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Ultrastructural Comparison of Two Human Malignant Melanoma Cell Lines¹

Department of Pathology, Temple University Health Sciences Center, Philadelphia, Pennsylvania 19140, and Department of Surgery, M. D. Anderson Hospital and Tumor Institute, University of Texas, Houston, Texas 77025

The ultrastructure of 2 established human melanoma cell lines (LeCa and MeGo) and their clones was investigated. All strains of line LeCa had premelanosomes with the typical arrangement of "helical filaments" and with cross-striated melanosomes; only the amount of melanosomes produced varied in the different strains.

The strains in line MeGo varied widely in the appearance of their premelanosomes. The helical arrangement of the matrix filaments was missing, and cross-striated melanosomes were not seen. Morphologically, premelanosomes tend to resemble lysosomes in varying degrees in the different strains. Because all strains of both lines are dihydroxyphenylalanine positive and show acid phosphatase activity in melanosomes, two possible explanations are considered: (a) hydrolytic enzymes function in the melanosome to terminate melanogenesis; or (b) the enzymes indicate hydrolysis of melanosomes as they accumulate in the melanoma cells.

¹ This research was supported by Grants CA 11654 and GM 15887 from the NIH. It was conducted in part at the M. D. Anderson Hospital and Tumor Institute, Houston, Texas.

Received 3/ 6/70. Accepted 7/29/70.