Transformation by oncogenic RAS sensitizes human colon cells to TRAIL-induced apoptosis by up-regulating death receptor 4 and death receptor 5 through a MEK-dependent pathway

The effect of microbial composition and proteomic on improvement of functional constipation by Chrysanthemum morifolium polysaccharide

In this paper, SD rat constipation model was established with loperamide hydrochloride to study the effect of Chrysanthemum morifolium polysaccharide on the improvement of functional constipation, and the mechanism of improving constipation was investigated with the proteomics and intestinal flora. The results showed that the HD group of C. morifolium polysaccharide could significantly increase the levels of water content of stool pellets, small intestine propulsion rate, gastrin (MTL), gastrin (GAS) and substance P (SP), decrease the level of growth inhibitor (SS) and improved gastrointestinal motility in rats. Gut microbial studies showed that C. morifolium polysaccharide could significantly increase species abundance and flora diversity and improve flora structure. The relative abundance of Lactobacillus and Romboutsia increased, while the relative abundance of Lachnospiraceae_NK4A136_group and Roseburia decreased compared with the MC group. Proteomics studies suggested that C. morifolium polysaccharides could reduce intestinal lesions, enhance intestinal homeostasis, increase amino acid uptake, promote intestinal motility and relieve constipation by regulating the expression of RAS, FABP1 and SLC1A5 proteins.

CD13 inhibition augments DR4-induced tumor cell death in a p-ERK1/2-independent manner

OBJECTIVE

Death receptor 4 (DR4; TRAIL-R1) critically mediates extrinsic apoptosis cascades via binding to TNF-related apoptosis-inducing ligand (TRAIL). However, intrinsic and/or acquired resistance are observed in the clinical application of TRAIL. The aim of this study was to investigate the function and molecular mechanism of CD13 in the TRAIL/DR4 pathway against tumor cells, and provide a new strategy for improving therapeutic efficacy or overcoming TRAIL-resistance.

METHODS

TRAIL protein was expressed as a secretory protein in a Pichia pastoris expression system and was isolated and purified by affinity chromatography. The cell viability and apoptosis were evaluated with MTT (thiazolyl blue tetrazolium bromide) assays and annexin V-FITC/PI staining with flow cytometry analysis, respectively. Western blot analysis was used to detect the levels of the indicated proteins in tumor cells. DR4 degradation or stability was examined with cycloheximide chase assays, and cell surface DR4 was assessed with flow cytometric analysis after staining with a FITC-conjugated antibody. The effects of cell migration were determined with Transwell and gelatin zymography assays. A xenograft nude mouse model was used to detect the anti-tumor effect in vivo, and the proliferation in tumor tissues was examined with immunohistochemical staining.

RESULTS

CD13 inhibition potently sensitized tumor cells to TRAIL-induced killing, including proliferation inhibition, increased apoptosis, and migration suppression. In addition, the inhibition of CD13 elevated both total cellular expression and cell surface DR4 through stabilizing DR4 by suppressing its degradation. DR4 siRNA attenuated the enhanced anti-tumor effects of TRAIL plus CD13 inhibition. Interestingly, these phenomena were p-ERK1/2 independent, although p-ERK1/2 down-regulation was tightly correlated with the cooperation of TRAIL and CD13 inhibition. Moreover, a synergistic decrease in tumor growth was surprisingly achieved in the xenograft model by treatment of TRAIL with a CD13 inhibitor (**P < 0.01, CDI = 0.47).

CONCLUSIONS

CD13 inhibition cooperates with TRAIL in enhancing DR4-mediated cell death, through the up-regulation and stabilization of DR4 in a p-ERK1/2-independent manner. Thus CD13 inhibition has emerged as an effective strategy for TRAIL/DR4-based therapy.

The Dual Role of Macropinocytosis in Cancers: Promoting Growth and Inducing Methuosis to Participate in Anticancer Therapies as Targets

Macropinocytosis is an important mechanism of internalizing extracellular materials and dissolved molecules in eukaryotic cells. Macropinocytosis has a dual effect on cancer cells. On the one hand, cells expressing RAS genes (such as K-RAS, H-RAS) under the stress of nutrient deficiency can spontaneously produce constitutive macropinocytosis to promote the growth of cancer cells by internalization of extracellular nutrients (like proteins), receptors, and extracellular vesicles(EVs). On the other hand, abnormal expression of RAS genes and drug treatment (such as MOMIPP) can induce a novel cell death associated with hyperactivated macropinocytosis: methuosis. Based on the dual effect, there is immense potential for designing anticancer therapies that target macropinocytosis in cancer cells. In view of the fact that there has been little review of the dual effect of macropinocytosis in cancer cells, herein, we systematically review the general process of macropinocytosis, its specific manifestation in cancer cells, and its application in cancer treatment, including anticancer drug delivery and destruction of macropinocytosis. This review aims to serve as a reference for studying macropinocytosis in cancers and designing macropinocytosis-targeting anticancer drugs in the future.

Levamisole enhances DR4-independent apoptosis induced by TRAIL through inhibiting the activation of JNK in lung cancer

THE HEADINGS AIMS

Levamisole has anti-parasite and antitumor activities, but the anti-lung cancer mechanism has not been studied. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a promising drug because of the ability to selectively target cancer cells. However, the tolerance of cancer cells to TRAIL limits its antitumor activity. Other drugs combined with TRAIL need to be explored to enhance its antitumor activity. Based on the adjuvant anticancer effect of levamisole on anticancer drugs activity, the antitumor activity of levamisole combined with TRAIL will be investigated.

MATERIALS AND METHODS

In vitro and in vivo experiments were employed to investigate the anti-tumor activity. Flow-cytometry analysis, western blotting and siRNA transfection were used to explore the molecular mechanism.

KEY FINDINGS

Levamisole decreased the proliferation of lung cancer cells in vitro and in vivo and induced cell cycle arrest in G0/G1 phase. Besides, levamisole also enhanced TRAIL-induced DR4-independent apoptosis by inhibiting the phosphorylation of cJUN. A new cellular protective pathway LC3B-DR4/Erk was also disclosed, in which levamisole only increased the expression of LC3B and then activated the phosphorylation of Erk and increased the expression of DR4, while p-Erk and DR4 inter-regulated.

SIGNIFICANCE

Levamisole may be used as an adjuvant of TRAIL in treating lung cancer. The discovery of LC3B-DR4/Erk as a new protective pathway provides a new direction for sensitizing lung cancer cells to TRAIL.

Resistance to ERK1/2 pathway inhibitors; sweet spots, fitness deficits and drug addiction

MEK1/2 inhibitors are clinically approved for the treatment of BRAF-mutant melanoma, where they are used in combination with BRAF inhibitors, and are undergoing evaluation in other malignancies. Acquired resistance to MEK1/2 inhibitors, including selumetinib (AZD6244/ARRY-142866), can arise through amplification of BRAFV600E or KRASG13D to reinstate ERK1/2 signalling. We have found that BRAFV600E amplification and selumetinib resistance are fully reversible following drug withdrawal. This is because resistant cells with BRAFV600E amplification become addicted to selumetinib to maintain a precise level of ERK1/2 signalling (2%-3% of total ERK1/2 active), that is optimal for cell proliferation and survival. Selumetinib withdrawal drives ERK1/2 activation outside of this critical "sweet spot" (~20%-30% of ERK1/2 active) resulting in a p57KIP2-dependent G1 cell cycle arrest and senescence or expression of NOXA and cell death with features of autophagy; these terminal responses select against cells with amplified BRAFV600E. ERK1/2-dependent p57KIP2 expression is required for loss of BRAFV600E amplification and determines the rate of reversal of selumetinib resistance. Growth of selumetinib-resistant cells with BRAFV600E amplification as tumour xenografts also requires the presence of selumetinib to "clamp" ERK1/2 activity within the sweet spot. Thus, BRAFV600E amplification confers a selective disadvantage or "fitness deficit" during drug withdrawal, providing a rationale for intermittent dosing to forestall resistance. Remarkably, selumetinib resistance driven by KRASG13D amplification/upregulation is not reversible. In these cells ERK1/2 reactivation does not inhibit proliferation but drives a ZEB1-dependent epithelial-to-mesenchymal transition that increases cell motility and promotes resistance to traditional chemotherapy agents. Our results reveal that the emergence of drug-addicted, MEKi-resistant cells, and the opportunity this may afford for intermittent dosing schedules ("drug holidays"), may be determined by the nature of the amplified driving oncogene (BRAFV600E vs. KRASG13D), further exemplifying the difficulties of targeting KRAS mutant tumour cells.

