Early growth response-1 is a regulator of DR5-induced apoptosis in colon cancer cells

Background:

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces tumour cell apoptosis by binding to death receptor 4 (DR4) and DR5. DR4 and DR5 activation however can also induce inflammatory and pro-survival signalling. It is not known how these different cellular responses are regulated and what the individual role of DR4 vs DR5 is in these processes.

Methods:

DNA microarray study was carried out to identify genes differentially expressed after DR4 and DR5 activation. RT–PCR and western blotting was used to examine the expression of early growth response gene-1 (Egr-1) and the proteins of the TRAIL signalling pathway. The function of Egr-1 was studied by siRNA-mediated knockdown and overexpression of a dominant-negative version of Egr-1.

Results:

We show that the immediate early gene, Egr-1, regulates TRAIL sensitivity. Egr-1 is constitutively expressed in colon cancer cells and further induced upon activation of DR4 or DR5. Our results also show that DR4 mediates a type II, mitochondrion-dependent apoptotic pathway, whereas DR5 induces a mitochondrion-independent, type I apoptosis in HCT15 colon carcinoma cells. Egr-1 drives c-FLIP expression and the short splice variant of c-FLIP (c-FLIP_S) specifically inhibits DR5 activation.

Conclusion:

Selective knockdown of c-FLIP_S sensitises cells to DR5-induced but not DR4-induced apoptosis and Egr-1 exerts an effect as an inhibitor of the DR5-induced apoptotic pathway, possibly by regulating the expression of c-FLIP_S.     

FTY720 enhances TRAIL-mediated apoptosis by up-regulating DR5 and down-regulating Mcl-1 in cancer cells

FTY720, Fingolimod, is a functional antagonist to the sphingosine-1-phoaphate (S1P) receptor and an inhibitor of sphingosine kinase 1. Here, we showed that a combination of FTY720 and TRAIL induced apoptosis in human renal, breast, and colon carcinoma cells. Most importantly, this combination had no effect on normal cells. Furthermore, the combined treatment with FTY720 and TRAIL reduced tumor growth in xenograft models. FTY720 up-regulated death receptor (DR)5 at post-translational level. Knockdown of DR5 markedly blocked apoptosis induced by the combined treatment. FTY720 also inhibited Mcl-1 expression at the post-translational level. Over-expression of Mcl-1 blocked apoptosis induced by FTY720 and TRAIL. Interestingly, phospho-FTY720 and inhibitors of sphingosine kinase failed to enhance TRAIL-induced apoptosis. Thus, FTY720 enables TRAIL-induced apoptosis through up-regulation of DR5 and down-regulation of Mcl-1 in human cancer cells.     

Embelin 通过上调死亡受体 DR4 / DR5 mRNA 表达增加 HL - 60 细胞对 TRAIL的敏感性

目的：探讨Embelin增加HL-60细胞对肿瘤坏死因子相关凋亡诱导配体（TRAIL）的敏感性及可能的作用机制.方法：TRAIL 1、5、10、50及100 ng/ml分别处理HL-60细胞6、12、24及48h,MTT法绘制细胞生长曲线;TRAIL 10 ng/ml±亚细胞毒浓度的Embelin处理HL-60细胞6、12、24及48h,Annexin V/PI复染流式细胞术检测细胞凋亡,Western blot检测24h时Caspase-3、8及9的表达;亚细胞毒浓度的Embelin处理HL-60细胞6、12、24及48h,实时荧光定量PCR检测DR4及DR5 mRNA 的表达.结果：TRAIL对HL-60 细胞具有增殖抑制作用.亚细胞毒浓度的Embelin联合10 ng/ml TRAIL作用于HL-60细胞时细胞凋亡率较单独应用TRAIL时增加,相应的Caspase-3、8及9的表达也随之增加.结论：亚细胞毒浓度的Embelin可以增加HL-60细胞对TRAIL的敏感性,其机制可能与上调DR4及DR5 mRNA表达并进而启动凋亡途径有关.     

