Identification and Mechanistic Profiling of Indolin-2-One Derivatives That Induce ROS-Driven Intrinsic Apoptosis in Prostate and Colorectal Cancer Cells

A series of 3-(2-oxo-2-arylethylidene)indolin-2-ones were synthesized and evaluated for cytotoxic efficacy in the prostate cancer cell lines (PC-3 and DU145), and the colon cancer cell line (HCT-116), and in noncancerous Madin-Darby canine kidney (MDCK) cells. The majority of the evaluated compounds had cytotoxic efficacy (IC₅₀ < 10 µM) in the prostate and colon cancer cell lines. Compound 3j (Raji 10), with a 4-Me substitution on the phenyl ring, was the most potent in decreasing the proliferation of prostate cancer cells (IC₅₀ < 5 µM; 3.56 ± 0.49 µM in PC-3 and 4.20 ± 0.62 µM in DU145). Similarly, compound 3o (Raji 16), with a 5-Br substitution in the isatin moiety and 4-F substitution in the phenyl ring, had maximal cytotoxic potency in HCT-116 cells (IC₅₀ value of 2.93 ± 0.49 µM). Furthermore, the IC₅₀ value of compounds, Raji 10 and Raji 16 was significantly greater (IC₅₀ > 60 μM) in the MDCK cells, compared to the prostate and colorectal cancer cells (HCT-116). The mechanism of cell death induced by the lead compounds; 3j (Raji 10) and 3o (Raji 16) in PC-3 and HCT-116 cells, respectively, was determined. Compounds Raji 10 and Raji 16 induced apoptotic cell death by activating the intrinsic apoptotic pathway, accompanied by an increase in the levels of reactive oxygen species, induction of nuclear fragmentation, and cell cycle arrest at the G1 phase in HCT-116 cells and S/G2 phase in PC-3 cells. Overall, the in vitro results suggest the potential of these compounds in the management of prostate and colon cancer.