Interleukin-4 Enhances the Sensitivity of Human Monocytes to Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Through Upregulation of Death Receptor 4

Interleukin (IL)-4 is generally thought to promote tumor cell growth and inhibit apoptosis. However, its role in characteristics of monocytic leukemia cells was rarely reported. In this study, we assessed the role of IL-4 in tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitivity of human monocytes. After incubation with IL-4 for 24 h, death receptor 4 (DR4) was significantly increased without downregulation of TRAIL decoy receptors and antiapoptotic proteins in THP-1 monocytes, and human primary monocytes and U-937 cells also exhibited increased TRAIL-induced apoptosis compared with control. Enhancement of TRAIL-mediated apoptosis by IL-4 was blocked by anti-DR4-neutralizing antibodies. Both upregulation of DR4 and enhancement of TRAIL-mediated apoptosis by IL-4 could be blocked by inhibitors of Janus kinase (JAK)/signal transducer and activator of transcription (STAT), phosphoinositol 3-kinase (PI3K)/Akt, and extracellular signal-regulated kinase to varying degrees. Thus, our data demonstrated a novel effect on TRAIL sensitivity on monocytes and monocytic leukemia cells of IL-4 and suggested that it may be necessary to reconsider the impact of current therapies against IL-4, JAK/STAT, and PI3K/Akt pathways with regard to TRAIL sensitivity.

Effects of Decitabine on the proliferation of K562 cells and the expression of DR4 gene

Objective

To investigate the role of DR4 gene in the occurrence, development and prognosis of acute myeloid leukemia (AML), find a new regulatory gene of Decitabine for the treatment of AML, namely DR4 gene, and explore the molecular mechanism of AML in the treatment of AML.

Methods

The methylation level and the mRNA expression level of DR4 gene promoters of bone marrow mononuclear cells in 122 patients with newly diagnosed AML and 24 patients with iron deficiency anemia (IDA) were detected using Methylation specific PCR (MS-PCR) and Q-RT-PCR, respectively, and a correlation analysis of them was conducted. The effects of Decitabine on the proliferation of K562 cells were detected using CCK-8 assay. Then, the effects of Decitabine on the methylation level and the mRNA expression level of DR4 genes of K562 cells treated with Decitabine were detected using MS-PCR and Q-RT-PCR, respectively. The effects of Decitabine on the cell cycle and apoptosis of K562 cells were detected using flow cytometry.

Results

Compared with the control group, the methylation level (P = .002) of DR4 genes of bone marrow mononuclear cells in patients with newly diagnosed AML was high. The methylation level (P = .01) of DR4 genes of bone marrow mononuclear cells in patients of the positive group of enlargement of liver, spleen and lymph node was lower than that of the negative group, and the methylation level (P = .006) of DR4 genes in patients of the high risk group of clinical stage was lower than that of the low risk group, and the methylation level (P = .03) of DR4 genes in patients of the group where patients did not achieve complete remission (CR1) after a course of induction chemotherapy was lower than that of the group where patients achieved complete remission (CR1) after a course of induction chemotherapy. There was a significant negative correlation (P < .01) between the methylation level and the mRNA expression level of DR4 genes of bone marrow mononuclear cells in 122 patients with newly diagnosed AML. After the K562 cells were treated with Decitabine for 48 h, the methylation level of DR4 gene promoters gradually decreased, while the mRNA expression level of DR4 genes gradually increased, both of which showed a concentration-dependent relationship. After the K562 cells were treated with 5 µmol/L Decitabine for 48 h, the K562 cells in G0/G1 phase and G2/M phase increased significantly, and the K562 cells in S phase decreased significantly.

Conclusion

DR4 gene played an important role in the occurrence and development of AML. Decitabine can effectively inhibit the proliferation of K562 cells, which probably partly because it can terminate the methylation effect of DR4 gene promoters and restore the mRNA expression of DR4 genes.

Targeting the metabolic pathway of human colon cancer overcomes resistance to TRAIL-induced apoptosis

Colon cancer is a leading cause of cancer-related mortality for which targeted therapy is needed; however, trials using apoptosis-inducing ligand monotherapy to overcome resistance to apoptosis have not shown clinical responses. Since colon cancer cells selectively uptake and rapidly metabolize glucose, a property utilized for clinical staging, we investigated mechanisms to alter glucose metabolism in order to selectively target the cancer cells and to overcome evasion of apoptosis. We demonstrate TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) resistance in the majority of human colon cancers tested and utilize the glucose analog 2-deoxy-d-glucose to sensitize TRAIL-resistant gastrointestinal adenocarcinoma cells, and not normal gastrointestinal epithelial cells, to TRAIL-induced apoptosis through enhanced death receptor 5 expression, downstream modulation of MAPK signaling and subsequent miRNA expression modulation by increasing the expression of miR-494 via MEK activation. Further, established human colon cancer xenografts treated with this strategy experience anti-tumor responses. These findings in colon adenocarcinoma support further investigation of manipulation of cellular energetics to selectively overcome resistance to apoptosis and to impart tumor regressions in established colon cancer tumors.

Macropinocytosis Exploitation by Cancers and Cancer Therapeutics

Macropinocytosis has long been known as a primary method for cellular intake of fluid-phase and membrane-bound bulk cargo. This review seeks to re-examine the latest studies to emphasize how cancers exploit macropinocytosis to further their tumorigenesis, including details in how macropinocytosis can be adapted to serve diverse functions. Furthermore, this review will also cover the latest endeavors in targeting macropinocytosis as an avenue for novel therapeutics.

ERK mediated upregulation of death receptor 5 overcomes the lack of p53 functionality in the diaminothiazole DAT1 induced apoptosis in colon cancer models: efficiency of DAT1 in Ras-Raf mutated cells

Background

p53 is a tumour suppressor protein that plays a key role in many steps of apoptosis, and malfunctioning of this transcription factor leads to tumorigenesis. Prognosis of many tumours also depends upon the p53 status. Most of the clinically used anticancer compounds activate p53 dependent pathway of apoptosis and hence require p53 for their mechanism of action. Further, Ras/Raf/MEK/ERK axis is an important signaling pathway activated in many cancers. Dependence of diaminothiazoles, compounds that have gained importance recently due to their anticancer and anti angiogenic activities, were tested in cancer models with varying p53 or Ras/Raf mutational status.

Methods

In this study we have used p53 mutated and knock out colon cancer cells and xenograft tumours to study the role of p53 in apoptosis mediated by diaminothiazoles. Colon cancer cell lines with varying mutational status for Ras or Raf were also used. We have also examined the toxicity and in vivo efficacy of a lead diaminothiazole 4-Amino-5-benzoyl-2-(4-methoxy phenylamino)thiazole (DAT1) in colon cancer xenografts.

Results

We have found that DAT1 is active in both in vitro and in vivo models with nonfunctional p53. Earlier studies have shown that extrinsic pathway plays major role in DAT1 mediated apoptosis. In this study, we have found that DAT1 is causing p53 independent upregulation of the death receptor 5 by activating the Ras/Raf/MEK/ERK signaling pathway both in wild type and p53 suppressed colon cancer cells. These findings are also confirmed by the in vivo results. Further, DAT1 is more efficient to induce apoptosis in colon cancer cells with mutated Ras or Raf.

Conclusions

Minimal toxicity in both acute and subacute studies along with the in vitro and in vivo efficacy of DAT1 in cancers with both wild type and nonfunctional p53 place it as a highly beneficial candidate for cancer chemotherapy. Besides, efficiency in cancer cells with mutations in the Ras oncoprotein or its downstream kinase Raf raise interest in diaminothiazole class of compounds for further follow-up.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0505-7) contains supplementary material, which is available to authorized users.

