Trichosanthin enhances sensitivity of non-small cell lung cancer (NSCLC) TRAIL-resistance cells.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) has a specific antitumour activity against many malignant tumours. However, more than half of lung cancer cells are resistant to TRAIL-relevant drugs. Trichosanthin (TCS) is a traditional Chinese medicine with strong inhibitive effects on various malignancies. Nevertheless, its function on TRAIL resistance has not been revealed in non-small cell lung cancer (NSCLC). To examine the molecular mechanisms of TCS-induced TRAIL sensitivity, we administrated TCS to TRAIL-resistance NSCLC cells, and found that the combination treatment of TCS and TRAIL inhibited cancer cell proliferation and invasion, and induced cell apoptosis and S-phase arrest. This combined therapeutic method regulated the expression levels of extrinsic apoptosis-associated proteins Caspase 3/8 and PARP; intrinsic apoptosis-associated proteins BCL-2 and BAX; invasion-associated proteins E-cadherin, N-cadherin, Vimentin, ICAM-1, MMP-2 and MMP-9; and cell cycle-associated proteins P27, CCNE1 and CDK2. Up-expression and redistribution of death receptors (DRs) on the cell surface were also observed in combined treatment. In conclusion, our results indicated that TCS rendered NSCLC cells sensitivity to TRAIL via upregulating and redistributing DR4 and DR5, inducing apoptosis, and regulating invasion and cell cycle related proteins. Our results provided a potential therapeutic method to enhance TRAIL-sensitivity.

Identification of miRNA-7 by genome-wide analysis as a critical sensitizer for TRAIL-induced apoptosis in glioblastoma cells.

Glioblastoma (GBM) is still one of the most lethal forms of brain tumor despite of the improvements in treatments. TRAIL (TNF-related apoptosis-inducing ligand) is a promising anticancer agent that can be potentially used as an alternative or complementary therapy because of its specific antitumor activity. To define the novel pathways that regulate susceptibility to TRAIL in GBM cells, we performed a genome-wide expression profiling of microRNAs in GBM cell lines with the distinct sensitivity to TRAIL-induced apoptosis. We found that the expression pattern of miR-7 is closely correlated with sensitivity of GBM cells to TRAIL. Furthermore, our gain and loss of function experiments showed that miR-7 is a potential sensitizer for TRAIL-induced apoptosis in GBM cells. In the mechanistic study, we identified XIAP is a direct downstream gene of miR-7. Additionally, this regulatory axis could also exert in other types of tumor cells like hepatocellular carcinoma cells. More importantly, in the xenograft model, enforced expression of miR-7 in TRAIL-overexpressed mesenchymal stem cells increased apoptosis and suppressed tumor growth in an exosome dependent manner. In conclusion, we identify that miR-7 is a critical sensitizer for TRAIL-induced apoptosis, thus making it as a promising therapeutic candidate for TRAIL resistance in GBM cells.

Soy isoflavones augment the effect of TRAIL-mediated apoptotic death in prostate cancer cells.

Prostate cancer represents an ideal disease for chemopreventive intervention. Genistein, daidzein and equol, the predominant soy isoflavones, have been reported to lower the risk of prostate cancer. Isoflavones exert their chemopreventive properties by affecting apoptosis signalling pathways in cancer cells. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is an endogenous anticancer agent that induces apoptosis selectively in tumour cells. Soluble or expressed in immune cells, TRAIL molecules play an important role in immune surveillance and defense mechanisms against tumour cells. However, various types of cancer cells are resistant to TRAIL-mediated apoptosis. We examined the cytotoxic and apoptotic effects of genistein, daidzein and equol in combination with TRAIL in LNCaP cells. Cytotoxicity was measured by MTT and LDH assays. Apoptosis was analyzed by flow cytometry and fluorescence microscopy using Annexin V-FITC. Mitochondrial membrane potential (ΔΨm) was evaluated by fluorescence microscopy using DePsipher staining. Flow cytometry detected the expression of death receptor TRAIL-R1 (DR4) and TRAIL-R2 (DR5) on cell surfaces. The soy isoflavones sensitized TRAIL-resistant prostate cancer cells to apoptotic death. The isoflavones did not alter death receptor expression, but significantly augmented TRAIL-induced disruption of ΔΨm in the LNCaP cells. We showed for the first time that the chemopreventive effects of soy foods on prostate cancer are associated with isoflavone-induced support of TRAIL-mediated apoptotic death.

