Cell adhesion molecules in the development and progression of malignant melanoma

Cell adhesion molecules belonging to the integrin, cadherin and immunoglobulin superfamilies have been implicated in tumor progression in cutaneous melanoma. Expression of the alpha v beta 3 integrin first appears with the change from radial to vertical growth, a step which is associated with the development of metastatic potential. VLA-4 expression is characteristic of advanced primary tumors and may mediate interaction of the tumor cells with VCAM-1 on vascular endothelium. Expression of these integrins is a marker of poor prognosis in patients and can confer invasive (alpha v beta 3) and metastatic (VLA-4) properties to human melanoma cells injected into nude mice. Expression of the immunoglobulin superfamily molecules MUC18/MCAM and ICAM-1 are associated with primary tumors and metastases. MUC18/MCAM expression confers metastatic potential and increased tumorigenicity to human melanoma cells. Expression of ICAM-1 has been shown to be a marker of poor prognosis in stage I tumors and interfering with its expression inhibits experimental metastasis by melanomas in nude mice. E-cadherin is used by epidermal melanocytes to interact with neighboring keratinocytes. Changes in E-cadherin expression and cellular localization is first observed in the radial growth phase, the earliest stage in melanoma development. Loss of E-cadherin function is associated with upregulation or induction of MUC18/MCAM and alpha v beta 3 in melanocytic cells in vitro and with alterations in the levels and cellular distribution of the transcriptional regulator beta-catenin in melanomas in vivo. These observations suggest that disturbances in E-cadherin function is not only important in carcinomas but may also be a critical event in melanoma tumor progression.