Establishment and characterization of human vaginal malignant melanoma xenotransplants.

Human vaginal malignant melanoma represents rare gynecological malignancies of poor prognosis. We have established a melanoma tumor line in nude mice, designated Mela-1, and have examined the histological and biological characteristics of this tumor. The Mela-1 tumor has preserved the histological, histochemical and biological characteristics of malignant melanoma even after 20 passages. Tumor cells are of epitheloid shape varying in size. An ultrastructural study revealed that the tumor cells were characterized by the presence of cells with deeply indented nuclei, and both types of melanosomes, eumelanosomes and pheomelanosomes, in various stages of maturation with vesiculo-globular bodies in the cytoplasm. Melanin analysis of the tumor indicated the Mela-1 tumor to be pheomelanic. Immunohistochemical examinations revealed that the Mela-1 cells were stained positively by melanoma-associated antibody (NKI/C3) and by antibodies for S-100 protein and vimentin, and negatively for keratin and CEA. The levels of AFP, CA125 and CEA in sera of tumor-bearing mice were within normal range. The 5-S-cysteinyldopa level in sera of tumor-bearing mice correlated well with the size of the tumor. Chromosomal analysis showed the human karyotype with great heterogeneity and a modal number of 102 chromosomes. Thus the Mela-1 tumor will be useful in establishing the biological characteristics in the search for an effective treatment of human malignant melanoma of the vagina.