Tumor-associated carbonic anhydrase isoform IX and XII inhibitory properties of certain isatin-bearing sulfonamides endowed with in vitro antitumor activity towards colon cancer

Three series of indolinone-based sulfonamides (3a-f, 6a-f and 9a-f) were in vitro evaluated as inhibitors of the tumor-associated carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA IX and XII, using a stopped-flow CO2 hydrase assay. All the investigated sulfonamides displayed single- or double-digit nanomolar inhibitory activities towards both hCA IX (KIs: 6.2-64.8 nM) and XII (KIs: 7.1-55.6 nM) isoforms. All sulfonamides (3a-f, 6a-f and 9a-f) were in vitro examined for their potential anticancer activity against colorectal cancer HCT-116 and breast cancer MCF-7 cell lines. Sulfonamide 9e was found to be the most potent counterpart against HCT-116 (IC50 = 3.67 ± 0.33 µM). Sulfonamide 9e displayed good selectivity profile for inhibition of the tumor-associated isoforms (CAs IX & XII) over the off-target cytosolic CAs I and II. 9e was screened for cell cycle disturbance and apoptosis induction in HCT-116 cells. It was found to persuade cell cycle arrest at G2-M stage as well as alter the Sub-G1 phase. Also, 9e induced the intrinsic apoptotic mitochondrial pathway in HCT-116 cells via down-regulation of the anti-apoptotic protein Bcl-2 level with concurrent boosting the pro-apoptotic Bax, caspase-9, caspase-3, cytochrome C and p53 levels.