Human melanoma cell lines established from metastases of a patient with a completely regressed primary site.

Two unique human melanoma cell lines were established from each of two metastases, with collections separated by a 1-year interval, in a patient with a spontaneously completely regressed primary cutaneous malignant melanoma. These cell lines were distinct, and under culture, they had characteristic features that correlated with those shown by the original tumors from which they were derived. Cells derived from the second metastasis were more aggressive and had a higher proliferative growth rate, serious chromosomal abnormalities, a greater capacity to form colonies on agar, and a lesser dependence on serum-derived growth factors. This study of malignant melanoma cell lines covered the range from the stage of complete spontaneous regression of the primary lesion through the development of the first metastasis (from which the cell line designated L1M1 was established) to the second metastasis (discovered 1 year later, from which the cell line G1M2 was established). These cell lines grow continuously in the laboratory and can be carried for an unlimited number of passages. They afford an opportunity to investigate and compare the malignant pattern and behavior of human malignant melanoma originating after a completely spontaneously regressed primary lesion.