Non-immunologically-mediated cytotoxicity of Lactobacillus casei and its derivative peptidoglycan against tumor cell lines.

Lactobacillus casei, which shows antitumoral activity mediated by the stimulation of cellular defence mechanisms, and its peptidoglycan were tested for their ability to inhibit in vitro the viability of various murine (Yac-1, P815, Ehrlich ascites tumor, mammary carcinoma) and human (K562, KB) tumor cell lines through primary cytotoxic activity. Treatment of these tumor line with L. casei or its peptidoglycan at different doses and for different times demonstrated a decrease in viability by 25-30%. This cytotoxic activity was revealed by 51Cr release, succinate dehydrogenase (SDH) activity, ATP assays and morphological alterations in the treated tumor cells. Immunoenzymatic assays (ELISA) showed a precise ratio of binding between Ehrlich ascites or YAC-1 cell membranes and peptidoglycan. This binding is discussed with regard to the structure of the peptidoglycan molecule. The results suggest that L. casei and its derivative peptidoglycan have both a stimulating activity in normal cells and an inhibiting activity in tumor cells, as has been found for other immunomodulatory complexes.