Ghrelin induces colon cancer cell proliferation through the GHS-R, Ras, PI3K, Akt, and mTOR signaling pathways

Colon cancer is the third most common malignancy worldwide. Recently, some interesting associations between ghrelin and cancer were reported, and it may participate in colon cancer development. In the present report, we explored the role of the growth hormone secretagogue receptor (GHS-R), Ras, phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR) pathways in the ghrelin-induced proliferation of human colon cancer cells. Ghrelin-caused HT-29 proliferation was reduced by [D-Lys3]-GHRP-6 (a GHS-R inhibitor). We also found that a dominant negative mutant of Ras (Ras DN), a PI3K inhibitor (LY 294002), an Akt DN, and an mTOR inhibitor (rapamycin) attenuated ghrelin-caused colon cancer cell proliferation. We found that ghrelin induced time-dependent increases in Ras activity. Moreover, ghrelin-mediated Akt Ser473 phosphorylation was attenuated by a Ras DN and LY 294002. Furthermore, a Ras DN, LY 294002, and an Akt DN all inhibited ghrelin-caused mTOR Ser2448 phosphorylation. These results indicate that the Ras/PI3K/Akt/mTOR cascade plays a critical role in ghrelin-induced colon cancer cell proliferation.

An RNA interference screen identifies new avenues for nephroprotection

Acute kidney injury is a major public health problem, which is commonly caused by renal ischemia and is associated with a high risk of mortality and long-term disability. Efforts to develop a treatment for this condition have met with very limited success. We used an RNA interference screen to identify genes (BCL2L14, BLOC1S2, C2ORF42, CPT1A, FBP1, GCNT3, RHOB, SCIN, TACR1, and TNFAIP6) whose suppression improves survival of kidney epithelial cells in in vitro models of oxygen and glucose deprivation. Some of the genes also modulate the toxicity of cisplatin, an anticancer agent whose use is currently limited by nephrotoxicity. Furthermore, pharmacological inhibition of TACR1 product NK1R was protective in a model of mouse renal ischemia, attesting to the in vivo relevance of our findings. These data shed new light on the mechanisms of stress response in mammalian cells, and open new avenues to reduce the morbidity and mortality associated with renal injury.

Delivery of tumor-homing TRAIL sensitizer with long-acting TRAIL as a therapy for TRAIL-resistant tumors

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) has attracted great interest as a cancer therapy because it selectively induces death receptor (DR)-mediated apoptosis in cancer cells while sparing normal tissue. However, recombinant human TRAIL demonstrates limited therapeutic efficacy in clinical trials, possibly due to TRAIL-resistance of primary cancers and its inherent short half-life. Here we introduce drug delivery approaches to maximize in vivo potency of TRAIL in TRAIL-resistant tumor xenografts by (1) extending the half-life of the ligand with PEGylated TRAIL (TRAILPEG) and (2) concentrating a TRAIL sensitizer, selected from in vitro screening, in tumors via tumor-homing nanoparticles. Antitumor efficacy of TRAILPEG with tumor-homing sensitizer was evaluated in HCT116 and HT-29 colon xenografts. Western blot, real-time PCR, immunohistochemistry and cell viability assays were employed to investigate mechanisms of action and antitumor efficacy of the combination. We discovered that doxorubicin (DOX) sensitizes TRAIL-resistant HT-29 colon cancer cells to TRAIL by upregulating mRNA expression of DR5 by 60% in vitro. Intravenously administered free DOX does not effectively upregulate DR5 in tumor tissues nor demonstrate synergy with TRAILPEG in HT-29 xenografts, but rather introduces significant systemic toxicity. Alternatively, when DOX was encapsulated in hyaluronic acid-based nanoparticles (HAC/DOX) and intravenously administered with TRAILPEG, DR-mediated apoptosis was potentiated in HT-29 tumors by upregulating DR5 protein expression by 70% and initiating both extrinsic and intrinsic apoptotic pathways with reduced systemic toxicity compared to HAC/DOX or free DOX combined with TRAILPEG (80% vs. 40% survival rate; 75% vs. 34% tumor growth inhibition). This study demonstrates a unique approach to overcome TRAIL-based therapy drawbacks using sequential administration of a tumor-homing TRAIL sensitizer and long-acting TRAILPEG.

H-Ras regulation of TRAIL death receptor mediated apoptosis

TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis through the death receptors (DRs) 4 and/or 5 expressed on the cell surface. Multiple clinical trials are underway to evaluate the antitumor activity of recombinant human TRAIL and agonistic antibodies to DR4 or DR5. However, their therapeutic potential is limited by the high frequency of cancer resistance. Here we provide evidence demonstrating the role of H-Ras in TRAIL receptor mediated apoptosis. By analyzing the genome wide mRNA expression data of the NCI60 cancer cell lines, we found that H-Ras expression was consistently upregulated in TRAIL-resistant cell lines. By contrast, no correlation was found between TRAIL sensitivity and K-Ras expression levels or their mutational profiles. Notably, H-Ras upregulation associated with a surface deficiency of TRAIL death receptors. Selective inhibition of H-Ras activity in TRAIL-resistant cells restored the surface expression of both DR4 and DR5 without changing their total protein levels. The resulting cells became highly susceptible to both TRAIL and agonistic DR5 antibody, whereas K-Ras inhibition had little or no effect on TRAIL-induced apoptosis, indicating H-Ras plays a distinct role in the regulation of TRAIL death receptors. Further studies are warranted to determine the therapeutic potential of H-Ras-specific inhibitors in combination with TRAIL receptor agonists.

Integrative analysis of kinase networks in TRAIL-induced apoptosis provides a source of potential targets for combination therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an endogenous secreted peptide and, in preclinical studies, preferentially induces apoptosis in tumor cells rather than in normal cells. The acquisition of resistance in cells exposed to TRAIL or its mimics limits their clinical efficacy. Because kinases are intimately involved in the regulation of apoptosis, we systematically characterized kinases involved in TRAIL signaling. Using RNA interference (RNAi) loss-of-function and cDNA overexpression screens, we identified 169 protein kinases that influenced the dynamics of TRAIL-induced apoptosis in the colon adenocarcinoma cell line DLD-1. We classified the kinases as sensitizers or resistors or modulators, depending on the effect that knockdown and overexpression had on TRAIL-induced apoptosis. Two of these kinases that were classified as resistors were PX domain-containing serine/threonine kinase (PXK) and AP2-associated kinase 1 (AAK1), which promote receptor endocytosis and may enable cells to resist TRAIL-induced apoptosis by enhancing endocytosis of the TRAIL receptors. We assembled protein interaction maps using mass spectrometry-based protein interaction analysis and quantitative phosphoproteomics. With these protein interaction maps, we modeled information flow through the networks and identified apoptosis-modifying kinases that are highly connected to regulated substrates downstream of TRAIL. The results of this analysis provide a resource of potential targets for the development of TRAIL combination therapies to selectively kill cancer cells.

Spatial dynamics of TRAIL death receptors in cancer cells

TNF-related apoptosis inducing ligand (TRAIL) selectively induces apoptosis in cancer cells without harming most normal cells. Currently, multiple clinical trials are underway to evaluate the antitumor activity of recombinant human TRAIL (rhTRAIL) and agonistic antibodies that target death receptors (DRs) 4 or 5. It is encouraging that these products have shown a tolerated safety profile in early phase studies. However, their therapeutic potential is likely limited by the emergence of tumor drug resistance phenomena. Increasing evidence indicates that TRAIL DRs are deficient on the plasma membrane of some cancer cells despite their total protein expression. Notably, the lack of surface DR4/DR5 is sufficient to render cancers resistant to TRAIL-induced apoptosis, regardless of the status of other apoptosis signaling components. The current review highlights recent findings on the dynamic expression of TRAIL death receptors, including the regulatory roles of endocytosis, autophagy, and Ras GTPase-mediated signaling events. This information could aid in the identification of novel predictive biomarkers of tumor response as well as the development of combinational drugs to overcome or bypass tumor drug resistance to TRAIL receptor-targeted therapies.

