Tumorigenicity of Green Turtle Fibropapilloma-Derived Fibroblast Lines in Immunodeficient Mice

Fibroblast lines derived from normal skin and spontaneous or experimentally induced fibropapillomas of green turtles (Chelonia mydas) were established and propagated in medium composed of a combination of Dulbecco's minimal essential with F12 medium plus 10% fetal bovine serum at 30°C. Fibropapilloma-derived fibroblasts were indistinguishable from normal skin fibroblasts in vitro. Tumor lines did not exhibit loss of contact inhibition, anchorage independence, or reduced serum requirements. Inoculation of primary and early-passage tumor cells into the medial margin of the pinna of C57BL/6J-nu/nu, C.B17-scid/scid, or NOD-scid/scid mice, however, resulted in fibroma formation, whereas inoculation of normal skin fibroblasts did not. Tumor-derived cells inoculated into the flanks of mice did not form tumors. The turtle origin of fibroblasts in tumors from mouse ears was confirmed by immunohistochemical and karyotype analysis. Fibroblast lines that were established from mouse ear fibromas had the normal karyotype (modal 2N = 55) of C. mydas. The cooler anatomic sites (ears) of immunodeficient mice are useful for confirming the tumorigenic (transformed) phenotype of green turtle fibropapillomatosis-derived fibroblasts. This mouse ear tumorigenicity test should facilitate studies of mechanisms of cellular transformation in green turtle fibropapillomatosis and other neoplastic diseases of poikilothermic vertebrates.