Approaches to prove the melanoma origin in amelanotic human melanoma cell lines.

The human melanoma B-HM8 cell line was derived from highly pigmented malignant skin melanoma. After 5 weeks of cultivation it entirely lost the pigmentation and has remained amelanotic since. Electron microscopy revealed neither premelanosomes nor melanosomes and the cells did not release detectable amount of dopa-oxidase activity into culture medium. Immunocytochemical studies using the polyclonal anti-S-100 antibody and detection of alpha-mannosidase activity in culture medium proved the melanoma origin of B-HM8 cells. Chromosomal changes in the karyotype of these cells were typical for human melanoma with chromosomes No. 1, 5, 7, 9, and 11 involved most frequently.