Regulation of ornithine decarboxylase mRNA levels in human breast cancer cells: pattern of expression and involvement of core enhancer promoter element.
מילות מפתח
תַקצִיר
Ornithine decarboxylase (ODC) expression is increased by growth factors and is obligatory for progression through the cell cycle in a wide variety of cell types. In this study, a variant human ODC cDNA was identified, sequenced, and used to probe mRNA levels in human breast tumor cell lines and xenografts. ODC mRNA was elevated about 3-fold in estrogen receptor-negative (ER-) tumors (MDA-MB-231) when compared with ER-positive (ER+) tumors (MCF-7), as assessed by quantitative autoradiographic analysis of in situ hybridization experiments. The pattern of ODC mRNA in MDA-MB-231 (ER-) xenografts was polarized to the extreme periphery of the tumor, whereas the distribution of ODC mRNA was more evenly distributed in MCF-7 (ER+) xenografts. This correlates with hematoxylin and eosin staining patterns, suggesting that ER+ and ER- xenografts have a differential dependence on host vasculature for growth factor supply. ODC mRNA was elevated 5-fold in MDA-MB-231 cells versus MCF-7 cells when analyzed in cell culture. These relative mRNA levels correlate with increased levels of "core" enhancer binding nuclear proteins in MDA-MB-231 cells over that detected in MCF-7 cells.