TRAIL receptor-mediated JNK activation and Bim phosphorylation critically regulate Fas-mediated liver damage and lethality

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family with potent apoptosis-inducing properties in tumor cells. In particular, TRAIL strongly synergizes with conventional chemotherapeutic drugs to induce tumor cell death. Thus, TRAIL has been proposed as a promising future cancer therapy. Little, however, is known regarding what the role of TRAIL is in normal untransformed cells and whether therapeutic administration of TRAIL, alone or in combination with other apoptotic triggers, may cause tissue damage. In this study, we investigated the role of TRAIL in Fas-induced (CD95/Apo-1-induced) hepatocyte apoptosis and liver damage. While TRAIL alone failed to induce apoptosis in isolated murine hepatocytes, it strongly amplified Fas-induced cell death. Importantly, endogenous TRAIL was found to critically regulate anti-Fas antibody-induced hepatocyte apoptosis, liver damage, and associated lethality in vivo. TRAIL enhanced anti-Fas-induced hepatocyte apoptosis through the activation of JNK and its downstream substrate, the proapoptotic Bcl-2 homolog Bim. Consistently, TRAIL- and Bim-deficient mice and wild-type mice treated with a JNK inhibitor were protected against anti-Fas-induced liver damage. We conclude that TRAIL and Bim are important response modifiers of hepatocyte apoptosis and identify liver damage and lethality as a possible risk of TRAIL-based tumor therapy.     

Normal thymocyte negative selection in TRAIL-deficient mice

The molecular basis of thymocyte negative selection, which plays a critical role in establishing and maintaining immunological tolerance, is not yet resolved. In particular, the importance of the death receptor subgroup of the tumor necrosis factor (TNF)-family has been the subject of many investigations, with equivocal results. A recent report suggested that TRAIL was a critical factor in this process, a result that does not fit well with previous studies that excluded a role for the FADD-caspase 8 pathway, which is essential for TRAIL and Fas ligand (FasL) signaling, in negative selection. We have investigated intrathymic negative selection of TRAIL-deficient thymocytes, using four well-established models, including antibody-mediated TCR/CD3 ligation in vitro, stimulation with endogenous superantigen in vitro and in vivo, and treatment with exogenous superantigen in vitro. We were unable to demonstrate a role for TRAIL signaling in any of these models, suggesting that this pathway is not a critical factor for thymocyte negative selection.     

TRAIL-expressing T cells induce apoptosis of vascular smooth muscle cells in the atherosclerotic plaque

Acute coronary syndromes (ACS) are precipitated by a rupture of the atherosclerotic plaque, often at the site of T cell and macrophage infiltration. Here, we show that plaque-infiltrating CD4 T cells effectively kill vascular smooth muscle cells (VSMC). VSMCs sensitive to T cell-mediated killing express the death receptor DR5 (TNF-related apoptosis-inducing ligand [TRAIL] receptor 2), and anti-TRAIL and anti-DR5 antibodies block T cell-mediated apoptosis. CD4 T cells that express TRAIL upon stimulation are expanded in patients with ACS and more effectively induce VSMC apoptosis. Adoptive transfer of plaque-derived CD4 T cells into immunodeficient mice that are engrafted with human atherosclerotic plaque results in apoptosis of VSMCs, which was prevented by coadministration of anti-TRAIL antibody. These data identify that the death pathway is triggered by TRAIL-producing CD4 T cells as a direct mechanism of VSMC apoptosis, a process which may lead to plaque destabilization.     

Atrial natriuretic peptide promotes uterine decidualization and a TRAIL-dependent mechanism in spiral artery remodeling

Atrial natriuretic peptide (ANP) is an important hormone in cardiovascular biology. It is activated by the protease corin. In pregnancy, ANP and corin promote uterine spiral artery remodeling, but the underlying mechanism remains unknown. Here we report an ANP function in uterine decidualization and TNF-related apoptosis-inducing ligand–dependent (TRAIL-dependent) death in spiral arterial smooth muscle cells (SMCs) and endothelial cells (ECs). In ANP- or corin-deficient mice, uterine decidualization markers and TRAIL expression were decreased, whereas in cultured human endometrial stromal cells (HESCs), ANP increased decidualization and TRAIL expression. In uterine spiral arteries from pregnant wild-type mice, SMC and EC loss occurred sequentially before trophoblast invasion. In culture, TRAIL from decidualized HESCs induced apoptosis in uterine SMCs, but not in ECs with low TRAIL receptor expression. Subsequently, cyclophilin B was identified from apoptotic SMCs that upregulated endothelial TRAIL receptor and caused apoptosis in ECs. These results indicate that ANP promotes decidualization and TRAIL expression in endometrial stromal cells, contributing to sequential events in remodeling of spiral arteries, including SMC death and cyclophilin B release, which in turn induces TRAIL receptor expression and apoptosis in ECs.     

