Gene therapy on renal-cell carcinoma: magic bullet or tragic insanity?

15-Deoxy-Δ12,14-prostaglandin J2 Inhibits Cell Migration on Renal Cell Carcinoma via Down-Regulation of Focal Adhesion Kinase Signaling

Renal cell carcinoma (RCC) is one of the chemoresistant cancers. There is a pressing need to establish therapeutic approaches to prevent RCC proliferation and metastasis. The electrophilic 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) is an endogenous anti-cancerous agent. Treatment with high concentrations of 15d-PGJ₂ is known to induce apoptosis of RCC cells, independent of the nuclear receptor, peroxisome proliferator-activated receptor-γ (PPARγ). In this study, we investigated the effects of 15d-PGJ₂ on the metastatic properties of RCC Caki-2 cells. The metastatic potential of RCC was evaluated by measuring the migratory ability of Caki-2 cells. Although treatment with low concentrations of 15d-PGJ₂ did not cause apoptosis, it did decrease the migration of Caki-2 cells in a concentration-dependent manner. PPARγ did not mediate the inhibitory effect of 15d-PGJ₂ on the migration of Caki-2 cells. Treatment with a low concentration of 15d-PGJ₂ resulted in disassembled focal adhesions and extensive filamentous actin reorganization. Furthermore, 15d-PGJ₂ significantly reduced phosphorylation of focal adhesion kinase (FAK). In conclusion, 15d-PGJ₂ attenuated the migratory ability of RCC, independent of PPARγ. Further, 15d-PGJ₂ appeared to suppress cell migration via inactivation of FAK and subsequent disassembly of focal adhesion. Our present study highlights the therapeutic potential of 15d-PGJ₂ for prevention of RCC metastasis.

Synergistic effects of 15-deoxy Δ12,14-prostaglandin J2 on the anti-tumor activity of doxorubicin in renal cell carcinoma

An endogenous anticancer agent, 15-deoxy -Δ^12,14-prostaglandin J₂ (15d-PGJ₂) induces apoptosis in the chemoresistant renal cell carcinoma (RCC). Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor for 15d-PGJ₂, and mediates the cytotoxicity of 15d-PGJ₂ in many cancerous cells. However, 15d-PGJ₂ induces apoptosis independently of PPARγ in human RCC cell line such as Caki-2. In the present study, we found that 15d-PGJ₂ ameliorated the chemoresistance to one of anthracycline antibiotics, doxorubicin, in Caki-2 cells. Doxorubicin alone exhibited weak cytotoxicity at the concentrations effective for other cancer cells such as Hela cells. In addition, it did not activate caspase 3. However, the cytotoxicity of doxorubicin was increased remarkably and accompanied with the caspase- 3 activation in the presence of 15d-PGJ₂. Doxorubicin alone damaged plasma membrane, and the combined application of 15d-PGJ₂ with doxorubicin increased the membrane permeability slightly. PPARγ was involved in neither the anti-tumor activity nor the synergistic effect of 15d-PGJ₂. 15d-PGJ₂ induces apoptosis in Caki-2 cells via suppressing the phosphoinositide 3-kinase (PI3K)-Akt pathway. The effect of PI3K inhibitor on the cytotoxicity of doxorubicin was additive, but not synergistic. Although the PI3K inhibitor mimicked the cytotoxicity of 15d-PGJ₂, it might not be involved in the synergism between 15d-PGJ₂ and doxorubicin. In conclusion, 15d-PGJ₂ enhanced the chemosensitivity of doxorubicin via the pathway independent of PPARγ and PI3K.

Treatment of etoposide combined with 15-deoxy-Δ12,14-prostaglandin J2 exerted synergistic antitumor effects against renal cell carcinoma via peroxisome proliferator-activated receptor-γ-independent pathways

Renal cell carcinoma (RCC) is characterized by diverse clinical manifestations, few early warning signs and a resistance to radiotherapy and chemotherapy. Although several clinical trials have investigated potential effective therapeutic strategies for RCC, the chemoresistance of RCC has not yet been overcome. An endogenous ligand for the peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), was shown to induce apoptosis in RCC. The aim of the present study was to investigate the synergistic effects of carcinostatics on the antitumor activity of 15d-PGJ₂ in the Caki-2 human RCC cell line with the MTT assay. Our results demonstrated that the topoisomerase-II inhibitor etoposide (VP-16) exhibited cytotoxic effects synergistically with 15d-PGJ₂. Furthermore, the presence of the PPARγ antagonist GW9662 did not protect Caki-2 cells against 15d-PGJ₂-induced cytotoxicity. Additionally, it was observed that the combined treatment of VP-16 and 15d-PGJ₂ activated caspase-3 more efficiently compared to each treatment alone. Therefore, the combined treatment with 15d-PGJ₂ and VP-16 exhibited synergistic antitumor activity independently of PPARγ.

15-Deoxy-Δ12,14-prostaglandin J2 enhanced the anti-tumor activity of camptothecin against renal cell carcinoma independently of topoisomerase-II and PPARγ pathways

Renal cell carcinoma (RCC) is chemoresistant cancer. Although several clinical trials were conducted to explore effective medications, the chemoresistance of RCC has not yet been conquered. An endogenous ligand for peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), induces apoptosis in RCC. Here, we examined synergistic effects of several carcinostatics on the anti-tumor activity of 15d-PGJ(2) in Caki-2 cell line by MTT assay. A topoisomerase-I inhibitor, camptothecin (CPT), exhibited synergistically toxicity with 15d-PGJ(2), but neither 5-fluorouracil nor cisplatin did. The combination of 15d-PGJ(2) and a topoisomerase-II inhibitor, doxorubicine, did not cause synergistic cell growth inhibition. The synergistic effect of topoisomerase-I and II inhibitors was not also detected. A PPARγ antagonist, GW9662, did not prevent Caki-2 from undergoing 15d-PGJ(2)-induced cytotoxicity. The treatment of CPT combined with 15d-PGJ(2) activated caspase-3 more than the separate treatment. These results suggest that 15d-PGJ(2) exhibited the anti-tumor activity synergistically with CPT independent of topoisomerase-II and PPARγ.