PAX3 expression in primary melanomas and nevi.

Melanoma is responsible for an estimated 62,000 new American cancer diagnoses and is projected to cause nearly 8000 deaths in 2008 alone. Although the histogenesis of the tumor is not well understood, it is thought to originate from a rare melanocyte stem cell that resides in the skin. The transcription factor PAX3 has a well-established role in the development of melanocytes during embryogenesis, and has recently been characterized as a molecular switch in the mature melanocyte. Based on this function, PAX3 promotes a melanocytic phenotype but blocks terminal differentiation. This mechanism may also contribute to the uncontrolled cell growth and loss of terminal differentiation in melanomas. Here, we find PAX3 expression in 8/8 melanoma cell lines. We also find that PAX3 is commonly expressed in primary melanoma samples (21/58) but significantly less frequently in benign pigmented lesions (9/75). Further analysis of our melanoma set revealed that PAX3 expression is strongly correlated with younger patients with low or no evidence of sun damage. Our data suggest that PAX3-expressing melanomas may be less environmentally dependent and more genetically linked.