EGFR-targeted TRAIL and a Smac mimetic synergize to overcome apoptosis resistance in KRAS mutant colorectal cancer cells

TRAIL is a death receptor ligand that induces cell death preferentially in tumor cells. Recombinant soluble TRAIL, however, performs poorly as an anti-cancer therapeutic because oligomerization is required for potent biological activity. We previously generated a diabody format of tumor-targeted TRAIL termed Db_αEGFR-scTRAIL, comprising single-stranded TRAIL molecules (scTRAIL) and the variable domains of a humanized variant of the EGFR blocking antibody Cetuximab. Here we define the bioactivity of Db_αEGFR-scTRAIL with regard to both EGFR inhibition and TRAIL receptor activation in 3D cultures of Caco-2 colorectal cancer cells, which express wild-type K-Ras. Compared with conventional 2D cultures, Caco-2 cells displayed strongly enhanced sensitivity toward Db_αEGFR-scTRAIL in these 3D cultures. We show that the antibody moiety of Db_αEGFR-scTRAIL not only efficiently competed with ligand-induced EGFR function, but also determined the apoptotic response by specifically directing Db_αEGFR-scTRAIL to EGFR-positive cells. To address how aberrantly activated K-Ras, which leads to Cetuximab resistance, affects Db_αEGFR-scTRAIL sensitivity, we generated stable Caco-2tet cells inducibly expressing oncogenic K-Ras^G12V. In the presence of doxycycline, these cells showed increased resistance to Db_αEGFR-scTRAIL, associated with the elevated expression of the anti-apoptotic proteins cIAP2, Bcl-xL and Flip_S. Co-treatment of cells with the Smac mimetic SM83 restored the Db_αEGFR-scTRAIL-induced apoptotic response. Importantly, this synergy between Db_αEGFR-scTRAIL and SM83 also translated to 3D cultures of oncogenic K-Ras expressing HCT-116 and LoVo colorectal cancer cells. Our findings thus support the notion that Db_αEGFR-scTRAIL therapy in combination with apoptosis-sensitizing agents may be promising for the treatment of EGFR-positive colorectal cancers, independently of their KRAS status.

TRAIL induces apoptosis in oral squamous carcinoma cells--a crosstalk with oncogenic Ras regulated cell surface expression of death receptor 5

TNF-related apoptosis inducing ligand (TRAIL) induces apoptosis through its death receptors (DRs) 4 and/or 5 expressed on the surface of target cells. The selectivity of TRAIL towards cancer cells has promoted clinical evaluation of recombinant human TRAIL (rhTRAIL) and its agonistic antibodies in treating several major human cancers including colon and non-Hodgkin's lymphoma. However, little is known about their ability in killing oral squamous cell carcinoma (OSCC) cells. In this study, we tested the apoptotic responses of a panel of seven human OSCC cell lines (HN31, HN30, HN12, HN6, HN4, Cal27, and OSCC3) to rhTRAIL and monoclonal antibodies against DR4 or DR5. We found that rhTRAIL is a potent inducer of apoptosis in most of the oral cancer cell lines tested both in vitro and in vivo. We also showed that DR5 was expressed on the surface of the tested cell lines which correlated with the cellular susceptibility to apoptosis induced by rhTRAIL and anti-DR5 antibody. By contrast, little or no DR4 was detected on the surface of OSCC3 and HN6 cells rendering cellular resistance to DR4 antibody and a reduced sensitivity to rhTRAIL. Notably, the overall TRAIL sensitivity correlated well with the levels of endogenous active Ras in the cell lines tested. Expression of a constitutively active Ras mutant (RasV12) in OSCC3 cells selectively upregulated surface expression of DR5, but not DR4, and restored TRAIL sensitivity. Our findings could have implications for the use of TRAIL receptor targeted therapies in the treatment of human OSCC tumors particularly the ones harboring constitutively active Ras mutant.

Regulation of TRAIL receptor expression by β-catenin in colorectal tumours

Tumour-necrosis-factor-related apoptosis-inducing ligand (TRAIL) is being investigated as a targeted cancer therapeutic and the expression of its pro-apoptotic receptors, DR4 and DR5, increases during colorectal carcinogenesis. This study investigated the role of β-catenin in the regulation of these receptors. In human colorectal adenoma and carcinoma cell lines, downregulation of β-catenin resulted in lower total DR4 and DR5 protein levels. Similarly, cell membrane expression of DR4 and DR5 was reduced after downregulation of β-catenin in colon carcinoma cells, whereas induction of β-catenin in HeLa cells led to increased cell membrane expression of DR4 and DR5. Downregulation of β-catenin decreased the recombinant human TRAIL sensitivity of human colon carcinoma cells. Activation of the transcription factor T-cell factor-4 (TCF-4) is an important function of β-catenin. Dominant-negative TCF-4 overexpression, however, did not significantly affect TRAIL receptor expression or recombinant human TRAIL sensitivity. Human colorectal adenomas (N = 158) with aberrant (cytoplasmic and nuclear) β-catenin expression had a higher percentage of immunohistochemical DR4 and DR5 staining per tumour (mean: 73 and 88%, respectively) than those with membranous β-catenin staining only (mean: 50 and 70%, respectively, P < 0.01 for both). Furthermore, aberrant β-catenin staining co-localized with DR4 and DR5 expression in 92% of adenomas. In 53 human colorectal carcinomas, aberrant β-catenin expression was present in most cases and DR4/5 expression was largely homogenous. Similarly, in adenomas from APC(min) mice, cytoplasmic β-catenin staining co-localized with staining for the murine TRAIL death receptor. In conclusion, the gradual increase in TRAIL receptor expression during colorectal carcinogenesis is at least partially mediated through increased β-catenin expression, independently of TCF-4-signalling.

Death receptors as targets in cancer

Anti-tumour therapies based on the use pro-apoptotic receptor agonists, including TNF-related apoptosis-inducing ligand (TRAIL) or monoclonal antibodies targeting TRAIL-R1 or TRAIL-R2, have been disappointing so far, despite clear evidence of clinical activity and lack of adverse events for the vast majority of these compounds, whether combined or not with conventional or targeted anti-cancer therapies. This brief review aims at discussing the possible reasons for the lack of apparent success of these therapeutic approaches and at providing hints in order to rationally design optimal protocols based on our current understanding of TRAIL signalling regulation or resistance for future clinical trials.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

The TRAIL of oncogenes to apoptosis

Despite the significant advances in clinical research, surgical resection, radiotherapy and chemotherapy are still used as the primary method for cancer treatment. As compared to conventional therapies that often induce systemic toxicity and eventually contribute to tumor resistance, the TNF-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that selectively triggers apoptosis in various cancer cells by interacting with its proapoptotic receptors DR4 and KILLER/DR5, while sparing the normal surrounding tissue. The intensive studies of TRAIL signaling pathways over the past decade have provided clues for understanding the molecular mechanisms of TRAIL-induced apoptosis in carcinogenesis and identified an array of therapeutic responses elicited by TRAIL and its receptor agonists. Analysis of its activity at the molecular level has shown that TRAIL improves survival either as monotherapies or combinatorial therapies with other mediators of apoptosis or anticancer chemotherapy. Combinatorial treatments amplify the activities of anticancer agents and widen the therapeutic window by overcoming tumor resistance to apoptosis and driving cancer cells to self-destruction. Although TRAIL sensitivity varies widely depending on the cell type, nontransformed cells are largely resistant to death mediated by TRAIL Death Receptors (DRs). Genetic alterations in cancer can contribute in tumor progression and often play an important role in evasion of apoptosis by tumor cells. Remarkably, RAS, MYC and HER2 oncogenes have been shown to sensitise tumor cells to TRAIL induced cell death. Here, we summarise the cross-talk of oncogenic and apoptotic pathways and how they can be exploited toward efficient combinatorial therapeutic protocols.

