Retinoic acid (RA)-resistance in breast cancer cells has been associated with irreversible loss of retinoic acid receptor beta, RARbeta, gene expression. Search of the causes affecting RARbeta gene activity has been oriented at identifying possible differences either at the level of one of the RARbeta promoters, RARbeta2, or at regulatory factors. We hypothesized that loss of RARbeta2 activity occurs as a result of multiple factors, including epigenetic modifications, which can pattern RARbeta2 chromatin state. Using methylation-specific PCR, we found hypermethylation at RARbeta2 in a significant proportion of both breast cancer cell lines and primary breast tumors. Treatment of cells with a methylated RARbeta2 promoter, by means of the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR), led to demethylation within RARbeta2 and expression of RARbeta indicating that DNA methylation is at least one factor, contributing to RARbeta inactivity. However, identically methylated promoters can differentially respond to RA, suggesting that RARbeta2 activity may be associated to different repressive chromatin states. This supposition is supported by the finding that the more stable repressive RARbeta2 state in the RA-resistant MDA-MB-231 cell line can be alleviated by the HDAC inhibitor, trichostatin A (TSA), with restoration of RA-induced RARbeta transcription. Thus, chromatin-remodeling drugs might provide a strategy to restore RARbeta activity, and help to overcome the hurdle of RA-resistance in breast cancer.

Evidence of epigenetic changes affecting the chromatin state of the retinoic acid receptor beta2 promoter in breast cancer cells / S.M. Sirchia, A.T. Ferguson, E. Sironi, S. Subramanyan, R. Orlandi, S. Sukumar, N. Sacchi. - In: ONCOGENE. - ISSN 0950-9232. - 19:12(2000 Mar 16), pp. 1556-1563.

Evidence of epigenetic changes affecting the chromatin state of the retinoic acid receptor beta2 promoter in breast cancer cells

S.M. Sirchia
Primo
;
N. Sacchi
Ultimo
2000

Abstract

Retinoic acid (RA)-resistance in breast cancer cells has been associated with irreversible loss of retinoic acid receptor beta, RARbeta, gene expression. Search of the causes affecting RARbeta gene activity has been oriented at identifying possible differences either at the level of one of the RARbeta promoters, RARbeta2, or at regulatory factors. We hypothesized that loss of RARbeta2 activity occurs as a result of multiple factors, including epigenetic modifications, which can pattern RARbeta2 chromatin state. Using methylation-specific PCR, we found hypermethylation at RARbeta2 in a significant proportion of both breast cancer cell lines and primary breast tumors. Treatment of cells with a methylated RARbeta2 promoter, by means of the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR), led to demethylation within RARbeta2 and expression of RARbeta indicating that DNA methylation is at least one factor, contributing to RARbeta inactivity. However, identically methylated promoters can differentially respond to RA, suggesting that RARbeta2 activity may be associated to different repressive chromatin states. This supposition is supported by the finding that the more stable repressive RARbeta2 state in the RA-resistant MDA-MB-231 cell line can be alleviated by the HDAC inhibitor, trichostatin A (TSA), with restoration of RA-induced RARbeta transcription. Thus, chromatin-remodeling drugs might provide a strategy to restore RARbeta activity, and help to overcome the hurdle of RA-resistance in breast cancer.
Antimetabolites, Antineoplastic ; Azacitidine ; Breast ; Breast Neoplasms; Cell Line ; Chromatin ; CpG Islands ; DNA Methylation ; Enzyme Inhibitors ; Epithelial Cells ; Female ; Gene Expression Regulation ; Histone Deacetylases ; Humans; Hydroxamic Acids ; Promoter Regions (Genetics) ; Receptors, Estrogen ; Receptors, Retinoic Acid; Tretinoin ; Tumor Cells, Cultured
Settore MED/03 - Genetica Medica
Settore BIO/11 - Biologia Molecolare
16-mar-2000
Article (author)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/182777
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