with low-response to chemotherapies and poor prognosis; Sorcin overexpression (with gene transfection techniques) increases MDR to doxorubicin, vincristine, etoposide and homoharringtonine in leukemia K562 cells and in lung tumors, to doxorubicin, vincristine, paclitaxel and 5-fluorouracil in SGC7901 cells, ovarian and breast cancer[22,69,72,74,76,87]. Conversely, Sorcin silencing reverses MDR in many tumor cell lines, as MD-resistant leukemia and Sorcin-transfected leukemia cells, breast cancer, HeLa, colorectal cancer and nasopharyngeal carcinoma cells[2,22,74-78,88-94]. In a lung cancer cell line, Sorcin silencing decreases ABCB1 protein levels and ABCB1 activity, thereby decreasing rhodamine123 efflux[Table 1].
Selected studies on the effects of sorcin overexpression and/or silencing in tumor cell lines
|Tumor cell lines||Resistance||Overexpression (O), silencing (S)||Reference|
|Leukemia (K562), breast cancer (MCF-7)||Doxorubicin||O,S|||
|Leukemia (K562)||Doxorubicin, vincristine||O,S|||
|Leukemia (K562)||Doxorubicin, etoposide, Homoharringtonine, vincristine||O,S|||
|Lung adenocarcinoma (A549)||Cisplatin||S|||
|Leukemia (K562), breast cancer (MCF-7)||Adriamycin||S|||
|Colorectal cancer (CRC)||5-fluorouracil, oxaliplatin, irinotecan||O,S|||
|Lung cancer (H1299)||Doxorubicin||O,S|||
|Gastric cancer (SGC7901)||Vincristine, adriamycin, taxol, 5-fluorouracil||O,S|||
|Cervical carcinoma (HeLa)||Vinblastine||O,S|||
|Nasopharingeal carcinoma (CNE2)||Cisplatin||S|||
|Ovarian carcinoma (2008)||Paclitaxel||O|||
|Breast cancer||Neoadjuvant chemotherapy||O|||
|Breast cancer (MDA-MB-231), lung adenocarcinoma (A549), lung fibrosarcoma (HT1080)||Adriamycin, etoposide||O,S|||
Sorcin is also able to bind directly and with high affinity several chemotherapeutic drugs, as doxorubicin, paclitaxel, vinblastine and cisplatin; Sorcin acts as a cytosolic drug scavenger, thereby reducing doxorubicin nuclear uptake, and allowing an increase of drug resistance and of cell survival. Sorcin binds doxorubicin with high affinity in a site at the EF5 hand, which is involved in Sorcin dimerization and does not bind calcium with high affinity [Figure 5], and changes cell localization upon doxorubicin treatment, and presumably upon drug binding.
Figure 5. Sorcin is able to bind with high affinity doxorubicin and other drugs: the crystal structure of the sorcin-doxorubicin complex shows that the drug binds to the EF5 hand
Sorcin overexpression increases migration, invasion and metastasis in vitro, while Sorcin silencing inhibits the epithelial-to-mesenchymal (EMT) transition in a human breast cancer cell line, possibly via E-cadherin and VEGF expression, and reduces breast cancer metastasis. Sorcin induces migration and invasion also in gastric cancer cells, while inhibition of Sorcin expression down-regulates the expression of markers of invasion, migration and proliferation as MMP2, MMP9, CTSZ and p-STAT3, followed by suppression of tumor growth and metastasis. Sorcin interacts with STAT3 and increases its phosphorylation, thereby negatively regulating NF-κB signaling.
Sorcin expression is upregulated in hepatocellular carcinoma, with respect to adjacent non-tumor liver tissues and to normal liver tissues. Sorcin expression correlates with hepatocellular carcinoma metastasis: patients with high Sorcin expression have shorter survival and higher recurrence compared with patients with low Sorcin expression. Sorcin increases proliferation, migration, and invasion in vitro in hepatocellular carcinoma and colorectal cancer cell, and facilitates cancer growth, metastasization and EMT, via activation of ERK and/or PI3K/Akt signaling pathways[79,97]. Sorcin is also involved in the regulation of Ca2+-mediated angiogenesis, via the VEGF/PI3K/Akt pathway in endometrial cells and plays a crucial role in preparing the endometrium for implantation.
Sorcin induces the expression of ABCB1 via a cAMP response element (CRE), located between -716 and -709 base pairs upstream the ABCB1 gene: Sorcin overexpression increases CRE-binding protein (CREB) phosphorylation and its binding to the CRE site in the ABCB1 promoter induces ABCB1 expression.
In the mitochondrion, Sorcin interacts with TRAP1, a mitochondrial chaperone with antioxidant and anti-apoptotic protein, upregulated in several human tumors. TRAP1 modulates apoptosis by exerting a quality control on the short (19-kDa) mitochondrial Sorcin isoform. TRAP1 silencing in colorectal carcinoma cells decreases mitochondrial Sorcin expression, and Sorcin silencing increases TRAP1 degradation, while overexpression of a TRAP1 mutant localized in the ER increases the expression of mitochondrial Sorcin and protects from paclitaxel-dependent apoptosis. Sorcin overexpression increases ER and mitochondrial calcium levels, while Sorcin silencing activates caspase-3, caspase-12 and GRP78/BiP, increases mitotic defects, blocks cell cycle progression in G2/M, increases the number of rounded polynucleated cells and induces apoptosis and cell death[10,22,78]. Sorcin overexpression in leukemia cells increases expression of Bcl-2 and decreases Bax levels.
Sorcin is an interesting oncoprotein and MDR marker, expressed in many cancer cell types, and whose overexpression results in the MDR phenotype. Sorcin has an important role in calcium homeostasis, and is able to interact/regulate several targets and to contribute to the onset of a MD-resistant phenotype in different ways.
Sorcin has no enzymatic activity, and targeting its activity may prove difficult. The modulation of Sorcin expression and activity for overcoming tumorigenesis, cancer-related EMT and MDR is a possible target: small molecules as dihydromyricetin have been used to target Sorcin, and administration of extracts from plants as Tegillarca granosa extract Haishengsu is another strategy used[76,99-101]. Sorcin-specific miR-1 or antagomiR-1 are possibly the most specific ways to target Sorcin, together with approaches of Sorcin silencing or the use of Crispr-Cas9.
Sorcin was identified as “resistance-related”, because it’s encoded by a gene co-amplified with ABCB1, i.e., the most important broad substrate specificity ATP-dependent efflux pump, able to pump xenobiotics (such as toxins or drugs) out of cells.
The human ABCB1 gene, in the chromosomal region 7q21.1, confers MDR when overexpressed or amplified[102-106]; increased ABCB1 expression upon treatment with chemotherapeutic drug has been largely reported in the last thirty years[107-115].
In many types of cancers, amplification of the chromosome 7q21 region containing genes of ABCB1 and Sorcin, has been reported in MD-resistant cell lines as neuroblastoma, lung cancer cells and leukemia cells. Often, genomic instability and chromosomal rearrangements result in genomic amplification, yielding an increase in the ABCB1 gene copy number and transactivation of ABCB1 overexpression[119-124].
