Bovine papillomavirus type 1-transformed primary mouse fibroblasts show no correlation between tumorigenicity and viral gene expression, but c-myc gene expression is elevated in tumorigenic cell lines.

Bovine papillomavirus type 1 (BPV-1)-transformed primary mouse fibroblasts containing episomal or integrated BPV-1 sequences were analysed for virus-specific transcripts and c-myc gene expression. Total BPV-1-specific expression was high in cell lines containing episomal BPV-1 DNA in comparison to lines containing integrated BPV-1 sequences, mainly due to higher expression of the E6/E7 sequences. No correlation was found between the viral transcription and tumorigenicity, although BPV-1 gene expression occurred in all cell lines. High levels of c-myc expression were found in all cell lines exhibiting a tumorigenic phenotype as compared to the nontumorigenic lines. These data suggest that expression of BPV-1 genes may be essential for transformation but not tumorigenicity, whereas high levels of expression of cellular oncogenes like c-myc may be associated with tumorigenicity.