芹菜素激活TRAIL死亡受体参与诱导胃癌SGC-7901细胞凋亡的实验研究

目的： 研究芹菜素（API）对人胃癌SGC-7901细胞的增殖抑制和凋亡诱导作用,并探讨API诱导胃癌细胞凋亡的机制。方法： 设置对照组及不同浓度（20、40、60、80 μmol/L）的API组,分别作用SGC-7901细胞12、24和48 h后,CCK-8法检测细胞增殖率。选择作用24 h为后续处理时间点,采用流式细胞术检测细胞凋亡率;Western blot检测TRAIL通路中死亡受体DR4、DR5蛋白的表达水平;采用RNAi技术,用DR4 siRNA和DR5 siRNA分别沉默TRAIL通路中死亡受体DR4和DR5表达,设置对照组、API组、DR4 siRNA+API组、DR5 siRNA+API组,作用细胞24 h后,流式细胞术检测各组细胞凋亡率。结果： 细胞增殖检测结果提示API对人胃癌SGC-7901细胞的增殖率具有明显抑制作用,呈现浓度依赖性（r_{12 h}=-0.99,r_{24 h}=-0.88,r_{48 h}=-0.89,均为P < 0.05）;流式细胞术检测结果提示细胞凋亡率随着API作用浓度的增加而升高（r=0.96,P < 0.05）;Western blot检测发现API作用可上调细胞中DR4、DR5蛋白的表达水平;DR4 siRNA和DR5 siRNA分别沉默DR4和DR5的表达后,与API组相比,DR4 siRNA+API组和DR5 siRNA+API组的细胞凋亡率均降低（P < 0.05）。结论： 芹菜素具有抑制人胃癌SGC-7901细胞增殖和诱导细胞凋亡的作用,其机制可能与TRAIL通路中死亡受体DR4、DR5蛋白的表达被激活有关。     

抗人DR5单克隆抗体诱导Ｕ343细胞凋亡研究

目的:探讨抗肿瘤坏死因子相关凋亡配体的死亡受体DR5单克隆抗体对神经胶质瘤细胞株U343的杀伤作用及机制.方法:采用流式细胞仪从蛋白质水平定量地检测DR5在U343的表达;用RT-PCR从mRNA水平检测DR5的表达;免疫细胞化学法明确DR5在U343的分布情况.通过MTT法、琼脂糖凝胶电泳、流式细胞仪DNA倍体分析,观察抗人DR5单克隆抗体对U343细胞增殖的抑制活性及其诱导凋亡效应.结果:神经胶质瘤细胞株U343表达死亡受体DR5,DR5分布于细胞内细胞核的周围.抗人DR5单克隆抗体3μg/ml作用4 h可明显杀伤U343细胞,其机制与诱导凋亡有关.结论:抗人DR5单克隆抗体可以诱导神经胶质瘤细胞株U343凋亡,以死亡受体为靶点的抗体制剂为肿瘤治疗提供新的途径.     

The novel proteasome inhibitor carfilzomib activates and enhances extrinsic apoptosis involving stabilization of death receptor 5

Carfilzomib (CFZ) is a second generation proteasome inhibitor approved for the treatment of patients with multiple myeloma. It induces apoptosis in human cancer cells; but the underlying mechanisms remain undefined. In the present study, we show that CFZ decreases the survival of several human cancer cell lines and induces apoptosis. Induction of apoptosis by CFZ occurs, at least in part, due to activation of the extrinsic apoptotic pathway, since FADD deficiency protected cancer cells from undergoing apoptosis. CFZ increased total and cell surface levels of DR5 in different cancer cell lines; accordingly it enhanced TRAIL-induced apoptosis. DR5 deficiency protected cancer cells from induction of apoptosis by CFZ either alone or in combination with TRAIL. These data together convincingly demonstrate that DR5 upregulation is a critical mechanism accounting for CFZ-induced apoptosis and enhancement of TRAIL-induced apoptosis. CFZ inhibited the degradation of DR5, suggesting that DR5 stabilization contributes to CFZ-induced DR5 upregulation. In summary, the present study highlights the important role of DR5 upregulation in CFZ-induced apoptosis and enhancement of TRAIL-induced apoptosis in human cancer cells.     