Several genes surrounding ABCB1 have recently been identified as contributors to the MD-resistant phenotype when overexpressed or amplified together with ABCB1 or suppressed in resistance-induced cancer cell lines. Many studies describe a genomic amplification of chromosome 7q21.12 region, where ABCB1 and other MDR-related genes reside [Figure 6], in MD-resistant tumors; the MD-resistant phenotype depends at least in part on the amplification and/or overexpression of these genes[1,66,106,116-118,125-136]. The ABCB1 amplicon in the chromosomal region 7q21.12 is formed by the SRI, ADAM22, DBF4, SLC25A40, RUNDC3B (RPIP9), ABCB1, ABCB4, CROT, TP53TG1 lncRNA, TMEM243 (MGC4175) and DMTF1 (DMP1) genes [Figure 6], that have been associated with tumorigenesis and MDR; DBF4 and Sorcin, among these genes, are possibly the most important contributors to the MD-resistant phenotype, together with the efflux pumps ABCB1 and ABCB4 (MDR3): DBF4 and Sorcin are both important markers of poor prognosis and drivers of MDR in several types of cancers, acting on different (although partially overlapping) mechanisms with respect to ABCB1.
Figure 6. The ABCB1 amplicon is formed by the genes SRI, ADAM22, DBF4, SLC25A40, RUNDC3B (RPIP9), ABCB1, ABCB4, CROT, TP53TG1 lncRNA, TMEM243 (MGC4175) and DMTF1 (DMP1)
In lung cancer cells with acquired paclitaxel resistance, the 7.q21.12 region is amplified, but ABCB1 expression is increased up to 1000-fold, showing a discrepancy between expression level and gene copy number. A regional activation on chromosome 7q21.11-13, of about 22 co-expressed genes over an area of 8 Mb, was identified in taxane-induced MD-resistant ovarian tumor cells; the amplified region (with increase in genes copy number) included ABCB1, MGC4175 (TMEM243), DMTF1, CROT, ABCB1, ABCB4, ADAM22, RUNDC3B, DBF4 and SRI. A gene copy number gain on chromosome 7q21.12, including the genes ABCB1, ABCB4, SRI, DMTF1, SLC25A40 and CROT, was observed in taxane-resistant breast tumor cell lines. On the other hand, MD-resistant ovarian tumor cells containing a translocation generating fused ABCB1 and SLC25A40 genes, determining the overexpression of ABCB1, were found only in MD-resistant cancers, while no evidence of this event occurs in drug-sensitive cancer cells. Deletions in the ABCB1 genes locus in breast cancer patients determine a 2-8-fold decreased expression of these MDR locus-related genes; cancer patients harboring these deletions display a better response to neoadjuvant chemotherapy.
In addition to genomic rearrangements and presence of high copy, other mechanisms may contribute to increased gene expression, such as transcriptional upregulation, mRNA stabilization, post-transcriptional regulation and epigenetic modifications. Non-coding RNAs, such as miRNAs and long non-coding RNAs, can possibly exert post-transcriptionally regulate oncogene functions on cancer cells, resulting in metastatic or drug-resistant phenotypes: the long non-coding RNA TP53TG1, present in the chromosomal region 7.q21.12, is down-regulated in A549 cisplatin-resistant lung cancer cells; miR-1, specifically targeting Sorcin, is frequently downregulated in various types of cancer, such as lung cancer, colon cancer, genitourinary cancer, head and neck tumor, thyroid cancer and sarcoma; low miR-1 levels have been shown to be associated with chemosensitivity[140,141].
Sorcin has an important role as a modulator of cellular calcium homeostasis, acting on Ca2+ channels, exchangers and pumps, thereby regulating ER and mitochondrial Ca2+ levels, reducing ER stress and mitochondrial dysfunction, and protecting the cell from apoptosis.
Sorcin is highly expressed in the heart and in the brain, it is overexpressed in cancers and other pathological conditions, and plays important roles in the onset of cancer, cardiac diseases and possibly neurodegenerative diseases.
Sorcin is overexpressed in MD-resistant cancer cells, co-amplified with ABCB1, ABCB4 and other proteins involved in the resistance to chemotherapy in cancer cells. Sorcin overexpression induces resistance to many different chemotherapeutic drugs, while Sorcin silencing reverts drug resistance, by acting on many pathways.
Sorcin is therefore an important MDR marker and may represent a therapeutic target for reversing MDR.
We acknowledge “Quality methods for Design of Experiments in Scientific Research”, in the FaReBio di Qualità Project: Quality and Project Management OpenLab: qPMO CNR; the Flagship Project Nanomax: “NADINE: Nanotechnology-based Diagnostics In Neurological diseases and Experimental oncology”; PRIN 20154JRJPP MIUR; Progetto Ricerca Finalizzata Min. Salute RF-2016-02364123 RAREST‐JHD.Authors’ contributions
Conception of the work: Ilari A, Colotti G
Draft and revision of the work: Genovese I, Ilari A, Battista T, Chiarini V, Fazi F, Fiorillo A, Colotti GAvailability of data and materials
Not applicable.Financial support and sponsorship
None.Conflicts of interest
All authors declared that there are no conflicts of interest.Ethical approval and consent to participate
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© The Author(s) 2018.
