Yeast therapy for the treatment of breast cancer: a nude mice model study.

Background: Studies have demonstrated that phagocytosis of yeast induces apoptosis in human breast cancer (BC) cells in vitro. Here, the in vivo apoptotic activity of the S. cerevisiae against human BC (MCF-7) bearing nude mice was investigated.

Materials And Methods: MCF-7 cells were injected into nude mice. Mice were then injected intratumorally with yeast on a weekly basis for 45 days. Tumors were excised and analyzed for phagocytosis/apoptosis via histopathological staining, electron microscopy (EM), and flow cytometry.

Results: The results demonstrate the ability of MCF-7 cells to phagocytize yeast and the effectiveness of yeast in triggering apoptosis in MCF-7 cells in vivo. Histological sections of yeast-treated tumors show extensive tumor apoptosis/fibrosis. EM studies clearly show apoptotic MCF-7 cells with nuclear margination and fragmentation. Flow cytometry confirmed this result. No noticeable adverse side-effects from the yeast treatment were observed.

Conclusion: S. cerevisiae is a promising anti-cancer agent that induces significant levels of apoptosis in malignant cells in vivo. However, yeast therapy for the treatment of breast cancer has yet to pass controlled clinical trials.