FGF expression allows nevus cells to survive in three-dimensional collagengel under conditions that induce apoptosis in normal human melanocytes

Melanocytes, the pigment forming cells of the skin, form an almost nonproli ferating cell population located to the lowermost part of the epidermis, No rmally melanocytes are not found higher in the epidermis or in the dermis. Nevi consist of melanocytes with altered growth characteristics and localiz ation. The common pigmented nevus, a benign skin lesion, develops when mela nocytes proliferate in the dermo-epidermal junction or in the dermis. Here we report growth characteristics of in vitro cultured normal human melanocy tes and dermal nevus-derived melanocytes. As previously reported, nevus cel ls have a moderate to high FGF-2 expression level. Here we demonstrate that dermal nevus cells are able to survive in three-dimensional type 1 collage n culture, while normal human melanocytes rapidly undergo apoptosis, Melano cytes also, however, survive in collagen cultures in the presence of exogen ous FGF-2, The survival of nevus cells in collagen is suppressed by protami ne, an inhibitor of FGF-mediated cell stimulation. The in vivo growth envir onment of dermal nevus cells consists largely of type I and type III collag ens. The results suggest that FGF-2 expression by nevus cells allows them t o adapt to grow in the dermis. FGF-2 obviously has importance as a melanocy te survival factor and probably also in the development of malignant melano ma.