Cytoplasmic fraction of Lactococcus lactis ssp. lactis induces apoptosis in SNU-1 stomach adenocarcinoma cells.

Lactic acid bacteria are known to have antitumor activity, but the underlying mechanisms remain unclear. Recently we showed that a cytoplasmic fraction - but not peptidoglycan - of Lactococcus lactis ssp. lactis (L.lac CF) had strong antiproliferative activity on SNU-1 human stomach adenocarcinoma cells. The present study investigated whether the antiproliferative activity of L.lac CF on SNU-1 is linked to the induction of apoptosis. Treatment of L.lac CF inhibited the proliferation of SNU-1 cells in a dose- and time-dependent manner. Furthermore, treatment of the cells with 50 microg/ml and 100 microg/ml L.lac CF resulted in DNA fragmentation and chromatin condensation, respectively. The results indicate that the inhibitory effect of L.lac CF on SNU-1 cell growth is mainly attributable to the induction of apoptosis.