Pseudomonas aeruginosa: mannose sensitive hemagglutinin inhibits the growth of human hepatocarcinoma cells via mannose-mediated apoptosis.

A vaccine derived from the outer membrane proteins of the Gram-negative bacterium Pseudomonas aeruginosa has been shown to have immune modulatory properties. An inactivated mutant strain of P. aeruginosa with mannose sensitive hemagglutinin fimbria (PA-MSHA) has been used for adjuvant therapy for malignant cancer. In this study, the growth of human hepatocellular carcinoma Hep G2 and BEL-7402 cells is inhibited by PA-MSHA, but not by mannose-cleaved PA-MSHA. PA-MSHA-treated cells arrested in the S phase of the cell cycle and underwent apoptosis. We hypothesize that apoptosis induced by treatment of Hep G2 and BEL-7402 cells with PA-MSHA is mediated by the mannose residues of PA-MSHA and is propagated through the extrinsic apoptosis pathway directly through caspase-8. These data provide mechanistic details for the potential application of PA-MSHA-based treatment of hepatocellular carcinoma.