Reversal of multidrug resistance in cancer cells by novel asymmetrical 1,4-dihydropyridines

Multidrug resistance (MDR) is an important obstacle that limits the efficacy of chemotherapy in many types of cancer. In this study, 14 novel asymmetrical DHPs possessing pyridyl alkyl carboxylate substitutions at C-3 and alkyl carboxylate groups at C-5 in addition to a nitroimidazole or nitrophenyl moiety at C-4 position were synthesized. Calcium channel blocking (CCB) activity was measured in guinea pig ileal longitudinal smooth muscle. Cytotoxicity was tested on 4 human cancer cell lines, while MDR reversal capacity was examined on P-glycoprotein overexpressing doxorubicin resistant MES-SA-DX5 and compared with non-resistant MES-SA cells. Compounds showed different CCB (IC50: 29.3 nM-4.75 mu M) and cytotoxic activities (IC50: 6.4 to more than 100 mu M). Several compounds having nitrophenyl moiety at C-4, could significantly reverse resistance to doxorubicin at 0.5 and 1 mu M. The most active ones were 7e and 7g containing ethyl carboxylate and isopropyl carboxylate at C-5, respectively. CCB activity, which is considered an undesirable effect for these agents, of 7e and 7g were 33 and 20 times lower than nifedipine, respectively. In conclusion, the newly synthesized asymmetrical DHP compounds showed promising MDR reversal and antitumoral activities with low CCB effects and could be of therapeutic value in drug resistant cancer.Multidrug resistance (MDR) is an important obstacle that limits the efficacy of chemotherapy in many types of cancer. In this study, 14 novel asymmetrical DHPs possessing pyridyl alkyl carboxylate substitutions at C-3 and alkyl carboxylate groups at C-5 in addition to a nitroimidazole or nitrophenyl moiety at C-4 position were synthesized. Calcium channel blocking (CCB) activity was measured in guinea pig ileal longitudinal smooth muscle. Cytotoxicity was tested on 4 human cancer cell lines, while MDR reversal capacity was examined on P-glycoprotein overexpressing doxorubicin resistant MES-SA-DX5 and compared with non-resistant MES-SA cells. Compounds showed different CCB (IC50: 29.3 nM-4.75 mu M) and cytotoxic activities (IC50: 6.4 to more than 100 mu M). Several compounds having nitrophenyl moiety at C-4, could significantly reverse resistance to doxorubicin at 0.5 and 1 mu M. The most active ones were 7e and 7g containing ethyl carboxylate and isopropyl carboxylate at C-5, respectively. CCB activity, which is considered an undesirable effect for these agents, of 7e and 7g were 33 and 20 times lower than nifedipine, respectively. In conclusion, the newly synthesized asymmetrical DHP compounds showed promising MDR reversal and antitumoral activities with low CCB effects and could be of therapeutic value in drug resistant cancer.A