The anti-tumor activity of exopolysaccharides from Pseudomonas strains against HT-29 colorectal cancer cell line.

The anti-tumor activity of extracted exopolysaccharides (EPSs) (without any side effects) of Pseudomonas aeruginosa on HT-29 colorectal cancer cell line has not been previously investigated. The extraction and partial characterization of EPS from the strains of P. aeruginosa including A (CIP A22(PTCC1310)), and B (a clinical strain) were performed. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and sulphorhodamine B (SRB) assays as well as microscopy were used to estimate the cell viability and morphological changes in HT-29 cells subjected to EPS at 0, 7.6, 15.8, 31.2, 62.5 and 125 μg/ml. The apoptotic effects of EPS were also examined by flow cytometry. The EPSs were found to be cytotoxic against HT-29 cells with IC50 values at 44.8 (EPS-A) and 12.7 (EPS-B) μg/ml. The counteraction of 125 μg/ml of EPS-A (87.5 and 56.7%) and EPS-B (86.7 and 59.2%) resulted in the highest repressive rates using the MTT and SRB assays, respectively. Flow cytometric results showed that EPS-A and EPS-B could induce apoptosis (33% and 39%) and necrosis (65% and 59%). The extracted EPSs of both bacterial strains can be used as natural, effective, efficient and anti-cancer drugs. However, more characterization at molecular and structural levels in this respect may be required.