Growth and ploidy of human osteosarcoma xenografts in serial passage in nude mice.

Six human osteosarcoma tumors have been transplanted to and maintained as xenografts in serial passage in nude mice. The xenografts, characterized by growth rate, histologic appearance, and DNA flow cytometric data, are now in the 6-17 passages in mice. Histologic appearances and growth rates of the xenografts were unchanged through all passages except for one xenograft in which the growth rate doubled in passage 3. All six tumors had hyperploid DNA contents. The ploidy levels were unchanged, compared to their original tumors, in all passages of five xenografts. One xenograft, concomitantly with the increase in growth rate, also doubled the ploidy from 2.8 to 5.6C. There was a good agreement between the proportion of S-phase cells and mitotic indices of the six xenografts. The growth rate, depending also on cell loss, was less related to the proliferative activity of the xenografts. It was concluded that osteosarcomas have a stable aneuploid DNA content in nude mice, but polyploidization can occur after a number of passages.