title: Hydrogen peroxide increases a 55-kDa tyrosinase concomitantly with induction of p53-dependent p21 waf1 expression and a greater Bax/Bcl-2 ratio in pigmented melanoma.
abstract: Differentiated melanocytic cells produce melanin, through several redox reactions including tyrosinase-catalyzed DOPA oxidation to DOPA quinone. We now developed a method based on DOPA oxidase in-gel detection and Sypro Ruby fluorometric normalization to investigate induction of specific DOPA oxidase isoforms in response to hydrogen peroxide-mediated stress, and to ask whether this is associated with p53-dependent adaptive responses. This report shows that hydrogen peroxide leads to comparable induction of 60 and 55 kDa DOPA oxidases in poorly pigmented B16 melanoma, in contrast to sole induction of a major 55 kDa DOPA oxidase in their highly pigmented counterparts. In the latter cells, this response also increases p53 concomitant with joint induction of p53-activated proteins like the cell-cycle inhibitor p21WAF1 and pro-apoptotic bax, with no comparable effect on expression of anti-apoptotic bcl-2. Together, these data suggest that response to hydrogen peroxide involves p53-mediated growth-restrictive signaling and unequal induction of specific DOPA oxidases in melanocytic cells with unequal basal pigmentation.
authors.affiliation: Tumor Cell Biology Laboratory, Centre of Microbiology and Cell Biology, IVIC, Apartado 21827, Caracas 1020 A, Venezuela.
authors.forename: Luis Alberto
authors.initials: LA
authors.lastname: Gomez Sarosi
authors.forename: Mary Strasberg
authors.initials: MS
authors.lastname: Rieber
authors.forename: Manuel
authors.initials: M
authors.lastname: Rieber
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D008546:Melanoma, Experimental / Q000378:metabolism* / Q000473:pathology; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012880:Skin Pigmentation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D006861:Hydrogen Peroxide; D014442:Monophenol Monooxygenase