1. Van der Bliek AM, Meyers MB, Biedler JL, Hes E, Borst P. A 22-kd protein (sorcin/V19) encoded by an amplified gene in multidrug-resistant cells, is homologous to the calcium-binding light chain of calpain. EMBO J 1986;5:3201-8.PubMedPMC
2. Colotti G, Poser E, Fiorillo A, Genovese I, Chiarini V, Ilari A. Sorcin, a calcium binding protein involved in the multidrug resistance mechanisms in cancer cells. Molecules 2014;19:13976-89.DOIPubMed
3. Hansen C, Tarabykina S, la Cour JM, Lollike K, Berchtold MW. The PEF family proteins sorcin and grancalcin interact in vivo and in vitro. FEBS Lett 2003;545:151-4.DOI
4. Maki M, Kitaura Y, Satoh H, Ohkouchi S, Shibata H. Structures, functions and molecular evolution of the penta-EF-hand Ca2+-binding proteins. Biochim Biophys Acta 2002;1600:51-60.DOI
5. Ilari A, Fiorillo A, Poser E, Lalioti VS, Sundell GN, Ivarsson Y, Genovese I, Colotti G. Structural basis of Sorcin-mediated calcium-dependent signal transduction. Sci Rep 2015;5:16828.DOIPubMedPMC
6. Ilari A, Johnson KA, Nastopoulos V, Verzili D, Zamparelli C, Colotti G, Tsernoglou D, Chiancone E. The crystal structure of the sorcin calcium binding domain provides a model of Ca2+-dependent processes in the full-length protein. J Mol Biol 2002;317:447-58.DOIPubMed
7. Colotti G, Zamparelli C, Verzili D, Mella M, Loughrey CM, Smith GL, Chiancone E. The W105G and W99G sorcin mutants demonstrate the role of the D helix in the Ca(2+)-dependent interaction with annexin VII and the cardiac ryanodine receptor. Biochemistry 2006;45:12519-29.DOIPubMed
8. Mella M, Colotti G, Zamparelli C, Verzili D, Ilari A, Chiancone E. Information transfer in the penta-EF-hand protein sorcin does not operate via the canonical structural/functional pairing. A study with site-specific mutants. J Biol Chem 2003;278:24921-8.DOIPubMed
9. Zamparelli C, Ilari A, Verzili D, Giangiacomo L, Colotti G, Pascarella S, Chiancone E. Structure-function relationships in sorcin, a member of the penta EF-hand family. Interaction of sorcin fragments with the ryanodine receptor and an Escherichia coli model system. Biochemistry 2000;39:658-66.DOIPubMed
10. Lalioti VS, Ilari A, O'Connell DJ, Poser E, Sandoval IV, Colotti G. Sorcin links calcium signaling to vesicle trafficking, regulates Polo-like kinase 1 and is necessary for mitosis. PLoS One 2014;9:e85438.DOIPubMedPMC
11. Maddalena F, Sisinni L, Lettini G, Condelli V, Matassa DS, Piscazzi A, Amoroso MR, La Torre G, Esposito F, Landriscina M. Resistance to paclitxel in breast carcinoma cells requires a quality control of mitochondrial antiapoptotic proteins by TRAP1. Mol Oncol 2013;7:895-906.DOIPubMedPMC
12. Clapham DE. Calcium signaling. Cell 2007;131:1047-58.DOIPubMed
13. Fowler MR, Colotti G, Chiancone E, Higuchi Y, Seidler T, Smith GL. Complex modulation of L-type Ca(2+) current inactivation by sorcin in isolated rabbit cardiomyocytes. Pflugers Arch 2009;457:1049-60.DOIPubMed
14. Fowler MR, Colotti G, Chiancone E, Smith GL, Fearon IM. Sorcin modulates cardiac L-type Ca2+ current by functional interaction with the alpha1C subunit in rabbits. Exp Physiol 2008;93:1233-8.DOIPubMed
15. Franceschini S, Ilari A, Verzili D, Zamparelli C, Antaramian A, Rueda A, Valdivia HH, Chiancone E, Colotti G. Molecular basis for the impaired function of the natural F112L sorcin mutant: X-ray crystal structure, calcium affinity, and interaction with annexin VII and the ryanodine receptor. FASEB J 2008;22:295-306.DOIPubMed
16. Matsumoto T, Hisamatsu Y, Ohkusa T, Inoue N, Sato T, Suzuki S, Ikeda Y, Matsuzaki M. Sorcin interacts with sarcoplasmic reticulum Ca(2+)-ATPase and modulates excitation-contraction coupling in the heart. Basic Res Cardiol 2005;100:250-62.DOIPubMed
17. Meyers MB, Fischer A, Sun YJ, Lopes CM, Rohacs T, Nakamura TY, Zhou YY, Lee PC, Altschuld RA, McCune SA, Coetzee WA, Fishman GI. Sorcin regulates excitation-contraction coupling in the heart. J Biol Chem 2003;278:28865-71.DOIPubMed
18. Suarez J, McDonough PM, Scott BT, Suarez-Ramirez A, Wang H, Fricovsky ES, Dillmann WH. Sorcin modulates mitochondrial Ca(2+) handling and reduces apoptosis in neonatal rat cardiac myocytes. Am J Physiol Cell Physiol 2013;304:C248-56.DOIPubMedPMC
19. Zamparelli C, Macquaide N, Colotti G, Verzili D, Seidler T, Smith GL, Chiancone E. Activation of the cardiac Na(+)-Ca(2+) exchanger by sorcin via the interaction of the respective Ca(2+)-binding domains. J Mol Cell Cardiol 2010;49:132-41.DOIPubMedPMC
20. Marmugi A, Parnis J, Chen X, Carmichael L, Hardy J, Mannan N, Marchetti P, Piemonti L, Bosco D, Johnson P, Shapiro JA, Cruciani-Guglielmacci C, Magnan C, Ibberson M, Thorens B, Valdivia HH, Rutter GA, Leclerc I. Sorcin links pancreatic β-cell lipotoxicity to ER Ca2+ stores. Diabetes 2016;65:1009-21.DOIPubMedPMC
21. Noordeen NA, Meur G, Rutter GA, Leclerc I. Glucose-induced nuclear shuttling of ChREBP is mediated by sorcin and Ca(2+) ions in pancreatic beta-cells. Diabetes 2012;61:574-85.DOIPubMedPMC
22. Hu Y, Cheng X, Li S, Zhou Y, Wang J, Cheng T, Yang M, Xiong D. Inhibition of sorcin reverses multidrug resistance of K562/A02 cells and MCF-7/A02 cells via regulating apoptosis-related proteins. Cancer Chemother Pharmacol 2013;72:789-98.DOIPubMed
23. Anthony DF, Beattie J, Paul A, Currie S. Interaction of calcium/calmodulin-dependent protein kinase IIdeltaC with sorcin indirectly modulates ryanodine receptor function in cardiac myocytes. J Mol Cell Cardiol 2007;43:492-503.DOIPubMed
24. Salzer U, Hinterdorfer P, Hunger U, Borken C, Prohaska R. Ca(++)-dependent vesicle release from erythrocytes involves stomatin-specific lipid rafts, synexin (annexin VII), and sorcin. Blood 2002;99:2569-77.DOIPubMed
