• Journal of Life Science
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• v.19 no.8
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• pp.1023-1032
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• 2009

Despite the fact that many cancer cells are sensitive to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, some cancer cells show either partial or complete resistance to TRAIL. Human leukemic K562 and CEM cells also show resistance to TRAIL-induced apoptosis. Novel molecular target and treatment strategies are required to overcome TRAIL resistance of human leukemia cells. Therefore, the purpose of this study was to target key anti-apoptotic molecules deciding TRAIL resistance for sensitization of TRAIL-resistant K562 and CEM cells, and to evaluate the effect of quercetin as a TRAIL sensitizer on these TRAIL-resistant cells. We found that quercetin acted in synergy with TRAIL to enhance TRAIL-induced apoptosis in K562 cells by inhibition of the DNA-PK/Akt signaling pathway, which leads to enhancement of TRAIL-mediated activation of caspases and concurrent cleavage of PARP and up-regulation of Bax. The findings suggest that the DNA-PK/Akt signaling pathway plays an essential role in regulating cells to escape from TRAIL-induced apoptosis, and quercetin could act in synergy with TRAIL to increase apoptosis by inhibition of the DNA-PK/Akt signaling pathway, which overcomes TRAIL-resistance of K562 and CEM cells. This study suggests that DNA-PK might interfere with TRAIL-induced apoptosis in human leukemic cells through activation of the Akt signaling pathway.

• Biomolecules & Therapeutics
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• v.20 no.1
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• pp.62-67
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• 2012

TNF-related apoptosis-inducing ligand (TRAIL) is a promising agent for management of cancer because of its selective cytotoxicity to cancer cells. However, some cancer cells have resistance to TRAIL. Accordingly, novel treatment strategies are required to overcome TRAIL resistance. Here, we examined the synergistic apoptotic effect of apigenin in combination with TRAIL in Huh-7 cells. We found that combined treatment of TRAIL and apigenin markedly inhibited Huh-7 cell growth compared to either agent alone by inducing apoptosis. Combined treatment with apigenin and TRAIL induced chromatin condensation and the cleavage of poly (ADP-ribose) polymerase (PARP). In addition, enhanced apoptosis by TRAIL/apigenin combination was quantified by annexin V/PI flow cytometry analysis. Western blot analysis suggested that apigenin sensitizes cells to TRAIL-induced apoptosis by activating both intrinsic and extrinsic apoptotic pathway-related caspases. The augmented apoptotic effect by TRAIL/apigenin combination was accompanied by triggering mitochondria-dependent signaling pathway, as indicated by Bax/Bcl-2 ratio up-regulation. Our results demonstrate that combination of TRAIL and apigenin facilitates apoptosis in Huh-7 cells.

• Journal of Life Science
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• v.19 no.9
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• pp.1209-1217
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• 2009

Many cancer cells are sensitive to the TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. However, some cancer cells show either partial or complete resistance to TRAIL. Human colon carcinoma KM12 cells have been shown to be insensitive to TRAIL-induced apoptosis. To overcome TRAIL resistance in KM12 cells, we targeted key anti-apoptotic molecules involved in the modulation of TRAIL resistance in the cells, and evaluated the effects of quercetin as a TRAIL sensitizer in the cells. We found that quercetin acted in synergy with TRAIL to enhance TRAIL-induced apoptosis in KM12 cells by the down-regulation of c-FLIP and DNA-PKcs/Akt and up-regulation of death receptors (DR4/DR5), which led to the enhancement of TRAIL-mediated activation of caspases and subsequent cleavage of PARP, as well as up-regulation of Bax. These findings suggest that the DNA-PKcs/Akt signaling pathway, as well as c-FLIP, play essential roles in regulating cells in the escape from TRAIL-induced apoptosis. Based on these results, this study provides a potential application of quercetin in combination with TRAIL in the treatment of human colon cancer.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.12
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• pp.4849-4852
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• 2015

