Disseminated Rhabdomyosarcomas Formed in Kittens by Cultured Human Rhabdomyosarcoma Cells

Cultured human rhabdomyosarcoma cells (RD cell, line #2) were inoculated into the fetuses of 3 pregnant cats at approximately 40 days' gestation. Three of five surviving kittens from two litters developed disseminated rhabdomyosarcomas 46, 55, and 60 days after birth, respectively. One full-grown stillborn kitten of the third cat' had rhabdomyosarcomas in the liver and thymus. The tumors in all kittens looked like the original rhabdomyosarcoma from which the RD cell line was derived. Cell lines derived by tumor cell isolation from 3 cat tumors consisted of 2 cytologic types resembling those of the original tumor—polygonal cells and strap cells. Metaphases of these cells contained many aberrations, but the chromosome pattern was like that of the original human rhabdomyosarcoma cells. Those lines tested had a rapid generation time, a high saturation density, formed colonies in agar, and contained myoglobin. One cell line was inoculated into fetal cats, and rhabdomyosarcomas composed of human cells formed in 2 of 3 surviving kittens at 43 and 47 days after birth, respectively. Although the parent RD cell line contained no detectable C-type virus particles, 2 cat tumors and 1 cell line derived from 1 of these tumors contained C-type virus particles of unknown origin.