ABSTRACT: Alcoholism is associated with breast cancer incidence and progression, and moderate chronic consumption of ethanol is a risk factor. The mechanisms involved in alcohol's oncogenic effects are unknown, but it has been speculated that they may be mediated by acetaldehyde. Here, we use the immortalized normal human epithelial breast cell line MCF-12A to determine whether short- or long-term exposure to ethanol or to acetaldehyde, using in vivo compatible ethanol concentrations, induces their oncogenic transformation and/or the acquisition of epithelial mesenchymal transition (EMT). Cultures of MCF-12A cells were incubated with 25 mM ethanol or 2.5 mM acetaldehyde for 1 week, or with lower concentrations (1.0-2.5 mM for ethanol, 1.0 mM for acetaldehyde) for 4 weeks. In the 4 wk incubation, cells were also tested for anchorage independence, including isolation of soft agar selected cells (SASC) from the 2.5 mM ethanol incubations. Cells were analyzed by immuno-cytofluorescence, flow cytometry, western blotting, DNA microarrays, RT/PCR, and assays for miRs. We found that short-term exposure to ethanol, but not, in general, to acetaldehyde, was associated with transcriptional upregulation of the metallothionein family genes, alcohol metabolism genes, and genes suggesting the initiation of EMT, but without related phenotypic changes. Long-term exposure to the lower concentrations of ethanol or acetaldehyde induced frank EMT changes in the monolayer cultures and in SASC as demonstrated by changes in cellular phenotype and mRNA expression. This suggests that low concentrations of ethanol, with little or no mediation by acetaldehyde, induce EMT and some traits of oncogenic transformation such as anchorage independence in normal breast epithelial cells. MCF12A monolayer cultures were exposed to ethanol or acetaldehyde for either 1 week or 4 weeks. Total RNA samples were assayed for gene expression and for microRNA expression.
