The
feline oncornavirus-associated cell membrane antigen (
FOCMA) acts as a target for natural immuno-surveillance against
tumor development in the cat. In the present study, mink and rat cells nonproductively transformed by feline
sarcoma virus (FeSV) were shown to express
FOCMA as well as 5'-terminal feline leukemia virus (FeLV) gag gene
proteins, p15 and p12. In contrast, such cells lack detectable levels of other FeLV gag gene-coded
proteins or the env gene product, gp70.
FOCMA, p15, and p12
antigen expression is initially in the form of an 80,000-100,000 molecular weight precursor which, upon post-translational cleavage, gives rise to a 65,000 molecular weight component that contains
FOCMA and a 25,000 molecular weight component containing p15 and p12. Feline
lymphoma cells, including those from several
tumors that lacked detectable levels of FeLV structural
protein expression, were shown to be
FOCMA-positive. These findings strongly suggest that
FOCMA represents an FeSV-coded transformation specific
protein and provide preliminary information regarding the position within the FeSV genome coding for its synthesis.