title: Sam68 Mediates the Activation of Insulin and Leptin Signalling in Breast Cancer Cells.
abstract: Obesity is a well-known risk factor for breast cancer development in postmenopausal women. High insulin and leptin levels seem to have a role modulating the growth of these tumours. Sam68 is an RNA-binding protein with signalling functions that has been found to be overexpressed in breast cancer. Moreover, Sam68 may be recruited to insulin and leptin signalling pathways, mediating its effects on survival, growth and proliferation in different cellular types. We aimed to study the expression of Sam68 and its phosphorylation level upon insulin and leptin stimulation, and the role of Sam68 in the proliferative effect and signalling pathways that are activated by insulin or leptin in human breast adenocarcinoma cells. In the human breast adenocarcinoma cell lines MCF7, MDA-MB-231 and BT-474, Sam68 protein quantity and gene expression were increased upon leptin or insulin stimulation, as it was checked by qPCR and immunoblot. Moreover, both insulin and leptin stimulation promoted an increase in Sam68 tyrosine phosphorylation and negatively regulated its RNA binding capacity. siRNA was used to downregulate Sam68 expression, which resulted in lower proliferative effects of both insulin and leptin, as well as a lower activation of MAPK and PI3K pathways promoted by both hormones. These effects may be partly explained by the decrease in IRS-1 expression by down-regulation of Sam68. These results suggest the participation of Sam68 in both leptin and insulin receptor signaling in human breast cancer cells, mediating the trophic effects of these hormones in proliferation and cellular growth.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology and Immunology, UGC Clinical Biochemistry, Virgen Macarena University Hospital, University of Seville, Seville, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pérez-Pérez
authors.affiliation: Department of Medical Biochemistry and Molecular Biology and Immunology, UGC Clinical Biochemistry, Virgen Macarena University Hospital, University of Seville, Seville, Spain.
authors.forename: Flora
authors.initials: F
authors.lastname: Sánchez-Jiménez
authors.affiliation: Department of Medical Biochemistry and Molecular Biology and Immunology, UGC Clinical Biochemistry, Virgen Macarena University Hospital, University of Seville, Seville, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Vilariño-García
authors.affiliation: UGC Clinical Oncology, Virgen Macarena University Hospital, Seville, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: de la Cruz
authors.affiliation: UGC Clinical Oncology, Virgen Macarena University Hospital, Seville, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Virizuela
authors.affiliation: Department of Medical Biochemistry and Molecular Biology and Immunology, UGC Clinical Biochemistry, Virgen Macarena University Hospital, University of Seville, Seville, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Sánchez-Margalet
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism*; D020738:Leptin / Q000494:pharmacology*; D010766:Phosphorylation; D016601:RNA-Binding Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C489559:KHDRBS1 protein, human; D020738:Leptin; D016601:RNA-Binding Proteins