The overexpression of survivin is usually accompanied by an increased resistance of cancer cells to chemotherapeutic agents in addition to cancer aggressiveness. Consequently, survivin is considered as an attractive target to develop new promising anticancer candidates. A series of novel 3-cyanopyridine derivatives was synthesized and assessed for their cytotoxic activity against three human cancer cell lines: prostate carcinoma (PC-3), breast cancer (MDA-MB-231) and hepatocellular carcinoma (HepG2). In addition, their activities were evaluated in comparison with a standard anticancer drug 5-FU. Compounds 5c and 5e both exhibited promising cytotoxicity against all the tested cell lines; especially, 5e showed better cytotoxic effect than the reference drug 5-FU. In order to evaluate the safety of these compounds, they were tested on the normal cell line WI-38, revealing their toxic selectivity toward cancer cells over normal ones. Further studies were performed in order to understand their mechanism of action; we examined the ability of our promising compounds 5c and 5e to induce cell cycle arrest. Both resulted in a notable induction of cell cycle arrest at the G2/M phase, along with an increase in the DNA content in the pre-G1 phase, giving us an indication of the incidence of apoptosis. 5c and 5e were further subjected to additional study using Annexin V-FITC assay in order to evaluate their ability to induce apoptosis. The results showed a marked increase in the early and late apoptotic cells, as well as an increase in the percentage of necrosis. Furthermore, Western blotting assay was accomplished using different concentrations of 5c and 5e. The results revealed a striking reduction in survivin expression through proteasome-dependent survivin degradation in addition to a decrease in the expression of some other inhibitor of apoptosis proteins (IAP) family proteins: Livin, XIAP, and C-IAP1 in a concentration-dependent manner. A docking study of 5c and 5e compounds in the dimerization site of survivin was also performed, showing agreement with the in vitro anti-survivin activity.
Keywords: 3-cyanopyridine; anticancer; apoptosis; cell cycle arrest; survivin; synthesis.