Establishment of cell line derived from human malignant melanoma

A new human cell line of malignant melanoma (MJM) was established with the use of the in vitro fragment technique. It has been maintained over 34 months of continuous cultivation. Three types of cells can be recognized by light microscope. The epitheloid elements predominate, less frequent are fibroblastoid and giant multinuclear cells. The pigment production is not macroscopically visible. Over 60 per cent of analyzed metabphases showed hyperdiploid number of chromosomes, the rest was mostly tetra and hexaploid. No marker chromosomes were detected. The growth studies indicate the MJM cells have 63-hr doubling time. Cytochemistry revealed positive pigment or propigment granules in 36 per cent of cells. Ultrastructural studies did not detect melanin granules but some particles resembling atypical premelanosomes and melanosomes were recognized in some sections.