P. acnes can enhance GC development by producing proinflammatory cytokines such as interleukin (IL)-15, whereas one cytoplasmic fraction of L. lactis has been reported to exert an antiproliferative effect on a human stomach cancer cell line, thereby protecting against carcinogenesis; the G0/G1 cell cycle arrest induced by such bacteria was associated with an increase in p53 and p21 expression, a reduction in cyclin D1 expression, and retinoblastoma protein phosphorylation, thereby inducing apoptosis. The gene discussed is TP53; the disease is gastric cancer.