The present invention relates to methods and compositions for the diagnosis, prevention, and treatment of tumor progression in cells involved in human tumors such as melanomas, breast, gastrointestinal, lung, and bone tumors, various types of skin cancers, and other neoplastic conditions such as leukemias and lymphomas. Genes are identified that are differentially expressed in benign (e.g., non-malignant) tumor cells relative to malignant tumor cells exhibiting a high metastatic potential. Genes are also identified via the ability of their gene products to interact with gene products involved in the progression to, and/or aggressiveness of, neoplastic tumor disease states. The genes and gene products identified can be used diagnostically or for therapeutic intervention.