Ras and rheb signaling in survival and cell death

One of the most obvious hallmarks of cancer is uncontrolled proliferation of cells partly due to independence of growth factor supply. A major component of mitogenic signaling is Ras, a small GTPase. It was the first identified human protooncogene and is known since more than three decades to promote cellular proliferation and growth. Ras was shown to support growth factor-independent survival during development and to protect from chemical or mechanical lesion-induced neuronal degeneration in postmitotic neurons. In contrast, for specific patho-physiological cases and cellular systems it has been shown that Ras may also promote cell death. Proteins from the Ras association family (Rassf, especially Rassf1 and Rassf5) are tumor suppressors that are activated by Ras-GTP, triggering apoptosis via e.g., activation of mammalian sterile 20-like (MST1) kinase. In contrast to Ras, their expression is suppressed in many types of tumours, which makes Rassf proteins an exciting model for understanding the divergent effects of Ras activity. It seems likely that the outcome of Ras signaling depends on the balance between the activation of its various downstream effectors, thus determining cellular fate towards either proliferation or apoptosis. Ras homologue enriched in brain (Rheb) is a protein from the Ras superfamily that is also known to promote proliferation, growth, and regeneration through the mammalian target of rapamycin (mTor) pathway. However, recent evidences indicate that the Rheb-mTor pathway may switch its function from a pro-growth into a cell death pathway, depending on the cellular situation. In contrast to Ras signaling, for Rheb, the cellular context is likely to modulate the whole Rheb-mTor pathway towards cellular death or survival, respectively.

Sensitivity of malignant peripheral nerve sheath tumor cells to TRAIL is augmented by loss of NF1 through modulation of MYC/MAD and is potentiated by curcumin through induction of ROS

Malignant peripheral nerve sheath tumor (MPNST) is a rare aggressive form of sarcoma often associated with the tumor syndrome neurofibromatosis type 1 (NF1). We investigated the effects of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) on NF1 associated MPNST and determinants of TRAIL sensitivity. MPNST cell lines with complete neurofibromin deficiency were sensitive to apoptotic cell death induced by TRAIL whereas MPNST cells with retained neurofibromin expression or normal human Schwann cells were resistant. Increased sensitivity to TRAIL was associated with overexpression of death receptors, especially DR5. Re-expression of the GAP related domain of neurofibromin (NF1-GRD) suppressed DR5 expression and decreased sensitivity to TRAIL. We show that death receptor expression and TRAIL sensitivity critically depend on c-MYC and that c-MYC amounts are increased by MEK/ERK and PI3K/AKT signalling pathways which are suppressed by neurofibromin. Furthermore PI3K/AKT signalling strongly suppresses the MYC-antagonist MAD1 which significantly contributes to TRAIL sensitivity. Re-expression of the NF1-GRD decreased c-MYC and increased MAD1 amounts suggesting that neurofibromin influences TRAIL sensitivity at least in part by modulating the MYC/MAX/MAD network. The phytochemical curcumin further increased the sensitivity of neurofibromin deficient MPNST cells to TRAIL. This was presumably mediated by ROS, as it correlated with increased ROS production, was blocked by N-acetylcysteine and mimicked by exogenous ROS.

Sub-toxic dose of apigenin sensitizes HepG2 cells to TRAIL through ERK-dependent up-regulation of TRAIL receptor DR5

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a promising candidate for anticancer therapy due to its selective toxicity to cancer cells. Nevertheless, because of TRAIL resistance in some cancer cells, combined treatment with sensitizing agents is required to enhance the anticancer potential of TRAIL. In this study, we investigated the underlying mechanism of apigenin-induced sensitization of HepG2 cells to TRAIL-induced cell death. Synergistic induction of apoptosis by combination was confirmed by examining the typical morphology changes of apoptosis, PARP-cleavage, and activation of effector caspases. Z-VAD-fmk, a pan-caspase inhibitor, inhibited the enhanced cell death by combined treatment of apigenin and TRAIL, demonstrating that a caspase-dependent pathway is involved in apigenin/TRAIL-mediated apoptosis. In addition, we found that apigenin/ TRAIL co-treatment up-regulates DR5 cell surface expression. The synergistic induction of cell death by the apigenin/ TRAIL combination was significantly attenuated by DR5 blocking chimera antibody. Next, using pharmacological inhibitors, we found that ERK activation is involved in the induction of DR5 expression. Inhibition of ERK1/2 by U0126 significantly decreased the apigenin/TRAIL-induced DR5 expression and apoptosis. Taken together, our results indicate that apigenin can enhance the apoptotic effect of TRAIL via ERK-induced up-regulation of DR5.

A randomized, placebo-controlled phase 2 study of ganitumab (AMG 479) or conatumumab (AMG 655) in combination with gemcitabine in patients with metastatic pancreatic cancer

BACKGROUND

We evaluated the efficacy and safety of ganitumab (a mAb antagonist of insulin-like growth factor 1 receptor) or conatumumab (a mAb agonist of human death receptor 5) combined with gemcitabine in a randomized phase 2 trial in patients with metastatic pancreatic cancer.

PATIENTS AND METHODS

Patients with a previously untreated metastatic pancreatic adenocarcinoma and an Eastern Cooperative Oncology Group (ECOG) performance status ≤1 were randomized 1 : 1 : 1 to i.v. gemcitabine 1000 mg/m(2) (days 1, 8, and 15 of each 28-day cycle) combined with open-label ganitumab (12 mg/kg every 2 weeks [Q2W]), double-blind conatumumab (10 mg/kg Q2W), or double-blind placebo Q2W. The primary end point was 6-month survival rate. Results In total, 125 patients were randomized. The 6-month survival rates were 57% (95% CI 41-70) in the ganitumab arm, 59% (42-73) in the conatumumab arm, and 50% (33-64) in the placebo arm. The grade ≥3 adverse events in the ganitumab, conatumumab, and placebo arms, respectively, included neutropenia (18/22/13%), thrombocytopenia (15/17/8%), fatigue (13/12/5%), alanine aminotransferase increase (15/5/8%), and hyperglycemia (18/2/3%).

CONCLUSIONS

Ganitumab combined with gemcitabine had tolerable toxicity and showed trends toward an improved 6-month survival rate and overall survival. Additional investigation into this combination is warranted. Conatumumab combined with gemcitabine showed some evidence of activity as assessed by the 6-month survival rate.

Glycogen synthase kinase-3 inhibition sensitizes pancreatic cancer cells to TRAIL-induced apoptosis

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) induces apoptosis in a variety of cancer cell lines with little or no effect on normal cells. However, its effect is limited as some cancers including pancreatic cancer show de novo resistance to TRAIL induced apoptosis. In this study we report that GSK-3 inhibition using the pharmacologic agent AR-18, enhanced TRAIL sensitivity in a range of pancreatic and prostate cancer cell lines. This sensitization was found to be caspase-dependent, and both pharmacological and genetic knock-down of GSK-3 isoforms resulted in apoptotic features as shown by cleavage of PARP and caspase-3. Elevated levels of reactive oxygen intermediates and disturbance of mitochondrial membrane potential point to a mitochondrial amplification loop for TRAIL-induced apoptosis after GSK-3 inhibition. Consistent with this, overexpression of anti-apoptotic mitochondrial targets such as Bcl-XL, Mcl-1, and Bcl-2 rescued PANC-1 and PPC-1 cells from TRAIL sensitization. However, overexpression of the caspase-8 inhibitor CrmA also inhibited the sensitizing effects of GSK-3 inhibitor, suggesting an additional role for GSK-3 that inhibits death receptor signaling. Acute treatment of mice bearing PANC-1 xenografts with a combination of AR-18 and TRAIL also resulted in a significant increase in apoptosis, as measured by caspase-3 cleavage. Sensitization to TRAIL occurred despite an increase in β-catenin due to GSK-3 inhibition, suggesting that the approach might be effective even in cancers with dysregulated β-catenin. These results suggest that GSK-3 inhibitors might be effectively combined with TRAIL for the treatment of pancreatic cancer.