肝细胞生长因子在肿瘤坏死因子相关凋亡诱导配体作用下对原代肝星状细胞增殖及凋亡的影响

背景:活化的肝星状细胞是肝纤维化的关键因素,研究表明肝细胞生长因子能促进星状细胞凋亡,其具体机制可能与增强肿瘤坏死因子相关凋亡诱导配体(TRAIL)诱导星状细胞凋亡有关。目的:观察肿瘤坏死因子相关凋亡诱导配体作用下,肝细胞生长因子对原代肝星状细胞增殖、凋亡的影响并初步探讨其可能机制。方法:将SD大鼠原代肝星状细胞复苏、传代,细胞增殖明显时用于实验。实验分为4组:空白对照组为单纯肝星状细胞培养;肝细胞生长因子组:将100μg/L肝细胞生长因子作用于肝星状细胞;TRAIL组:将2mg/L的TRAIL作用于肝星状细胞;肝细胞生长因子+TRAIL组:将肝细胞生长因子预先刺激肝星状细胞24h,再加入2mg/LTRAIL。结果与结论:MTT检测显示肝细胞生长因子及TRAIL分别在50～200μg/L、0.5～1.5mg/L各浓度下对肝星状细胞增殖抑制率无影响,TRAIL在2mg/L作用下对肝星状细胞有抑制作用。流式细胞仪检测肝细胞生长因子+TRAIL组的中晚期凋亡率明显高于空白对照组及肝细胞生长因子组(P<0.05);肝细胞生长因子+TRAIL组DR5荧光强度明显高于其他3组(P<0.01)。提示在TRAIL作用下,肝细胞生长因子能促进肝星状细胞的凋亡、抑制其增殖。可能与肝细胞生长因子上调活化肝星状细胞表面DR5表达有关。     

雌激素饥饿增强TRAIL诱导乳腺癌细胞凋亡

目的：探讨雌激素饥饿对肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导乳腺癌细胞MCF-7凋亡的影响及作用机制。方法：MCF-7细胞培养贴壁之后,用雌激素饥饿处理后加入TRAIL,用荧光染料Hoechst染色法检测细胞的凋亡,用细胞计数法检测细胞的存活。在雌激素饥饿处理MCF-7细胞后,收集对照和饥饿组蛋白用Westernblot法检测相关的蛋白表达。结果：单独使用雌激素饥饿处理或者单独使用TRAIL处理乳腺癌细胞MCF-7都能诱导细胞凋亡,但是它们诱导凋亡的活性较小,两种方法联合使用可以极大地增加诱导细胞凋亡的活性（P〈0.001）。雌激素饥饿处理后的乳腺癌细胞,死亡受体5（DR5）表达上调。结论：乳腺癌细胞MCF-7对TRAIL敏感度不高,雌激素饥饿可以增加TRAIL诱导乳腺癌细胞凋亡的活性,DR5与雌激素饥饿诱导TRAIL活性增加相关。     

In vivo inhibition of Fas ligand-mediated killing by TR6, a Fas ligand decoy receptor.

TR6, a member of the tumor necrosis factor (TNF) receptor superfamily, has recently been shown to bind to Fas ligand (FasL) and inhibit FasL-mediated cell killing in vitro. In the current study, we demonstrate that TR6 can block the lethal activity of FasL in multiple in vitro systems, and extend this finding to an in vivo model of hepatitis. The binding of human TR6 to human FasL was verified with BIAcore chip technology. Human primary hepatocytes, HT-29 cells and Jurkat cells were assayed for viability to demonstrate TR6 inhibition of FasL-mediated cytotoxicity in vitro. Human TR6 was also shown to cross-react with membrane-bound mouse FasL, since the in vitro cytotoxic activity of L929 cells transfected with murine FasL was inhibited in the presence of human TR6. In vivo, FasL-induced acute, lethal, fulminant hepatic apoptosis resulting in death within 2 h of intravenous injection into Fas+ mice, but not Fas- MRL/lpr mice. Pretreatment of mice with TR6 blocked FasL-induced mortality, presumably by attenuating FasL-induced hepatic apoptosis. Thus, in both in vitro and in vivo systems, TR6 acts as a functional FasL decoy receptor and may be clinically useful in the treatment of hepatitis and other diseases associated with FasL-mediated tissue injury.     

