Carcinogenic properties of proteins with pro-inflammatory activity from Streptococcus bovis

Abstract Several studies reported linkage between bacterial infections and carcinogenesis. S. bovis , was traditionally considered as a lower grade pathogen frequently involved in bacteremia and endocarditis. This bacteria became important in human health since it was shown that 25% to 80% of patients who presented a S. bovis bacteremia had also a colorectal tumour. Moreover, in previous experiments, we demonstrated that S. bovis or S. bovis wall extracted antigens (WEA) were able to promote carcinogenesis in rats. The aim of the present study was (i) to identify the S. bovis proteins responsible for in vitro proinflammatory properties, (ii) to purify them, (iii) to examine their ability to stimulate in vitro IL-8 and COX-2 expression by human colon cancer cells and (iv) to assess in vivo their pro-carcinogenic potential in a rat model of colon carcinogenesis. The purified S300 fraction, as determined by proteomic analysis, contained72 protein spots in 2D gel electrophoresis representing 12 different proteins able to trigger human epithelial colonic Caco-2 cells and rat colonic mucosa to release CXC chemokines (human IL-8 or rat CINC/GRO) and PGE