Thymoquinone Crosstalks with DR5 to Sensitize TRAIL Resistance and Stimulate ROS-Mediated Cancer Apoptosis

Objective: Cancer treatment using a targeted inducer of apoptosis like tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) faced the obstacle of resistance, thus providing a plus drug like Thymoquinone (TQ) could be of great interest to tackle breast cancer cells. The aim of the present work is to examine the genetic modulation impacts of the TRAIL receptors and apoptotic markers upon the combinatorial remedy of TRAIL plus TQ on human breast cancer cell lines. Methods: To achieve this rationale, the protein content-based cytotoxicity using SRB assay, as well as the genetic expressions of the TRAIL receptors (DR4 and DR5) and apoptotic markers (Bcl-2, Cas-8, and FADD) using real time qRT-PCR technique were preceded against breast cancer MCF-7 and MDA-MB-231 cancerous cell lines. Results: The current study showed that the combination therapy of TQ+TRAIL significantly inhibited the protein content-based proliferation of MDA-MB-231 cells more than MCF-7 cells. The synergistic effect of them significantly up-regulated the genetic expressions of DR4, DR5, Cas-8, and FADD genes and inhibited the genetic expression of the Bcl-2 gene in the proposed cell lines treated for 24 h. The induction of the apoptotic genes using the combined therapy was stimulated by the elevation of the reactive oxygen species (ROS); nitric oxide (NO) and malondialdehyde (MDA) levels. Conclusions: The synergistic influence between TQ which induced the DR5 and TRAIL, facilitating the connection between TRAIL and its receptors on the cancerous cell membrane. Hence, the proposed combination therapy induced the ROS-mediated apoptotic stimulus.     

Enhancement of TRAIL/Apo2L-mediated apoptosis by adriamycin through inducing DR4 and DR5 in renal cell carcinoma cells

Renal cell carcinoma (RCC) is one of the most drug-resistant malignancies in humans. We show that adriamycin (ADR) and TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L have a synergistic cytotoxic effect against RCC cells. This synergistic cytotoxicity was obtained in ACHN, A704, Caki-1 and Caki-2 human RCC cell lines and freshly derived RCC cells from 6 patients. This synergistic effect, however, was not achieved in 5 samples of freshly isolated normal kidney cells. We further explored the mechanisms underlying this synergistic effect and found that the synergistic cytotoxicity of TRAIL/Apo2L and ADR was realized by inducing apoptosis. Sequential treatment with ADR followed by TRAIL/Apo2L induced significantly more cytotoxicity than the reverse treatment. ADR increased the expression of DR4 and DR5 in RCC cells, but not in the normal kidney cells. Furthermore, the synergistic cytotoxicity was significantly inhibited by DR4:Fc and DR5:Fc fusion proteins, which inhibit TRAIL/Apo2L-mediated apoptosis. In addition, caspase activity assays and treatment of caspase inhibitors demonstrated that the combination treatment with ADR and TRAIL/Apo2L activated caspase cascade, including caspase-9, -8, -6 and -3, which were the downstream molecules of death receptors. These findings indicate that ADR sensitizes RCC cells to TRAIL/Apo2L-mediated apoptosis through induction of DR4 and DR5, suggesting that the combination therapy of TRAIL/Apo2L and ADR might be effective for RCC therapy.     

