Viral transduction of c-myc gene in naturally occurring feline leukaemias

Feline leukaemia virus (FeLV) is epidemiologically associated with induction of the majority of lymphoid tumours of the domestic cat 1 . However, about one-third of these tumours are devoid of exogenous virus or show evidence of virus integration only after tumour outgrowth 1,2 . To help define the genetic mechanisms of feline lymphomagenesis we have explored here the possibility that cellular oncogenes (c- onc genes) are rearranged in tumour cell DNA. Of 16 FeLV-positive T-cell tumours among 31 naturally occurring lymphomas, 2 showed evidence of recombinant FeLV proviruses containing myc oncogene sequences. One of the two produced a transmissible myc -containing FeLV. In both cases c- myc and its surrounding DNA appeared unaltered. We believe that the association of myc with FeLV may result in its activation and play a part in the development of a significant fraction of cat T-cell lymphomas. Our findings contrast with studies of experimental induction of chicken lymphoma, in which myc activation occurs by retrovirus promoter insertion near c- myc (refs 3–5), rather than by incorporation into virus.