Up-regulation of transcription of smooth muscle myosin alkali light chain by ethanol in human breast cancer cells

Both epidemiological and experimental studies indicate that ethanol is a tu mor promoter and that chronic ethanol exposure enhances metastasis of breas t cancer cells, and with an in vitro model (T47D human breast cancer cells) , we have previously demonstrated that ethanol exposure stimulated the migr ation of breast cancer cells. In the present study, differential display re verse transcription polymerase chain reaction was used to identify ethanol- responsive genes in T47D cells. Three differentially displayed, ethanol-res ponsive gene fragments were identified, and their expression was confirmed by Northern blot hybridization. Sequence analysis revealed that one cDNA fr agment represented the myosin alkali light chain (MLC Ism) of human smooth muscle. The expression of MLC Ism was found to be significantly higher in b reast cancer cells than in normal mammary epithelial cells. With T47D cells , ethanol induced an additional duration-and concentration-dependent up-reg ulation of MLC Ism. At 400 mg/dl, an ethanol-mediated increase was evident at 6 h (55% increase), peaked at 24 h (2.7-fold increase) following exposur e, and diminished thereafter. At pharmacologically relevant concentrations (e.g., 100 mg/dl), ethanol produced a significant increase of MLC Ism expre ssion, and progressively higher ethanol concentrations resulted in more up- regulation. The half-life of MLC Ism mRNA was not altered, however, the tra nscription rate of MLC Ism was significantly increased by ethanol. MLC is a structural component of the cytoskeleton of eukaryotic cells, and it plays critical roles in the regulation of cell shaping, movement, and growth. Th us, ethanol-mediated up-regulation of MLC may be an underlying molecular me chanism for its tumor promoting effect.