Diosgenin induces death receptor-5 through activation of p38 pathway and promotes TRAIL-induced apoptosis in colon cancer cells

Previously, we demonstrated that diosgenin induced apoptosis in colorectal cancer cell lines HCT-116 and HT-29. HT-29 cells have been reported to be one of the most resistant colorectal cancer cell lines to TRAIL-induced apoptosis. In this study, we investigated the effect of diosgenin on TRAIL-induced apoptosis in HT-29 cells. We showed that diosgenin sensitizes HT-29 cells to TRAIL-induced apoptosis. Mechanisms underlying this sensitization mainly involved diosgenin-induced p38 MAPK pathway activation and subsequent DR5 overexpression. Furthermore, we showed that diosgenin alone, TRAIL alone or combination treatment increased COX-2 expression and that the use of a COX-2 inhibitor further increased apoptosis induction.     

Correlation between the Sensitivity to TRAIL and the Expression Level of DR5 on the Surface of Tumor Cells

OBJECTIVE To investigate the correlation between the sensitivity to the tumor necrosis factor- related apoptosis inducing ligand (TRAIL) and the level of expression of the death receptor 5 (DR5) on the surface of tumor cells.METHODS Anti-DR5 mAbs were used to directly detect the level of expression of DR5 on the surface of tumor cells. Using a TRAIL apoptosis kit and flow cytometry, the sensitivity of the tumor cells to TRAIL-induced apoptosis was determined and the correlation between DR5 expression and sensitivity to TRAIL analyzed.RESULTS The expression level of DR5 on the surface of different tumor cells was as follows: 97.9% in U937 cells, 95.1% in Jurkat cells, 93.8% in SW480 cells, 86.2% in HCT116 cells, 64.2% in HL-60 cells, 46.6% in Hela cells and 13.1% in K562 cells. The TRAIL-induced apoptotic rate was 72.6% in U937 cells, 85.2% in Jurkat cells, 78.6% in SW480 cells, 70.2% in HCT116 cells,60.1% in HL-60 cells, 45.4% in Hela cells and 12.3% in K562 cells. Statistical analysis showed there was a significant positive correlation (r=0.997, P<0.001) between DR5 expression and sensitivity to TRAIL.CONCLUSION The sensitivity of tumor cells to TRAIL is related to the level of expression of DR5 on the surface of tumor cells. These results confirm the importance of DR5 expression for induction of apoptosis by TRAIL.     

Nutlin-3 enhances tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis through up-regulation of death receptor 5 (DR5) in human sarcoma HOS cells and human colon cancer HCT116 cells

MDM2 is a critical negative regulator of the p53 tumor suppressor protein. Recently, nutlins, small-molecule antagonists of MDM2, have been developed to inhibit the p53-MDM2 interaction and activate p53 signaling. The expressions of DR4 and DR5, Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, are regulated by p53. In this study, the combined effects of nutlin-3 and TRAIL on apoptosis were investigated in HOS and HCT116 cells, which express wild-type p53. Nutlin-3 and TRAIL synergistically enhanced apoptosis owing to their intrinsic and extrinsic pathway signals, respectively. The increase in the Bid expression level and the decrease in the expression levels of anti-apoptotic proteins, c-FLIP and XIAP, were involved in this apoptosis enhancement. Furthermore, nutlin-3 activated the DR5 promoter and increased the expression levels of DR5 at mRNA and protein levels. These results indicate that the combination, treated with nutlin-3 and TRAIL, is useful for apoptosis induction in malignant cells expressing wild-type p53.     

Delphinidin sensitizes prostate cancer cells to TRAIL-induced apoptosis,by inducing DR5 and causing caspase-mediated HDAC3 cleavage

TRAIL can induce apoptosis in some cancer cells and is an immune effector in the surveillance and elimination of developing tumors. Yes, some cancers are resistant to TRAIL. Delphinidin, a polyphenolic compound contained in brightly colored fruits and vegetables, has anti-inflammatory, anti-oxidant, and anti-tumorigenic activities. Here we showed that delphinidin sensitized TRAIL-resistant human prostate cancer cells to undergo apoptosis. Cells treated with delphinidin and TRAIL activated the extrinsic and intrinsic pathways of caspase activation. TRAIL-induced apoptosis in prostate cancer cells pretreated with delphinidin was dependent on death receptor 5 (DR5) and downstream cleavage of histone deacetylase 3 (HDAC3). In conclusion, delphinidin sensitizes prostate cancer cells to TRAIL-induced apoptosis by inducing DR5, thus causing caspase-mediated HDAC3 cleavage. Our data reveal a potential way of chemoprevention of prostate cancer by enabling TRAIL-mediated apoptosis.     

