Cytogenetic findings in a malignant melanoma and its derived cell line

A cell line, MEL #26, was established from a metastatic solid tumor specimen obtained from a patient with malignant melanoma. Cytogenetic analyses were performed on both the fresh biopsy specimen (using short-term culture; 2 days) and an established cell line at three different passages. The chromosome number of the fresh biopsy specimen was in the near-triploid range and the chromosome number of the cell line was tetraploid. Three stable marker chromosomes involving #1, #6, and #7 were observed both in the original tumor and cell line. The marker chromosomes involving #1 and #7 were consistently present in all passages of this line, whereas, i(6p) was not present in every metaphase; a 15p+ marker completely disappeared after passage 20. Based on the results of the present study, we conclude that exclusive of one marker chromosome, the nonrandom chromosome changes seen in the original tumor were retained by the cell line and no particular additional clonal changes occurred during in vitro growth and establishment of this cell line. These considerations are of importance in the interpretation of results of various other studies that have been (or could be) performed with this cell line.