title: Ras and Rac1, frequently mutated in melanomas, are activated by superoxide anion, modulate Dnmt1 level and are causally related to melanocyte malignant transformation.
abstract: A melanocyte malignant transformation model was developed in our laboratory, in which different melanoma cell lines were obtained after submitting the non-tumorigenic melanocyte lineage melan-a to sequential cycles of anchorage impediment. Our group has already showed that increased superoxide level leads to global DNA hypermemethylation as well increased Dnmt1 expression few hours after melanocyte anchorage blockade. Here, we showed that Ras/Rac1/ERK signaling pathway is activated in melanocytes submitted to anchorage impediment, regulating superoxide levels, global DNA methylation, and Dnmt1 expression. Interestingly, Ras and Rac1 activation is not related to codon mutations, but instead regulated by superoxide. Moreover, the malignant transformation was drastically compromised when melan-a melanocytes were submitted to sequential cycles of anchorage blockage in the presence of a superoxide scavenger. This aberrant signaling pathway associated with a sustained stressful condition, which might be similar to conditions such as UV radiation and inflammation, seems to be an early step in malignant transformation and to contribute to an epigenetic reprogramming and the melanoma development.
authors.affiliation: Departamento de Farmacologia, Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Molognoni
authors.affiliation: Departamento de Farmacologia, Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil ; Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil.
authors.forename: Fabiana Henriques Machado
authors.initials: FH
authors.lastname: de Melo
authors.affiliation: Departamento de Farmacologia, Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil.
authors.forename: Camila Tainah
authors.initials: CT
authors.lastname: da Silva
authors.affiliation: Departamento de Farmacologia, Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil.
authors.forename: Miriam Galvonas
authors.initials: MG
authors.lastname: Jasiulionis
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D020935:MAP Kinase Signaling System / Q000235:genetics; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology*; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D015398:Signal Transduction / Q000235:genetics; D013481:Superoxides / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D013481:Superoxides; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619381:Dnmt1 protein, mouse; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins