title: Comparative studies of two types of "spontaneous" malignant alteration of ST/A mouse lung fibroblasts propagated in vitro.
abstract: Two types of apparently spontaneous malignant alterations of fibroblastlike ST/a mouse lung cells (ST-L cells) grown in vitro are described. One type is characterized by a high tumorigenic potential of the altered cells in nonconditioned syngeneic recipients, a fibroblastlike morphology with cell surface showing very few microvilli by scanning electron-microscopy (SEM), and a growth pattern typical of nontransformed cells. These cells were described as R- cells. The other type is characterized bya low tumorigenic potential in non-conditioned, immunocompetent syngeneic recipients, rounding up of the cells which by SEM showed numerous microvilli on the surface, and a growth pattern typical  of transformed cells. These cells were described as round cells or R+ cells. In immunoincompetent mice, R+ cells readily produced sarcomas, which grew faster than those produced by R- cells. Both types of ST-L cells expressed murine leukemia virus (MuLV) when tested in  a peroxidase anti-p30 plaque test. The concentration of murine leukemia virus envelope glycoprotein (gp70) has previously (5) been shown to be threefold higher in R+ cells compared to R- cells. Furthermore, round-cell transformation was accompanied by the development of crossreacting rejection antigens protective against a secondary shallenge with Ehrlich ascites tumor and with syngeneic dimethylbenzanthracene induced ST/a mouse leukemia (STABAL). A similar protection was obtained by preimmunization with a cloned embryonic feral mouse cell line (SC-1) infected with ST-L virus as well as with virus-free SC-1 cells, suggesting the presence of rejection antigens both of viral (gp70) and nonviral origin.
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology; D002455:Cell Division; D002460:Cell Line; D002462:Cell Membrane / Q000648:ultrastructure; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D005260:Female; D005347:Fibroblasts; D007114:Immunization; D007621:Karyotyping; D009052:Leukemia Virus, Murine / Q000254:growth & development; D008168:Lung; D051379:Mice; D009374:Neoplasms, Experimental / Q000209:etiology / Q000276:immunology
chemical_list: D000951:Antigens, Neoplasm