Integrin expression in uveal melanoma differs from cutaneous melanoma

During the process of metastasis, changes in cell-cell and cell-matrix contacts occur; therefore, expression of integrins, a superfamily of adhesion molecules, may be important. Expression of integrins has been studied extensively in cutaneous melanoma. Because it is known that uveal melanoma has a metastatic behavior different from cutaneous melanoma, the authors investigated integrin expression in uveal melanoma. The authors used monoclonal antibodies recognizing integrin subunits alpha 1-6, alpha v, beta 1, and beta 4 and integrins alpha v beta 3 and alpha v beta 5 on frozen sections of 32 human primary uveal melanomas and 4 metastases, followed by an avidin-biotin-peroxidase complex-immunoperoxidase technique. As in cutaneous melanoma, alpha 4 expression was rare, but most lesions expressed alpha 3 and alpha 6. In contrast to cutaneous melanoma, in which alpha 2 is well expressed in most lesions and alpha 5 is expressed only in a small percentage of lesions, alpha 2 expression was rare in uveal melanoma and alpha 5 expression was found in all lesions. A major difference was observed with regard to the alpha v beta 3 vitronectin receptor. In contrast to cutaneous melanoma, in which alpha v beta 3 is expressed in advanced primary melanomas and metastases, alpha v beta 3 was not detected in any of the primary uveal melanomas, but all lesions strongly expressed alpha v beta 5. Integrin expression in uveal melanoma cannot be correlated with cell type or invasiveness. In contrast to cutaneous melanoma, it seems that determination of the integrin expression profile is not suitable for categorizing uveal melanomas as less malignant and highly malignant lesions.