Sensitization of (colon) cancer cells to death receptor related therapies: a report from the FP6-ONCODEATH research consortium

The objective of the ONCODEATH consortium [EU Research Consortium "ONCODEATH" (2006-2010)] was to achieve sensitization of solid tumor cells to death receptor related therapies using rational mechanism-based drug combinations of targeted therapies. In this collaborative effort, during a period of 42 mo, cell and animal model systems of defined oncogenes were generated. Exploitation of generated knowledge and tools enabled the consortium to achieve the following research objectives: (1) elucidation of tumor components which confer sensitivity or resistance to TRAIL-induced cell death; (2) providing detailed knowledge on how small molecule Hsp90, Aurora, Choline kinase, BRAF inhibitors, DNA damaging agents, HDAC and DNMT inhibitors affect the intrinsic apoptotic amplification and execution machineries; (3) optimization of combined action of TRAIL with these therapeutics for optimum effects with minimum concentrations and toxicity in vivo. These findings provide mechanistic basis for a pharmacogenomic approach, which could be exploited further therapeutically, in order to reach novel personalized therapies for cancer patients.

Deep Sequence Analysis of Non-Small Cell Lung Cancer: Integrated Analysis of Gene Expression, Alternative Splicing, and Single Nucleotide Variations in Lung Adenocarcinomas with and without Oncogenic KRAS Mutations

KRAS mutations are highly prevalent in non-small cell lung cancer (NSCLC), and tumors harboring these mutations tend to be aggressive and resistant to chemotherapy. We used next-generation sequencing technology to identify pathways that are specifically altered in lung tumors harboring a KRAS mutation. Paired-end RNA-sequencing of 15 primary lung adenocarcinoma tumors (8 harboring mutant KRAS and 7 with wild-type KRAS) were performed. Sequences were mapped to the human genome, and genomic features, including differentially expressed genes, alternate splicing isoforms and single nucleotide variants, were determined for tumors with and without KRAS mutation using a variety of computational methods. Network analysis was carried out on genes showing differential expression (374 genes), alternate splicing (259 genes), and SNV-related changes (65 genes) in NSCLC tumors harboring a KRAS mutation. Genes exhibiting two or more connections from the lung adenocarcinoma network were used to carry out integrated pathway analysis. The most significant signaling pathways identified through this analysis were the NFκB, ERK1/2, and AKT pathways. A 27 gene mutant KRAS-specific sub network was extracted based on gene-gene connections from the integrated network, and interrogated for druggable targets. Our results confirm previous evidence that mutant KRAS tumors exhibit activated NFκB, ERK1/2, and AKT pathways and may be preferentially sensitive to target therapeutics toward these pathways. In addition, our analysis indicates novel, previously unappreciated links between mutant KRAS and the TNFR and PPARγ signaling pathways, suggesting that targeted PPARγ antagonists and TNFR inhibitors may be useful therapeutic strategies for treatment of mutant KRAS lung tumors. Our study is the first to integrate genomic features from RNA-Seq data from NSCLC and to define a first draft genomic landscape model that is unique to tumors with oncogenic KRAS mutations.

Oncogenic Ras and B-Raf proteins positively regulate death receptor 5 expression through co-activation of ERK and JNK signaling

Oncogenic mutations of ras and B-raf frequently occur in many cancer types and are critical for cell transformation and tumorigenesis. Death receptor 5 (DR5) is a cell surface pro-apoptotic death receptor for tumor necrosis factor-related apoptosis-inducing ligand and has been targeted in cancer therapy. The current study has demonstrated induction of DR5 expression by the oncogenic proteins Ras and B-Raf and revealed the underlying mechanisms. We demonstrated that both Ras and B-Raf induce DR5 expression by enforced expression of oncogenic Ras (e.g. H-Ras12V or K-Ras12V) or B-Raf (i.e. V600E) in cells and by analyzing gene expression array data generated from cancer cell lines and from human cancer tissues. This finding is further supported by our results that knockdown of endogenous K-Ras or B-Raf (V600E) reduced the expression of DR5. Importantly, we have elucidated that Ras induces DR5 expression through co-activation of ERK/RSK and JNK signaling pathways and subsequent cooperative effects among the transcriptional factors CHOP, Elk1, and c-Jun to enhance DR5 gene transcription. Moreover, we found that the majority of cancer cell lines highly sensitive to the DR5 agonistic antibody AMG655 have either Ras or B-Raf mutations. Our findings warrant further study on the biology of DR5 regulation by Ras and B-Raf, which may provide new insight into the biology of Ras and B-Raf, and on the potential impact of Ras or B-Raf mutations on the outcome of DR5-targeted cancer therapy.

TRAIL and DR5 promote thyroid follicular cell apoptosis in iodine excess-induced experimental autoimmune thyroiditis in NOD mice

Death receptor-mediated apoptosis has been implicated in target organ destruction in patients with chronic autoimmune thyroiditis. Several apoptosis signaling pathways, such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), have been shown to be active in thyroid cells and may be involved in destructive thyroiditis. Thyroid toxicity of iodide excess has been demonstrated in animals fed with an iodide-rich diet, but its pathogenic role remains unclear. The effects of excessive iodine on TRAIL and its death receptor expression in thyroid were investigated. Experimental autoimmune thyroiditis (EAT) was induced by excessive iodine and thyroglobulin (Tg) in non-obese diabetic mice. The expression of TRAIL and its death receptor DR5 was detected by immunofluorescence staining. Following administration of excessive iodine alone, Tg, and excessive iodine combined with Tg, TRAIL-positive cells appear not only in follicular cells but also in lymphocytes infiltrated in the thyroid, whereas DR5-positive cells appear only in follicular cells. Large numbers of CD3-positive cells and a few CD22-positive cells were detected in thyroid. A great amount of follicular cells were labeled specifically by terminal deoxynucleotide transferase-mediated deoxynucleotide triphosphate nick-end labeling assay. Taken together, our results suggest that excessive iodine could induce TRAIL and DR5 abnormal expression in thyroid. TRAIL band with DR5 to promote follicular cells apoptosis thus mediate thyroid destruction in EAT.

Selective BRAFV600E inhibitor PLX4720, requires TRAIL assistance to overcome oncogenic PIK3CA resistance

Documented sensitivity of melanoma cells to PLX4720, a selective BRAFV600E inhibitor, is based on the presence of mutant BRAF(V600E) alone, while wt-BRAF or mutated KRAS result in cell proliferation. In colon cancer appearance of oncogenic alterations is complex , since BRAF, like KRAS mutations, tend to co-exist with those in PIK3CA and mutated PI3K has been shown to interfere with the successful application of MEK inhibitors. When PLX4720 was used to treat colon tumours, results were not encouraging and herein we attempt to understand the cause of this recorded resistance and discover rational therapeutic combinations to resensitize oncogene driven tumours to apoptosis. Treatment of two genetically different BRAF(V600E) mutant colon cancer cell lines with PLX4720 conferred complete resistance to cell death. Even though p-MAPK/ ERK kinase (MEK) suppression was achieved, TRAIL, an apoptosis inducing agent, was used synergistically in order to achieve cell death by apoptosis in RKO(BRAFV600E/PIK3CAH1047) cells. In contrast, for the same level of apoptosis in HT29(BRAFV600E/PIK3CAP449T) cells, TRAIL was combined with 17-AAG, an Hsp90 inhibitor. For cells where PLX4720 was completely ineffective, 17-AAG was alternatively used to target mutant BRAF(V600E). TRAIL dependence on the constitutive activation of BRAF(V600E) is emphasised through the overexpression of BRAF(V600E) in the permissive genetic background of colon adenocarcinoma Caco-2 cells. Pharmacological suppression of the PI3K pathway further enhances the synergistic effect between TRAIL and PLX4720 in RKO cells, indicating the presence of PIK3CA(MT) as the inhibitory factor. Another rational combination includes 17-AAG synergism with TRAIL in a BRAF(V600E) mutant dependent manner to commit cells to apoptosis, through DR5 and the amplification of the apoptotic pathway. We have successfully utilised combinations of two chemically unrelated BRAF(V600E) inhibitors in combination with TRAIL in a BRAF(V600E) mutated background and provided insight for new anti-cancer strategies where the activated PI3KCA mutation oncogene should be suppressed.

Inhibition of IGF-1R-dependent PI3K activation sensitizes colon cancer cells specifically to DR5-mediated apoptosis but not to rhTRAIL

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) initiates apoptosis in tumor cells upon binding to its cognate agonistic receptors, death receptors 4 and 5 (DR4 and DR5). The activity of the insulin-like growth factor 1 (IGF-1) survival pathway is often increased in cancer, influencing both cell proliferation and apoptosis. We hypothesized that inhibiting the IGF-1 receptor (IGF-1R) using NVP-AEW541, a small molecular weight tyrosine kinase inhibitor of the IGF-1R, could increase death receptor (DR)-mediated apoptosis in colon cancer cells.

METHODS

The analyses were performed by caspase assay, flow cytometry, Western blotting, immunoprecipitation and fluorescent microscopy.

RESULTS

Preincubation with NVP-AEW541 surprisingly decreased apoptosis induced by recombinant human TRAIL (rhTRAIL) or an agonistic DR4 antibody while sensitivity to an agonistic DR5 antibody was increased. NVP-AEW541 could inhibit IGF-1-induced activation of the phosphatidylinositol 3-kinase (PI3K) pathway. The effects of the PI3K inhibitor LY294002 on TRAIL-induced apoptosis were similar to those of NVP-AEW541, further supporting a role for IGF-1R-mediated activation of PI3K. We show that PI3K inhibition enhances DR5-mediated caspase 8 processing but also lowers DR4 membrane expression and DR4-mediated caspase 8 processing. Inhibition of PI3K reduced rhTRAIL sensitivity independently of the cell line preference for either DR4- or DR5-mediated apoptosis signaling.

CONCLUSIONS

Our study indicates that individual effects on DR4 and DR5 apoptosis signaling should be taken into consideration when combining DR-ligands with PI3K inhibition.

Targeted expression of tumor necrosis factor-related apoptosis-inducing ligand TRAIL in skin protects mice against chemical carcinogenesis

Background

Gene ablation studies have revealed that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL, Apo2L, TNFSF10) plays a crucial role in tumor surveillance, as TRAIL-deficient mice exhibit an increased sensitivity to different types of tumorigenesis. In contrast, possible tumor-protective effect of increased levels of endogenous TRAIL expression in vivo has not been assessed yet. Such models will provide important information about the efficacy of TRAIL-based therapies and potential toxicity in specific tissues.

Methods

To this aim, we engineered transgenic mice selectively expressing TRAIL in the skin and subjected these mice to a two-step chemical carcinogenesis protocol that generated benign and preneoplastic lesions. We were therefore able to study the effect of increased TRAIL expression at the early steps of skin tumorigenesis.

Results

Our results showed a delay of tumor appearance in TRAIL expressing mice compared to their wild-type littermates. More importantly, the number of tumors observed in transgenic animals was significantly lower than in the control animals, and the lesions observed were mostly benign. Interestingly, Wnt/β-catenin signaling differed between tumors of wild-type and TRAIL transgenics.

Conclusion

Altogether, these data reveal that, at least in this model, TRAIL is able on its own to act on pre-transformed cells, and reduce their tumorigenic potential.

F-box protein 10, an NF-κB-dependent anti-apoptotic protein, regulates TRAIL-induced apoptosis through modulating c-Fos/c-FLIP pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces selective apoptotic death of human cancer cells while sparing normal human cells. Although TRAIL holds great promise as a potential anticancer agent, some tumors develop resistance to TRAIL. Previously, we have shown that the activator protein 1 (AP-1) family member, c-Fos, is an important modulator of apoptosis. Although F- box protein 10 (FBXL10) has been implicated to regulate an AP-1 family protein, c-Jun, its role in mediating apoptotic pathways has not been previously investigated. Here, we report that FBXL10 is a transcriptional repressor of c-Fos and a target gene of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-p65 in human cancers. We demonstrate that FBXL10 is an important anti-apoptotic molecule, which directly binds and represses c-Fos promoter in order for cancer cells to resist TRAIL-induced apoptosis. FBXL10 indirectly regulates c-FLIP(L) levels via c-Fos-dependent pathways. Silencing of FBXL10 sensitizes resistant cells to TRAIL, while, overexpression of FBXL10 represses TRAIL-induced apoptosis. Moreover, our results indicate that expression of FBXL10 functions via an NF-κB-dependent pathway, and TRAIL or proteasome inhibitors downregulate FBXL10 via inhibiting NF-κB signaling. Taken together, we find a novel functional role for FBXL10 as an anti-apoptotic molecule, and describe a new apoptotic-related pathway that involves NF-κB/FBXL10/c-Fos/c-FLIP. Therefore, silencing FBXL10 can help overcome resistant cancer cells for pro-apoptotic therapies.

Death pathways triggered by activated Ras in cancer cells

Ras GTPases are best known for their ability to serve as molecular switches regulating cell growth, differentiation and survival. Gene mutations that result in expression of constitutively active forms of Ras have been linked to oncogenesis in animal models and humans. However, over the past two decades, evidence has gradually accumulated to support a paradoxical role for Ras proteins in the initiation of cell death pathways. In this review we survey the literature pointing to the ability of activated Ras to promote cell death under conditions where cancer cells encounter apoptotic stimuli or Ras is ectopically expressed. In some of these cases Ras acts through known effectors and well defined apoptotic death pathways. However, in other cases it appears that Ras operates by triggering novel non-apoptotic death mechanisms that are just beginning to be characterized. Understanding these mechanisms and the factors that go into changing the nature of Ras signaling from pro-survival to pro-death could set the stage for development of novel therapeutic approaches aimed at manipulating pro-death Ras signaling pathways in cancer.

ERK/ribosomal S6 kinase (RSK) signaling positively regulates death receptor 5 expression through co-activation of CHOP and Elk1

Death receptor 5 (DR5) is a death domain-containing transmembrane receptor that triggers apoptosis upon binding to its ligand or when overexpressed. Its expression is induced by certain small molecule drugs, including celecoxib, through mechanisms that have not been fully elucidated. The current study has revealed a novel ERK/ribosomal S6 kinase (RSK)-dependent mechanism that regulates DR5 expression primarily using celecoxib as a DR5 inducer. Both C/EBP homologous protein (CHOP) and Elk1 are required for celecoxib-induced DR5 expression based on promoter deletion and mutation analysis and siRNA-mediated gene silencing results. Co-expression of both CHOP and Elk1 exhibited enhanced effects on increasing DR5 promoter activity and DR5 expression, indicating that CHOP and Elk1 co-operatively regulate DR5 expression. Because Elk1 is an ERK-regulated protein, we accordingly found that celecoxib increased the levels of phosphorylated ERK1/2, RSK2, and Elk1. Inhibition of either ERK signaling with a MEK inhibitor or ERK1/2 siRNA, or RSK2 signaling with an RSK2 inhibitor or RSK2 siRNA abrogated DR5 up-regulation by celecoxib as well as other agents. Moreover, these inhibitions suppressed celecoxib-induced CHOP up-regulation. Thus, ERK/RSK-dependent, CHOP and Elk1-mediated mechanisms are critical for DR5 induction. Additionally, celecoxib increased CHOP promoter activity in an ATF4-dependent manner, and siRNA-mediated blockade of ATF4 abrogated both CHOP induction and DR5 up-regulation, indicating that ATF4 is involved in celecoxib-induced CHOP and DR5 expression. Collectively, we conclude that small molecules such as celecoxib induce DR5 expression through activating ERK/RSK signaling and subsequent Elk1 activation and ATF4-dependent CHOP induction.

Prognostic significance of TRAIL death receptors in Middle Eastern colorectal carcinomas and their correlation to oncogenic KRAS alterations

Background

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumour necrosis factor cytokine family that induces apoptosis upon binding to its death domain containing receptors, TRAIL receptor 1 (DR4) and TRAIL receptor 2 (DR5). Expression of TRAIL receptors is higher in colorectal carcinoma (CRC) as compared to normal colorectal mucosa and targeted therapy with TRAIL leads to preferential killing of tumor cells sparing normal cells.

Methods

We investigated the expression of TRAIL and its receptors in a tissue microarray cohort of 448 Middle Eastern CRC. We also studied the correlation between TRAIL receptors and various clinico-pathological features including key molecular alterations and overall survival.

