The plasminogen activation system in melanoma cell lines and in melanocytic lesions.

A large body of evidence suggests a role for the proteolytic plasminogen activation system in invasion and metastatic spread of tumor cells including melanoma cells. Plasminogen activation by human melanoma cell lines and B16 mouse melanoma cell lines has been extensively studied. Apart from expression of urokinase-type plasminogen activator, melanoma cells differ from cells derived from other tumors in the abundant expression of tissue-type plasminogen activator. The possible role of both types of plasminogen activator in metastatic spread of melanoma cells is discussed. In recent years the localization of mRNAs and proteins of the plasminogen activation system and of related proteins in cutaneous melanocytic tumor progression has been well documented. A possible mechanism for migration of melanoma cells in vivo is suggested.