The metabolism of arachidonic acid by either the cyclooxygenase or lipoxygenase (LOX) pathway is believed to play an important role in tumor promotion. We investigated the expression of 5- and 12-LOX in renal cell carcinoma (RCC), as well as the effects of their inhibitors on cell proliferation in 2 RCC cell lines (Caki-1 and A498). Expression of 5- and 12-LOX was detected by immunohistochemistry and RT-PCR. Effects of LOX inhibitors on RCC cell growth were examined by MTT assay, and Hoechst staining was used to determine whether or not the LOX inhibitors induce apoptosis. While 5- and 12-LOX expression levels were slightly detected in NK tissues, marked expressions of 5- and 12-LOX were detected in RCC tissues. 5-LOX inhibitors caused marked reduction of RCC cells in a concentration- and time-dependent manner. The effect of the 5-LOX inhibitor was stronger than the 12-LOX inhibitor. Furthermore, the 5-LOX inhibitor caused a marked reduction of RCC cells through apoptosis. LOX, especially 5-LOX, is induced in RCC, and the results suggest that the 5-LOX inhibitor may mediate potent anti-proliferative effects against RCC cells. Thus, 5-LOX may become a new target in treatment of RCC.

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