RESUMEN
Germline mutations in the breast cancer susceptibility gene BRCA1, encoding a tumor suppressor protein, greatly enhance the risk of breast and ovarian cancer. This tissue-specificity implicates the role of ovarian hormones. Indeed, BRCA1 has been demonstrated to regulate the signalling axis of the hormone, progesterone, and its receptor, the progesterone receptor (PR), and progesterone action has been implicated in BRCA1-related tumorigenesis. BRCA1 also plays important roles in oxidative stress and activating nuclear factor kappaB (NFκB) signalling pathways. Like wildtype BRCA1 function, PR signalling has also been shown to inhibit NFκB activation. Although PR and BRCA1 networks are known to interact, their interaction at the level of NFκB activation in the human breast is not understood. This study investigates the effect of reduced BRCA1 expression on proliferation and NFκB activation in human breast cells, and the impact of progesterone on these effects. The major findings are that: 1) Reduced BRCA1 levels inhibit cell growth in normal human mammary cells and breast cancer cells; 2) Reduced BRCA1 levels stimulated inflammatory targets and NFκB activity in normal human mammary cells; 3) Wildtype BRCA1 inhibited the pro-proliferative effects of progesterone in normal mammary epithelial cells, and; 4) Progesterone attenuated BRCA1-mediated NFκB activation in normal human mammary cells. These data have important implications for our understanding of progesterone action in BRCA1 mutation carriers, and how inhibition of this action may potentially delay tumorigenesis or impart a more favourable prognosis.
Asunto(s)
Proteína BRCA1/metabolismo , Neoplasias de la Mama/patología , Mama/patología , Proliferación Celular , Células Epiteliales/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , FN-kappa B/metabolismo , Progesterona/farmacología , Proteína BRCA1/antagonistas & inhibidores , Proteína BRCA1/genética , Biomarcadores de Tumor/genética , Mama/efectos de los fármacos , Mama/metabolismo , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Transformación Celular Neoplásica , Células Cultivadas , Femenino , Perfilación de la Expresión Génica , Humanos , FN-kappa B/genética , Progestinas/farmacología , ARN Interferente Pequeño/genética , Transducción de SeñalRESUMEN
Progesterone is critical in normal breast development and its synthetic derivatives are emerging as major drivers of breast cancer risk. The recent demonstration that progesterone regulates the stem cell compartment in the murine mammary gland, despite the absence of progesterone receptor (PR) in mammary stem cells, highlights the fact that PR distribution in progenitor cell subsets in the human breast remains to be conclusively shown. By utilising two independent cell sorting strategies to fractionate cells into distinct subpopulations enriched for different cell lineage characteristics, we have demonstrated a consistent enrichment of PR transcripts, relative to estrogen receptor transcripts, in the bipotent progenitor subfraction in the normal human breast. We have also shown co-expression of both steroid hormone receptors with basal markers in a subset of human breast cells, and finally we have demonstrated that PR+ bipotent progenitor cells are estrogen-insensitive, and that estrogen regulates PR in mature luminal cells only.
Asunto(s)
Mama/citología , Mama/metabolismo , Receptores de Estrógenos/metabolismo , Receptores de Progesterona/metabolismo , Adulto , Animales , Antígenos de Neoplasias/metabolismo , Biomarcadores/metabolismo , Moléculas de Adhesión Celular/metabolismo , Diferenciación Celular/efectos de los fármacos , Separación Celular , Células Cultivadas , Molécula de Adhesión Celular Epitelial , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Estrógenos/farmacología , Femenino , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Integrina alfa6/metabolismo , Queratina-14/metabolismo , Ratones , Persona de Mediana Edad , Modelos Biológicos , Células 3T3 NIH , ARN Mensajero/genética , ARN Mensajero/metabolismo , Receptores de Estrógenos/genética , Receptores de Progesterona/genética , Células Madre/citología , Células Madre/efectos de los fármacos , Células Madre/metabolismo , Adulto JovenRESUMEN
Prolactin and progesterone act together to regulate mammary alveolar development, and both hormones have been implicated in breast cancer initiation and progression. Here we show that Elf5, a prolactin-induced ETS transcription factor that specifies the mammary secretory cell lineage, is also induced by progestins in breast cancer cells via a direct mechanism. To define the transcriptional response to progestin elicited via Elf5, we made an inducible Elf5 short hairpin-RNA knock-down model in T47D breast cancer cells and used it to prevent the progestin-induction of Elf5. Functional analysis of Affymetrix gene expression data using Gene Ontologies and Gene Set Enrichment Analysis showed enhancement of the progestin effects on cell cycle gene expression. Cell proliferation assays showed a more efficacious progestin-induced growth arrest when Elf5 was kept at baseline levels. These results showed that progestin induction of Elf5 expression tempered the antiproliferative effects of progestins in T47D cells, providing a further mechanistic link between prolactin and progestin in the regulation of mammary cell phenotype.
