Steroid hormone modulation of RET through two estrogen responsive enhancers in breast cancer
- Authors
- Stine, Z.E., McGaughey, D.M., Bessling, S.L., Li, S., and McCallion, A.S.
- ID
- ZDB-PUB-110713-41
- Date
- 2011
- Source
- Human molecular genetics 20(19): 3746-56 (Journal)
- Registered Authors
- McCallion, Andy
- Keywords
- none
- MeSH Terms
-
- Animals
- Binding Sites
- Breast Neoplasms/genetics*
- Breast Neoplasms/metabolism
- Cell Line, Tumor
- Enhancer Elements, Genetic*
- Estradiol/metabolism*
- Estrogen Receptor alpha/genetics
- Estrogen Receptor alpha/metabolism
- Estrogens/metabolism*
- Female
- Gene Expression Regulation, Neoplastic*
- Humans
- Male
- Protein Binding
- Proto-Oncogene Proteins c-ret/genetics*
- Proto-Oncogene Proteins c-ret/metabolism
- Response Elements*
- Tretinoin/metabolism*
- Zebrafish
- PubMed
- 21737465 Full text @ Hum. Mol. Genet.
RET, a gene causatively mutated in Hirschsprung disease and cancer, has recently been implicated in breast cancer estrogen (E2) independence and tamoxifen resistance. RET displays both E2 and retinoic acid (RA)-dependent transcriptional modulation in E2-responsive breast cancers. However, the regulatory elements through which the steroid hormone transcriptional regulation of RET is mediated are poorly defined. Recent genome-wide chromatin immunoprecipitation-based studies have identified 10 putative E2 receptor-alpha (ESR1) and RA receptor alpha-binding sites at the RET locus, of which we demonstrate only two (RET 49.8 and RET +32.8) display significant E2 regulatory response when assayed independently in MCF-7 breast cancer cells. We demonstrate that endogenous RET expression and RET 49.8 regulatory activity are cooperatively regulated by E2 and RA in breast cancer cells. We identify key sequences that are required for RET 49.8 and RET +32.8 E2 responsiveness, including motifs known to be bound by ESR1, FOXA1 and TFAP2C. We also report that both RET 49.8 regulatory activity and endogenous RET expression are completely dependent on ESR1 for their (E2)-induction and that ESR1 is sufficient to mediate the E2-induced enhancer activity of RET 49.8 and RET +32.8. Finally, using zebrafish transgenesis, we also demonstrate that RET 49.8 directs reporter expression in the central nervous system and peripheral nervous system consistent with the endogenous ret expression. Taken collectively, these data suggest that RET transcription in breast cancer cells is modulated by E2 via ESR1 acting on multiple elements collectively.