DHFR and cancer: In response to chemotherapeutic drugs, cancer cells could adopt several strategies to develop their resistance such as the control of the transmembrane entry/efflux of the compounds; the activation of DNA repair machinery (ERCC1 and 2, NER genes...); the adaptation of the drug target (dihydrofolate reductase (DHFR), topoisomerase...); or the synthesis of detoxication proteins (gluthation-S-transferase (GST), metallothioneins...) for example (reviewed in11).