Mutation of p53 Gene and Its Correlation with the Clinical Outcome in Dogs with Lymphoma

BACKGROUND: p53 plays a key role in the apoptotic event induced by chemotherapeutic agents. Mutation of p53 gene has been observed in various spontaneous tumors in humans and is associated with a poor prognosis. p53 abnormalities have been evaluated in several tumors in dogs; however, the association of p53 gene mutation with clinical outcome in dogs with lymphoma has not been documented. HYPOTHESIS/OBJECTIVES: The aim of this study was to examine p53 mutation in canine lymphoma cells and its association with the clinical outcome. ANIMALS: Forty‐three dogs with previously untreated high‐grade lymphoma referred to the University of Tokyo were included in this study. METHODS: Prospective cohort study. We examined p53 gene (exon 4–8) mutation in the tumor tissues from 43 dogs with lymphoma using PCR‐SSCP (polymerase chain reaction – single‐strand conformational polymorphism) analysis, followed by nucleotide sequencing of the abnormal bands. RESULTS: Of the 43 dogs, 7 dogs (16%) had p53 mutation, whereas 36 dogs (84%) were devoid of p53 mutation. Overall response rate after remission induction was significantly lower (33% versus 88%, P = .002) in dogs with lymphomas having p53 mutation than those with lymphomas devoid of p53 mutation. Overall survival time was significantly shorter (67 days versus 264 days, P = .004) in dogs with lymphoma with p53 mutation than those with lymphoma retaining wild‐type p53. CONCLUSION AND CLINICAL IMPORTANCE: Mutations of p53 gene were detected in a proportion of canine lymphoma cells from untreated dogs and can be associated with a poor prognosis.