Design and Synthesis of DNA-Interactive β-Carboline-Oxindole Hybrids as Cytotoxic and Apoptosis-Inducing Agents.

A new series of (E)-3-[(1-aryl-9H-pyrido[3,4-b]indol-3-yl)methylene]indolin-2-one hybrids were synthesized and evaluated for their in vitro cytotoxic activity against a panel of selected human cancer cell lines, namely, HCT-15, HCT-116, A549, NCI-H460, and MCF-7, including HFL. Among the tested compounds, (E)-1-benzyl-5-bromo-3-{[1-(2,5-dimethoxyphenyl)-9H-pyrido[3,4-b]indol-3-yl]methylene}indolin-2-one (10 s) showed potent cytotoxicity against HCT-15 cancer cells with an IC50 value of 1.43±0.26 μm and a GI50 value of 0.89±0.06 μm. Notably, induction of apoptosis by 10 s on the HCT-15 cell line was characterized by using different staining techniques, such as acridine orange/ethidium bromide (AO/EB) and DAPI. Further, to understand the mechanism of anticancer effects, various assays such as annexin V-FITC/PI, DCFDA, and JC-1were performed. The flow cytometric analysis revealed that compound 10 s arrests the HCT-15 cancer cells at the G0/G1 phase of the cell cycle. Additionally, western blot analysis indicated that treatment of 10 s on HCT-15 cancer cells led to decreased expression of anti-apoptotic Bcl-2 and increased protein expression of both pro-apoptotic Bax and caspase-3, -8, and -9, and cleaved PARP with reference to actin. Next, a clonogenic assay revealed the inhibition of colony formation in HCT-15 cancer cells by 10 s in a dose-dependent manner. Moreover, upon testing on normal human lung cells (HFL), the compounds were observed to be safer with a low toxicity profile. In addition, viscosity and molecular-docking studies showed that compound 10 s has typical intercalation with DNA.