Enhancement of anti-tumor activity by low-dose combination of the recombinant urokinase kringle domain and celecoxib in a glioma model

The kringle domain of urokinase-type plasminogen activator (UK1) has anti-angiogenic and anti-tumor effects. Celecoxib, an inhibitor of cyclooxygenase type 2, also suppresses angiogenesis and tumor growth. To look for potential additive effects in their activities, we examined the anti-angiogenic and anti-tumor effects of the combination of UK1 and celecoxib for malignant gliomas. In vitro, the combination of UK1 and celecoxib enhanced inhibition of proliferation, migration, and tube formation of endothelial cells, although showing no enhancement of inhibition of U87 cell growth. However, in vivo models, combination treatment of intracerebral U87 malignant glioma xenografts in nude mice with UK1 (10 mg/kg/day) and celecoxib (10 mg/kg/day) at lower doses resulted in even more potent inhibition of tumor growth than each monotherapy (by 81% compared to untreated tumors), with drastic decrease of the expression of angiogenesis-related factors and increase of apoptosis in the tumor tissues. Interestingly, UK1 inhibited VEGF or bFGF-induced phosphorylation of ERK1/2 in ECs, whereas celecoxib showed no such effects. However, celecoxib inhibited U87 cell growth and directly suppressed their VEGF production. Therefore, our data suggest that combined use at low doses of UK1 and celecoxib with different anti-angiogenic mechanisms provides a desirable strategy for anti-glioma therapy.