Results

CRC subset with TRAIL-R1 expression was associated with a less aggressive phenotype characterized by early stage (p = 0.0251) and a histology subtype of adenocarcinomas (p = 0.0355). Similarly CRC subset with TRAIL-R2 expression was associated with a well-differentiated tumors (p < 0.0001), histology subtype of adenocarcinomas (p = 0.0010) and tumors in left colon (p = 0.0009). Over expression of pro apoptotic markers: p27^KIP1 and KRAS4A isoforms was significantly higher in CRC subset with TRAIL-R1 and TRAIL-R2 expression; TRAIL-R1 expression was also associated with cleaved caspase-3(p = 0.0011). Interestingly, TRAIL-R2 expression was associated with a microsatellite stable (MS--S/L) phenotype (p = 0.0003) and with absence of KRAS mutations (p = 0.0481).

Conclusion

TRAIL-R1 expression was an independent prognostic marker for better survival in all CRC samples and even in the CRC group that received adjuvant therapy. The biological effects of TRAIL in CRC models, its enhancement of chemosensitivity towards standard chemotherapeutic agents and the effect of endogenous TRAIL receptor levels on survival make TRAIL an extremely attractive therapeutic target.

Phase I dose-escalation study of recombinant human Apo2L/TRAIL, a dual proapoptotic receptor agonist, in patients with advanced cancer

PURPOSE

Apoptosis ligand 2/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL)-a member of the tumor necrosis factor cytokine family-induces apoptosis by activating the extrinsic pathway through the proapoptotic death receptors DR4 and DR5. Recombinant human Apo2L/TRAIL (rhApo2L/TRAIL) has broad potential as a cancer therapy. To the best of our knowledge, this is the first in-human clinical trial to assess the safety, tolerability, pharmacokinetics, and antitumor activity of multiple intravenous doses of rhApo2L/TRAIL in patients with advanced cancer.

PATIENTS AND METHODS

This phase I, open-label, dose-escalation study treated patients with advanced cancer with rhApo2L/TRAIL doses ranging from 0.5 to 30 mg/kg/d, with parallel dose escalation for patients without liver metastases and with normal liver function (cohort 1) and for patients with liver metastases and normal or mildly abnormal liver function (cohort 2). Doses were given daily for 5 days, with cycles repeating every 3 weeks. Assessments included adverse events (AEs), laboratory tests, pharmacokinetics, and imaging to evaluate antitumor activity.

RESULTS

Seventy-one patients received a mean of 18.3 doses; seven patients completed all eight treatment cycles. The AE profile of rhApo2L/TRAIL was similar in cohorts 1 and 2. The most common AEs were fatigue (38%), nausea (28%), vomiting (23%), fever (23%), anemia (18%), and constipation (18%). Liver enzyme elevations were concurrent with progressive metastatic liver disease. Two patients with sarcoma (synovial and undifferentiated) experienced serious AEs associated with rapid tumor necrosis. Two patients with chondrosarcoma experienced durable partial responses to rhApo2L/TRAIL.

CONCLUSION

At the tested schedule and dose range, rhApo2L/TRAIL was safe and well tolerated. Dose escalation achieved peak rhApo2L/TRAIL serum concentrations equivalent to those associated with preclinical antitumor efficacy.

ERK and cell death: mechanisms of ERK-induced cell death--apoptosis, autophagy and senescence

The Ras/Raf/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in almost all cell functions and therefore requires exquisite control of its spatiotemporal activity. Depending on the cell type and stimulus, ERK activity will mediate different antiproliferative events, such as apoptosis, autophagy and senescence in vitro and in vivo. ERK activity can promote either intrinsic or extrinsic apoptotic pathways by induction of mitochondrial cytochrome c release or caspase-8 activation, permanent cell cycle arrest or autophagic vacuolization. These unusual effects require sustained ERK activity in specific subcellular compartments and could depend on the presence of reactive oxygen species. We will summarize the mechanisms involved in Ras/Raf/ERK antiproliferative functions.

Zerumbone enhances TRAIL-induced apoptosis through the induction of death receptors in human colon cancer cells: Evidence for an essential role of reactive oxygen species

Identification of the active component and mechanisms of action of traditional medicines is highly desirable. We investigated whether zerumbone, a sesquiterpene from tropical ginger, can enhance the anticancer effects of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We found that zerumbone potentiated TRAIL-induced apoptosis in human HCT116 colon cancer cells and that this correlated with the up-regulation of TRAIL death receptor (DR) 4 and DR5. Induction of DRs occurred at the transcriptional level, and this induction was not cell-type specific, as its expression was also up-regulated in prostate, kidney, breast, and pancreatic cancer cell lines. Deletion of DR5 or DR4 by small interfering RNA significantly reduced the apoptosis induced by TRAIL and zerumbone. In addition to up-regulating DRs, zerumbone also significantly down-regulated the expression of cFLIP but not that of other antiapoptotic proteins. The induction of both DRs by zerumbone was abolished by glutathione and N-acetylcysteine (NAC), and this correlated with decreased TRAIL-induced apoptosis, suggesting a critical role of reactive oxygen species. Inhibition of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase but not of Jun NH(2)-terminal kinase abolished the effect of zerumbone on DR induction. Zerumbone also induced the p53 tumor suppressor gene but was found to be optional for DR induction or for enhancement of TRAIL-induced apoptosis. Both bax and p21, however, were required for zerumbone to stimulate TRAIL-induced apoptosis. Overall, our results show that zerumbone can potentiate TRAIL-induced apoptosis through the reactive oxygen species-mediated activation of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase leading to DR4 and DR5 induction and resulting in enhancement of the anticancer effects of TRAIL.

Origin and pathogenesis of nodular lymphocyte-predominant Hodgkin lymphoma as revealed by global gene expression analysis

The pathogenesis of nodular lymphocyte–predominant Hodgkin lymphoma (NLPHL) and its relationship to other lymphomas are largely unknown. This is partly because of the technical challenge of analyzing its rare neoplastic lymphocytic and histiocytic (L&H) cells, which are dispersed in an abundant nonneoplastic cellular microenvironment. We performed a genome-wide expression study of microdissected L&H lymphoma cells in comparison to normal and other malignant B cells that indicated a relationship of L&H cells to and/or that they originate from germinal center B cells at the transition to memory B cells. L&H cells show a surprisingly high similarity to the tumor cells of T cell–rich B cell lymphoma and classical Hodgkin lymphoma, a partial loss of their B cell phenotype, and deregulation of many apoptosis regulators and putative oncogenes. Importantly, L&H cells are characterized by constitutive nuclear factor κB activity and aberrant extracellular signal-regulated kinase signaling. Thus, these findings shed new light on the nature of L&H cells, reveal several novel pathogenetic mechanisms in NLPHL, and may help in differential diagnosis and lead to novel therapeutic strategies.

TATA box-binding protein-associated factor 12 is important for RAS-induced transformation properties of colorectal cancer cells

Activating mutations in the RAS proto-oncogene result in constant stimulation of its downstream pathways, further leading to tumorigenesis. Transcription factor IID (TFIID) can be regulated by cellular signals to specifically alter transcription of particular subsets of genes. To investigate potential links between the regulation of TFIID function and the RAS-induced carcinogenesis, we monitored the expression of the TATA box-binding protein and its associated factors (TAF) in human colon carcinoma cells. We primarily identified TAF12 levels as being up-regulated in cell lines bearing natural RAS mutations or stably overexpressing a mutated RAS isoform via a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-dependent pathway. We further showed by electrophoretic mobility shift assays and chromatin immunoprecipitation that the ETS1 protein was interacting with an ETS-binding site on the TAF12 promoter and was regulating TAF12 expression. The binding was enhanced in extracts from oncogenic RAS-transformed cells, pointing to a role in the RAS-mediated regulation of TAF12 expression. Reduction of TAF12 levels by small interfering RNA treatment induced a destabilization of the TFIID complex, enhanced E-cadherin mRNA and protein levels, and reduced migration and adhesion properties of RAS-transformed cells with epithelial to mesenchymal transition. Overall, our study indicates the importance of TAF12 in the process of RAS-induced transformation properties of human colon cells and epithelial to mesenchymal transition, most notably those related to increased motility, by regulating specifically expression of genes such as E-cadherin.