Human dihydrofolate reductase inhibition effect of 1-Phenylpyrazolo[3,4-d]pyrimidines: Synthesis, antitumor...

A new series of pyrazolo[3,4-d]pyrimidine analogues bearing different amino acid conjugates 10_a-m were synthesized with the aim to evaluate their antitumor effect through simultaneous inhibition of human dihydrofolate reductase (hDHFR). All novel compounds were tested to screen their enzyme inhibition activity against (hDHFR) beside their in vitro cytotoxicity against six human MTX resistant cancer cell lines namely, human prostate cancer (PC-3), pancreatic human cancer cell lines (BxPC-3), colorectal carcinoma (HCT-116), human hepatocellular carcinoma (HepG-2), cervical carcinoma (HeLa), and mammary gland breast cancer (MCF-7), besides normal immortalized pancreatic cell line (HPDE). Compounds 10_e, 10_f, 10_g inhibited DHFR at considerable low (IC₅₀ < 1 µM) in comparison to MTX (IC₅₀ = 5.61 µM) beside their characteristic cytotoxic effects on different resistant cancer cell lines. Flow cytometry was done for the most active candidate compound 10_e against MCF-7 breast cancer cell line. The results illustrated that compound 10_e induced apoptosis and arrested MCF-7 cell cycle in the G1/S phase. Western blot for visualization and quantification was used to confirm the capability of compound 10_e to induce the expression of proapoptotic caspases and Bax proteins in MCF-7 breast cancer cell line beside its ability to reduce the expression of antiapoptotic Bcl-2 protein. Molecular modeling studies demonstrated that compound 10_e elucidated binding energy of (S= - 8.4390 Kcal/mol) that exceed that of the normal ligand MTX (S= - 8.3951Kcal/mol) in addition to several favorable binding interactions with the active site residues.