Novel triazolophthalazine-hydrazone hybrids as potential PCAF inhibitors: Design, synthesis, in vitro anticancer evaluation, apoptosis, and molecular docking studies

Three novel series of triazolophthalazine derivatives bearing hydrazone moiety were designed, synthesized, and evaluated for their anticancer activity against four human cancer cell lines by MTT assay. Six derivatives demonstrated comparable activity with Doxorubicin reference drug against the selected cancer cells. Especially, compound 16 showed the most potent activity with IC50 values of 5.70, 8.04, 11.15, and 4.25, µM against HePG2, MCF-7, PC3, and HCT-116 respectively. Also, compound 26 exhibited comparable inhibitory effect with that of Doxorubicin against the selected cancer cell lines with IC50 values of 6.45, 8.63, 12.28, and 7.03 µM against HePG2, MCF-7, PC3, and HCT-116 respectively. Investigation of the apoptotic activity of the two most active compounds revealed that compounds 16 and 26 could induce both the early and the late apoptosis of HePG2. Further mechanistic study of the HePG2 cell cycle confirmed the spectacular cytotoxic and apoptotic effects of both compounds. Compounds 16 and 26 showed a pronounced increase in cells in G2/M and Pre G1 phases with a concomitant reduction of cells in G0-G1 and S phases. A follow up enzymatic assay indicated that these two compounds have comparable activities with that of bromosporine as PCAF inhibitors with IC50 values of 8.13 and 5.31 µM respectively. Moreover, molecular docking study for all the synthesized compounds was performed to predict their binding affinities toward the active site of histone acetyltransferase GCN5. Results of molecular docking were strongly correlated with that of the cytotoxicity study.