Design, synthesis, cytotoxicity screening and molecular docking of new 3-cyanopyridines as survivin inhibitors and apoptosis inducers.

Recently, targeting survivin proved to be an attractive strategy for developing anticancer agents. Survivin overexpression is highly correlated with cancer aggressiveness, recurrence and resistance to chemotherapeutic treatment and radiotherapy. Additionally, survivin is overexpressed selectively in most cancer types with a very little expression in completely differentiated cells, which encouraged us to design and synthesize a novel series of 3-cyanopyridine derivatives targeting survivin. The newly synthesized compounds were evaluated for their cytotoxic activities against three cancer cell lines; PC-3, HepG2 and MDA-MB-231. Compounds 4a, 4b, 5c and 6c showed significant cytotoxic activities that were more potent than the reference drug, 5-FU. Hence, these compounds were selected to be further studied regarding their apoptotic potential in PC-3 cells. Interestingly, they decreased the level of Bcl-2 by 1.9-3.8 folds and increased the level of Bax by 6.1-8.8 folds compared to the control. Moreover, they elevated the level of active caspase-3 by 7.1-8.5 folds in comparison to the control. In order to estimate the cytotoxicity level of these compounds in non-tumorigenic cells, WI38 cells were treated with these compounds. They showed high IC50 values (148.57-193.64 µM), indicating selective cytotoxicity to the tumor cells, and much less toxic effect to the normal ones. Additional studies on the mechanism of 4a, the most active compound, revealed that it induced cell cycle arrest at the G2/M phase in addition to an increase in the percentage of pre-G1 apoptotic cells. Furthermore, western blotting was carried out using different concentrations of 4a. Results showed that 4a markedly suppressed survivin expression in PC-3 cells and caused a decrease in the caspase-7/cleaved caspase-7 ratio and in Bcl-2/Bax ratio, in addition to an increase in the level of the cleaved PARP. Finally, docking study of the most active compound in the active site (dimerization site) of survivin was in agreement with the in vitro survivin inhibitory activity.