Resveratrol: Biological and pharmaceutical properties as anticancer molecule.

There is ample evidence that shows an inverse relationship between consumption of fruit/vegetable-rich diets and the risk of cancer at various anatomical sites. In this review, we will assess and summarize recent advances on cancer prevention by resveratrol, a natural stilbenoid present in red grapes, peanuts, some common drinks, and dietary supplements. We will focus on data published within the past few years on in vivo model tumor animal studies that reinforce the chemopreventive efficacy of resveratrol against a multitude of cancers, as well as on its sensitization/enhancing activities against tumor cells when used in combination with established chemotherapeutic and pharmaceutical agents. In addition, we will review examples resveratrol-target proteins, denoted RTPs, including the 24-kDa cytosolic protein quinone reductase 2 (NQO2) discovered in our laboratory that may confer resveratrol responsiveness to cancer cells. We will discuss the possible role of NQO2 in mediating cancer prevention by resveratrol. Our analysis of published data strengthen support that resveratrol displays novel roles in various cellular processes, and help to establish an expanded molecular framework for cancer prevention by resveratrol in vivo.

Nitric oxide sensitizes tumor cells to TRAIL-induced apoptosis via inhibition of the DR5 transcription repressor Yin Yang 1.

Treatment of TRAIL-resistant tumor cells with the nitric oxide donor DETANONOate sensitizes the tumor cells to TRAIL-induced apoptosis concomitantly with DR5 upregulation. The mechanism of sensitization was examined based on the hypothesis that DETANONOate inhibits a transcription repressor Yin Yang 1 (YY1) that negatively regulates DR5 transcription. Treatment of the prostate carcinoma cell lines with DETANONOate inhibited both NF-kappaB and YY1 DNA-binding activities concomitantly with upregulation of DR5 expression. The direct role of YY1 in the regulation of TRAIL resistance was demonstrated in cells treated with YY1 siRNA resulting in TRAIL-induced apoptosis. The role of YY1 in the transcriptional regulation of DR5 was examined in cells treated with a DR5 luciferase reporter system (pDR5) and two constructs, namely, the pDR5/-605 construct with a deletion of the putative YY1 DNA-binding region (-1224 to -605) and a construct pDR5-YY1 with a mutation of the YY1 DNA-binding site. A significant (3-fold) augmentation of luciferase activity over baseline transfection with pDR5 was observed in cells transfected with the modified constructs. ChIP analysis corroborated the YY1 binding to the DR5 promoter. In vivo, tissues from nude mice bearing the PC-3 xenograft and treated with DETANONOate showed inhibition of YY1 and upregulation of DR5. The present findings demonstrate that YY1 negatively regulates DR5 transcription and expression and these correlated with resistance to TRAIL-induced apoptosis. DETANONOate inhibits both NF-kappaB and YY1 and in combination with TRAIL reverses tumor cell resistance to TRAIL apoptosis.

Role of tumor necrosis factor-alpha and TRAIL in high-dose radiation-induced bystander signaling in lung adenocarcinoma.

In the present study, ionizing radiation (IR)-induced bystander effects were investigated in two lung cancer cell lines. A549 cells were found to be more resistant to radiation-conditioned medium (RCM) obtained from A549 cells when compared with the H460 exposed to RCM procured from H460 cells. Significant release of tumor necrosis factor-alpha (TNF-alpha) was observed in A549 cells after IR/RCM exposure, and the survival was reversed with neutralizing antibody against TNF-alpha. In H460 cells, significant release of TNF-related apoptosis-inducing ligand (TRAIL), but not TNF-alpha, was observed in response to IR, RCM exposure, or RCM + 2Gy, and neutralizing antibody against TRAIL diminished clonogenic inhibition. Mechanistically, TNF-alpha present in RCM of A549 was found to mediate nuclear factor-kappaB (NF-kappaB) translocation to nucleus, whereas the soluble TRAIL present in RCM of H460 cells mobilized the nuclear translocation of PAR-4 (a proapoptotic protein). Analysis of IR-inducible early growth response-1 (EGR-1) function showed that EGR-1 was functional in A549 cells but not in H460 cells. A significant decrease in RCM-mediated apoptosis was observed in both A549 cells stably expressing small interfering RNA EGR-1 and EGR-1(-/-) mouse embryonic fibroblast cells. Thus, the high-dose IR-induced bystander responses in A549 may be dependent on the EGR-1 function and its target gene TNF-alpha. These findings show that the reduced bystander response in A549 cells is due to activation of NF-kappaB signaling by TNF-alpha, whereas enhanced response to IR-induced bystander signaling in H460 cells was due to release of TRAIL associated with nuclear translocation of PAR-4.

