Novel chloropyridazine sulfonamides as aromatase inhibitors and apoptotic inducers in breast cancer.

Aromatase catalyzes the rate-limiting and final step in the biosynthesis of estrogen. Inhibitors of this enzyme are effective targeted therapy for breast cancer. Molecular hybridization is a promising strategy in drug discovery that combines two or more biologically active moieties in a single structure. In this work, we aim at combining sulfonamide, chloropyridazine and pyrrole in a single design as potential aromatase inhibitors for breast cancer. The synthesized compounds were subjected to in vitro cytotoxic screening against MCF-7 breast cancer cell line, then were assessed for their ability to inhibit aromatase enzyme. Compound 10 exhibited a promising cytotoxic activity (IC 1.83 μM) that nearly equal to the reference drug (doxorubicin, IC 1.94 μM) on MCF-7 cells. Also, compound 10 was the most potent aromatase inhibitor with the lowest IC (0.06 μM) compared to letrozole (IC 0.05 μM). Based on the promising results of compound 10, it was selected to investigate its apoptotic effect that disclosed a marked increase in Bax level to 5.42 folds and down-regulation in Bcl-2 expression to 0.34 folds in MCF-7 cells compared to letrozole. Moreover, compound 10 increased caspase 9 level by 4.84 folds. Also, compound 10 arrested the cell cycle at G1 phase and caused induction of early and late apoptosis in an AnnexinV-FITC assay. Compound 10 had been evaluated to study its synergistic effect with γ-radiation by evaluating the cytotoxicity against MCF-7 after exposure to gamma rays (8 Gy). In addition, compound 10 showed low toxicity against human normal breast (MCF-10 A) cell line. Docking study of compound 10 was performed and showed binding with the key amino acids in aromatase active site.