25. Brownawell AM, Creutz CE. Creutz, Calcium-dependent binding of sorcin to the N-terminal domain of synexin (annexin VII). J Biol Chem 1997;272:22182-90.DOI
26. Tomas A, Futter C, Moss SE. Moss, Annexin 11 is required for midbody formation and completion of the terminal phase of cytokinesis. J Cell Biol 2004;165:813-22.DOIPubMedPMC
27. Lai RC, Chen TS, Lim SK. Mesenchymal stem cell exosome: a novel stem cell-based therapy for cardiovascular disease. Regen Med 2011;6:481-92.DOIPubMed
28. Buschow SI, van Balkom BW, Aalberts M, Heck AJ, Wauben M, Stoorvogel W. MHC class II-associated proteins in B-cell exosomes and potential functional implications for exosome biogenesis. Immunol Cell Biol 2010;88:851-6.DOIPubMed
29. Demory Beckler M, Higginbotham JN, Franklin JL, Ham AJ, Halvey PJ, Imasuen IE, Whitwell C, Li M, Liebler DC, Coffey RJ. Proteomic analysis of exosomes from mutant KRAS colon cancer cells identifies intercellular transfer of mutant KRAS. Mol Cell Proteomics 2013;12:343-55.DOIPubMedPMC
30. Gonzales PA, Pisitkun T, Hoffert JD, Tchapyjnikov D, Star RA, Kleta R, Wang NS, Knepper MA. Large-scale proteomics and phosphoproteomics of urinary exosomes. J Am Soc Nephrol 2009;20:363-79.DOIPubMedPMC
31. Keerthikumar S, Gangoda L, Liem M, Fonseka P, Atukorala I, Ozcitti C, Mechler A, Adda CG, Ang CS, Mathivanan S. Proteogenomic analysis reveals exosomes are more oncogenic than ectosomes. Oncotarget 2015;6:15375-96.DOIPubMedPMC
32. Kharaziha P, Chioureas D, Rutishauser D, Baltatzis G, Lennartsson L, Fonseca P, Azimi A, Hultenby K, Zubarev R, Ullén A, Yachnin J, Nilsson S, Panaretakis T. Molecular profiling of prostate cancer derived exosomes may reveal a predictive signature for response to docetaxel. Oncotarget 2015;6:21740-54.DOIPubMedPMC
33. Liang B, Peng P, Chen S, Li L, Zhang M, Cao D, Yang J, Li H, Gui T, Li X, Shen K. Characterization and proteomic analysis of ovarian cancer-derived exosomes. J Proteomics 2013;80:171-82.DOIPubMed
34. Pienimaeki-Roemer A, Kuhlmann K, Böttcher A, Konovalova T, Black A, Orsó E, Liebisch G, Ahrens M, Eisenacher M, Meyer HE, Schmitz G. Lipidomic and proteomic characterization of platelet extracellular vesicle subfractions from senescent platelets. Transfusion 2015;55:507-21.DOIPubMed
35. Pisitkun T, Shen RF, Knepper MA. Identification and proteomic profiling of exosomes in human urine. Proc Natl Acad Sci U S A 2004;101:13368-73.DOIPubMedPMC
36. Ali R, Huang Y, Maher SE, Kim RW, Giordano FJ, Tellides G, Geirsson A. miR-1 mediated suppression of Sorcin regulates myocardial contractility through modulation of Ca2+ signaling. J Mol Cell Cardiol 2012;52:1027-37.DOIPubMed
37. Bers DM, Despa S, Bossuyt J. Regulation of Ca2+ and Na+ in normal and failing cardiac myocytes. Ann N Y Acad Sci 2006;1080:165-77.DOIPubMed
38. Seidler T, Miller SL, Loughrey CM, Kania A, Burow A, Kettlewell S, Teucher N, Wagner S, Kögler H, Meyers MB, Hasenfuss G, Smith GL. Effects of adenovirus-mediated sorcin overexpression on excitation-contraction coupling in isolated rabbit cardiomyocytes. Circ Res 2003;93:132-9.DOIPubMed
39. Lokuta AJ, Meyers MB, Sander PR, Fishman GI, Valdivia HH. Modulation of cardiac ryanodine receptors by sorcin. J Biol Chem 1997;272:25333-8.DOIPubMed
40. Collis LP, Meyers MB, Zhang J, Phoon CK, Sobie EA, Coetzee WA, Fishman GI. Expression of a sorcin missense mutation in the heart modulates excitation-contraction coupling. FASEB J 2007;21:475-87.DOIPubMed
41. Farrell EF, Antaramian A, Rueda A, Gómez AM, Valdivia HH. Sorcin inhibits calcium release and modulates excitation-contraction coupling in the heart. J Biol Chem 2003;278:34660-6.DOIPubMed
42. Frank KF, Bölck B, Ding Z, Krause D, Hattebuhr N, Malik A, Brixius K, Hajjar RJ, Schrader J, Schwinger RH. Overexpression of sorcin enhances cardiac contractility in vivo and in vitro. J Mol Cell Cardiol 2005;38:607-15.DOIPubMed
43. Suarez J, Belke DD, Gloss B, Dieterle T, McDonough PM, Kim YK, Brunton LL, Dillmann WH. In vivo adenoviral transfer of sorcin reverses cardiac contractile abnormalities of diabetic cardiomyopathy. Am J Physiol Heart Circ Physiol 2004;286:H68-75.DOIPubMed
44. Chen X, Weber C, Farrell ET, Alvarado FJ, Zhao YT, Gómez AM, Valdivia HH. Sorcin ablation plus beta-adrenergic stimulation generate an arrhythmogenic substrate in mouse ventricular myocytes. J Mol Cell Cardiol 2018;114:199-210.DOIPubMed
45. Alzheimer's Association Calcium Hypothesis Workgroup. Calcium hypothesis of Alzheimer's disease and brain aging: a framework for integrating new evidence into a comprehensive theory of pathogenesis. Alzheimers Dement 2017;13:178-182.e17.DOIPubMed
46. Surmeier DJ, Halliday GM, Simuni T. Calcium, mitochondrial dysfunction and slowing the progression of Parkinson's disease. Exp Neurol 2017;298:202-9.DOIPubMed
47. Del Prete D, Checler F, Chami M. Ryanodine receptors: physiological function and deregulation in Alzheimer disease. Mol Neurodegener 2014;9:21.DOIPubMedPMC
48. Pack-Chung E, Meyers MB, Pettingell WP, Moir RD, Brownawell AM, Cheng I, Tanzi RE, Kim TW. Presenilin 2 interacts with sorcin, a modulator of the ryanodine receptor. J Biol Chem 2000;275:14440-5.DOIPubMed
49. Woods WS, Boettcher JM, Zhou DH, Kloepper KD, Hartman KL, Ladror DT, Qi Z, Rienstra CM, George JM. Conformation-specific binding of alpha-synuclein to novel protein partners detected by phage display and NMR spectroscopy. J Biol Chem 2007;282:34555-67.DOIPubMed
