title: In vitro induction of malignant transformation and in vivo resistance to tumor growth in the X/Gf mouse.
abstract: Inbred X/Gf mice are reported to have a very low incidence of spontaneous and induced tumors. Experiments were performed to determine whether the cells of the X/Gf mouse are themselves resistant to in vitro oncogenesis or the organism as a whole is surveyed by a homeostatic mechanism that prevents the expression of potential neoplasia. Cultures of X/Gf or C57BL/6J embryonic fibroblasts were exposed to the chemical carcinogens 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene to test whether the cells of the X/Gf mouse are themselves resistant to oncogenesis. The chemical carcinogens caused transformation of both X/Gf and C57BL/6 fibroblasts into cells that demonstrated altered growth patterns in liquid culture and grew in a clonal fashion in soft agar. Cloned transformed cells were shown to be malignant and resulted in the growth of sarcomas in vivo. X/Gf mice were decidedly more resistant than were C57BL/6 mice to their respective clones of transformed cells. The resistance to neoplastic growth demonstrated by the X/Gf mice was inherited by (C57BL/6J X X/Gf)F1 mice that were resistant to the growth of X/Gf-transformed and C57BL/6-transformed cells at cell doses at which the parental X/Gf mice had survived but at which the C57BL/6 had succumbed to progressively growing tumors. It has thus been established that the tumor resistance of the X/Gf mice is not based on the resistance of isolated cells from these animals to malignant transformation, but rather is attributable to an in vivo homeostatic mechanism that prevents tumor growth.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000362:Agar; D000818:Animals; D001551:Benz(a)Anthracenes / Q000633:toxicity*; D001564:Benzo(a)pyrene; D001580:Benzopyrenes / Q000633:toxicity*; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005260:Female; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009368:Neoplasm Transplantation; D012513:Sarcoma, Experimental / Q000139:chemically induced
chemical_list: D001551:Benz(a)Anthracenes; D001580:Benzopyrenes; D001564:Benzo(a)pyrene; D015127:9,10-Dimethyl-1,2-benzanthracene; D000362:Agar