Estrogen‐mediated downregulation of CD24 in breast cancer cells

Abstract

We have previously reported on the relevance of the prevalence of CD44 1 /CD24 2/low cells in primary breast tumors. To study regulation of CD24, we queried a number of publicly available expression array studies in breast cancer cells and found that CD24 was downregulated upon estrogen treatment. We confirmed this estrogen-mediated repression of CD24 mRNA by quantitative realtime PCR in MCF7, T47D and ZR75-1 cells. Repression was also seen at the protein level as measured by flow cytometry. CD24 was not downregulated in the ERa negative MDA-MB-231 cells suggesting that ERa was necessary. This was further confirmed by ERa silencing in MCF7 cells resulting in increased CD24 levels and by reintroduction of ERa into C4-12 cells resulting in decreased CD24 levels. Estrogen treatment did not alter half-life of CD24 mRNA and new protein synthesis was not essential for repression, suggesting a primary transcriptional effect. Histone deacetylase inhibition by Trichostatin A completely abolished the repression, but decrease of the ERa corepressors NCoR, LCoR, RIP140, silencing mediator of retinoid and thyroid hormone receptors, SAFB1 and SAFB2 by siRNA or overexpression of SAFB2, NCoR and silencing mediator of retinoid and thyroid hormone receptors had no effect. In silico promoter analyses led to the identification of two estrogen responsive elements in the CD24 promoter, one of which was able to bind ERa as shown by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Together, our results show that CD24 is repressed by estrogen and that this repression is a direct transcriptional effect depending on ERa and histone deacetylases. ' 2008 Wiley-Liss, Inc.Key words: CD24; ERa; breast cancer; estrogen-mediated repression CD24 is a small, heavily glycosylated, mucin-like glycosylphophatidyl-inositol-linked cell surface protein that localizes in lipid rafts.1 CD24 has recently generated considerable attention in tumor biology due to its role as a potential breast cancer stem cell marker 2 and its function in cell adhesion and metastatic tumor spread. Particularly, CD24 is expressed in a wide variety of human malignancies and has been associated with an unfavorable prognosis in breast cancer. 1,3 In experimental animals, CD24 has been suggested to regulate numerous processes associated with tumor growth and metastasis. 4 In humans, CD24 has been identified as a molecular marker that allows distinction between luminal epithelial, nonepithelial and myoepithelial cells.5 Moreover, the marker combination CD44 1 /CD24 2/low has been reported to characterize putative breast cancer stem cells.2 Our own studies demonstrated that the high prevalence of CD44 1 /CD24 2/low cells in primary breast cancers favored distant metastasis, especially to the bone. 6 Although the lack of CD24 has been highlighted within the context of putative breast cancer stem cells recent gene expression signatures designed to predict distant metastasis, prognosis and therapeutic planning pointed to a relationship between the breast c...

Histone Deacetylase 7 and FoxA1 in Estrogen-Mediated Repression of RPRM

“…The siRNAs used were as follows: siGENOME nontargeting siRNA 2, ER␣, HDACs 1 to 10 (Dharmacon), and FoxA1 (4). NCoR, SMRT, LCoR, and NRIP1 siRNA experiments were performed as described previously (31).…”

“…For example, gene expression profiling has demonstrated that greater than 50% of ER␣ target genes are downregulated upon E2 treatment in MCF7 breast cancer cells as well as in breast tumors (5,8,16,53). We (31,54) and others (1,3,19,21,52,58,59,65,70) have shown that critical genes like those coding for CD24, E-cadherin, BASE, interleukin-6 (IL-6), IR, retinoblastoma protein (Rb), ERBB2, vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNF-␣), and CD36 are repressed by E2. Many of these E2-repressed genes are cell cycle inhibitors like cyclin G2 (CCNG2) (66), proapoptotic genes, or tumor suppressor genes, and thus their repression could be a critical step in augmenting the growth and survival of a tumor and thereby in the development and/or progression of breast cancer.…”

Attenuated Listeria monocytogenes as a cancer vaccine vector for the delivery of CD24, a biomarker for hepatic cancer stem cells

“…These markers are crucial for the identification and isolation of CSCs. Another biomarker, CD24, a heavily glycosylated mucin-like cell surface protein, is expressed in many human malignancies including lymphomas, 19 small cell and non-small cell lung carcinomas, 20 nasopharyngeal carcinomas, 21 breast cancers, 22 clear cell renal carcinomas 23 and hepatocellular carcinomas. 24 Recently, Irene Oi Lin Ng, of Hong Kong University, noted that CD24 is upregulated in chemoresistant and recurrent HCC patients and that it is an important biomarker for hepatic CSCs.…”

The anti-diabetic drug metformin suppresses the metastasis-associated protein CD24 in MDA-MB-468 triple-negative breast cancer cells

“…In this regard, it has been suggested that estrogen/ER· functionally regulates putative breast cancer stem cells because CD24 is repressed by estrogen. and this repression is a direct transcriptional effect depending on ER· and histone deacetylases (HDACs), while CD44 is up-regulated by estrogenbound ER· (11,32,33). It is interesting to note that metformininduced down-regulation of CD24 was accompanied by a significant up-regulation of CD44, thus suggesting that a CD24/CD44 cross-talk could take place also in ER·-negative breast cancer cells; obviously, it should involve other yet to be explored estrogen/ER·-independent regulatory mechanisms such as epigenetic silencing or involvement of other transcription factors.…”