title: Estradiol-independent modulation of breast cancer transcript profile by 17beta-hydroxysteroid dehydrogenase type 1.
abstract: 17beta-hydroxysteroid dehydrogenase type 1 (17β-HSD1) is a steroidal enzyme which, in breast cancer cells, mainly synthesizes 17-beta-estradiol (E2), an estrogenic hormone that stimulates breast cancer cell growth. We previously showed that the enzyme increased breast cancer cell proliferation via a dual effect on E2 and 5α-dihydrotestosterone (DHT) levels and impacted gene expression and protein profile of breast cancer cells cultured in E2-contained medium. Here, we used RNA interference technique combined with microarray analyses to investigate the effect of 17β-HSD1 expression on breast cancer cell transcript profile in steroid-deprived condition. Our data revealed that knockdown of 17β-HSD1 gene, HSD17B1, modulates the transcript profile of the hormone-dependent breast cancer cell line T47D, with 105 genes regulated 1.5 fold or higher (p < 0.05) in estradiol-independent manner. Using Ingenuity Pathway Analysis (IPA), we additionally assessed functional enrichment analyses, including biological functions and canonical pathways, and found that, in concordance with the role of 17β-HSD1 in cancer cell growth, most regulated genes are cancer-related genes. Genes that primarily involved in the cell cycle progression, such as the cyclin A2 gene, CCNA2, are generally down-regulated whereas genes involved in apoptosis and cell death, including the pro-apoptotic gene XAF1, IFIH1 and FGF12, are on the contrary up-regulated by 17β-HSD1 knockdown, and 21% of the modulated genes belong to this latter functional category. This indicates that 17β-HSD1 may be involved in oncogenesis by favoring anti-apoptosis pathway in breast cancer cells and correborates with its previously shown role in increasing breast cancer cell proliferation. The gene regulation occurring in steroid-deprived conditions showed that 17β-HSD1 can modulate endogenous gene expression in steroid-independent manners. Besides, we tested the ability of estrogen to induce or repress endogenous genes of T47D by microarray analysis. Expression of a total of 130 genes were found to increase or decrease 1.5-fold or higher (p < 0.05) in response to E2 treatment (1 nM for 48 h), revealing a list of potential new estrogen-responsive genes and providing useful information for further studies of estrogen-dependent breast cancer mechanisms. In conclusion, in breast cancer cells, in addition to its implication in the E2-dependent gene transcription, the present study demonstrates that 17β-HSD1 also modulates gene expression via mechanisms independent of steroid actions. Those mechanisms that may include the ligand-independent gene transcription of estrogen receptor alpha (ERα), whose expression is positively correlated with that of the enzyme, and that may implicate 17β-HSD1 in anti-apoptosis pathways, have been discussed.
authors.affiliation: Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Universitaire de Québec Research Centre (CHUQ, CHUL) and Department of Molecular Medicine, Laval University, 2705 Boulevard Laurier, Québec, G1V 4G2, Canada.
authors.forename: Juliette A
authors.initials: JA
authors.lastname: Aka
authors.affiliation: Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Universitaire de Québec Research Centre (CHUQ, CHUL) and Department of Molecular Medicine, Laval University, 2705 Boulevard Laurier, Québec, G1V 4G2, Canada.
authors.forename: Ezequiel-Luis
authors.initials: EL
authors.lastname: Calvo
authors.affiliation: Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Universitaire de Québec Research Centre (CHUQ, CHUL) and Department of Molecular Medicine, Laval University, 2705 Boulevard Laurier, Québec, G1V 4G2, Canada. Electronic address: Sheng-Xiang.Lin@crchul.ulaval.ca.
authors.forename: Sheng-Xiang
authors.initials: SX
authors.lastname: Lin
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics*; D045744:Cell Line, Tumor; D003470:Culture Media; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D055785:Gene Knockdown Techniques; D053263:Gene Regulatory Networks / Q000187:drug effects; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
chemical_list: D003470:Culture Media; D012333:RNA, Messenger; D004958:Estradiol; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase
keywords: 17beta-HSD1; Cancer cells; Estradiol; Gene expression modulation; Steroid-deprived medium