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been investigated as an effective agent to treat various cancers. Cancer stem cells are resistant to TRAIL treatment, but the mechanism of TRAIL resistance remains unknown. In this study, brain cancer stem cells were isolated by CD133 magnetic sorting, and the number of CD133 positive cells detected by flow cytometry. The self-renewing capacity of brain cancer stem cells was examined by a neurosphere formation assay, and the percentage of cell death after TRAIL treatment was examined by an MTS assay. Expression of DR5, FADD, caspase 8 and BCL2 proteins was detected by western blot. The amount of CD133 positive cells was enriched to 71% after CD133 magnetic sorting. Brain cancer stem cell neurosphere formation was significantly increased after TRAIL treatment. TRAIL treatment also reduced the amount of viable cells and this decrease was inhibited by a caspase 8 inhibitor or by the pan-caspase inhibitor z-VAD (P<0.05). Brain cancer stem cells expressed lower levels caspase 8 protein and higher levels of BCL2 protein when compared with CD133 negative cells (P<0.05). Our data suggest that TRAIL resistance is related to overexpression of BCL2 and low expression of caspase 8 which limit activation of caspase 8 in brain cancer stem cells.

• Journal of Life Science
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• v.21 no.11
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• pp.1641-1651
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• 2011

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL/Apo2L) is a recently identified member of the TNF ligand family that can initiate apoptosis through the activation of their death receptors. TRAIL has been paid attention as a potential anti-cancer drug, because it selectively induces apoptosis in tumor cells in vitro and in vivo but not in most normal cells. However, recent studies have shown that some cancer cells including malignant renal cell carcinoma and hepatocellular carcinoma, are resistant to the apoptotic effects of TRAIL. Therefore, single treatment with TRAIL may not be sufficient for the treatment of various malignant tumor cells. Understanding the molecular mechanisms of TRAIL resistance and identification of sensitizers capable of overcoming TRAIL resistance in cancer cells is needed for the establishment of more effective TRAIL-based cancer therapies. Chemotherapeutic drugs induce apoptosis and the upregulation of death receptors or activation of intracellular signaling pathways of TRAIL. Numerous chemotherapeutic drugs have been shown to sensitize tumor cells to TRAIL-mediated apoptosis. In this study, we summarize biological agents and drugs that sensitize tumors to TRAIL-mediated apoptosis and discuss the potential molecular basis for their sensitization.

• Herbal Formula Science
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• v.25 no.2
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• pp.145-154
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• 2017

Objectives : Bufalin is one of the bioactive component of 'Sum Su (蟾酥)', which is obtained from the skin and parotid venom gland of toad. Bufalin has been known to possess the inhibitory effects on cell proliferation and inducing apoptosis in various cancer cells. The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has concerned, because it can selectively induce apoptotic cell death in many types of malignant cells, while it is relatively non-toxic to normal cells. Here, we investigated whether bufalin can trigger TRAIL-induced apoptotic cell death in EJ human bladder cancer cells. Methods : Effects on the cell viability and apoptotic activity were quantified using MTT assay and flow cytometry analysis, respectively. To investigate the morphological change of nucleus, DAPI staining was performed. Protein expressions were measured by immunoblotting. Results : A combined treatment with bufalin (10 nM) and TRAIL (50 ng/ml) significantly promoted TRAIL-mediated growth inhibition and apoptosis in EJ cells. The apoptotic effects were associated with the up-regulation of death receptor proteins, and the down-regulation of cFLIP and XIAP. Moreover, our data showed that bufalin and TRAIL combination activated caspases and subsequently increased degradation of poly(ADP-ribose) polymerase. Conclusions : Taken altogether, the nontoxic doses of bufalin sensitized TRAIL-mediated apoptosis in EJ cells. Therefore, bufalin might be an effective therapeutic strategy for the safe treatment of TRAIL-resistant bladder cancers.

• YAKHAK HOEJI
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• v.55 no.1
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• pp.49-55
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• 2011

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is one of the promising anti-cancer agent because of its ability to selectively induce apoptosis in tumor cell lines but not in normal cells. However, TRAIL resistance has been reported in some cancer cells including hepatocarcinoma cells. Therefore, studies of agents that sensitize TRAIL-resistant cancer cells could be a effective therapeutic approach in cancer management. In our study, we examined the effect of combination of TRAIL with apigenin in human hepatocellular carcinoma cells. As a result, the combined use of TRAIL and apigenin significantly enhanced the cytotoxicity in PLC-PRF5 cells. Flow cytometry analysis after annexin V-FITC/PI dual staining showed that this increase of cell cytotoxicity was related to enhanced apoptosis in combined treatment of TRAIL with apigenin. Furthermore, synergistic induction of apoptosis was also confirmed by observation of morphological changes and annexin V-FITC/PI fluorescence. Our findings suggests that apigenin has the potential to improve the efficiency of TRAIL-based therapies in human hepatocellular carcinoma cells. Further study is needed to reveal the molecular mechanisms of this combined therapy.