Human dendritic cells mediate cellular apoptosis via tumor necrosis factor-related apoptosis-inducing ligand (TRAIL).

TRAIL (TNF-related apoptosis-inducing ligand) is a member of the TNF family that induces apoptosis in a variety of cancer cells. In this study, we demonstrate that human CD11c(+) blood dendritic cells (DCs) express TRAIL after stimulation with either interferon (IFN)-gamma or -alpha and acquire the ability to kill TRAIL-sensitive tumor cell targets but not TRAIL-resistant tumor cells or normal cell types. The DC-mediated apoptosis was TRAIL specific, as soluble TRAIL receptor blocked target cell death. Moreover, IFN-stimulated interleukin (IL)-3 receptor (R)alpha(+) blood precursor (pre-)DCs displayed minimal cytotoxicity toward the same target cells, demonstrating a clear functional difference between the CD11c(+) DC and IL-3Ralpha(+) pre-DC subsets. These results indicate that TRAIL may serve as an innate effector molecule on CD11c(+) DCs for the elimination of spontaneously arising tumor cells and suggest a means by which TRAIL-expressing DCs may regulate or eliminate T cells responding to antigen presented by the DCs.     

Chemotherapy and TRAIL-mediated colon cancer cell death: the roles of p53, TRAIL receptors, and c-FLIP

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has recently attracted attention as a potential therapeutic agent in the treatment of cancer. We assessed the roles of p53, TRAIL receptors, and cellular Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein (c-FLIP) in regulating the cytotoxic effects of recombinant TRAIL (rTRAIL) alone and in combination with chemotherapy [5-fluorouracil (5-FU), oxaliplatin, and irinotecan] in a panel of colon cancer cell lines. Using clonogenic survival and flow cytometric analyses, we showed that chemotherapy sensitized p53 wild-type, mutant, and null cell lines to TRAIL-mediated apoptosis. Although chemotherapy treatment did not modulate mRNA or cell surface expression of the TRAIL receptors death receptor 4, death receptor 5, decoy receptor 1, or decoy receptor 2, it was found to down-regulate expression of the caspase-8 inhibitor, c-FLIP. Stable overexpression of the long c-FLIP splice form but not the short form was found to inhibit chemotherapy/rTRAIL-induced apoptosis. Furthermore, siRNA-mediated down-regulation of c-FLIP, particularly the long form, was found to sensitize colon cancer cells to rTRAIL-induced apoptosis. In addition, treatment of a 5-FU-resistant cell line with 5-FU down-regulated c-FLIP expression and sensitized the chemotherapy-resistant cell line to rTRAIL. We conclude that TRAIL-targeted therapies may be used to enhance conventional chemotherapy regimens in colon cancer regardless of tumor p53 status. Furthermore, inhibition of c-FLIP may be a vital accessory strategy for the optimal use of TRAIL-targeted therapies.     

TRAIL-R deficiency in mice enhances lymph node metastasis without affecting primary tumor development

TRAIL is a promising anticancer agent due to its ability to selectively induce apoptosis in established tumor cell lines but not nontransformed cells. Herein, we demonstrate a role for the apoptosis-inducing TRAIL receptor (TRAIL-R) as a metastasis suppressor. Although mouse models employing tumor transplantation have shown that TRAIL can reduce tumor growth, autochthonous tumor models have generated conflicting results with respect to the physiological role of the TRAIL system during tumorigenesis. We used a multistage model of squamous cell carcinoma to examine the role of TRAIL-R throughout all steps of tumor development. DMBA/TPA-treated TRAIL-R-deficient mice showed neither an increase in number or growth rate of benign papillomas nor an increase in the rate of progression to squamous cell carcinoma. However, metastasis to lymph nodes was significantly enhanced, indicating a role for TRAIL-R specifically in the suppression of metastasis. We also found that adherent TRAIL-R-expressing skin carcinoma cells were TRAIL resistant in vitro but were sensitized to TRAIL upon detachment by inactivation of the ERK signaling pathway. As detachment from the primary tumor is an obligatory step in metastasis, this provides a possible mechanism by which TRAIL-R could inhibit metastasis. Hence, treatment of cancer patients with agonists of the apoptosis-inducing receptors for TRAIL may prove useful in reducing the incidence of metastasis.     

