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

Type II DNA Topoisomerases in trypanosomatid and apicomplexan parasites

Diseases caused by trypanosomatid parasites have no commercially available vaccines for human application. Treatment modalities completely rely on chemotherapeutics strategies that often exhibit clinical drawbacks, like host toxicity, side effects and treatment failure for drug resistance. These, in many instances, are costly, making them unaffordable for certain groups of beneficiaries. To find reasonable solutions, researchers are attempting to identify and validate new drug targets that would offer parasite specificity. DNA topoisomerases in parasites present a consolidated class of drug targets due to their multiple structural and functional differences with host homologs. Type II DNA topoisomerases in these parasites, in particular, have been attracting interest of scientific community attributable to their pivotal role in the replication of the atypical DNA. In this article, we present a detailed review of structural and functional features of type II DNA topoisomerases of clinically-relevant trypanosomatid and apicomplexan parasites. Also, we provide up-to-date information on different molecules that target these enzymes. Altogether, the review will largely help in understanding the rationale for exploiting type II DNA topoisomerases in these groups of parasites as drug targets.

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.

4,4-Diisothiocyanatostilbene Disulfonic Acid Enhanced 15-Deoxy-Δ12,14-prostaglandin J2-Induced Neuronal Apoptosis

4,4-Diisothiocyanatostilbene disulfonic acid (DIDS), an antagonist of anion channel including voltage-dependent anion channel (VDAC), acts as both neurotoxicant and neuroprotectant, resulting in the controversy. VDAC contributes to neuronal apoptosis and is a candidate target protein of 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂). Caspase-3 is activated during neuronal apoptosis caused by 15d-PGJ₂. In the present study, we ascertained whether DIDS was neuroprotective or neurotoxic in the primary culture of rat cortical neurons. Neuronal cell viabilities were primarily evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) reduction assay. Plasma membrane integrity and apoptosis were detected by the staining of propidium iodide (PI) and Hoechst33342, respectively. Alternatively, apoptosis was also measured by caspase-3 assay kit. DIDS did not prevent neurons from undergoing the 15d-PGJ₂-induced apoptosis. In contrast, DIDS caused neuronal cell death in a concentration-dependent manner by itself, confirming its neurotoxicity. The sublethal application of DIDS did not decrease MTT-reducing activity, increase caspase-3 activity, condense chromatin, allow PI to enter neuron and degenerate neuronal morphology significantly. Interestingly, DIDS enhanced the 15d-PGJ₂-induced neuronal apoptosis markedly under the sublethal condition. To our knowledge, this is the first report of synergistic effects of DIDS on the neurotoxicity of 15d-PGJ₂.

Comparison of the effect of three different topoisomerase II inhibitors combined with cisplatin in human glioblastoma cells sensitized with double strand break repair inhibitors

Topoisomerase II (Topo2) inhibitors in combination with cisplatin represent a common treatment modality used for glioma patients. The main mechanism of their action involves induction of DNA double-strand breaks (DSBs). DSBs are repaired via the homology-dependent DNA repair (HRR) and non-homologous end-joining (NHEJ). Inhibition of the NHEJ or HRR pathway sensitizes cancer cells to the treatment. In this work, we investigated the effect of three Topo2 inhibitors-etoposide, NK314, or HU-331 in combination with cisplatin in the U-87 human glioblastoma cell line. Etoposide as well as NK314 inhibited Topo2 activity by stabilizing Topo2-DNA cleavable complexes whereas HU-331 inhibited the ATPase activity of Topo2 using a noncompetitive mechanism. To increase the effectiveness of the treatment, we combined cisplatin and Topo2 inhibitor treatment with DSB repair inhibitors (DRIs). The cells were sensitized with NHEJ inhibitor, NU7441, or the novel HRR inhibitor, YU238259, prior to drug treatment. All of the investigated Topo2 inhibitors in combination with cisplatin efficiently killed the U-87 cells. The most cytotoxic effect was observed for the cisplatin + HU331 treatment scheme and this effect was significantly increased when a DRI pretreatment was used; however, we did not observed DSBs. Therefore, the molecular mechanism of cytotoxicity caused by the cisplatin + HU331 treatment scheme is yet to be evaluated. We observed a concentration-dependent change in DSB levels and accumulation at the G2/M checkpoint and S-phase in glioma cells incubated with NK314/cisplatin and etoposide/cisplatin. In conclusion, in combination with cisplatin, HU331 is the most potent Topo2 inhibitor of human glioblastoma cells.

15-deoxy-Δ12, 14-prostaglandin J2 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 von Hippel–Lindau (VHL) gene. VHL-positive Caki-2 cells are killed by an endogenous anticancer substance, 15-deoxy-Δ^{12, 14}-prostaglandin J₂ (15d-PGJ₂). 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-PGJ₂ exhibited the synergistic effect in VHL-positive Caki-2 cells. However, 15d-PGJ₂ did not increase cytotoxicities of topoisomerase inhibitors on VHL-negative 786-O cells. In addition, the 15d-PGJ₂-enhanced antitumor activity of topoisomerase inhibitors was detected in neither VHL-positive nor VHL-negative RCC4 cells. Our finding indicated that 15d-PGJ₂ enhanced the antitumor activity of topoisomerase inhibitors independently of VHL.

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.

Anticancer effect of deoxypodophyllotoxin induces apoptosis of human prostate cancer cells

Deoxypodophyllotoxin (DPPT) is extracted and separated from citrus-related plants, including Podophyllum (P.) peltatum, P. pleianthum, P. emodi (also called P. hexandrum) and Diphylleia grayi. DPPT has significant antitumor and antiviral activity. However, due to its strong toxicity and side effects, its use is limited in practical applications. The in vitro antitumor efficacy of DPPT on human prostate cancer (PCa) cells remains to be determined. The present study investigated the anticancer effect of DPPT on human PCa cells and its potential mechanism. The data revealed that DPPT markedly reduced cell proliferation and activated the caspase-3 expression level by an increase in apoptotic cell death in DU-145 cells. In addition, treatment with DPPT markedly downregulated the levels of phosphorylated Akt and activated the p53/B-cell lymphoma 2 associated X protein (Bax)/phosphatase and tensin homolog (PTEN) signaling pathway in DU-145 cells, suggesting that caspase-mediated pathways were involved in DPPT-induced apoptosis. The present study suggested the role of DPPT as a novel chemotherapeutic drug for human PCa, which may function through the Akt/p53/Bax/PTEN signaling pathway.