Exopolysaccharide (LHEPS-1) from Lactobacillus helveticus MB2-1 Induced Apoptosis and G2/M Arrest in Human Liver Cancer HepG-2 Cells

The aim of this study was to investigate the antitumor activity of exopolysaccharide (EPS) isolated from Lactobacillus helveticus MB2-1. Crude EPS from L. helveticus MB2-1 (LHEPS) was divided into three fractions (LHEPS-1, LHEPS-2, and LHEPS-3). Compared with LHEPS-2 and LHEPS-3, LHEPS-1 exhibited stronger growth inhibition against HepG-2 cells. Thus, the antitumor mechanism of LHEPS-1 with 100 and 600 μg/mL on the HepG-2 cells was evaluated, and we found that LHEPS-1 could enhance the release of lactate dehydrogenase (LDH) in cell culture medium and the amount of reactive oxygen species (ROS). Morphological analysis was performed and indicated that LHEPS-1 could promote HepG-2 cell apoptosis. Additionally, flow cytometric analysis showed that LHEPS-1 exerted a stimulatory effect on apoptosis of HepG-2 cells and induced the cell-cycle arrest at the G2/M phase. Moreover, caspase-3 and caspase-9 could be activated by LHEPS-1, and the results indicated that the induction of caspase-3 and caspase-9 activities may be involved in LHEPS-1-induced apoptosis.