Establishment and characterization of human uveal malignant melanoma xenografts in nude mice.

The purpose of this study was to develop a suitable animal model for the investigation of the pathogenesis and therapy of uveal malignant melanoma. Eight choroidal malignant melanomas from eight patients were transplanted into nude mice in an attempt to establish a serially transplantable tumour model. Tumour tissue blocks (2 x 2 x 2 mm) from enucleated eyes with choroidal malignant melanoma were transplanted subcutaneously into the flanks of nude mice. The growing tumours were measured and serially transplanted. The tumour samples were investigated by histology, immunohistochemistry and electron microscopy. Only one of the eight transplanted primary tumours (13%) was established as a xenograft in nude mice. Furthermore, the take rate of the transplantable tumour was low (13%). The growth of the tumour fitted a Gompertz function, and the calculated tumour volume doubling time was 54 days. The transplanted tumour cells were epithelioid and slightly larger than the primary tumour cells and had prominent nucleoli. However, the transplanted tumour retained a morphological appearance similar to that of the primary tumour. Immunohistochemical examinations demonstrated that the cells preserved the characteristic properties of malignant melanoma. However, the transplanted cells demonstrated vimentin reactivity, whereas the primary tumour cells were negative for vimentin. It can be concluded that a new experimental model of malignant uveal melanoma with tumours that were easy to observe and access was established in nude mice.