EXPRESSION OF INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) IN NEVI AND MELANOMAS

Expression of IGF-I mRNA and protein was evaluated in pigmented lesion s by in situ hybridization and immunohistochemistry. An IGF-I cDNA clo ne (phigfl) was subcloned into pBluescript KS II-. Both sense and anti sense S-35 riboprobes were prepared and used for in situ hybridization on formalin-fixed, paraffin-embedded specimens. Control hybridization s with a beta-actin probe were also performed. Grains were counted in 787-mum2 melanocytic areas of sections hybridized with the antisense I GF-I probe. Seven common nevi contained a mean of 218 grains; nine dys plastic nevi, a mean of 463 grains; eight early primary melanomas, a m ean of 402 grains; five advanced primary melanomas, a mean of 217 grai ns; and nine metastatic melanomas, a mean of 194 grains. The differenc es between common and dysplastic nevus, common nevus and early melanom a, early and advanced primary melanoma, and early primary melanoma and metastatic melanoma were statistically significant. Keratinocytes als o expressed abundant IGF-I message. IGF-I protein was demonstrable by immunohistochemistry in melanocytes and keratinocytes. These results s uggest that progression-associated variation occurs in the net express ion of IGF-I mRNA in melanocytic tumors.