Expression of insulin-like growth factor-1 receptor (IGF-1R) and p27Kip1 in melanocytic tumors:: A potential regulatory role of IGF-1 pathway in distribution of p27Kip1 between different cyclins

Insulin-like growth factor-1 receptor (IGF-1R) has been shown to be important for melanoma cell growth and survival, In this study me first show, using immunohistochemistry, that progression from benign nevi to malignant melanoma is paralleled by an increased expression of IGF-1R and a down-regulation of the cyclin-dependent kinase inhibitor p27(Kip1), Even though the expression of p27(Kip1) was drastically reduced compared to benign tumors, detectable amounts of it could be assayed by Western blotting in cultured melanoma cells, To analyze whether there is a causative relationship between the IGF-I pathway and p27(Kip1) expression, melanoma cells mere treated with alpha IR-3, an antibody blocking the IGF-1 binding to IGF-1R, or Tunicamycin, which inhibits the translocation of IGF-1R to the cell surface, From these studies me could conclude that the overall expression of p27(Kip1) is independent of the IGF-1 pathway. In contrast, the association of p27(Kip1) with the different cyclins was drastically affected. Both TM and alpha IR-3 decreased the binding of p27(Kip1) to cyclin D1, whose expression was drastically reduced, On the other hand there was an increased binding of p27(Kip1) to cyclin E and cyclin A. This redistribution of p27(Kip1) mag be a mechanism for growth arrest and induction of apoptosis following interruption of the IGF-I pathway in melanoma cells.