We have recently demonstrated that breast cancer cell (BCC) lines undergo apoptosis following phagocytosis of S. cerevisiae. Arabinoxylan rice bran extract (MGN-3/Biobran) (also known as Lentin Plus 1000) has been shown to enhance this effect. Since previous data were obtained using cells in suspension, the present study was undertaken to examine monolayer BCC that more closely model cancer cell growth. Monolayers of both breast cancer (MCF-7) and non-tumorgenic breast epithelial (MCF-10A) cells grown on glass coverslips were cultured with heat-killed S. cerevisiae at a ratio of 1:10, respectively. MCF-7 cells phagocytized yeast in a time-dependent manner, 6.9% to 14.3% from 1 h to 4 h, respectively, with a 2-fold increase in the presence of MGN-3. On the other hand, there was virtually no phagocytosis of yeast by MCF-10A cells. Similarly, yeast-induced apoptosis of MCF-7 cells occurred in a time-dependent manner from 11.5% after 1 h to 21. 7% after 4 h, and was enhanced in the presence of MGN-3. These data may have implications in the treatment of breast cancer.