Cytotoxicity of 15-Deoxy-Δ(12,14)-prostaglandin J(2) through PPARγ-independent Pathway and the Involvement of the JNK and Akt Pathway in Renal Cell Carcinoma

Introduction: Agonists of peroxisome proliferator-activated receptor gamma (PPARγ) have been examined as chemopreventive and chemotherapeutic agents. The aim was to investigate the cytotoxicity and action mechanisms of 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), one of endogenous ligands for PPARγ, in terms of PPARγ-dependency and the mitogen-activated protein kinase (MAPK) and Akt pathway in three human renal cell carcinoma (RCC)-derived cell lines. Methods: 786-O, Caki-2 and ACHN cells were used as human RCC-derived cell lines. Cell viability and caspase-3 activity was detected by fluorescent reagents, and chromatin-condensation was observed with a brightfield fluorescent microscope after staining cells with Hoechst33342. The expression levels of proteins were detected by Western blot analysis. Results: 15d-PGJ(2) showed cytotoxicity in dose-dependent manner. 15d-PGJ(2) induced chromatin-condensation and elevated caspase-3 activity, and the cell viability was restored by co-treatment with a pan-caspase inhibitor, Z-VAD-FMK, indicating the involvement of caspase-dependent apoptosis. The cytotoxicity was not impaired by a PPARγ inhibitor, GW9662, suggesting that 15d-PGJ(2) exerted the cytotoxicity in a PPARγ-independent manner. Some antioxidants rescued cells from cell death induced by 15d-PGJ(2), but some did not, suggesting that reactive oxygen species (ROS) did not contribute to the apoptosis. 15d-PGJ(2) also increased the expression levels of phospho-c-Jun N terminal kinase (JNK) in Caki-2 cells, and decreased those of phospho-Akt in 786-O cells, indicating that the JNK MAPK and the Akt pathways participated in the anticancer effects of 15d-PGJ(2) in some cell lines. Conclusion: 15d-PGJ(2) exerted cytotoxic effects accompanying caspase-dependent apoptosis, and this effect was elicited in a PPARγ-independent manner in three cell lines. In addition, the JNK MAPK and Akt pathway was involved in the cytotoxicity of 15d-PGJ(2) to some extent in some cell line. Therefore, our study showed the 15d-PGJ(2) to potentially be an interesting approach for RCC treatment.