Loss of AP-2 results in up-regulation of MCAM/MUC18 and an increase in tumor growth and metastasis of human melanoma cells.
MCAM/MUC18 is a cell-surface glycoprotein of 113 kDa, originally identified as a melanoma antigen, whose expression is associated with tumor progression and the development of metastatic potential. We have previously shown that enforced expression of MCAM/MUC18 in primary cutaneous melanoma led to increased tumor growth and metastatic potential in nude mice. The mechanism for up-regulation of MCAM/MUC18 during melanoma progression is unknown. Here we show that up-regulation of MCAM/MUC18 expression in highly metastatic cells correlates with loss of expression of the transcription factor AP-2. The MCAM/MUC18 promoter contains four binding sites for AP-2, and electrophoretic mobility shift assay gels demonstrated that the AP-2 protein bound directly to the MCAM/MUC18 promoter. Transfection of AP-2 into highly metastatic A375SM melanoma cells (AP-2-negative and MCAM/MUC18-positive) inhibited MCAM/MUC18 promoter-driven chloramphenicol acetyltransferase reporter gene in a dose-dependent manner. MCAM/MUC18 mRNA and protein expression were down-regulated in AP-2-transfected but not in control cells. In addition, re-expression of AP-2 in A375SM cells inhibited their tumorigenicity and metastatic potential in nude mice. These results indicate that the expression of MCAM/MUC18 is regulated by AP-2 and that enforced AP-2 expression suppresses tumorigenicity and metastatic potential of human melanoma cells, possibly by down-regulating MCAM/MUC18 gene expression. Since AP-2 also regulates other genes that are involved in the progression of human melanoma such as c-KIT, E-cadherin, MMP-2, and p21(WAF-1), we propose that loss of AP-2 is a crucial event in the development of malignant melanoma.
Jean
D
D
Department of Cell Biology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Gershenwald
J E
JE
Huang
S
S
Luca
M
M
Hudson
M J
MJ
Tainsky
M A
MA
Bar-Eli
M
M
D000818:Animals; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism; D051929:CD146 Antigen; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D008297:Male; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009362:Neoplasm Metastasis / Q000235:genetics / Q000473:pathology; D019006:Neural Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000502:physiology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D014408:Biomarkers, Tumor; D051929:CD146 Antigen; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497902:MCAM protein, human; C497903:Mcam protein, mouse; D008562:Membrane Glycoproteins; D019006:Neural Cell Adhesion Molecules; D050656:Transcription Factor AP-2; D014157:Transcription Factors