Specific tyrosinases associated with melanoma replicative senescence and melanogenesis.
Replicative senescence occurs in normal cells, in contrast to their malignant counterparts which are generally immortal in vitro. We now show that induction of melanogenesis in subconfluent B16 melanoma cells deprived of growth factors can lead to irreversible growth arrest but continued cell viability, concurrent with the expression of specific glycosylated high molecular weight tyrosinases. These tyrosinase activities identify withdrawal from the cell cycle since they were not detected in reversibly arrested quiescent melanocytes, serum-deprived melanoma, or apoptotic melanoma. Our data suggest that different tyrosinases can distinguish cycling and noncycling cells of melanocytic origin and also imply that replicative senescence can be restored in some tumor cells when induced to terminal differentiation in the absence of growth-promoting agents.
IVIC, Tumor Cell Biology Laboratory, Caracas, Venezuela.
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D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002455:Cell Division; D016922:Cellular Senescence / Q000502:physiology*; D016895:Culture Media, Serum-Free; D006031:Glycosylation; D007106:Immune Sera / Q000494:pharmacology; D008544:Melanocytes / Q000201:enzymology / Q000473:pathology; D008546:Melanoma, Experimental / Q000201:enzymology* / Q000503:physiopathology; D051379:Mice; D008970:Molecular Weight; D014442:Monophenol Monooxygenase / Q000096:biosynthesis* / Q000737:chemistry; D014443:Tyrosine / Q000494:pharmacology
D016895:Culture Media, Serum-Free; D007106:Immune Sera; D014443:Tyrosine; D014442:Monophenol Monooxygenase