Promotion of intestinal carcinogenesis by Streptococcus bovis

The involvement of Streptococcus bovis, an member of the human gut flora, i n colorectal neoplastic diseases is an object of controversy. The aim of th is study was to determine the effects of S.bovis and of antigens extracted from the bacterial cell wall on early preneoplastic changes in the intestin al tract. Adult rats received i.p, injections of azoxymethane (15 mg/kg bod y weight) once per week for 2 weeks. Fifteen days (week 4) after the last i njection of the carcinogen, the rats received, by gavage twice per week dur ing 5 weeks, either S.bovis (10(10) bacteria) or wall-extracted antigens (1 00 mu g) One week after the last gavage (week 10), we found that administra tion of either S.bovis or of antigens from this bacterium promoted the prog ression of preneoplastic lesions through the increased formation of hyperpr oliferative aberrant colonic crypts, enhanced the expression of proliferati on markers and increased the production of IL-8 in the colonic mucosa, Our study suggests that S.bovis acts as a promoter of early preneoplastic lesio ns in the colon of rats. The fact that bacterial wall proteins are more pot ent inducers of neoplastic transformation than the intact bacteria may have important implications in colon cancer prevention.