Objectives—To investigate the role of tumor suppressor
gene p53 mutation in feline vaccine site-associated
sarcoma (VSS) development and to evaluate
the relationship between p53 nucleotide sequence
and protein expression.
Sample Population—Formalin-fixed paraffinembedded
tissues of 8 feline VSS with dark p53
immunostaining (high p53 expression) and 13 feline
VSS with faint or no staining (normal p53 expression).
Procedure—DNA was extracted from neoplastic and
normal tissue from each paraffin block. The following
3 regions of the p53 gene were amplified by polymerase
chain reaction: 379 base pair (bp) region of
exon 5, intron 5, and exon 6, 108 bp region of exon 7,
and 140 bp region of exon 8. Amplified p53 products
were sequenced and compared with published feline
p53. The p53 mutations identified were correlated
with p53 mutations predicted by immunostaining.
Results—Neoplastic cells of 5 of 8 (62.5%) VSS that
had high p53 expression harbored single missense
mutations within the p53 gene regions examined. The
p53 gene mutations were not detected in the 13
tumors with normal p53 immunostaining.
Nonneoplastic tissues adjacent to all 21 VSS lacked
mutations of these p53 gene regions.
Conclusions—The p53 gene mutations were restricted
to neoplastic tissue and, therefore, were unlikely
to predispose to VSS. However, p53 mutations may
have contributed to cancer progression in 5 of the 21
VSS. There was very good (κ quotient = 0.67 with a
confidence limit of 0.3 to 1.0), although not complete,
agreement between prediction of mutation by p53
immunostaining and identification of mutations by
sequencing of key p53 gene regions. (Am J Vet Res