50. Tu H, Nelson O, Bezprozvanny A, Wang Z, Lee SF, Hao YH, Serneels L, De Strooper B, Yu G, Bezprozvanny I. Presenilins form ER Ca2+ leak channels, a function disrupted by familial Alzheimer's disease-linked mutations. Cell 2006;126:981-93.DOIPubMedPMC
51. Takeda T, Asahi M, Yamaguchi O, Hikoso S, Nakayama H, Kusakari Y, Kawai M, Hongo K, Higuchi Y, Kashiwase K, Watanabe T, Taniike M, Nakai A, Nishida K, Kurihara S, Donoviel DB, Bernstein A, Tomita T, Iwatsubo T, Hori M, Otsu K. Presenilin 2 regulates the systolic function of heart by modulating Ca2+ signaling. FASEB J 2005;19:2069-71.DOIPubMed
52. Kim SI, Lee HJ, Kim SS, Kwon YS, Chun W. Sequestration of sorcin by aberrant forms of tau results in the defective calcium homeostasis. Korean J Physiol Pharmacol 2016;20:387-97.DOIPubMedPMC
53. Xie H, Chang M, Hu X, Wang D, Tian M, Li G, Jiang H, Wang Y, Dong Z, Zhang Y, Hu L. Proteomics analysis of MPP+-induced apoptosis in SH-SY5Y cells. Neurol Sci 2011;32:221-8.DOIPubMed
54. Werner CJ, Heyny-von Haussen R, Mall G, Wolf S. Proteome analysis of human substantia nigra in Parkinson's disease. Proteome Sci 2008;6:8.DOIPubMedPMC
55. Jin J, Hulette C, Wang Y, Zhang T, Pan C, Wadhwa R, Zhang J. Proteomic identification of a stress protein, mortalin/mthsp70/GRP75: relevance to Parkinson disease. Mol Cell Proteomics 2006;5:1193-204.DOIPubMed
56. Andreev VP, Petyuk VA, Brewer HM, Karpievitch YV, Xie F, Clarke J, Camp D, Smith RD, Lieberman AP, Albin RL, Nawaz Z, El Hokayem J, Myers AJ. Label-free quantitative LC-MS proteomics of Alzheimer's disease and normally aged human brains. J Proteome Res 2012;11:3053-67.DOIPubMedPMC
57. Musunuri S, Wetterhall M, Ingelsson M, Lannfelt L, Artemenko K, Bergquist J, Kultima K, Shevchenko G. Quantification of the brain proteome in Alzheimer's disease using multiplexed mass spectrometry. J Proteome Res 2014;13:2056-68.DOIPubMed
58. Seyfried NT, Dammer EB, Swarup V, Nandakumar D, Duong DM, Yin L, Deng Q, Nguyen T, Hales CM, Wingo T, Glass J, Gearing M, Thambisetty M, Troncoso JC, Geschwind DH, Lah JJ, Levey AI. A multi-network approach identifies protein-specific co-expression in asymptomatic and symptomatic Alzheimer's disease. Cell Syst 2017;4:60-72.e4.DOIPubMedPMC
59. Drummond E, Nayak S, Faustin A, Pires G, Hickman RA, Askenazi M, Cohen M, Haldiman T, Kim C, Han X, Shao Y, Safar JG, Ueberheide B, Wisniewski T. Proteomic differences in amyloid plaques in rapidly progressive and sporadic Alzheimer's disease. Acta Neuropathol 2017;133:933-54.DOIPubMedPMC
60. Hondius DC, Eigenhuis KN, Morrema THJ, van der Schors RC, van Nierop P, Bugiani M, Li KW, Hoozemans JJM, Smit AB, Rozemuller AJM. Proteomics analysis identifies new markers associated with capillary cerebral amyloid angiopathy in Alzheimer's disease. Acta Neuropathol Commun 2018;6:46.DOIPubMedPMC
61. Umoh ME, Dammer EB, Dai J, Duong DM, Lah JJ, Levey AI, Gearing M, Glass JD, Seyfried NT. A proteomic network approach across the ALS-FTD disease spectrum resolves clinical phenotypes and genetic vulnerability in human brain. EMBO Mol Med 2018;10:48-62.DOIPubMedPMC
62. Kalathur RK, Giner-Lamia J, Machado S, Barata T, Ayasolla KR, Futschik ME. The unfolded protein response and its potential role in Huntington's disease elucidated by a systems biology approach. Version 2. F1000Res 2015;4:103.DOIPubMedPMC
63. Gracy KN, Clarke CL, Meyers MB, Pickel VM. N-methyl-D-aspartate receptor 1 in the caudate-putamen nucleus: ultrastructural localization and co-expression with sorcin, a 22,000 mol. wt calcium binding protein. Neuroscience 1999;90:107-17.DOI
64. Clemen CS, Herr C, Hövelmeyer N, Noegel AA. The lack of annexin A7 affects functions of primary astrocytes. Exp Cell Res 2003;291:406-14.DOIPubMed
65. Meyers MB, Biedler JL. Increased synthesis of a low molecular weight protein in vincristine-resistant cells. Biochem Biophys Res Commun 1981;99:228-35.DOI
66. Van der Bliek AM, Baas F, Van der Velde-Koerts T, Biedler JL, Meyers MB, Ozols RF, Hamilton TC, Joenje H, Borst P. Genes amplified and overexpressed in human multidrug-resistant cell lines. Cancer Res 1988;48:5927-32.PubMed
67. Deng L, Su T, Leng A, Zhang X, Xu M, Yan L, Gu H, Zhang G. Upregulation of soluble resistance-related calcium-binding protein (sorcin) in gastric cancer. Med Oncol 2010;27:1102-8.DOIPubMed
68. Padar S, van Breemen C, Thomas DW, Uchizono JA, Livesey JC, Rahimian R. Differential regulation of calcium homeostasis in adenocarcinoma cell line A549 and its Taxol-resistant subclone. Br J Pharmacol 2004;142:305-16.DOIPubMedPMC
69. Qi J, Liu N, Zhou Y, Tan Y, Cheng Y, Yang C, Zhu Z, Xiong D. Overexpression of sorcin in multidrug resistant human leukemia cells and its role in regulating cell apoptosis. Biochem Biophys Res Commun 2006;349:303-9.DOIPubMed
70. Qu Y, Yang Y, Liu B, Xiao W. Comparative proteomic profiling identified sorcin being associated with gemcitabine resistance in non-small cell lung cancer. Med Oncol 2010;27:1303-8.DOIPubMed
71. Tan Y, Li G, Zhao C, Wang J, Zhao H, Xue Y, Han M, Yang C. Expression of sorcin predicts poor outcome in acute myeloid leukemia. Leuk Res 2003;27:125-31.DOI
72. Yamagishi N, Nakao R, Kondo R, Nishitsuji M, Saito Y, Kuga T, Hatayama T, Nakayama Y. Increased expression of sorcin is associated with multidrug resistance in leukemia cells via up-regulation of MDR1 expression through cAMP response element-binding protein. Biochem Biophys Res Commun 2014;448:430-6.DOIPubMed
73. Yang YX, Chen ZC, Zhang GY, Yi H, Xiao ZQ. A subcelluar proteomic investigation into vincristine-resistant gastric cancer cell line. J Cell Biochem 2008;104:1010-21.DOIPubMed
74. Zhou Y, Xu Y, Tan Y, Qi J, Xiao Y, Yang C, Zhu Z, Xiong D. Sorcin, an important gene associated with multidrug-resistance in human leukemia cells. Leuk Res 2006;30:469-76.DOIPubMed
