Expression of cyclooxygenase-2 in canine renal cell carcinoma

Cyclooxygenase-2 (COX-2) has been shown to be the primary enzyme responsibl e for prostaglandin production during inflammation but is absent in most ti ssues under normal physiological states. High levels of COX-2 expression ha ve been observed in the macula densa and thick ascending limbs of fetal kid neys; this expression declines to minimal levels during renal maturation. W e hypothesized that the neoplastic cells of renal cell carcinoma (RCC) may revert to high expression of COX-2, and we evaluated its expression in thre e spontaneous cases of canine RCC by using immunohistochemical methods. The neoplastic cells of two of the three cases exhibited moderate to marked CO X-2 immunoreactivity. These results suggest that some canine renal cell car cinomas express high levels of COX-2, which may play a role in the modulati on of neoplastic cell growth.