Nutlin-3 preferentially sensitises wild-type p53-expressing cancer cells to DR5-selective TRAIL over rhTRAIL

Background:

Tumour cell-selective activation of apoptosis by recombinant human TNF-related apoptosis-inducing ligand (rhTRAIL) is enhanced through co-activation of p53 by chemotherapeutic drugs. The novel anticancer agent nutlin-3 provides a promising alternative for p53 activation by disrupting the interaction between p53 and its negative feedback regulator MDM2.

Methods:

We examined whether nutlin-3 enhances apoptosis induction by rhTRAIL and the DR5-selective TRAIL variant D269H/E195R in wild-type p53-expressing ovarian, colon and lung cancer cell lines and in an ex vivo model of human ovarian cancer.

Results:

Nutlin-3 enhanced p53, p21, MDM2 and DR5 surface expression. Although nutlin-3 did not induce apoptosis, it preferentially enhanced D269H/E195R-induced apoptosis over rhTRAIL. Combination treatment potentiated the cleavage of caspases 8, 9, 3 and PARP. P53 and MDM2 siRNA experiments showed that this enhanced apoptotic effect was mediated by wild-type p53. Indeed, nutlin-3 did not enhance rhTRAIL-induced apoptosis in OVCAR-3 cells harbouring mutant p53. Addition of the chemotherapeutic drug cisplatin to the combination further increased p53 and DR5 levels and rhTRAIL- and D269H/E195R-induced apoptosis. As a proof of concept, we show that the combination of D269H/E195R, nutlin-3 and cisplatin induced massive apoptosis in ex vivo tissue slices of primary human ovarian cancers.

Conclusion:

Nutlin-3 is a potent enhancer of D269H/E195R-induced apoptosis in wild-type p53-expressing cancer cells. Addition of DNA-damaging agents such as cisplatin further enhances DR5-mediated apoptosis.     

Low-dose 5-fluorouracil sensitizes HepG2 cells to TRAIL through TRAIL receptor DR5 and survivin-dependent mechanisms

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising candidate for cancer treatment due to its highly selective apoptosis-inducing action on tumour cells without harming normal cells. However, because of TRAIL resistance by some cancer cells, combined treatment with sensitizing agents is required to enhance the anticancer potential of TRAIL. In the present study, we investigated the sensitizing effect of 5-fluorouracil (5-FU) on TRAIL-induced apoptosis in TRAIL-resistant HepG2 hepatocarcinoma cells. The results show that 5-FU pretreatment could sensitize HepG2 cells to TRAIL-mediated apoptosis. The enhanced induction of cell death by the 5-FU/TRAIL combination was mediated by DR5 up-regulation and survivin down-regulation. Furthermore, this combination treatment significantly inhibited the growth of human xenografts in vivo. In conclusion, this study demonstrates that the combination of a sensitizing agent and TRAIL may be a novel and effective therapeutic regimen for treating human hepatocellular carcinoma.     

IRX5 promotes colorectal cancer metastasis by negatively regulating the core components of the RHOA pathway

