NS-398, a selective cyclooxygenase-2 inhibitor, reduces experimental bladder carcinoma outgrowth by inhibiting tumor cell proliferation

Objectives. To evaluate the efficacy of the selective cyclooxygenase-2 (COX-2) inhibitor NS-398 in treating experimental T24 bladder carcinoma, and to assess its effect on tumor cell proliferation and survival and tumor vascularization. COX-2 overexpression is frequently observed in bladder carcinoma and has been correlated with an increased disease stage and with reduced patient survival. Methods. NS-398 was used to inhibit COX-2 selectively in human T24 bladder carcinoma cells. Lentiviral transduction of the firefly luciferase gene allowed us to assess the effect of NS-398 on orthotopic bladder carcinoma growth over time in a noninvasive manner. Immunohistochemistry on bladder tissue sections was performed to determine the effect of NS-398 treatment on tumor cell proliferation (Ki-67), apoptosis (cleaved caspase-3), and angiogenesis (von Willebrand factor; CD31). Results. T24 cells expressed COX-2 and secreted prostaglandin E-2 (PGE(2)). Selective COX-2 inhibition using NS-398 abrogated PGE2 secretion and inhibited cell proliferation in vitro in a dose-dependent manner, without affecting cell viability. In vivo administration of NS-398 reduced the outgrowth of experimental orthotopic T24 bladder carcinoma. This was accompanied by a significant reduction in Ki-67-positive tumor cells but not by a reduction in tumor cell viability or tumor vascularization. Conclusions. Selective COX-2 inhibition by NS-398 reduces the outgrowth of T24 human bladder carcinoma in an orthotopic mouse model. The therapeutic activity was most likely caused by inhibition of tumor cell proliferation, rather than by inhibition of angiogenesis or tumor cell survival.