title: PPAR gamma regulates MITF and beta-catenin expression and promotes a differentiated phenotype in mouse melanoma S91.
abstract: Melanoma represents one of the most rapidly metastasizing, hence deadly tumors due to its high proliferation rate and invasiveness, characteristics of undifferentiated embryonic tissues. Given the absence of effective therapy for metastatic melanoma, understanding more fully the molecular mechanisms underlying melanocyte differentiation may provide opportunities for novel therapeutic intervention. Here we show that in mouse melanoma S91 cells activation of the peroxisome proliferator activated receptor (PPAR) gamma induces events resembling differentiation, such as growth arrest accompanied by apoptosis, spindle morphology and enhanced tyrosinase expression. These events are preceded by an initial transient increase in expression from the Microphthalmia-associated transcription factor gene, (MITF) promoter, whereas exposure to a PPAR gamma ligand- ciglitazone that exceeds 8 h, causes a gradual decrease of MITF, until by 48 h MITF expression is substantially reduced. Beta-catenin, an MITF transcriptional activator, shows a similar pattern of decline during ciglitazone treatment, consistent with previous reports that activated PPAR gamma inhibits the Wnt/beta-catenin pathway through induction of beta-catenin proteasomal degradation. We suggest that the PPAR gamma-mediated beta-catenin down-regulation is likely to be responsible for changes in MITF levels. The data suggest that PPAR gamma, besides its well-established role in mesenchymal cell differentiation towards adipocytes, might regulate differentiation in the melanocytic lineage.
authors.affiliation: Department of Food Biotechnology, Faculty of Food Technology, Agricultural University of Krakow, Krakow, Poland. mgrabacka@ar.krakow.pl
authors.forename: Maja
authors.initials: M
authors.lastname: Grabacka
authors.forename: Wojciech
authors.initials: W
authors.lastname: Placha
authors.forename: Krystyna
authors.initials: K
authors.lastname: Urbanska
authors.forename: Piotr
authors.initials: P
authors.lastname: Laidler
authors.forename: Przemysław M
authors.initials: PM
authors.lastname: Płonka
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Reiss
mesh_terms: D000077556:Alitretinoin; D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis; D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D048430:Cell Shape / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D008544:Melanocytes / Q000166:cytology; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D047495:PPAR gamma / Q000502:physiology*; D010641:Phenotype; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D045162:Thiazolidinediones / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000943:Antigens, Differentiation; D000970:Antineoplastic Agents; D051739:Microphthalmia-Associated Transcription Factor; D047495:PPAR gamma; D045162:Thiazolidinediones; D051176:beta Catenin; D000077556:Alitretinoin; D014212:Tretinoin; D014442:Monophenol Monooxygenase; C039671:ciglitazone