Activation of a cellular proto-oncogene in spontaneous XXXX tissue of the B6C3F1 @entity19 .

@entity1 @entity96 @entity19 @entity5 @entity99
The controversy surrounding the interpretation of observed increases in the high spontaneous @entity96 incidence of the B6C3F1 @entity19 after administration of certain chemical agents necessitates a mechanistic understanding into the nature of @entity5 development in this particular strain of @entity19 . Recently, @entity5 genes (oncogenes) have been detected in the DNA from a variety of @entity1 @entity5 and @entity5 cell lines. These genes have been implicated to play a role in the transformation of normal cells into cancerous ones. To investigate the role that cellular oncogenes might play in the development of spontaneous @entity96 in the B6C3F1 @entity19 , DNA was isolated from spontaneously occurring @entity96 and transfected into NIH 3T3 fibroblasts. DNA from this @entity5 tissue was capable of transforming NIH 3T3 cells from 82% of the animals examined strongly suggesting the presence of an active cellular oncogene. In contrast, DNA isolated from surrounding non-tumorous liver tissue and liver tissue from non- @entity5 bearing @entity19 did not cause any transformation in the NIH 3T3 assay. These data demonstrate that the active cellular oncogene is not present in the hepatic tissue via a germ-line transmission but is activated only in those cells of the @entity5 tissue. Experiments using Southern blot hybridization analysis have identified this active cellular oncogene to be a member of the ras oncogene family. Identification of this cellular oncogene will now allow the evaluation of factors which might modify its expression. These future studies will lead to an increased understanding of potential mechanisms by which @entity99 are enhanced and should provide more informed estimates of risk for @entity1 based on bioassay data generated in this strain of @entity19 .
