Alcohol increases the cancer stem-like cell (CSC) population. A: Human breast cancer cell lines MCF7 or MCF7 overexpressing ErbB2 cells (MCF7-ErbB2) were exposed to alcohol (0 or 100 mg/dl) for 10 days, and then evaluated for CSCs by the ALDEFLUOR assay. * denotes significant difference from respective control groups. # denotes significant difference from alcohol-treated MCF7 cells. B: MCF7-ErbB2 cells were exposed to alcohol (0, 100 mg/dl) for 10 days and then mammosphere formation was evaluated under the microscope. C: MCF7, MCF7-ErbB2 or BT474 cells were exposed to alcohol (0, 100 mg/dl) for 10 days. The number of mammospheres was determined. * denotes significant difference from respective control groups. # denotes significant difference from alcohol-treated MCF7 cells. D: FVB MMTV Neu mice were fed with a liquid diet containing ethanol (0 or 6.7%). After alcohol exposure, the mammary tumor tissues were assessed for the expression of CD44. * denotes significant difference from respective control groups. Alcohol significantly increased CSC population in vitro and in vivo [33].