Novel [(<i>N</i>-alkyl-3-indolylmethylene)hydrazono]oxindoles arrest cell cycle and induce cell apoptosis by inhibiting CDK2 and Bcl-2: synthesis, biological evaluation and <i>in silico</i> studies

Abstract

As a continuation for our previous work, a novel set of <i>N</i>-alkylindole-isatin conjugates (<b>7</b>, <b>8a-c</b>, <b>9</b> and <b>10a-e</b>) is here designed and synthesised with the prime aim to develop more efficient isatin-based antitumor candidates. Utilising the SAR outputs from the previous study, our design here is based on appending four alkyl groups with different length (ethyl and n-propyl), bulkiness (iso-propyl) and unsaturation (allyl) on <i>N</i>-1 of indole motif, with subsequent conjugation with different <i>N</i>-unsubstituted isatin moieties to furnish the target conjugates. As planned, the adopted strategy achieved a substantial improvement in the growth inhibitory profile for the target conjugates in comparison to the reported lead <b>VI</b>. The best results were obtained with <i>N</i>-propylindole -5-methylisatin hybrid <b>8a</b> which displayed broad spectrum anti-proliferative action with efficient sub-panel GI₅₀ (MG-MID) range from 1.33 to 4.23 µM, and promising full-panel GI₅₀ (MG-MID) equals 3.10 µM, at the NCI five-dose assay. Also, hybrid <b>8a</b> was able to provoke cell cycle disturbance and apoptosis in breast T-47D cells as evidenced by the DNA flow cytometry and Annexin V-FITC/PI assays. Furthermore, hybrid <b>8a</b> exhibited good inhibitory action against cell cycle regulator CDK2 protein kinase and the anti-apoptotic Bcl-2 protein (IC₅₀= 0.85 ± 0.03 and 0.46 ± 0.02 µM, respectively). Interestingly, molecular docking for hybrid <b>8a</b> in CDK2 and Bcl-2 active sites unveiled that <i>N</i>-propyl group is involved in significant hydrophobic interactions. Taken together, the results suggested conjugate <b>8a</b> as a promising lead for further development and optimisation as an efficient antitumor drug.