Aberrant p53 Expression in Feline Vaccine-Associated Sarcomas and Correlation with Prognosis

Vet Pathol 42:805-811 (2005)

A. E. Hershey, R. R. Dubielzig, M. L. Padilla and S. C. Helfand

Departments of Medical Sciences (AEH, MLP, SCH ), Comprehensive Cancer Center (SCH), and Pathobiological Sciences (RRD), University of Wisconsin–Madison, School of Veterinary Medicine, Madison, WI

Eighty spontaneously occurring feline vaccine-associated sarcomas (VAS) were evaluated to determine the immunohistochemical expression of the tumor suppressor gene p53. Sixty-five of 80 VAS (81%) exhibited positive immunoreactivity with Mab240, a murine monoclonal antibody that specifically recognizes mutated p53. Only 44 of 81 tumors (55%) were positive with rabbit polyclonal antibody CM-1. CM-1 often yielded nonspecific staining of nonneoplastic tissues. Nonspecific staining was greatly reduced or absent with Mab240. Cytoplasmic staining for p53 was a consistent pattern of VAS, occurring in 44% of tumors evaluated. Cats with tumors that exhibited cytoplasmic p53 had significantly shorter time to tumor recurrence compared to those cats with tumors that exhibited nuclear p53 staining (P = 0.0284), but no significant difference in survival outcome was observed. Immunohistochemical detection of p53 offers a prognostic tool for VAS, and, because abnormal p53 expression appears to be a common feature of feline VAS, molecular targeting of mutant p53, may offer a promising new therapeutic opportunity for this cancer.