• BMB Reports
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• v.52 no.2
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• pp.119-126
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• 2019

The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) initiates the extrinsic apoptotic pathway through formation of the death-inducing signaling complex (DISC), followed by activation of effector caspases. TRAIL receptors are composed of death receptors (DR4 and DR5), decoy receptors (DcR1 and DcR2), and osteoprotegerin. Among them, only DRs activate apoptotic signaling by TRAIL. Since the levels of DR expressions are higher in cancer cells than in normal cells, TRAIL selectively activates apoptotic signaling pathway in cancer cells. However, multiple mechanisms, including down-regulation of DR expression and pro-apoptotic proteins, and up-regulation of anti-apoptotic proteins, make cancer cells TRAIL-resistant. Therefore, many researchers have investigated strategies to overcome TRAIL resistance. In this review, we focus on protein regulation in relation to extrinsic apoptotic signaling pathways via ubiquitination. The ubiquitin proteasome system (UPS) is an important process in control of protein degradation and stabilization, and regulates proliferation and apoptosis in cancer cells. The level of ubiquitination of proteins is determined by the balance of E3 ubiquitin ligases and deubiquitinases (DUBs), which determine protein stability. Regulation of the UPS may be an attractive target for enhancement of TRAIL-induced apoptosis. Our review provides insight to increasing sensitivity to TRAIL-mediated apoptosis through control of post-translational protein expression.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.9
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• pp.1363-1369
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• 2013

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis by targeting cancer cells. However, some cancer cells are resistant to TRAIL-induced cytotoxicity. One method of overcoming TRAIL resistance is combination treatment with reagents to sensitize cells to TRAIL. Luteolin, a flavonoid, has been shown to have anti-cancer effects by inducing apoptosis and cell cycle arrest in various cancer cell lines in vitro. In this study, we investigated the effects of combination treatment with non-toxic concentration of TRAIL and luteolin in T24 human bladder cancer cells. Combined treatment with luteolin and TRAIL significantly inhibits cell proliferation via activation of caspases by inducing Bid truncation, up-regulation of Bax and down-regulation of X-linked inhibitor of apoptosis protein (XIAP). However, the apoptotic effects of combination treatment with luteolin and TRAIL were significantly inhibited by specific caspases inhibitors. Taken together, these results indicate that combination treatment with TRAIL and luteolin can induce apoptosis in TRAIL-resistant cancer cells through down-regulation of XIAP and modulation of tBid and Bax expression.

• Journal of Life Science
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• v.30 no.8
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• pp.661-671
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• 2020

The resistance of cancer cells to anti-cancer drugs is the leading cause of chemotherapy failure. The clinical use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been gradually extended to cancer treatment through combination with anti-cancer drugs. In the current study, we investigated whether NSAIDs including celecoxib (CCB), 2,5-dimethyl celecoxib (DMC), and ibuprofen (IBU) could enhance the cytotoxic effects of imatinib and TNF-related apoptosis inducing ligand (TRAIL) on human cancer cells. We found that the NSAIDs potentiated TRAIL and imatinib cytotoxicity against human hepatocellular carcinoma (HCC) cell lines SNU-354, SNU-423, SNU-449, and SNU-475/TR and against leukemic K562 cells with high level of CD44 (CD44^highK562), respectively. More specifically, CCB induced endoplasmic reticulum stress via up-regulation of ATF4/CHOP which is associated with the induction of autophagy against HCC and CD44^high K562 cells. NSAID-induced autophagic activity accelerated TRAIL cytotoxicity of HCC cells through up- and down-regulation of DR5 and c-FLIP, respectively. The NSAIDs also potentiated imatinib-induced cytotoxicity and apoptosis through down-regulation of markers in CD44^highK562 cells that express a stemness phenotype. Our results suggest that the ability of NSAIDs to induce autophagy could enhance the cytotoxicity of TRAIL and imatinib, leading to a reverse resistance to these drugs in the cancer cells. In conclusion, NSAIDs in combination with low-dose TRAIL or imatinib may constitute a novel clinical strategy that maximizes therapeutic efficacy of each drug and effectively reduces the toxic side effects.