Abstract 526: Tetraspanin CD81/TAPA-1 up-regulates MT1-MMP involved in melanoma cell motility through Akt-dependent Sp1 activation signaling pathways

Abstract

Abstract Tetraspanin CD81 is a member of transmembrane 4 superfamily proteins that have four putative membrane-spanning domains, short C- and N-terminal cytoplasmic domains, two extracellular loops and small intracellular loop. Tetraspanin CD81 is involved in cell adhesion, cell proliferation, motility and metastasis. In this study, to reveal the role of CD81 in tumor invasion, we examined the effect of CD81 overexpression on invasive phenotype in human melanoma cells. We also investigated the intracellular signaling pathways mediated by CD81 involved in these invasive phenotypes. For this study, we generated MelJuSo human melanoma cell lines stably expressing CD81. Cell invasion and motility of the CD81-transfected cells was enhanced significantly as compared to control transfectant cells lacking CD81 expression. In addition, MT1-MMP expression is up-regulated in CD81 transfectant cells as compared to control transfectant cells. MT1-MMP knockdown in CD81 transfectant cells abolished the increase of cell motility by CD81 expression, suggesting the role of MT1-MMP in CD81-induced cell motility. Through the studies using chemical inhibitors and siRNAs for gene knockdown, we found that Akt/PI3K signaling pathway is involved in CD81-mediated MT1-MMP expression. The enhancement of cell motility by CD81 expression was abolished by knockdown of Akt. Finally, we found the involvement of Sp1 transcription factor in the induction of MT1-MMP expression mediated by CD81. Sp1 binding site in MT1-MMP gene promoter was indispensable for the induction of MT1-MMP expression by CD81. Electrophoretic mobility shift assay confirmed the involvement of Sp1 in MT1-MMP expression by CD81. Taken together, these results suggest that tetraspanin CD81 stimulates melanoma cell invasion and motility by up-regulating MT1-MMP expression through the activation of AKT signaling pathways and Sp1 transcription factor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 526.