Comparative analysis of integrins in vitro and in vivo in uveal and cutaneous melanomas.

Changes in integrin expression have been shown to be important for the growth and metastatic capacity of melanoma cells. In this study, we have examined the expression of alphav integrins by three uveal and four cutaneous malanoma lines. No lines expressed alphavbeta6 and only TXM13, a cutaneous line, expressed alphavbeta8. All lines expressed alphavbeta5 and alphavbeta3 (four out of four cutaneous, two out of three uveal) or avpl (OM431, an uveal line). Thus, OM431 is the second uveal melanoma we have described that expresses alphavbeta1 and this, we report again, functions as an alternative vitronectin/fibronectin receptor. Subcutaneous growth of cell lines in athymic mice correlated with an alphavbeta3-positive, alphavbeta1 -negative phenotype. Analysis of clinical material from cutaneous melanoma showed that although alphav expression was increased in 88% of metastases, this could not all be explained by up-regulation of alphavbeta3, with only 2 out of eight skin metastases expressing this heterodimer. Using antibody SZ.21, which as we report here works in archival material, only 1 out of 15 uveal metastases expressed detectable beta3. Thus, acquisition of alphavbeta3 expression, which has been implicated in cutaneous melanoma progression, may not be required for development of metastases from uveal melanoma or indeed for skin, as distinct from lymph node, metastases of cutaneous melanoma.