75. Gao Y, Li W, Liu X, Gao F, Zhao X. Reversing effect and mechanism of soluble resistance-related calcium-binding protein on multidrug resistance in human lung cancer A549/DDP cells. Mol Med Rep 2015;11:2118-24.DOIPubMed
76. Sun Y, Wang C, Meng Q, Liu Z, Huo X, Sun P, Sun H, Ma X, Peng J, Liu K. Targeting P-glycoprotein and SORCIN: dihydromyricetin strengthens anti-proliferative efficiency of adriamycin via MAPK/ERK and Ca2+ -mediated apoptosis pathways in MCF-7/ADR and K562/ADR. J Cell Physiol 2018;233:3066-79.DOIPubMed
77. Dabaghi M, Rahgozar S, Moshtaghian J, Moafi A, Abedi M, Pourabutaleb E. Overexpression of SORCIN is a prognostic biomarker for multidrug-resistant pediatric acute lymphoblastic leukemia and correlates with upregulated MDR1/P-gp. Genet Test Mol Biomarkers 2016;20:516-21.DOIPubMed
78. Maddalena F, Laudiero G, Piscazzi A, Secondo A, Scorziello A, Lombardi V, Matassa DS, Fersini A, Neri V, Esposito F, Landriscina M. Sorcin induces a drug-resistant phenotype in human colorectal cancer by modulating Ca(2+) homeostasis. Cancer Res 2011;71:7659-69.DOIPubMed
79. Tong W, Sun D, Wang Q, Suo J. Sorcin enhances metastasis and promotes epithelial-to-mesenchymal transition of colorectal cancer. Cell Biochem Biophys 2015;72:453-9.DOIPubMed
80. Mangia A, Caldarola L, Dell'Endice S, Scarpi E, Saragoni L, Monti M, Santini D, Brunetti O, Simone G, Silvestris N. The potential predictive role of nuclear NHERF1 expression in advanced gastric cancer patients treated with epirubicin/oxaliplatin/capecitabine first line chemotherapy. Cancer Biol Ther 2015;16:1140-7.DOIPubMedPMC
81. Xu P, Jiang YF, Wang JH. shRNA-mediated silencing of sorcin increases drug chemosensitivity in myeloma KM3/DDP and U266/ADM cell lines. Int J Clin Exp Pathol 2015;8:2300-10.PubMedPMC
82. Pomeroy SL, Tamayo P, Gaasenbeek M, Sturla LM, Angelo M, McLaughlin ME, Kim JY, Goumnerova LC, Black PM, Lau C, Allen JC, Zagzag D, Olson JM, Curran T, Wetmore C, Biegel JA, Poggio T, Mukherjee S, Rifkin R, Califano A, Stolovitzky G, Louis DN, Mesirov JP, Lander ES, Golub TR. Prediction of central nervous system embryonal tumour outcome based on gene expression. Nature 2002;415:436-42.DOIPubMed
83. French PJ, Swagemakers SM, Nagel JH, Kouwenhoven MC, Brouwer E, van der Spek P, Luider TM, Kros JM, van den Bent MJ, Sillevis Smitt PA. Gene expression profiles associated with treatment response in oligodendrogliomas. Cancer Res 2005;65:11335-44.DOIPubMed
84. Shai R, Shi T, Kremen TJ, Horvath S, Liau LM, Cloughesy TF, Mischel PS, Nelson SF. Gene expression profiling identifies molecular subtypes of gliomas. Oncogene 2003;22:4918-23.DOIPubMed
85. Sun L, Hui AM, Su Q, Vortmeyer A, Kotliarov Y, Pastorino S, Passaniti A, Menon J, Walling J, Bailey R, Rosenblum M, Mikkelsen T, Fine HA. Neuronal and glioma-derived stem cell factor induces angiogenesis within the brain. Cancer Cell 2006;9:287-300.DOIPubMed
86. Yokota T, Kouno J, Adachi K, Takahashi H, Teramoto A, Matsumoto K, Sugisaki Y, Onda M, Tsunoda T. Identification of histological markers for malignant glioma by genome-wide expression analysis: dynein, alpha-PIX and sorcin. Acta Neuropathol 2006;111:29-38.DOIPubMed
87. Genovese I, Fiorillo A, Ilari A, Masciarelli S, Fazi F, Colotti G. Binding of doxorubicin to Sorcin impairs cell death and increases drug resistance in cancer cells. Cell Death Dis 2017;8:e2950.DOIPubMedPMC
88. Hamada H, Okochi E, Oh-hara T, Tsuruo T. Purification of the Mr 22,000 calcium-binding protein (sorcin) associated with multidrug resistance and its detection with monoclonal antibodies. Cancer Res 1988;48:3173-8.PubMed
89. He Q, Zhang G, Hou D, Leng A, Xu M, Peng J, Liu T. Overexpression of sorcin results in multidrug resistance in gastric cancer cells with up-regulation of P-gp. Oncol Rep 2011;25:237-43.PubMed
90. Kawakami M, Nakamura T, Okamura N, Komoto C, Markova S, Kobayashi H, Hashimoto N, Okumura K, Sakaeda T. Knock-down of sorcin induces up-regulation of MDR1 in HeLa cells. Biol Pharm Bull 2007;30:1065-73.DOIPubMed
91. Liu X, Chen L, Feng B, Liu G. Reversing effect of sorcin in the drug resistance of human nasopharyngeal carcinoma. Anat Rec (Hoboken) 2014;297:215-21.DOIPubMed
92. Parekh HK, Deng HB, Choudhary K, Houser SR, Simpkins H. Overexpression of sorcin, a calcium-binding protein, induces a low level of paclitaxel resistance in human ovarian and breast cancer cells. Biochem Pharmacol 2002;63:1149-58.DOI
93. Gong Z, Sun P, Chu H, Zhu H, Sun D, Chen J. Overexpression of sorcin in multidrug-resistant human breast cancer. Oncol Lett 2014;8:2393-8.DOIPubMedPMC
94. Hu Y, Li S, Yang M, Yan C, Fan D, Zhou Y, Zhang Y, Yagüe E, Xiong D. Sorcin silencing inhibits epithelial-to-mesenchymal transition and suppresses breast cancer metastasis in vivo. Breast Cancer Res Treat 2014;143:287-99.DOIPubMed
95. Tuo H, Shu F, She S, Yang M, Zou XQ, Huang J, Hu HD, Hu P, Ren H, Peng SF, Yang YX. Sorcin induces gastric cancer cell migration and invasion contributing to STAT3 activation. Oncotarget 2017;8:104258-71.DOIPubMedPMC
96. Li X, Liu Y, Wang Y, Liu J, Li X, Cao H, Gao X, Zheng SJ. Negative regulation of hepatic inflammation by the soluble resistance-related calcium-binding protein via signal transducer and activator of transcription 3. Front Immunol 2017;8:709.DOI
97. Lei X, Liang Y, Chen J, Xiao S, Lei J, Li J, Duanmu J, Jiang Q, Liu D, Tang C, Li T. Sorcin predicts poor prognosis and promotes metastasis by facilitating epithelial-mesenchymal transition in hepatocellular carcinoma. Sci Rep 2017;7:10049.DOIPubMedPMC
