Regulation of Estrogen Receptor mRNA Stability in Human Breast Cancer Cells

摘要

The growth and metastases of approximately 40 percent of human breast cancers is dependent on 17 beta- estradiol-estrogen receptor (E2-ER) complex. ER levels are controlled in part, through an autoregulatory loop in which E2-ER complex (and mitogens) down-regulate ER mRNA levels. We have created tetracycline (TET)-regulated expression plasmids which transcribe either the full length 6.4 kb human ER mRNA or truncated mini-ER' mRNAs, identified improved methods for delivering the plasmids encoding these mRNAs to cells in transient transfections, and developed a novel quantitative PCR procedure, which allows quantitative PCR of RNA from cells transiently transfected with DNA plasmids encoding the RNA. Utilizing both the TET system and quantitative RT- PCR, we demonstrated that TPA was unable to post- transcriptionally destabilize ER mRNA in MDA-MB-231 breast cancer cells transiently transfected with the TET- regulated full length human ER expression vector. We have shown that the TET- regulated full length ER expression plasmid produces functional ER protein in cell culture which is estrogen-responsive and activates the 2ERE-PS2-CAT expression vector in MDA-MB-231 cells. We have developed new techniques for measuring mRNA degradation and are currently determining the extent to which destabilization contributes to ER mRNA down-regulation in human breast cancer cells.