Progesterone receptor activation downregulates GATA3 by transcriptional repression and increased protein turnover promoting breast tumor growth

Abstract

IntroductionThe transcription factor GATA3 is involved in mammary gland development and is crucial for the maintenance of the differentiated status of luminal epithelial cells. The role of GATA3 in breast cancer as a tumor suppressor has been established, although insights into the mechanism of GATA3 expression loss are still required.MethodsChromatin immunoprecipitation assays were conducted to study progestin modulation of recruitment of transcription factors to GATA3 promoter. We performed western blot and reverse RT-qPCR experiments to explore progestin regulation of GATA3 protein and mRNA expression respectively. Confocal microscopy and in vitro phosphorylation studies were conducted to examine progestin capacity to induce GATA3 serine phosphorylation in its 308 residue. GATA3 participation in progestin-induced breast cancer growth was addressed in in vitro proliferation and in vivo tumor growth experiments.ResultsIn this study, we demonstrate that progestin-activated progesterone receptor (PR) reduces GATA3 expression through regulation at the transcriptional and post-translational levels in breast cancer cells. In the former mechanism, the histone methyltransferase enhancer of zeste homolog 2 is co-recruited with activated PR to a putative progesterone response element in the GATA3 proximal promoter, increasing H3K27me3 levels and inducing chromatin compaction, resulting in decreased GATA3 mRNA levels. This transcriptional regulation is coupled with increased GATA3 protein turnover through progestin-induced GATA3 phosphorylation at serine 308 followed by 26S proteasome-mediated degradation. Both molecular mechanisms converge to accomplish decreased GATA3 expression levels in breast cancer cells upon PR activation. In addition, we demonstrated that decreased GATA3 levels are required for progestin-induced upregulation of cyclin A2, which mediates the G1 to S phase transition of the cell cycle and was reported to be associated with poor prognosis in breast cancer. Finally, we showed that downregulation of GATA3 is required for progestin stimulation of both in vitro cell proliferation and in vivo tumor growth.ConclusionsIn the present study, we reveal that progestin-induced PR activation leads to loss of GATA3 expression in breast cancer cells through transcriptional and post-translational regulation. Importantly, we demonstrate that GATA3 downregulation is required for progestin-induced upregulation of cyclin A2 and for progestin-induced in vitro and in vivo breast cancer cell growth.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-014-0491-x) contains supplementary material, which is available to authorized users.

Stat3 regulates ErbB-2 expression and co-opts ErbB-2 nuclear function to induce miR-21 expression, PDCD4 downregulation and breast cancer metastasis

“…76 To study the expression of urokinasetype plasminogen activator, conditioned media were concentrated using Centricon spin columns (Amino, Beverly, MA, USA). Zymographic analysis was performed as described.…”

Steroid Hormones, Steroid Receptors, and Breast Cancer Stem Cells

“…Krüppel-like factor 5 (KLF5) is another transcription factor upregulated by progesterone in breast cancer cells [61, 100]; knockdown of KLF5 impaired progesterone-mediated induction of CK5, whereas overexpression of KLF5 in the absence of progesterone was able to increase CK5 expression [109]. Progestins also downregulate the transcription factor (and Notch target gene) GATA3, which is associated with maintaining the luminal epithelial phenotype [110]. Using a high content screen, we found that several retinoic acid (RA) compounds were potent inhibitors of progesterone induction of CK5 in T47D breast cancer cells [59].…”

“…miR-29a inhibition also potentiated the progestin-mediated increases in both the CD44+ and CK5+ breast cancer cell populations [53]. Progesterone also downregulates GATA3 in breast cancer cells [110], which has been shown to increase miR-29b expression to promote a differentiated phenotype and suppress metastasis [118]; the progestin-induced down-regulation of miR-29b could therefore increase the breast CSC population partially through lowering GATA3.…”

Prognostic Factor Analysis for Breast Cancer Using Gene Expression Profiles

“…The role of GATA3 in breast cancer as a tumor suppressor has been established. Interestingly, the GATA3 down-regulation is required for the progestin-induced upregulation of cyclin A2(CCNA2) and for progestininduced in vivo and in vitro breast cancer cell growth [25]. Thompsons et al presented low expression of LRIG1 is a prognostic factor for breast cancer patients [26].…”