RETINOIC ACID INDUCES LOSS OF VIRAL-DNA, PHENOTYPIC REVERSION AND TRANSFORMATION-RESISTANCE OF BOVINE PAPILLOMAVIRUS TYPE-1 DNA-TRANSFORMEDCELLS

Two revertant cell lines were obtained by treatment of bovine papillom avirus type 1 (BPV-1) DNA-transformed cell lines B3 and BF3 with 5 muM of all-trans-retinoic acid (RA) for 10 weeks. The revertant cells wer e devoid of detectable viral DNA, no longer exhibited a transformed mo rphology and lost the ability to form multilayered transformed foci. T hey replicated with a population doubling time of 16-18 hours, which w as also characteristic of the C127, B3 and BF3 cells. They attained a similar saturation density as the C127 cells. However, the revertant c ells were at least 5- to 7-fold more resistant than the parental C127 cells to neoplastic transformation induced by BPV-1 DNA.