Prostaglandins, Leukotrienes and Essential Fatty Acids 72 (2005) 181–186 Pretreatment tumor prostaglandin E 2 concentration and cyclooxygenase-2 expression are not associated with the response of canine naturally occurring invasive urinary bladder cancer to cyclooxygenase inhibitor therapy A.J. Mutsaers a,1 , S.I. Mohammed b , D.B. DeNicola b,2 , P.W. Snyder b , N.W. Glickman c , P.F. Bennett a,3 , A.E. de Gortari a , P.L. Bonney a , D.W. Knapp a,d,Ã a Department of Veterinary Clinical Sciences, Purdue University, Lynn Hall of Veterinary Medicine, 625 Harrison St., West Lafayette, IN 47907-2026, USA b Department of Veterinary Pathobiology, Purdue University, Lynn Hall of Veterinary Medicine, 625 Harrison St., West Lafayette, IN 47907-2027, USA c Office of Research Programs, Purdue University, West Lafayette, IN, USA d Purdue Cancer Center, West Lafayette, IN, USA Received 14 September 2004; accepted 15 October 2004 Preliminary results presented at the 93rd annual meeting of the American Association for Cancer Research, 2002, San Francisco, CA. There is no financial relationship between any of the authors and the subject matter. Summary The purpose of this study was to determine the extent to which pretreatment prostaglandin E 2 (PGE 2 ) concentration and cyclooxygenase-2(cox-2)expressioncouldbeusedtopredicttheantitumoractivityofcoxinhibitortreatmentinnaturallyoccurring canine transitional cell carcinoma of the urinary bladder (TCC). Snap frozen tissues (to measure PGE 2 ) and formalin-fixed TCC samples(forcox-2immunohistochemistry)wereobtainedbycystoscopyorsurgery.Completetumorstagingwasperformedbefore and after one month of treatment with the cox inhibitor, piroxicam (0.3mg/kg q24h po). The pretreatment PGE 2 concentration rangedfrom57to1624ng/gofTCCtissue; n ¼ 18dogs).Cox-2immunoreactivitywasobservedinallTCCsamples.Therewasno association between PGE 2 concentration, cox-2 expression, and change in tumor volume with piroxicam treatment. In conclusion, cox-2 expression or PGE2 concentration alone, or the combination of the two was not useful in predicting response to piroxicam treatment in canine TCC. r 2004 Published by Elsevier Ltd. 1. Introduction Arachidonic acid metabolites have been linked to cancer development and progression in several studies (reviewed by Lupulescu [1] and Ara [2]). Prostaglandin E 2 (PGE 2 ), one of the metabolites of cyclooxygenase (cox, including cox-1 and cox-2 isoforms) enzyme activity on arachidonic acid, is especially important. PGE 2 has been found to have a role in carcinogenesis, cancer progression, metastasis, tumor angiogenesis and tumor-associated immunosuppression [1–12]. High ARTICLE IN PRESS www.elsevier.com/locate/plefa 0952-3278/$-see front matter r 2004 Published by Elsevier Ltd. doi:10.1016/j.plefa.2004.10.017 Ã Corresponding author. Department of Veterinary Clinical Sciences, Purdue University, Lynn Hall of Veterinary Medicine, 625 Harrison St., West Lafayette, IN 47907-2026, USA. Tel.: +17654941107;fax:+17654961108. E-mail address: knappd@purdue.edu (D.W. Knapp). 1 Current address: Department of Medical Biophysics, University of Toronto, Toronto, Ontario. 2 Currentaddress:IDEXXLaboratories,NorthGrafton,MA,USA. 3 Current address: Melbourne Veterinary Referral Centre, Glen Waverley, Victoria, Australia.