Exceptional Lethality for Nude Mice of Cells Derived from a Primary Human Melanoma

BRO human melanoma cells, obtained from a biopsy of a highly aggressive and malignant primary tumor, were grown as xenografts in nude mice and in cell culture. These cells were exceptionally tumorigenic and malignant for nude mice. NIH-II nude mice survived 11.0 ± 0.4 (S.E.) and 14.1 ± 0.4 days after i.p. inoculation of 107 or 106 BRO cells, respectively, and lethal tumors developed in all mice inoculated i.p. with only 103 cells. The doubling time (2.3 days) of the volume of tumors formed after s.c. inoculation was comparable to the doubling time of these cells in culture. After i.p. or s.c. inoculation, BRO cells metastasized to the diaphragm and lungs, causing respiratory failure in most of the host mice. The original tumor and the cell line derived from it had undifferentiated structures with prominent nuclei and very large nucleoli. Karyotype abnormalities included a gigantic A group chromosome, a large D group chromosome, and an unusual double centromere chromosome not found typically in human melanoma cells. Due to the short and reproducible survival times of nude mice inoculated i.p. with BRO cells, this model system may be useful for rapidly determining the effects of experimental treatment on the survival of hosts bearing human tumor cells.