Our study demonstrated that heat-killed Bifidobacterium and Lactobacillus induced apoptosis of human gastric cancer MKN1 cells in vitro, and heat-killed B. bifidum MG731 had outstanding anti-tumor effects in an MKN1 cell-implanted xenograft mouse model through p53 signaling, including p-Akt, p53, Bax, Bak, caspase-9 and -3, and PARP. The gene discussed is BAK1; the disease is neoplasm.