The pathogenic role of growth factors in melanoma

Some early changes associated with atypical nevi, presumed to be progressing toward malignancy, include chromosomal abnormalities and altered production of growth factors, and/or growth factor receptors. Though normal epidermal melanocytes require a number of exogenous growth factors, nevi require fewer growth factors, and most metastatic melanomas are frequently capable of growing without an exogenous supply of growth factors. This is apparently caused by endogenous production of essential growth factors. Our laboratory focuses on melanoma growth stimulatory activity (MGSA), one of the endogenously produced growth factors, and the role it plays in tumor progression. MGSA is a member of the beta-thromboglobulin super family. These genes code for cytokines, which modulate the inflammatory response. The MGSA protein is highly chemotactic for neutrophils and competes with 125I-interleukin-8 for binding sites on neutrophil receptors. When normal immortalized mouse melanocytes are manipulated so that they overexpress the MGSA gene, the melanocytes form large colonies in soft agar and melanoma tumors in nude mice. These data suggest that the MGSA protein can potentially play a role in melanoma tumor progression.