The NEDD8-activating enzyme inhibitor, MLN4924, cooperates with TRAIL to augment apoptosis through facilitating c-FLIP degradation in head and neck cancer cells

TNF-related apoptosis-inducing ligand (TRAIL) is a tumor-selective cytokine with potential anticancer activity and is currently under clinical testing. Head and neck squamous cell carcinoma (HNSCC), like other cancer types, exhibits varied sensitivity to TRAIL. MLN4924 is a newly developed investigational small molecule inhibitor of NEDD8-activating enzyme with potent anticancer activity. This study reveals a novel function of MLN4924 in synergizing with TRAIL to induce apoptosis in HNSCC cells. MLN4924 alone effectively inhibited the growth of HNSCC cells and induced apoptosis. When combined with TRAIL, synergistic effects on decreasing the survival and inducing apoptosis of HNSCC cells occurred. MLN4924 decreased c-FLIP levels without modulating death receptor 4 and death receptor 5 expression. Enforced expression of c-FLIP substantially attenuated MLN4924/TRAIL-induced apoptosis. Thus c-FLIP reduction plays an important role in mediating MLN4924/TRAIL-induced apoptosis. Moreover, MLN4924 decreased c-FLIP stability, increased c-FLIP ubiquitination, and facilitated c-FLIP degradation, suggesting that MLN4924 decreases c-FLIP levels through promoting its degradation. MLN4924 activated c-jun-NH(2)-kinase (JNK) signaling, evidenced by increased levels of phospho-c-Jun in MLN4924-treated cells. Chemical inhibition of JNK activation not only prevented MLN4924-induced c-FLIP reduction, but also inhibited MLN4924/TRAIL-induced apoptosis, suggesting that JNK activation mediates c-FLIP downregulation and subsequent enhancement of TRAIL-induced apoptosis by MLN4924. Because knockdown of NEDD8 failed to activate JNK signaling and downregulate c-FLIP, it is likely that MLN4924 reduces c-FLIP levels and enhances TRAIL-induced apoptosis independent of NEDD8 inhibition.     

重组TRAIL抑制7402肝癌细胞生长的实验研究

目的　重组TRAIL对BALB/c裸鼠肝癌细胞皮下移植模型的抑瘤作用。方法　建立裸鼠 740 2肝癌细胞皮下移植瘤模型 ,纯化后的质粒DNA与PEI混合后经肌肉注射进行基因转染 ,体内验证重组蛋白的抑瘤活性 ,采用原位缺如末端标记 (TUNEL)法 ,进行肿瘤组织凋亡检测。结果　肿瘤体积测定显示TRAIL对肝癌生长有明显抑制作用 ,凋亡检测表明实验组镜下有蓝紫色凋亡细胞。结论　荷瘤小鼠经肌肉注射TRAIL质粒DNA后 ,能引起肿瘤细胞的凋亡 ,有效抑制 740 2肝癌细胞在裸鼠体内的生长。     

TRAIL/死亡受体5途径在缺氧再给氧诱导人肝细胞凋亡中的作用及相关机制

目的:研究肿瘤坏死因子相关凋亡诱导配体(TNF-related apoptosis-inducing ligand,TRAIL)/死亡受体5(Death receptor 5,DR5)途径在人肝细胞缺氧/再给氧(Hypoxia/reoxygenation,H/R)损伤中的作用,并探讨其作用机制。方法:在体外建立肝细胞H/R模型,模拟肝脏的缺血再灌注。H/R处理后,培养基中加入不同浓度外源性TRAIL蛋白,噻唑盐比色法(MTT)和流式细胞术检测细胞活力和凋亡率。半定量RT-PCR检测DR5mRNA的表达。结果:以正常人肝细胞为对照,H/R使人肝细胞的DR5 mRNA的表达上调,再给氧2小时达峰值,此后直至再给氧20小时维持在相对高的水平。单纯缺氧6小时不能引起肝细胞的大量凋亡。TRAIL诱导H/R处理后的肝细胞发生凋亡,并呈浓度依赖性。H/R大大增强TRAIL的肝毒性。结论:H/R使DR5在人肝细胞的表达上调,增加TRAIL的肝毒性。TRAIL/DR5途径可能在IRI诱导人肝细胞凋亡过程中发挥重要作用。     

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an inhibitor of autoimmune inflammation and cell cycle progression

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis of tumor cells but not normal cells; its role in normal nontransformed tissues is unknown. We report here that chronic blockade of TRAIL in mice exacerbated autoimmune arthritis, and that intraarticular TRAIL gene transfer ameliorated the disease. In vivo, TRAIL blockade led to profound hyperproliferation of synovial cells and arthritogenic lymphocytes and heightened the production of cytokines and autoantibodies. In vitro, TRAIL inhibited DNA synthesis and prevented cell cycle progression of lymphocytes. Interestingly, TRAIL had no effect on apoptosis of inflammatory cells either in vivo or in vitro. Thus, unlike other members of the tumor necrosis factor superfamily, TRAIL is a prototype inhibitor protein that inhibits autoimmune inflammation by blocking cell cycle progression.     

