Characterization of the CDKN2A and ARF genes in UV-induced melanocytic hyperplasias and melanomas of an opossum (Monodelphis domestica)

We examined the involvement of the cyclin-dependent kinase inhibitor 2A (CD KN2A) locus in the pathogenesis of ultraviolet (UV) radiation-induced melan omas in an opossum (Monodelphis domestica) melanoma model in which suckling young were exposed to UVB to produce melanocytic lesions. Monodelphis CDKN 2A and alternated reading frame (ARF) cDNAs were cloned and sequenced, and the expression patterns of these genes were determined by reverse transcrip tion-polymerase chain reaction in normal tissues, 39 primary melanocytic sk in lesions, and two tumor-derived cell lines, one nonmetastatic and one met astatic. Primary melanocytic lesions, including hyperplasias, benign melano mas, melanomas metastatic to lymph nodes, and melanomas metastatic to nodes and additional visceral organs, were categorized accordingly as types I-IV . Levels of CDKN2A transcripts were most abundant in type ill tumor samples and the metastatic cell line but absent in the nonmetastatic cell line. AR F transcripts were expressed in all tumors and cell lines. A UV-signature m utation was detected with the wild-type allele at the CDKN2A locus in type Ii and III primary tumor samples and in the nonmetastatic cell line. Intere stingly, in the metastatic cell line, only the mutant allele was present an d expressed. These data suggest dynamic changes in the expression and/or st ructure of the CDKN2A and ARF genes represent one molecular defect associat ed with the etiology of melanoma formation and progression in the Monodelph is model system. (C) 2001 Wiley-Liss, inc.