15-deoxy-Δ-prostaglandin J enhances anticancer activities independently of VHL status in renal cell carcinomas.

Renal cell carcinoma (RCC) is relatively resistant to chemotherapy and radiotherapy. Clear cell RCC (ccRCC) accounts for the majority of RCC, which have mutations or epigenetic silencing of the () gene. VHL-positive Caki-2 cells are killed by an endogenous anticancer substance, 15-deoxy-Δ-prostaglandin J (15d-PGJ). The MTT reduction assay reflecting mitochondrial succinate dehydrogenase activity was employed for assessment of cell viability. We confirmed anticancer activities of camptothecin (topoisomerase I inhibitor), etoposide (topoisomerase II inhibitor), doxorubicin (topoisomerase II inhibitor) in VHL-positive Caki-2 cells. Combination of topoisomerase inhibitors with 15d-PGJ exhibited the synergistic effect in VHL-positive Caki-2 cells. However, 15d-PGJ did not increase cytotoxicities of topoisomerase inhibitors on VHL-negative 786-O cells. In addition, the 15d-PGJ-enhanced antitumor activity of topoisomerase inhibitors was detected in neither VHL-positive nor VHL-negative RCC4 cells. Our finding indicated that 15d-PGJ enhanced the antitumor activity of topoisomerase inhibitors independently of VHL.