fig1

Figure 1. Reduced intracellular drug accumulation. (A) Decreased expression of the reduced folate transporter (RFC) or decreasing transporter function promotes methotrexate resistance. (B) Overexpression of dihydrofolate reductase (DHFR) responsible for the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF) or alterations in the binding affinity of DHFR for methotrexate (MTX) are related with MTX resistance. (C) Decreased expression or mutation of topoisomerase II (Topo II) is associated with doxorubicin (DOX) resistance. (D) High levels of excision repair cross-complement protein 1 (ERCC1) proteins are related to cisplatin resistance. (E) Increased expression of multidrug resistance gene encoding the ATP-binding cassette (ABC) family leads to increased drug efflux and decreased intracellular drug accumulation increasing resistance to DOX and MTX.