USE OF HT-29, A CULTURED HUMAN COLON-CANCER CELL-LINE, TO STUDY THE EFFECT OF FERMENTED MILKS ON COLON-CANCER CELL-GROWTH AND DIFFERENTIATION

Epidemiological and in vivo and in vitro experimental studies have sug gested that fermented milks may interfere with the emergence and/or th e development of colon cancer. The results, however, remain inconclusi ve. This prompted us to develop a new approach based on the use of HT- 29, a cultured human colon cancer cell line, to study at the cellular level the effect of fermented milks on colon cancer cell growth and di fferentiation characteristics. Undifferentiated HT-29 cells have been grown in the continuous presence of milks fermented by one of the foll owing bacterial populations: L.actobacillus helveticus, Bifidobacteriu m, L.acidophilus or a mix of Streptococcus thermophilus and L.bulgaric us. Penicilin G was added to the cell culture medium, resulting in a c omplete blockade of bacterial growth without significant effect on bac terial viability. One out of the four bacteria species studied, namely L.acidophilus, was without effect on both cell growth and differentia tion. The three other bacterial strains induced a significant, althoug h variable, reduction in the growth rate of HT-29 cells, which resulte d in a 10-50% decrease in the cell number at steady-state (i.e. at cel l confluency). The most efficient strains in lowering the HT-29 growth rate were L.helveticus and Bifidobacterium. Concomitantly, the specif ic activities of dipeptidyl peptidase IV (DPP IV), a sensitive and spe cific marker of HT-29 cell differentiation, and that of three other br ush border enzymes (sucrase, aminopeptidase N and alkaline phosphatase ) were significantly increased, thus suggesting that these cells may h ave entered a differentiation process. Altogether, these results indic ate that the use of cultured colon cancer cells may be a useful tool t o further study the effect of fermented milks on colon cancer and that bacterial strains may exert a different and specific effect on cancer cell growth and differentiation when used in fermented milk products.