Progression-related expression of beta 3 integrin in melanomas and nevi

The expression of the PS integrin subunit was investigated in 130 fixed, pa raffin-embedded specimens of human melanomas and nevi using two different m onoclonal antibodies. Expression was not observed in melanocytes and was ab sent or low in most nevi. In primary melanomas, expression was absent or lo w in the nontumorigenic radial growth phase, which includes the classes of in situ and microinvasive melanomas. In contrast, expression was high in th e tumorigenic or vertical growth phase compartment of many primary melanoma s and in most metastatic melanomas. Expression patterns were similar with t he two antibodies, SSA6 and SAP, and was membrane-related as well as cytopl asmically expressed. In those nevi that reacted focally, the reactivity ten ded to occur in the dermal component of neurotized nevi, and in Spitz nevi, where the reactivity was stronger and more diffuse. A few dysplastic nevi showed focal reactivity of the junctional component. These results are cons istent with tumor progression-related expression of the PS integrin, which is expressed in melanocytic tumors as the alpha nu beta(3) integrin, having affinity for matrix molecules, including vitronectin and fibronectin. In a ll melanomas, and in the subset of tumorigenic vertical growth phase melano mas, expression increased with thickness (P < .01). For this reason, and be cause ligation of this integrin has been shown in vitro to have several pro perties that may be related to the malignant phenotype, it is likely that e xpression of this marker may have prognostic value. However, because of its consistent and strong expression in Spitz nevi, the diagnostic utility of this marker will likely be limited. HUM PATHOL 33:562-567. Copyright (C) 19 99 by W.B. Saunders Company.