We have confirmed that the polycomb protein BMI-1 is expressed at much higher levels in melanoma cells than in their benign counterpart, normal human melanocytes. This high level of expression is apparently conserved in human melanoma tissue and often is found in a distinctive punctate nuclear distribution. Expression of BMI-1 in human melanoma cells appears to be post-transcriptionally regulated.We have developed retroviral and lentiviral vectors that permit us to reduce BMI-1 expression in these cells using RNA interference. Additionally, we have formulated and acquired approval of an animal protocol permitting us to assess the effects of BMI-1 loss in these cells in vivo. We have expanded the scope of these investigations to include the use of microarray analysis to screen for functional gene groups whose expression is modified by reduction of BMI-1 expression. Also, we are looking at other polycomb proteins, such as EZH2, for their potential role in melanoma and utilizing expression tools to initiate a gain-of-function approach to determining its role in melanocytes and melanoma malignant progression. We also plan to utilize an approved clinical protocol to analyze the expression of BMI-1 and other relevant proteins in human melanocytes.