The inhibitory effect of heat-killed Bifidobacterium and Lactobacillus on the growth of RKO cell-derived tumors in xenograft model mice. BALB/c nude mice were subcutaneously injected with 1 × 106 RKO cells/mouse into the dorsum next to the right hind leg. The mice were orally administered drinking water, heat-killed single strains, or their mixtures every day for another 19 days. (a) Photographs represent tumor size. (b) Tumor growth curves. (c) Tumor weight. (d) Body weight changes. Data represent mean ± SD (n = 5), * p < 0.05 vs. control. Control, drinking water; MG731, B. bifidum MG731 (1 × 109 cells/mouse); MG5346, L. reuteri MG5346 (1 × 109 cells/mouse); MG4584, L. casei MG4584 (1 × 109 cells/mouse); 2Mix, mixture of L. reuteri MG5346 (1 × 109 cells/mouse) and L. casei MG4584 (1 × 109 cells/mouse); 3Mix, mixture of B. bifidum MG731 (1 × 109 cells/mouse), L. reuteri MG5346 (1 × 109 cells/mouse), and L. casei MG4584 (1 × 109 cells/mouse).