title: Differential regulation of breast cancer-associated genes by progesterone receptor isoforms PRA and PRB in a new bi-inducible breast cancer cell line.
abstract: Progesterone receptor isoforms (PRA and PRB) are expressed at equal levels in normal mammary cells. However, alteration in PRA/PRB expression is often observed in aggressive breast cancer suggesting differential contribution of PR isoforms in carcinogenesis. The mechanisms underlying such processes remain to be established mainly due to paucity of appropriate cellular models. To investigate the role of PR isoforms and the impact of imbalanced PRA/PRB ratio in transcriptional regulation, we have generated an original human breast cancer cell line conditionally expressing PRA and/or PRB in dose-dependence of non-steroid inducers. We first focused on PR-dependent transcriptional regulation of the paracrine growth factor gene amphiregulin (AREG) playing important role in cancer. Interestingly, unliganded PRA increases AREG expression, independently of estrogen receptor, yet inhibitable by antiprogestins. We show that functional outcome of epidermal growth factor (EGF) on such regulation is highly dependent on PRA/PRB ratio. Using this valuable model, genome-wide transcriptomic studies allowed us to determine the differential effects of PRA and PRB as a function of hormonal status. We identified a large number of novel PR-regulated genes notably implicated in breast cancer and metastasis and demonstrated that imbalanced PRA/PRB ratio strongly impact their expression predicting poor outcome in breast cancer. In sum, our unique cell-based system strongly suggests that PRA/PRB ratio is a critical determinant of PR target gene selectivity and responses to hormonal/growth factor stimuli. These findings provide molecular support for the aggressive phenotype of breast cancers with impaired expression of PRA or PRB.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale Unité, Steroid Receptors: Endocrine and Metabolic Pathophysiology, Le Kremlin-Bicêtre, France.
authors.forename: Junaid A
authors.initials: JA
authors.lastname: Khan
authors.forename: Catherine
authors.initials: C
authors.lastname: Bellance
authors.forename: Anne
authors.initials: A
authors.lastname: Guiochon-Mantel
authors.forename: Marc
authors.initials: M
authors.lastname: Lombès
authors.forename: Hugues
authors.initials: H
authors.lastname: Loosfelt
mesh_terms: D066258:Amphiregulin; D001940:Breast / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D066255:EGF Family of Proteins; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000235:genetics; D066257:Heparin-binding EGF-like Growth Factor; D006727:Hormone Antagonists / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011980:Receptors, Progesterone / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: C587848:AREG protein, human; D066258:Amphiregulin; D066255:EGF Family of Proteins; D006023:Glycoproteins; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D006727:Hormone Antagonists; D036341:Intercellular Signaling Peptides and Proteins; D020033:Protein Isoforms; D011980:Receptors, Progesterone; C101118:progesterone receptor A; C097314:progesterone receptor B; D015735:Mifepristone