title: Inhibition of melanoma inhibitory activity (MIA) expression in melanoma cells leads to molecular and phenotypic changes.
abstract: The secreted protein melanoma inhibitory activity (MIA) is highly expressed in malignant melanoma but not in melanocytes and is associated with tumor progression in vivo. Here, we further investigated the functional role of MIA by inhibiting MIA expression of the human melanoma cell line HMB2 via stable antisense MIA cDNA transfection, and subsequent analysis of the cell clones. MIA-deficient cell clones showed several changes in cell morphology and growth pattern. In monolayer and three-dimensional culture enhanced cell-cell contacts were formed. Furthermore, a re-induction of pigment synthesis in comparison with the amelanotic parental cell line HMB2 was observed. Molecular analyses revealed a re-expression of tyrosinase-related protein 1 (Trp-1) and tyrosinase in the MIA-deficient cell clones necessary for melanin synthesis. In accordance, re-expression of MIA in the MIA-deficient melanoma cell clones resulted in downregulation of Trp-1. To identify the molecular mechanisms of MIA regulating pigmentation, MITF and PAX3, two positive regulators of Trp-1 and tyrosinase transcription, and PIAS3, a negative regulator of MITF activity, were analyzed. Only in MIA-deficient cells, expression of PAX3 mRNA and MITF protein was found. In contrast, strong expression of PIAS3 was detected in HMB2 but not in the MIA-deficient cells. To our knowledge this is the first report demonstrating a correlation between MIA expression and pigmentation and morphology of melanocytic cells.
authors.affiliation: Institute of Pathology, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Tatzel
authors.forename: Ina
authors.initials: I
authors.lastname: Poser
authors.forename: Josef
authors.initials: J
authors.lastname: Schroeder
authors.forename: Anja K
authors.initials: AK
authors.lastname: Bosserhoff
mesh_terms: D000107:Acetylation; D002460:Cell Line; D016373:DNA, Antisense / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000378:metabolism; D006801:Humans; D008544:Melanocytes / Q000378:metabolism / Q000648:ultrastructure; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D051739:Microphthalmia-Associated Transcription Factor; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics; D014442:Monophenol Monooxygenase / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*; D050828:Protein Inhibitors of Activated STAT; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
chemical_list: D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; D006657:Histones; C090059:MIA protein, human; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; C484745:PIAS3 protein, human; D051761:Paired Box Transcription Factors; D050828:Protein Inhibitors of Activated STAT; D014157:Transcription Factors; D010088:Oxidoreductases; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase