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Cyclin D1 determines estrogen dependent signaling in human breast cancer cell line MCF7

ABSTRACT: The CCND1 gene, which is frequently overexpressed in cancers, encodes the regulatory subunit of a holoenzyme that phosphorylates the retinoblastoma protein (pRb). It is known that cyclin D1 regulates ERα transactivation using heterologous reporter systems, the significance of this observation to E2 dependent gene activation is unknow. E2 stimulated MCF7 cells treated with cyclin D1 siRNA in order to analyze the genes regulated by estradiol in a cyclin D1 dependent manner. Hormone deprived MCF7 cells were treated with cyclin D1 siRNA or control siRNA and stimulated with E2 or vehicle Four separate 10cm plates of MCF7 cells treated with control siRNA were compared to four 10cm plates of MCF7 cells treated with cyclin D1 siRNA. 2 plates in each group treated with vehicle and two plates treated with E2.

ORGANISM(S): Homo sapiens

SUBMITTER: Casimiro Mathew

PROVIDER: S-ECPF-GEOD-48989 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:BACKGROUND: Cyclin D1 is a well-characterised cell cycle regulator with established oncogenic capabilities. Despite these properties, studies report contrasting links to tumour aggressiveness. It has previously been shown that silencing cyclin D1 increases the migratory capacity of MDA-MB-231 breast cancer cells with concomitant increase in 'inhibitor of differentiation 1' (ID1) gene expression. Id1 is known to be associated with more invasive features of cancer and with the epithelial-mesenchymal transition (EMT). Here, we sought to determine if the increase in cell motility following cyclin D1 silencing was mediated by Id1 and enhanced EMT-features. To further substantiate these findings we aimed to delineate the link between CCND1, ID1 and EMT, as well as clinical properties in primary breast cancer. METHODS: Protein and gene expression of ID1, CCND1 and EMT markers were determined in MDA-MB-231 and ZR75 cells by western blot and qPCR. Cell migration and promoter occupancy were monitored by transwell and ChIP assays, respectively. Gene expression was analysed from publicly available datasets. RESULTS: The increase in cell migration following cyclin D1 silencing in MDA-MB-231 cells was abolished by Id1 siRNA treatment and we observed cyclin D1 occupancy of the Id1 promoter region. Moreover, ID1 and SNAI2 gene expression was increased following cyclin D1 knock-down, an effect reversed with Id1 siRNA treatment. Similar migratory and SNAI2 increases were noted for the ER-positive ZR75-1 cell line, but in an Id1-independent manner. In a meta-analysis of 1107 breast cancer samples, CCND1low/ID1high tumours displayed increased expression of EMT markers and were associated with reduced recurrence free survival. Finally, a greater percentage of CCND1low/ID1high tumours were found in the EMT-like 'claudin-low' subtype of breast cancer than in other subtypes. CONCLUSIONS: These results indicate that increased migration of MDA-MB-231 cells following cyclin D1 silencing can be mediated by Id1 and is linked to an increase in EMT markers. Moreover, we have confirmed a relationship between cyclin D1, Id1 and EMT in primary breast cancer, supporting our in vitro findings that low cyclin D1 expression can be linked to aggressive features in subgroups of breast cancer.

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Cyclin D1 determines estrogen dependent signaling in human breast cancer cell line MCF7

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