Behavior of Two Cell Strains Derived From Rat Rhabdomyosarcomas23

Abstract

Cells from rat rhabdomyosarcomas have been serially cultured in Connaught's H597 growth medium supplemented with 20 percent calf serum, 0.08 percent sodium bicarbonate, and 100 IU per ml of potassium penicillin G. One cell strain (ALA), derived from a nickel sulfide-induced tumor, has been propagated since February, 1961, while another strain (#79), obtained from a similar tumor, has been maintained since September, 1961. The primary cultures and the early subcultures of these 2 strains were morphologically identical in that both exhibited a loose net of pleomorphic cells reminiscent of early mesenchyme. Subsequently, the ALA strain changed its morphological pattern to fibroblast-like cells of uniform size forming a heavily packed monolayer or multilayer, while #79 strain still remains unchanged. In the primary cultures of ALA strain, 12 percent of the mitotic cells had the normal diploid rat complement, the remaining cells being heteroploids. The percentage of diploids in ALA strain increased to over 50 percent after the first 5 months, and this strain continues to this day (June 25, 1962) to be predominantly diploid. The primary cultures of strain #79 had only 3 percent diploid cells, and this strain is still predominantly heteroploid. The primary ALA culture cells produced sarcomas when injected intramuscularly into weanling Fischer rats; however, cells from the subsequent subcultures failed to produce tumors. The heteroploid strain, #79, consistently produced sarcomas in rats when injected through intramuscular or intraperitoneal routes. The difference in the morphological, chromosomal, and malignant traits of these 2 strains and the possible mechanisms involved in the evolution of a "normal" cell strain (ALA) from a histologically characteristic rhabdomyosarcoma tissue are discussed.