Predominant p53 mutations in enzootic bovine leukemic cell lines

The role of the p53 tumor suppressor gene in bovine lymphosarcomas, a fragment of about 1100 bp corresponding to approximately 97% of the open reading frame of the p53 gene was first amplified from single-strand cDNA originated from calf thymus by polymerase chain reaction (PCR) and sequenced to obtain the bovine wild-type p53 gene. At the amino acid level, the homologies of the bovine p53 gene with the human, mouse, chicken and cat p53 genes were 80.9%, 72.8%, 52.7% and 82.3%, respectively. Moreover, eight bovine leukemic cell lines were studied for alterations in the p53 gene. These lines showed no significant somatic alterations in Southern blot analysis, and expressed 2.5 kb p53-specific transcripts in Northern blot analysis. In mutation analysis using the reverse transcriptase-PCR technique, we detected three missense point mutations in four of these bovine leukemic cell lines. These mutations occurred in the ‘hotspots’ of the p53 gene. Thus p53 mutations predominantly occur in BLV-transformed cell lines and seem to be necessary for development of enzootic bovine leukosis (EBL).