[Involvement of cAMP dependent protein kinase in the reversion of a NIH/3T3 cell line transformed by a ras oncogene (EJ-NIH/3T3)].

cAMP production and the activity of cAMP dependent protein kinase (Kinase-A) were examined in a mutant clone of a NIH/3T3 cell line transformed by a human activated H-ras-1 oncogene (EJ-NIH/3T3). The mutant (R1) shows the characteristics of a flat revertant. The amount of cAMP increases more significantly in R1 than that in EJ-NIH/3T3 in the presence of PGE1. Enhanced activity of Kinase-A was also noted in R1 when compared to that in EJ-NIH/3T3. Further, EJ-NIH/3T3 treated with agents which increase intracellular cAMP content partially lost some characteristics of malignantly transformed phenotypes in vitro. These data suggest that Kinase-A might be involved in the reversion of EJ-NIH/3T3. In addition, reduced cytosolic free Ca2+ concentration measured with Ca2+ indicator in R1 cells was noted. This might also be associated with the reversion of the malignantly transformed cell line.