Apoptosis of Breast Cancer MCF-7 Cells In Vitro is Induced Specifically by Yeast and Not by Fungal Mycelia

It was recently demonstrated that breast cancer cell lines undergo apoptosis following phagocytosis of S. cerevisiae. The present study was undertaken to determine whether other strains of fungi also induce apoptosis in cancer cells. Eight strains of yeast: C. albicans, C. krusei, C. glabrata, C. kefyr, C. neoformans, Y. lipolytica, S. cerevisiae and R. rubra, were evaluated at different developmental stages (small yeast cells, large yeast cells and pseudohyphae). In addition, conidia from four strains of fungal mycelia: Aspergillus, Aspergillus sp., T. rubrum and T. tonsurans were evaluated. Breast cancer MCF-7 cells in monolayer were cultured with fungi at a ratio of 1:10, respectively, after which phagocytosis and fungi-induced apoptosis of MCF-7 cells were examined. The MCF-7 cells were found to phagocytize all strains of heat-killed yeast, regardless of their developmental stage. Phagocytosis followed a graduated series: C. krusei > C. glabrata > R. rubra > S. cerevisiae > C. kefyr > C. neoformans > C. albicans > Y. lipolytica. Yeast-induced apoptosis also followed a graded pattern: S. cerevisiae > C. kefyr > C. krusei > C. neoformans > R. rubra > C. albicans > C. glabrata > Y. lipolytica, as examined by flow cytometry. In contrast, MCF-7 did not phagocytize or undergo apoptosis post-culture with conidia. This data may have clinical implications for the treatment of breast cancer.