98. Gupta K, Sirohi VK, Kumari S, Shukla V, Manohar M, Popli P, Dwivedi A. Sorcin is involved during embryo implantation via activating VEGF/PI3K/Akt pathway in mice. J Mol Endocrinol 2018;60:119-132.DOIPubMed
99. Li GY, Zhang L, Liu JZ, Chen SG, Xiao TW, Liu GZ, Wang JX, Wang LX, Hou M. Marine drug Haishengsu increases chemosensitivity to conventional chemotherapy and improves quality of life in patients with acute leukemia. Biomed Pharmacother 2016;81:160-5.DOIPubMed
100. Sun Y, Wang C, Meng Q, Liu Z, Huo X, Sun P, Sun H, Ma X, Peng J, Liu K. Targeting P-glycoprotein and SORCIN: Dihydromyricetin strengthens anti-proliferative efficiency of adriamycin via MAPK/ERK and Ca(2+) -mediated apoptosis pathways in MCF-7/ADR and K562/ADR. J Cell Physiol 2018;233:3066-79.DOIPubMed
101. Li GY, Liu JZ, Zhang B, Yang M, Chen SG, Hou M, Wang LX. Tegillarca granosa extract Haishengsu (HSS) suppresses expression of mdr1, BCR/ABL and sorcin in drug-resistant K562/ADM tumors in mice. Adv Med Sci 2013;58:112-7.DOIPubMed
102. Callen DF, Baker E, Simmers RN, Seshadri R, Roninson IB. Localization of the human multiple drug resistance gene, MDR1, to 7q21.1. Hum Genet 1987;77:142-4.DOIPubMed
103. Fojo AT, Ueda K, Slamon DJ, Poplack DG, Gottesman MM, Pastan I. Expression of a multidrug-resistance gene in human tumors and tissues. Proc Natl Acad Sci U S A 1987;84:265-9.DOIPubMedPMC
104. Schoenlein PV. Molecular cytogenetics of multiple drug resistance. Cytotechnology 1993;12:63-89.DOIPubMed
105. Scotto KW, Biedler JL, Melera PW. Amplification and expression of genes associated with multidrug resistance in mammalian cells. Science 1986;232:751-5.DOIPubMed
106. Van der Bliek AM, Van der Velde-Koerts T, Ling V, Borst P. Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line. Mol Cell Biol 1986;6:1671-8.DOIPubMedPMC
107. Abolhoda A, Wilson AE, Ross H, Danenberg PV, Burt M, Scotto KW. Rapid activation of MDR1 gene expression in human metastatic sarcoma after in vivo exposure to doxorubicin. Clin Cancer Res 1999;5:3352-6.PubMed
108. Atalay C, Deliloglu Gurhan I, Irkkan C, Gunduz U. Multidrug resistance in locally advanced breast cancer. Tumour Biol 2006;27:309-18.DOIPubMed
109. Brügger D, Brischwein K, Liu C, Bader P, Niethammer D, Gekeler V, Beck JF. Induction of drug resistance and protein kinase C genes in A2780 ovarian cancer cells after incubation with antineoplastic agents at sublethal concentrations. Anticancer Res 2002;22:4229-32.PubMed
110. Chin KV, Tanaka S, Darlington G, Pastan I, Gottesman MM. Heat shock and arsenite increase expression of the multidrug resistance (MDR1) gene in human renal carcinoma cells. J Biol Chem 1990;265:221-6.PubMed
111. Gekeler V, Frese G, Diddens H, Probst H. Expression of a P-glycoprotein gene is inducible in a multidrug-resistant human leukemia cell line. Biochem Biophys Res Commun 1988;155:754-60.DOI
112. Hu XF, Slater A, Wall DM, Kantharidis P, Parkin JD, Cowman A, Zalcberg JR. Rapid up-regulation of mdr1 expression by anthracyclines in a classical multidrug-resistant cell line. Br J Cancer 1995;71:931-6.DOI
113. Liu ZL, Onda K, Tanaka S, Toma T, Hirano T, Oka K. Induction of multidrug resistance in MOLT-4 cells by anticancer agents is closely related to increased expression of functional P-glycoprotein and MDR1 mRNA. Cancer Chemother Pharmacol 2002;49:391-7.DOIPubMed
114. Park J, Shinohara N, Liebert M, Noto L, Flint A, Grossman HB. P-glycoprotein expression in bladder cancer. J Urol 1994;151:43-6.DOI
115. Schneider J, Efferth T, Centeno MM, Mattern J, Rodríguez-Escudero FJ, Volm M. High rate of expression of multidrug resistance-associated P-glycoprotein in human endometrial carcinoma and normal endometrial tissue. Eur J Cancer 1993;29A:554-8.DOI
116. Flahaut M, Mühlethaler-Mottet A, Martinet D, Fattet S, Bourloud KB, Auderset K, Meier R, Schmutz NB, Delattre O, Joseph JM, Gross N. Molecular cytogenetic characterization of doxorubicin-resistant neuroblastoma cell lines: evidence that acquired multidrug resistance results from a unique large amplification of the 7q21 region. Genes Chromosomes Cancer 2006;45:495-508.DOIPubMed
117. Kitada K, Yamasaki T. The MDR1/ABCB1 regional amplification in large inverted repeats with asymmetric sequences and microhomologies at the junction sites. Cancer Genet Cytogenet 2007;178:120-7.DOIPubMed
118. Kadioglu O, Efferth T. Peptide aptamer identified by molecular docking targeting translationally controlled tumor protein in leukemia cells. Invest New Drugs 2016;34:515-21.DOIPubMed
119. Chen GK, Lacayo NJ, Durán GE, Wang Y, Bangs CD, Rea S, Kovacs M, Cherry AM, Brown JM, Sikic BI. Preferential expression of a mutant allele of the amplified MDR1 (ABCB1) gene in drug-resistant variants of a human sarcoma. Genes Chromosomes Cancer 2002;34:372-83.DOIPubMed
120. Duesberg P, Li R, Sachs R, Fabarius A, Upender MB, Hehlmann R. Cancer drug resistance: the central role of the karyotype. Drug Resist Updat 2007;10:51-8.DOIPubMed
121. Katoh H, Shibata T, Kokubu A, Ojima H, Loukopoulos P, Kanai Y, Kosuge T, Fukayama M, Kondo T, Sakamoto M, Hosoda F, Ohki M, Imoto I, Inazawa J, Hirohashi S. Genetic profile of hepatocellular carcinoma revealed by array-based comparative genomic hybridization: identification of genetic indicators to predict patient outcome. J Hepatol 2005;43:863-74.DOIPubMed
122. Mickley LA, Spengler BA, Knutsen TA, Biedler JL, Fojo T. Gene rearrangement: a novel mechanism for MDR-1 gene activation. J Clin Invest 1997;99:1947-57.DOIPubMedPMC
