title: Effect of passage in culture on a clone of BALB/c 3T3 cells transformed by simian virus 40.
abstract: Most simian virus 40 (SV40)-transformed BALB/c 3T3 clones employed for biochemical studies have been used without regard to passage level. To determine whether virus-induced properties are stable as a function of passage, we have extensively characterized one transformed clone, FNE, which was isolated after SV40 infection BALB/c 3T3 cells in factor-free medium. From the initial testing at passage 5 and for at least 50 subsequent subcultures, the cells stably maintained many transformed growth properties, including high saturation density, morphology, colony formation on contact-inhibited monolayers, tumorigenicity, and synthesis of viral-specific RNA. However, other properties varied as a function of passage. There was a slight decrease in viral genome equivalents per cell from 1.1 copy/cell at passage 5 to 0.7 copies at passage 40. Initially, the cells were negative for all type C virus; however, cells carried at low density for 13 to 20 passages (65 to 100 generations) began to release an endogenous type C virus that then persisted in the culture. Spontaneous release of type C virus did not occur in control BALB/c 3T3 cells carried under identical culture conditions for 90 passages. When the cultures were releasing type C viruses they stained uniformly and brightly positive for SV40 tumor (T) antigen by immunofluorescence, whereas T antigen staining was variable at early passage. These experiments suggest that subtle but perhaps important differences in viral gene expression can occur as a function of passage; they also demonstrate the importance of evaluating the interactions between SV40 and endogenous type C viruses.
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000032:analysis; D000956:Antigens, Viral / Q000032:analysis; D001483:Base Sequence; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002999:Clone Cells; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D005347:Fibroblasts; D051379:Mice; D008807:Mice, Inbred BALB C / Q000196:embryology; D009368:Neoplasm Transplantation; D012334:RNA, Neoplasm / Q000032:analysis; D012367:RNA, Viral / Q000032:analysis; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism; D012190:Retroviridae / Q000201:enzymology / Q000302:isolation & purification; D013539:Simian virus 40 / Q000032:analysis / Q000254:growth & development / Q000276:immunology
chemical_list: D000951:Antigens, Neoplasm; D000956:Antigens, Viral; D004279:DNA, Viral; D012334:RNA, Neoplasm; D012367:RNA, Viral; D012194:RNA-Directed DNA Polymerase