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide. As tumor metastasis is the leading cause of death in patients with CRC, it is important to elucidate the molecular mechanisms that drive CRC metastasis. Studies have shown a close relationship between Iroquois homeobox (IRX) family genes and multiple cancers, while the mechanism by which IRX5 promotes CRC metastasis is unclear. Therefore, we focused on the involvement of IRX5 in CRC metastasis. In this study, analyses of clinical data indicated that the expression of IRX5 was coincided with metastatic colorectal tumors tissues and was negatively correlated with the overall survival of patients with CRC. Functional analysis showed that IRX5 promoted the migration and invasion of CRC cells, accompanied by a large number of cellular protrusions. IRX5‐overexpressing cells were more likely to form metastatic tumors in nude mice. Further analysis demonstrated that the core components of the RHOA/ROCK1/LIMK1 pathway were significantly inhibited in IRX5‐overexpressing cells. Overexpression of LIMK1 effectively reversed the enhanced cellular motility caused by IRX5 overexpression. Moreover, we found that high levels of IRX5 in intestinal tissues were correlated with the inflammatory response. IRX5 was significantly increased in azoxymethane/dextran sodium sulfate intestinal tissue of mice and IRX5‐overexpressing may also enhance chemokines CXCL1 and CXCL8. In summary, our findings suggested that IRX5 promoted CRC metastasis by inhibiting the RHOA‐ROCK1‐LIMK1 axis, which correlates with a poor prognosis.     

间变性星形细胞瘤中DR4及DR5的表达

目的研究肿瘤坏死因子相关凋亡诱导配体(TRAIL)的死亡受体(death receptor,DR)DR4和DR5在间变性星形细胞瘤中的表达,并探讨其临床意义.方法联合采用免疫组化和原位杂交方法检测24间变性星形细胞瘤和16例正常脑组织中DR的表达.结果免疫组化染色显示,24例间变性星形细胞瘤均大量表达死亡受体DR4和DR5,而16例正常脑组织中7例(43.8%)表达DR4,5例(31.3%)表达DR5.间变性星形细胞瘤组织中DR蛋白的表达显著高于正常脑组织中DR蛋白的表达,两者差异有显著性(P<0.01).原位杂交显示,DR在全部24例间变性星形细胞瘤组织和大部分正常脑组织中均呈强阳性表达,二者差异无显著性(P>0.05).结论间变性星形细胞瘤细胞中普遍存在DR的高表达,这可能为间变性星形细胞瘤的凋亡诱导治疗提供新的靶点.DR蛋白在正常脑组织和间变性星形细胞瘤中的表达差异,可能是TRAIL选择性诱导凋亡的机制之一.     

Simvastatin inhibition of mevalonate pathway induces apoptosis in human breast cancer cells via activation of JNK/CHOP/DR5 signaling pathway

Simvastatin (SVA) was shown to up-regulate expression of death receptor-5 (DR5), CCAAT/enhancer binding protein homologous protein (CHOP) and phosphorylated c-Jun N-terminal kinase (pJNK) in human breast cancer cell lines. siRNA knockdown of DR5, CHOP or JNK significantly blocked SVA-induced apoptosis, demonstrating the importance of JNK/CHOP/DR5 signaling pathway in SVA-induced apoptosis. Exogenous addition of either mevalonate or geranylgeranyl pyrophosphate (GGPP) inhibited SVA activation of JNK/CHOP/DR5 pro-apoptotic pathway, indicating that activation of JNK/CHOP/DR5 pro-apoptotic pathway is dependent on SVA inhibition of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase and its intermediate GGPP. Data provide novel insight into better understanding the anticancer mechanisms of SVA.     

MiRNA-1469 promotes lung cancer cells apoptosis through targeting STAT5a

MicroRNAs play key roles in cell growth, differentiation, and apoptosis. In this study, we described the regulation and function of miR-1469 in apoptosis of lung cancer cells (A549 and NCI-H1650). Expression analysis verified that miR-1469 expression significantly increased in apoptotic cells. Overexpression of miR-1469 in lung cancer cells increased cell apoptosis induced by etoposide. Additionally, we identified that Stat5a is a downstream target of miR-1469, which can bind directly to the 3’-untranslated region of the Stat5a, subsequently reducing both the mRNA and protein levels of Stat5a. Finally, co-expression of miR-1469 and Stat5a in A549 and NCI-H1650 cells partially abrogated the effect of miR-1469 on cell apoptosis. Our results show that miR-1469 functions as an apoptosis enhancer to regulate lung cancer apoptosis through targeting Stat5a and may become a critical therapeutic target in lung cancer.