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  • 1
    Keywords: CANCER ; CELLS ; EXPRESSION ; IN-VITRO ; INHIBITOR ; tumor ; TUMOR-CELLS ; carcinoma ; CELL ; COMBINATION ; MODEL ; VITRO ; SITE ; SITES ; GENE ; GENE-EXPRESSION ; GENES ; PROTEIN ; TISSUE ; LINES ; DNA ; CARCINOGENESIS ; BREAST ; breast cancer ; BREAST-CANCER ; PROGRESSION ; genetics ; DNA methylation ; inactivation ; PCR ; REGION ; TRANSFORMATION ; EPITHELIAL-CELLS ; CARCINOMAS ; NETHERLANDS ; histone deacetylase inhibitor ; METHYLATION ; HYPERMETHYLATION ; ESTRADIOL ; PATTERN ; SCIENCE ; CPG ISLANDS ; ESTROGEN ; 17-BETA-ESTRADIOL ; EPIGENETIC CHANGES ; MESENCHYMAL TRANSITION ; Genetic ; heregulin ; Cell transformation ; ERBB RECEPTOR FAMILY ; HISTONE-DEACETYLASE INHIBITORS ; Neuregulin
    Abstract: Epigenetic inactivation of genes by DNA hypermethylation plays an important role in carcinogenesis An in vitro model of human breast epithelial cell transformation was used to study epigenetic changes induced by estradiol during the neoplastic process Different stages of tumor initiation and progression are represented in this model being MCF-10F the normal stage; trMCF cells, the transformed stage, bsMCF cells, the invasive stage and, caMCF cells, the tumor stage Global methylation studies by restriction landmark genomic scanning (RLGS) showed an increased DNA methylation during the in the invasive and tumor stages Expression studies showed that NRG1 (neuregulin 1), CSS3 (chondroitin sulfate synthase 3) and SNIP (SNAP-25-interacting protein) were downregulated in the invasive and tumor cells. The transformed cells showed low expression of STXBP6(amysin)compared to the parental cells MCF-10F The treatment of these cells with the demethylating agent 5-aza-dC alone or in combination with the histone deacetylase inhibitor trichostatin increased the expression of NRG1, STXBP6, CSS3 and SNIP confirming that DNA methylation plays an Important role in the regulation of the expression of these genes The NRG1 exon 1 has a region located between -136 and +79 (considering +1, the translational initiation site) rich in CpG sites that was analyzed by methylation specific PCR (MSP) NRG1 exon 1 showed progressive changes in the methylation pattern associated with the progression of the neoplastic process in this model; NRG1 exon 1 was unmethylated in MCF-10F and trMCF cells, becoming hypermethylated in the invasive (bsMCF) and tumor (caMCF) stages Studies of human breast tissue samples showed that NRG1 exon 1 was partially methylated in 14 out of 17 (82.4%) invasive carcinomas although it was unmethylated in normal tissues (8 out of 10 normal breast tissue samples) Furthermore, NRG1 exon 1 was partially methylated in 9 out of 14(64.3%) morphologically normal tissue samples adjacent to invasive carcinomas. (C) 2010 Elsevier B V. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 20193695
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  • 2
    ISSN: 1573-7217
    Keywords: breast epithelium ; cell proliferation ; differentiation ; estrogen receptors ; progesterone receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Since cell proliferation is indispensable for the growth and development of the breast, and estrogens are considered to play a major role in promoting cell proliferation, while progesterone influences its differentiation, the present work was designed with the purpose of verifying the relationship between cells containing steroid hormone receptors and proliferating cells in the normal human breast. Twelve breast samples were analyzed for their content of lobules type 1 (Lob1), Lob2, Lob3, and Lob4, and the number of cells containing estrogen receptor alpha (ER-α), progesterone receptor (PgR), or expressing Ki67 antibody was determined by double immunocytochemical technique with specific antibodies. The highest percentage of ER-α, PgR, and Ki67 positive cells was found in Lob1, with a progressive reduction in the more differentiated Lob2 and Lob3. ER-α and PgR positive cells were found exclusively in the breast epithelium and were negative for Ki67, while cells positive for Ki67 did not express receptors. These findings were compared with the distribution of ER-α and PgR in the autoradiographs of mammary gland of young virgin rats inoculated with 3H-thymidine for determination of the DNA labeling index (DNA-LI). Both the DNA-LI and the percentage of ER-α and PgR positive cells were maximal in the epithelium of terminal end buds, and these values were reduced in alveolar buds and lobules. ER-α and PgR positive cells did not proliferate, and those cells that had incorporated 3H-thymidine were negative for both receptors. Our results led us to conclude that the content of ER-α and PgR in the normal mammary tissue varies with the degree of lobular development, in parallel with cell proliferation. However, the expression of receptors occurs in cells other than the proliferating cells, indicating that they represent at least two separate cell populations. These findings open new avenues towards the understanding of the mechanisms through which estrogens and progesterone affect the proliferative activity of breast epithelial cells, and their role in the initiation of the cascade of events that leads a normal cell to cancer.
    Type of Medium: Electronic Resource
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