COX‐2 Expression in Feline Oral Squamous Cell Carcinoma (FOSCC)– An Immunohistochemical Study and Analysis of Survival

Abstract

Introduction: Cyclooxygenase‐2 (COX‐2) catalyses the rate‐limiting step in the conversion of arachidonic acid to eicosanoids and has been found to be overexpressed in many human and some animal cancers. Overexpression of COX‐2 in head and neck SCC in humans is associated with shorter survival times. Non‐resectable, FOSCC is a devastating disease with no effective therapy. Overexpression of COX‐2 in FOSCC may support the anecdotal use of NSAID therapy. Identification of a prognostic marker in cats may permit more effective, targeted therapy.Methods: Immunohistochemistry was performed on formalin‐fixed, paraffin‐embedded tissue from 59 FOSCC cases using an indirect staining technique and feline foetal kidney as positive control. Polyclonal antiserum specific to COX‐1 and COX‐2 were used after antigen retrieval with pH6 citrate buffer. Retrospective, observational data were collected by practitioner questionnaires. A Kaplan‐Meier survival plot was derived.Results: 55/59 questionnaires were returned (93% response rate). Median age at presentation was 10.9 years (range 7–15.5). Median survival time was 44 days (95% CL: 31, 79). Preliminary results show that COX‐1 staining was positive in all tumour tissues and in 86.7%(13/15 cases) of normal tissues. COX‐2 staining was positive in 67.3%(37/55) of tumour tissues and absent in normal tissue. Results of proportional hazards regression for survival and multiple logistic regression for COX expression including age, sex, breed, prior NSAID administration, other medication and COX expression as potential explanatory variables will be presented.Conclusions: These results indicated that COX‐1 and COX‐2 expression is seen in FOSCC but may not be predictive for survival.