Regulation of tumor cell sensitivity to TRAIL-induced apoptosis by the metastatic suppressor Raf kinase inhibitor protein via Yin Yang 1 inhibition and death receptor 5 up-regulation.

Raf-1 kinase inhibitor protein (RKIP) has been implicated in the regulation of cell survival pathways and metastases, and is poorly expressed in tumors. We have reported that the NF-kappaB pathway regulates tumor resistance to apoptosis by the TNF-alpha family via inactivation of the transcription repressor Yin Yang 1 (YY1). We hypothesized that RKIP overexpression may regulate tumor sensitivity to death ligands via inhibition of YY1 and up-regulation of death receptors (DRs). The TRAIL-resistant prostate carcinoma PC-3 and melanoma M202 cell lines were examined. Transfection with CMV-RKIP, but not with control CMV-EV, sensitized the cells to TRAIL-mediated apoptosis. Treatment with RKIP small interfering RNA (siRNA) inhibited TRAIL-induced apoptosis. RKIP overexpression was paralleled with up-regulation of DR5 transcription and expression; no change in DR4, decoy receptor 1, and decoy receptor 2 expression; and inhibition of YY1 transcription and expression. Inhibition of YY1 by YY1 siRNA sensitized the cells to TRAIL apoptosis concomitantly with DR5 up-regulation. RKIP overexpression inhibited several antiapoptotic gene products such as X-linked inhibitor of apoptosis (XIAP), c-FLIP long, and Bcl-x(L) that were accompanied with mitochondrial membrane depolarization. RKIP overexpression in combination with TRAIL resulted in the potentiation of these above effects and activation of caspases 8, 9, and 3, resulting in apoptosis. These findings demonstrate that RKIP overexpression regulates tumor cell sensitivity to TRAIL via inhibition of YY1, up-regulation of DR5, and modulation of apoptotic pathways. We suggest that RKIP may serve as an immune surveillance cancer gene, and its low expression or absence in tumors allows the tumor to escape host immune cytotoxic effector cells.

Hyperthermia enhances tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in human cancer cells.

PURPOSE: This study investigated whether hyperthermia can enhance TRAIL-induced apoptotic death. METHODS: Human prostate adenocarcinoma DU-145, human pancreatic carcinoma MIA PaCa-2 and BxPC-3, human colon fibroblast CCD-33Co and rat prostate endothelial YPEN-1 cells were treated with various concentrations of TRAIL (0-200 ngml(-1)) with hyperthermia (40-42 degrees C). RESULTS: It was observed in human cancer cells, but not in normal cells, that TRAIL induced apoptotic death and also that hyperthermia (40-42 degrees C) promoted TRAIL-induced apoptotic death. Enhancement of TRAIL-mediated apoptosis by hyperthermia was detected by an increase in PARP cleavage, the hallmark feature of apoptosis, as well as by activation of caspases. There were no significant changes in the intra-cellular levels of death receptors (DRs), decoy receptors (DcRs) and anti-apoptotic proteins. Interestingly, data from in vitro enzyme kinetics assay demonstrated that hyperthermia promoted caspase enzyme activity. CONCLUSIONS: These data suggest that cancer cells are more susceptible to TRAIL in the condition of hyperthermia (40-42 degrees C). The promotion of caspase enzyme activity by hyperthermia may be responsible for enhancement of TRAIL-induced apoptotic death.