Synergistic enhancement of TRAIL- and tumor necrosis factor alpha-induced cell death by a phenoxazine derivative

2-Amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1) has been developed as a novel phenoxazine derivative having an anticancer activity on a variety of cancer cell lines as well as transplanted tumors in mice with minimal toxicity to normal cells. We examined the effects of Phx-1 on Jurkat cells, a human T cell line. Phx-1 inhibited proliferation of the cells in a dose-dependent manner but hardly induced cell death, suggesting that Phx-1 acts primarily as an antiproliferative reagent but not as a cytocidal drug. Phx-1 enhanced tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptotic cell death about 100-fold. Tumor necrosis factor alpha, which alone does not induce cell death of Jurkat cells, caused apoptosis in combination with Phx-1. These enhancements of cell death were not due to up-regulation of the death receptors. Phx-1 decreased serum-induced phosphorylation of Akt, a kinase involved in cell proliferation and survival, and inhibited complex III of mitochondrial respiratory chain. Considering that both TRAIL and Phx-1 have only marginal cytotoxicity to most normal cells, Phx-1 may provide an ideal combination for cancer therapy with TRAIL.     

TRAIL limits excessive host immune responses in bacterial meningitis

Apart from potential roles in anti-tumor surveillance, the TNF-related apoptosis-inducing ligand (TRAIL) has important regulatory functions in the host immune response. We studied antiinflammatory effects of endogenous and recombinant TRAIL (rTRAIL) in experimental meningitis. Following intrathecal application of pneumococcal cell wall, a TLR2 ligand, we found prolonged inflammation, augmented clinical impairment, and increased apoptosis in the hippocampus of TRAIL^–/– mice. Administration of rTRAIL into the subarachnoid space of TRAIL^–/– mice or reconstitution of hematopoiesis with wild-type bone marrow cells reversed these effects, suggesting an autoregulatory role of TRAIL within the infiltrating leukocyte population. Importantly, intrathecal application of rTRAIL in wild-type mice with meningitis also decreased inflammation and apoptosis. Moreover, patients suffering from bacterial meningitis showed increased intrathecal synthesis of TRAIL. Our findings provide what we believe is the first evidence that TRAIL may act as a negative regulator of acute CNS inflammation. The ability of TRAIL to modify inflammatory responses and to reduce neuronal cell death in meningitis suggests that it may be used as a novel antiinflammatory agent in invasive infections.     

2-methoxy-5-amino-N-hydroxybenzamide sensitizes colon cancer cells to TRAIL-induced apoptosis by regulating death receptor 5 and survivin expression

TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis is a crucial event in the control of tumor growth. However, many cancer cells, including colon cancer cells, are resistant to TRAIL-driven cell death. We have recently shown that 2-methoxy-5-amino-N-hydroxybenzamide (herein termed 2-14), a novel derivative of mesalamine, induces endoplasmic reticulum stress in colon cancer cells. Because endoplasmic reticulum stress-induced signals regulate the expression of molecules involved in TRAIL-driven apoptosis, we examined whether 2-14 makes colon cancer cells sensitive to TRAIL. Colon cancer cells were cultured with 2-14 and/or TRAIL. Death receptor (DR) 4/DR5 were analyzed by real-time PCR and flow cytometry. TRAIL pathway-associated proteins and extracellular signal-regulated kinase (ERK) were assessed by Western blotting. The in vivo capability of 2-14 to sensitize colon cancer cells to TRAIL-induced apoptosis was evaluated in a syngenic colon cancer model in which CT26-derived grafts were induced in mice. 2-14 promoted ERK-dependent induction of DR5, thereby enhancing TRAIL-mediated caspase-8 activation and apoptosis. Analysis of TRAIL-related pro- and antiapoptotic factors and functional studies revealed that survivin is involved in the protection of colon cancer cells against TRAIL-driven apoptosis. Notably, 2-14 enhanced ubiquitination and proteasome-mediated degradation of survivin. These data were confirmed in a murine model of TRAIL-resistant colon cancer in which 2-14 upregulated DR5, reduced survivin expression, and synergized with TRAIL in inhibiting tumor growth. Similarly, intraperitoneal administration of 2-14 to mice upregulated DR5 and downregulated survivin in a model of colitis-associated colon cancer. These findings indicate that 2-14 acts as a sensitizer for TRAIL-induced apoptosis and suggest that 2-14 can be useful in the therapy for TRAIL-resistant colon cancer.     

