Pyridine-Based 1,2,4-Triazolo-Tethered Indole Conjugates Potentially Affecting TNKS and PI3K in Colorectal Cancer.

A library of pyridine-based 1,2,4-triazolo-tethered indole conjugates were designed, synthesized, and evaluated for anti-proliferative activity against a panel of six human cancer cell lines. All the synthesized conjugates (14a-q) were found to be effective against the HT-29 cell line. Particularly conjugates 14a, 14n, and 14q exhibited promising cytotoxicity, with IC50 values of 1 µM, 2.4 µM, and 3.6 µM, respectively, compared to the standard 5-fluorouracil (IC50 = 5.31 µM). Cell cycle arrest at the G0/G1 phase was observed with these compounds, the mitochondrial membrane potential was interrupted, and the total ROS production was enhanced. Western blot and immunofluorescence experiments illustrated that these compounds inhibit the expression of markers that are involved in ß-catenin and PI3K pathways. Molecular dynamics simulations demonstrated that compound 14a has major hydrophobic interactions and few H-bonding interactions with both PI3K and tankyrase proteins.

Synthesis and Cytotoxic Activity of 1,2,4-Triazolo-Linked Bis-Indolyl Conjugates as Dual Inhibitors of Tankyrase and PI3K.

A series of new 1,2,4-triazolo-linked bis-indolyl conjugates (15a-r) were prepared by multistep synthesis and evaluated for their cytotoxic activity against various human cancer cell lines. It was observed that they were more susceptible to colon and breast cancer cells. Conjugates 15o (IC50 = 2.04 µM) and 15r (IC50 = 0.85 µM) illustrated promising cytotoxicity compared to 5-fluorouracil (5-FU, IC50 = 5.31 µM) against the HT-29 cell line. Interestingly, 15o and 15r induced cell cycle arrest at the G0/G1 phase and disrupted the mitochondrial membrane potential. Moreover, these conjugates led to apoptosis in HT-29 at 2 µM and 1 µM, respectively, and also enhanced the total ROS production as well as the mitochondrial-generated ROS. Immunofluorescence and Western blot assays revealed that these conjugates reduced the expression levels of the PI3K-P85, ß-catenin, TAB-182, ß-actin, AXIN-2, and NF-κB markers that are involved in the ß-catenin pathway of colorectal cancer. The results of the in silico docking studies of 15r and 15o further support their dual inhibitory behaviour against PI3K and tankyrase. Interestingly, the conjugates have adequate ADME-toxicity parameters based on the calculated results of the molecular dynamic simulations, as we found that these inhibitors (15r) influenced the conformational flexibility of the 4OA7 and 3L54 proteins.