123. Pang E, Hu Y, Chan KY, Lai PB, Squire JA, Macgregor PF, Beheshti B, Albert M, Leung TW, Wong N. Karyotypic imbalances and differential gene expressions in the acquired doxorubicin resistance of hepatocellular carcinoma cells. Lab Invest 2005;85:664-74.DOIPubMed
124. Kim IW, Han N, Kim MG, Kim T, Oh JM. Copy number variability analysis of pharmacogenes in patients with lymphoma, leukemia, hepatocellular, and lung carcinoma using the cancer genome Atlas data. Pharmacogenet Genomics 2015;25:1-7.DOIPubMed
125. Bonte D, Lindvall C, Liu H, Dykema K, Furge K, Weinreich M. Cdc7-Dbf4 kinase overexpression in multiple cancers and tumor cell lines is correlated with p53 inactivation. Neoplasia 2008;10:920-31.DOIPubMedPMC
126. Chao CC, Ma CM, Lin-Chao S. Co-amplification and over-expression of two mdr genes in a multidrug-resistant human colon carcinoma cell line. FEBS Lett 1991;291:214-8.DOI
127. Cheng AN, Jiang SS, Fan CC, Lo YK, Kuo CY, Chen CH, Liu YL, Lee CC, Chen WS, Huang TS, Wang TY, Lee AY. Increased Cdc7 expression is a marker of oral squamous cell carcinoma and overexpression of Cdc7 contributes to the resistance to DNA-damaging agents. Cancer Lett 2013;337:218-25.DOIPubMed
128. Finalet Ferreiro J, Rouhigharabaei L, Urbankova H, van der Krogt JA, Michaux L, Shetty S, Krenacs L, Tousseyn T, De Paepe P, Uyttebroeck A, Verhoef G, Taghon T, Vandenberghe P, Cools J, Wlodarska I. Integrative genomic and transcriptomic analysis identified candidate genes implicated in the pathogenesis of hepatosplenic T-cell lymphoma. PLoS One 2014;9:e102977.DOIPubMedPMC
129. Hansen SN, Ehlers NS, Zhu S, Thomsen MB, Nielsen RL, Liu D, Wang G, Hou Y, Zhang X, Xu X, Bolund L, Yang H, Wang J, Moreira J, Ditzel HJ, Brünner N, Schrohl AS, Stenvang J, Gupta R. The stepwise evolution of the exome during acquisition of docetaxel resistance in breast cancer cells. BMC Genomics 2016;17:442.DOIPubMedPMC
130. Litviakov NV, Cherdyntseva NV, Tsyganov MM, Slonimskaya EM, Ibragimova MK, Kazantseva PV, Kzhyshkowska J, Choinzonov EL. Deletions of multidrug resistance gene loci in breast cancer leads to the down-regulation of its expression and predict tumor response to neoadjuvant chemotherapy. Oncotarget 2016;7:7829-41.DOIPubMedPMC
131. Patch AM, Christie EL, Etemadmoghadam D, Garsed DW, George J, Fereday S, Nones K, Cowin P, Alsop K, Bailey PJ, Kassahn KS, Newell F, Quinn MC, Kazakoff S, Quek K, Wilhelm-Benartzi C, Curry E, Leong HS, Australian Ovarian Cancer Study Group, Hamilton A, Mileshkin L, Au-Yeung G, Kennedy C, Hung J, Chiew YE, Harnett P, Friedlander M, Quinn M, Pyman J, Cordner S, O'Brien P, Leditschke J, Young G, Strachan K, Waring P, Azar W, Mitchell C, Traficante N, Hendley J, Thorne H, Shackleton M, Miller DK, Arnau GM, Tothill RW, Holloway TP, Semple T, Harliwong I, Nourse C, Nourbakhsh E, Manning S, Idrisoglu S, Bruxner TJ, Christ AN, Poudel B, Holmes O, Anderson M, Leonard C, Lonie A, Hall N, Wood S, Taylor DF, Xu Q, Fink JL, Waddell N, Drapkin R, Stronach E, Gabra H, Brown R, Jewell A, Nagaraj SH, Markham E, Wilson PJ, Ellul J, McNally O, Doyle MA, Vedururu R, Stewart C, Lengyel E, Pearson JV, Waddell N, deFazio A, Grimmond SM, Bowtell DD. Whole-genome characterization of chemoresistant ovarian cancer. Nature 2015;521:489-94.DOIPubMed
132. Torigoe K, Sato S, Kusaba H, Kohno K, Kuwano M, Okumura K, Green ED, Tsui LC, Scherer SW, Schlessinger D, Wada M. A YAC-based contig of 1.5 Mb spanning the human multidrug resistance gene region and delineating the amplification unit in three human multidrug-resistant cell lines. Genome Res 1995;5:233-44.DOIPubMed
133. Yabuki N, Sakata K, Yamasaki T, Terashima H, Mio T, Miyazaki Y, Fujii T, Kitada K. Gene amplification and expression in lung cancer cells with acquired paclitaxel resistance. Cancer Genet Cytogenet 2007;173:1-9.DOIPubMed
134. Januchowski R, Sterzyńska K, Zawierucha P, Ruciński M, Świerczewska M, Partyka M, Bednarek-Rajewska K, Brązert M, Nowicki M, Zabel M, Klejewski A. Microarray-based detection and expression analysis of new genes associated with drug resistance in ovarian cancer cell lines. Oncotarget 2017;8:49944-58.DOIPubMedPMC
135. Lee S, Kim K, Ho JN, Jin H, Byun SS, Lee E. Analysis of resistance-associated gene expression in docetaxel-resistant prostate cancer cells. Oncol Lett 2017;14:3011-8.DOIPubMedPMC
136. Sasi NK, Bhutkar A, Lanning NJ, MacKeigan JP, Weinreich M. DDK Promotes Tumor Chemoresistance and Survival via Multiple Pathways. Neoplasia 2017;19:439-50.DOIPubMedPMC
137. Genovese I, Ilari A, Assaraf YG, Fazi F, Colotti G. Not only P-glycoprotein: amplification of the ABCB1-containing chromosome region 7q21 confers multidrug resistance upon cancer cells by coordinated overexpression of an assortment of resistance-related proteins. Drug Resist Updat 2017;32:23-46.DOIPubMed
138. Wang YC, Juric D, Francisco B, Yu RX, Duran GE, Chen GK, Chen X, Sikic BI. Regional activation of chromosomal arm 7q with and without gene amplification in taxane-selected human ovarian cancer cell lines. Genes Chromosomes Cancer 2006;45:365-74.DOIPubMed
139. Yang Y, Li H, Hou S, Hu B, Liu J, Wang J. The noncoding RNA expression profile and the effect of lncRNA AK126698 on cisplatin resistance in non-small-cell lung cancer cell. PLoS One 2013;8:e65309.DOIPubMedPMC
140. Han C, Yu Z, Duan Z, Kan Q. Role of microRNA-1 in human cancer and its therapeutic potentials. Biomed Res Int 2014;2014:428371.DOIPubMedPMC
141. Kim CH, Kim HK, Rettig RL, Kim J, Lee ET, Aprelikova O, Choi IJ, Munroe DJ, Green JE. miRNA signature associated with outcome of gastric cancer patients following chemotherapy. BMC Med Genomics 2011;4:79.DOIPubMedPMC
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