Gene therapy with TRAIL against renal cell carcinoma

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in cancer cells. However, TRAIL is not toxic against most normal cells. We have accordingly examined by in vivo electroporation whether TRAIL induces apoptosis in renal cell carcinoma. In addition, combination treatment with TRAIL and 5-fluorouracil (5-FU) against renal cell carcinoma was also investigated. The NC65 renal cell carcinoma line was used as a target. pCAGGS TRAIL was injected into the NC65 tumors in the right flanks of severe combined immunodeficient mice. Tumors were pulsed with the CUY21 electroporator. Electroporation was done once on day 0 or thrice on days 0, 2, and 4. Apoptosis was determined by terminal deoxyribonucleotide transferase-mediated nick-end labeling assay. When TRAIL gene therapy using in vivo i.t. electroporation was done once only, the growth of NC65 tumors was not inhibited. However, when TRAIL gene therapy was done thrice, growth suppression of the NC65 tumors was observed. Transfection of the TRAIL gene by in vivo electroporation induced apoptosis in NC65 tumors. When NC65 cells were treated with TRAIL gene therapy in combination with 5-FU, stronger growth suppression was obtained. TRAIL gene therapy did not induce liver dysfunction in severe combined immunodeficient mice. This study shows that TRAIL gene therapy induced growth suppression and apoptosis in NC65 tumors without severe side effects, and that combination treatment of NC65 cells with TRAIL gene therapy and 5-FU resulted in higher antitumor activity. These findings suggest that TRAIL gene therapy and/or 5-FU may be effective against renal cell carcinoma without harmful toxic effects.     

Enhanced anticancer effect of the combination of cisplatin and TRAIL in triple-negative breast tumor cells

Women with triple-negative breast cancer (TNBC) have a worse prognosis compared with other breast cancer subtypes. Hormonal or Herceptin-based therapies were found to be ineffective because of the loss of target receptors, such as ER, PR, and HER-2 amplification. Conventional chemo- and/ or radiation therapy also seems to have limited efficacy in TNBC patients. We studied the effects of cisplatin plus TRAIL on 1 normal and 2 TNBC cells in vitro. The in vitro studies indicate that cisplatin plus TRAIL significantly enhanced cell death in TNBC cell lines CRL2335 and MDA-MB-468 by approximately 60%-70% compared with approximately 10%-15% in CRL8799 normal breast cell line. Treatment with cisplatin/TRAIL also inhibited the expression of EGFR, p63, survivin, Bcl-2, and Bcl-xL in TNBC cells. Specific inhibition of EGFR and/or p63 protein in TNBC cells by small interfering RNA (siRNA) does not increase TRAIL-induced apoptosis. However, inhibition of survivin by siRNA enhances TRAIL-induced apoptosis. These observations suggested the possibility that survivin played an important role in cisplatin plus TRAIL-induced apoptosis in TNBC cells. In vivo experiments, treatment of mice with cisplatin plus TRAIL resulted in a significant inhibition of CRL2335 xenograft tumors compared with untreated control tumors. Taken together the data suggest that cisplatin plus TRAIL treatment have the potential of providing a new strategy for improving the therapeutic outcome in TNBC patients.     

Monocyte-mediated tumoricidal activity via the tumor necrosis factor-related cytokine, TRAIL

TRAIL (tumor necrosis factor [TNF]-related apoptosis-inducing ligand) is a molecule that displays potent antitumor activity against selected targets. The results presented here demonstrate that human monocytes rapidly express TRAIL, but not Fas ligand or TNF, after activation with interferon (IFN)-gamma or -alpha and acquire the ability to kill tumor cells. Monocyte-mediated tumor cell apoptosis was TRAIL specific, as it could be inhibited with soluble TRAIL receptor. Moreover, IFN stimulation caused a concomitant loss of TRAIL receptor 2 expression, which coincides with monocyte acquisition of resistance to TRAIL-mediated apoptosis. These results define a novel mechanism of monocyte-induced cell cytotoxicity that requires TRAIL, and suggest that TRAIL is a key effector molecule in antitumor activity in vivo.