Effects of dibutyryl cyclic AMP on the expression of the transformed phenotype in a Kirsten sarcoma virus-transformed mouse cell line

The effects of dibutyryl 3'; 5' cyclic monophosphate (dbcAMP) on several parameters of transformation were studied using a Kirsten sarcoma virus (Ki-MSV)-transformed mouse cell line (K-A31). Treated cells showed changes in morphology, decreased motility, saturation density and growth rate, and lost the capacity for anchorage-independent growth. In contrast to many other transformed cell lines, fibronectin and an elaborate cytoskeleton were present in K-A31 cells. The transcription of the proviral genome was examined using both reverse-transcribed and nick-translated ('3)H-DNA probes, and certain viral-specific RNAs were found restricted to the nucleus of dbcAMP-treated cells. Additive hybridization experiments suggested these RNAs were transcribed from rat-derived sequences located in the 5'-half of the proviral genome. These results are discussed with respect to the properties most closely associated with cellular malignancy, and the possible mechanism of dbcAMP-mediated reverse-transformation in K-A31 cells