title: Oxidized LDL triggers pro-oncogenic signaling in human breast mammary epithelial cells partly via stimulation of MiR-21.
abstract: Dyslipidemia and obesity are primary risk factors for the development of atherosclerosis and are also epidemiologically linked to increased susceptibility to a variety of cancers including breast cancer. One of the prominent features of dyslipidemia is enhanced production of oxidized LDL (ox-LDL), which has been shown to be implicated in key steps of atherogenesis including inflammatory signaling and proliferation of vascular cells. In this study we analyzed the effects of ox-LDL in human mammary epithelial cells (MCF10A). MCF10A cells avidly internalized dil-ox-LDL and exhibited increased proliferative response to ox-LDL within the range of 1-50 µg/ml in a dose-dependent manner. Treatment of cells with 20 µg/ml ox-LDL for 2 and 12 hours was associated with upregulation of LOX-1 and CD36 scavenger receptors while MSR1 and CXLC16 receptors did not change. Ox-LDL-treated cells displayed significant upregulation of NADPH oxidases (subunits P22(phox) and P47(phox)), lipoxygenases-12 and -15, and cytoplasmic, but not mitochondrial, SOD. Ox-LDL also triggered phosphorylation of IκBα coupled with nuclear translocation of NF-κB and stimulated p44/42 MAPK, PI3K and Akt while intracellular PTEN (PI3K/Akt pathway inhibitor and target of miR-21) declined. Quantitative PCR revealed increased expression of hsa-miR-21 in ox-LDL treated cells coupled with inhibition of miR-21 target genes. Further, transfection of MCF10A cells with miR-21 inhibitor prevented ox-LDL mediated stimulation of PI3K and Akt. We conclude that, similarly to vascular cells, mammary epithelial cells respond to ox-LDL by upregulation of proliferative and pro-inflammatory signaling. We also report for the first time that part of ox-LDL triggered reactions in MCF10A cells is mediated by oncogenic hsa-miR-21 through inhibition of its target gene PTEN and consequent activation of PI3K/Akt pathway.
authors.affiliation: Central Arkansas Veteran Healthcare System and the University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America. mkhaidakov@uams.edu
authors.forename: Magomed
authors.initials: M
authors.lastname: Khaidakov
authors.forename: Jawahar L
authors.initials: JL
authors.lastname: Mehta
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism* / Q000494:pharmacology; D042361:Mammary Glands, Human / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051116:Receptors, Scavenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: D008077:Lipoproteins, LDL; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D015513:Oncogene Proteins; D051116:Receptors, Scavenger; C000606290:SOD1 protein, human; C099252:oxidized low density lipoprotein; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases