THE PROBLEM: The identity of various dominantly acting, recessive, or dominant-negative mutations in different genes represents one of the most significant advances in our understanding of the origins of human cancer. The strides made in some forms of human cancer, eg. colorectal carcinoma, lung carcinomas and, breast cancer, have been particularly impressive. Malignant melanoma stands out as a conspicuous exception against this background of successes. Despite its rapid rise in incidence, the availability of clinical material and established cell lines, and the great extent to which it is being studied, no dominant oncogene - with the possible exception of ectopic expression of the bFGF gene, or suppressor type anti-oncogene - has been consistently noted in human malignant melanoma. HYPOTHESES and OBJECTIVES: Chromosome transfer experiments and the stepwise evolutionary development of human melanoma strongly implicate the involvement of a number of genes in the development and progression of this disease, at least one or more of which appear to be recessive tumor suppressor genes based on recent chromosome transfer experiments. It is hypothesized that the identity of some of these genes can be uncovered by the technique of retrovirus vector insertional mutagenesis (provirus tagging) and molecular cloning. EXPERIMENTAL APPROACH: Two human cell lines, one a radial growth phase (RGP melanoma known to be non-tumorigenic in nude mice, the other an early-stage vertical growth phase (VGP) melanoma known to be tumorigenic - but metastatically-incompetent - will be infected with an amphotrophic packaged murine retrovirus containing a dominant drug selectable genetic marker. Successfully viral infected cells will be injected into athymic nude mice using orthotopic (subdermal) transplantation procedures. Resultant RGP-derived primary tumors or VGP derived metastases will be analyzed for sites of common proviral integration. Host genomic DNA flanking such integration sites will be cloned as a means of identifying putative dominant or recessive genes which contribute to melanoma progression.