Antiproliferative activity and possible mechanism of action of certain 5-methoxyindole tethered C-5 functionalized isatins

BACKGROUND: Cancer is one of the most dreaded human diseases, that has become an ever-increasing health problem and is a prime cause of death globally. The potential antiproliferative activity of certain indole–isatin molecular hybrids 5a-w was evaluated in vitro against three human cancer cell lines. METHODS: Standard protocols were adopted to examine the antiproliferative potential and mechanisms of compounds 5a-w. Western blot analysis was carried out on compound 5o. RESULTS: Compounds 5a-w demonstrated in vitro antiproliferative activity in the range of 22.6–97.8%, with compounds 5o and 5w being the most active antiproliferative compounds with IC(50) values of 1.69 and 1.91 µM, which is fivefold and fourfold more potent than sunitinib (IC(50)=8.11 µM), respectively. Compound 5o was selected for in-depth pharmacological testing to understand its possible mechanism of antiproliferative activity. It caused a lengthening of the G1 phase and a reduction in the S and G2/M phases of the cell cycle and had an IC(50) value of 10.4 μM with the resistant NCI-H69AR cancer cell line. Moreover, compound 5o significantly decreased the amount of phosphorylated Rb protein in a dose-dependent fashion, which was confirmed via Western blot analysis. CONCLUSION: The current investigation highlighted the potential antiproliferative activity of compounds 5a-w as well as the antiproliferative profile of compound 5o. These compounds can be harnessed as new lead antiproliferatives in the preclinical studies of cancer chemotherapy.