Overexpression of protein kinase C-alpha in MCF-7 breast cancer cells results in differential regulation and expression of alphavbeta3 and alphavbeta5.
MCF-7 breast cancer cells stably transfected with protein kinase C-alpha (MCF-7-PKC-alpha cells) show anchorage-independent growth and exhibit increased tumorigenicity in nude mice. Since integrins are involved in tumor growth and metastatic spread, we investigated whether integrin expression is differentially regulated in MCF-7-PKC-alpha cells. Fluorescence-activated cell sorting revealed that alphavbeta3 is highly expressed on MCF-7-PKC-alpha cells, but is undetectable on MCF-7V cells (MCF-7 cells transfected with vector only). In contrast, MCF-7-PKC-alpha cells have reduced expression of alphavbeta5. Blocking experiments with antibodies to alphavbeta3 and alphavbeta5 revealed that these receptors are used by MCF-7-PKC-alpha cells to adhere primarily to vitronectin and osteopontin. Consistent with heterodimer expression, MCF-7-PKC-alpha cells express increased beta3 and decreased beta5 on their surface. Surface expression of alphav on MCF-7-PKC-alpha cells is unchanged. Western blotting, Northern analysis, and nuclear run-on assays indicated that post-translational mechanisms increase the surface expression of beta3 on MCF-7-PKC-alpha cells. In contrast, reduced beta5 transcription diminishes beta5 surface expression on MCF-7-PKC-alpha cells. These results indicate that overexpression of PKC-alpha in MCF-7 cells alters beta5 and beta3 expression by transcriptional and post-translational mechanisms, respectively, resulting in altered heterodimer expression. These findings suggest that the increased metastatic capacity of tumor cells with elevated protein kinase C levels may result, in part, from modulation of integrin expression.
Carey
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Laboratory of Molecular Biology, Guthrie Research Institute, Sayre, PA 18840, USA.
Williams
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CL
Ways
D K
DK
Noti
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JD
D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion; D019281:Dimerization; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D016023:Integrins / Q000096:biosynthesis* / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D009368:Neoplasm Transplantation; D053495:Osteopontin; D011493:Protein Kinase C / Q000235:genetics / Q000502:physiology*; D051571:Protein Kinase C-alpha; D019030:Receptors, Vitronectin / Q000096:biosynthesis* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012795:Sialoglycoproteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D019096:Vitronectin / Q000378:metabolism
D016023:Integrins; D007527:Isoenzymes; D009363:Neoplasm Proteins; D019030:Receptors, Vitronectin; D011993:Recombinant Fusion Proteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D019096:Vitronectin; C064660:integrin alphaVbeta5; D053495:Osteopontin; C496628:PRKCA protein, human; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate