Downregulation of SNAIL sensitizes hepatocellular carcinoma cells to TRAIL-induced apoptosis by regulating the NF-κB pathway

Sufentanil Inhibits the Proliferation and Metastasis of Esophageal Cancer by Inhibiting the NF-κB and Snail Signaling Pathways

Sufentanil is a μ-opioid receptor agonist, widely used in intraoperative and postoperative analgesia of esophageal cancer. This study investigated the effects of sufentanil on the proliferation, invasion, and metastasis of esophageal carcinoma cells and its molecular mechanisms. Human esophageal carcinoma cells CaES-17 and Eca-109 were cultured in vitro. Different concentrations of sufentanil (1 and 10 μmol/L) were added to the experimental group. MTT was used to detect the proliferative activity of esophageal carcinoma cells. The migration ability of esophageal carcinoma cells was measured by the scratch test. Transwell was used to detect the invasive ability of esophageal carcinoma cells. The EMT marker expression was detected by qPCR. Meanwhile, effects of sufentanil on NF-κB and Snail expression and nucleation were evaluated. Establish a subcutaneous xenograft tumor model of nude mice with esophageal carcinoma cells and evaluate the antitumor effect of sufentanil. Sufentanil can inhibit the proliferation, invasion, and migration of CaES-17 and Eca-109 cells and has a dose-dependent relationship. The molecular mechanism showed that sufentanil could upregulate the expression of E-cadherin and inhibit the expression of vimentin. Sufentanil can inhibit the expression of NF-κB and Snail, as well as the nuclear expression of NF-κB and Snail. Xenograft tumor model results showed that sufentanil could inhibit tumor proliferation and NF-κB and Snail expression in tumor tissues of nude mice. Sufentanil inhibits esophageal cancer epithelial-mesenchymal transition (EMT) by acting on NF-κB and Snail signaling pathways to inhibit proliferation and metastasis of esophageal cancer.

Harnessing TRAIL-Induced Apoptosis Pathway for Cancer Immunotherapy and Associated Challenges

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has attracted rapidly evolving attention as a cancer treatment modality because of its competence to selectively eliminate tumor cells without instigating toxicity in vivo. TRAIL has revealed encouraging promise in preclinical reports in animal models as a cancer treatment option; however, the foremost constraint of the TRAIL therapy is the advancement of TRAIL resistance through a myriad of mechanisms in tumor cells. Investigations have documented that improvement of the expression of anti-apoptotic proteins and survival or proliferation involved signaling pathways concurrently suppressing the expression of pro-apoptotic proteins along with down-regulation of expression of TRAILR1 and TRAILR2, also known as death receptor 4 and 5 (DR4/5) are reliable for tumor cells resistance to TRAIL. Therefore, it seems that the development of a therapeutic approach for overcoming TRAIL resistance is of paramount importance. Studies currently have shown that combined treatment with anti-tumor agents, ranging from synthetic agents to natural products, and TRAIL could result in induction of apoptosis in TRAIL-resistant cells. Also, human mesenchymal stem/stromal cells (MSCs) engineered to generate and deliver TRAIL can provide both targeted and continued delivery of this apoptosis-inducing cytokine. Similarly, nanoparticle (NPs)-based TRAIL delivery offers novel platforms to defeat barricades to TRAIL therapeutic delivery. In the current review, we will focus on underlying mechanisms contributed to inducing resistance to TRAIL in tumor cells, and also discuss recent findings concerning the therapeutic efficacy of combined treatment of TRAIL with other antitumor compounds, and also TRAIL-delivery using human MSCs and NPs to overcome tumor cells resistance to TRAIL.

Critical signaling pathways governing hepatocellular carcinoma behavior; small molecule-based approaches

Hepatocellular carcinoma (HCC) is the second leading cause of death due to cancer. Although there are different treatment options, these strategies are not efficient in terms of restricting the tumor cell's proliferation and metastasis. The liver tumor microenvironment contains the non-parenchymal cells with supportive or inhibitory effects on the cancerous phenotype of HCC. Several signaling pathways are dis-regulated in HCC and cause uncontrolled cell propagation, metastasis, and recurrence of liver carcinoma cells. Recent studies have established new approaches for the prevention and treatment of HCC using small molecules. Small molecules are compounds with a low molecular weight that usually inhibit the specific targets in signal transduction pathways. These components can induce cell cycle arrest, apoptosis, block metastasis, and tumor growth. Devising strategies for simultaneously targeting HCC and the non-parenchymal population of the tumor could lead to more relevant research outcomes. These strategies may open new avenues for the treatment of HCC with minimal cytotoxic effects on healthy cells. This study provides the latest findings on critical signaling pathways governing HCC behavior and using small molecules in the control of HCC both in vitro and in vivo models.

The Problem of Apoptotic Processes Reversibility

Apoptosis is the best understood variant of regulated cell death, which has been considered irreversible for a long time. To date, an increasing amount of data has been accumulating indicating that key events of apoptosis, such as the externalization of phosphatidylserine, mitochondrial outer membrane permeabilization, caspase activation, DNA damage, and cytoplasmic blebbing are not irreversible and can be involved in the normal cell functioning not associated with the induction of apoptosis. Anastasis - cell recovery after induction of apoptosis - can occur following elimination of proapoptotic stimuli. This can facilitate survival of damaged or tumor cells. This review describes key processes of apoptosis, which do not necessarily lead to cell death during normal cell activity as well as anastasis. Understanding mechanisms and consequences of apoptotic processes reversibility, on the one hand, could contribute to the improvement of existing therapeutic approaches for various diseases, including malignant neoplasms, and, on the other hand, could open up new possibilities for protecting cellular elements of tissues and organs from death during treatment of degenerative pathologies.

miR-34a-5p might have an important role for inducing apoptosis by down-regulation of SNAI1 in apigenin-treated lung cancer cells

Apigenin is a flavonoid with antioxidant and anticancer effects. It has been reported that apigenin inhibits proliferation, migration, and invasion and induces apoptosis in cultured lung cancer cells. However, there is little information on the involvement of microRNAs (miRNAs) in its effects. miRNA microarray analysis and polymerase-chain-reaction analysis of miRNAs revealed that treatment of human lung cancer A549 cells with apigenin up-regulated the level of miR-34a-5p. Furthermore, mRNA microarray analysis and the results of three microRNA target prediction tools showed that Snail Family Transcriptional Repressor 1 (SNAI1), which inhibits the induction of apoptosis, had its mRNA expression down-regulated in A549 cells treated with apigenin. Our findings suggest that apigenin might induce apoptosis by down-regulation of SNAI1 through up-regulation of miR-34a-5p in A549 cells.

Prognostic values of SNAI family members in breast cancer patients

Background

Breast cancer (BC) is one of the most lethal malignant tumors and the leading cause of cancer-related death worldwide. Although early diagnostic techniques for BC have been well developed, 40% of cases are still diagnosed at the advanced stage, while for BC patients with distant metastases, the 5-year survival rate is usually lower than 30%. The Snail family, generally regarded as transcriptional repressors, has been indicated to be an essential prognostic factor in malignant tumors. However, limited data exist on public databases concerning the prognostic value of individual Snail family members in BC, especially SNAI3.

Methods

Data from public databases including cBioPortal for Cancer Genomics, Gene Expression Omnibus, UCSC Xena Browser, and Human Protein Atlas (HPA) were downloaded. Based on the Kaplan¬–Meier plotter platform, correlation of the three members of the Snail family and prognosis in BC were analyzed. Individual Snail family members and their co-expressed genes were respectively enriched on different pathways and biological processes via the functional enrichment analysis (FunRich) tool.

Results

High SNAI1 mRNA expression was associated with shorter distant metastasis-free survival (DMFS) in all BC patients regardless of PAM50 subtype. Conversely, high SNAI3 mRNA expression was associated with longer DMFS. Although the presence of SNAI2 expression was significantly associated with DMFS in the whole cohort, no significant correlation was found in patients with luminal A or HER2 subtype. For patients with the most diverse clinicopathological features, high SNAI1 expression was associated with poor survival, with the converse being true for SNAI3. However, the impact on prognosis of patients with different clinicopathological features produced by SNAI2 expression was inconclusive. Furthermore, we discovered that SNAI1 or SNAI2 and their co-expressed genes frequently enriched receptor tyrosine kinase (RTK) signaling and integrin-related pathways which mainly functioned on epithelial-mesenchymal transition and were further involved in several processes of signal transduction and cell communication. Furthermore, as SNAI3, along with its co-expressed genes, enriched immune-related pathways, it may thus play a role in mediating the immune system.

Conclusions

Our analysis revealed that SNAI1 mRNA expression may potentially be a negative prognostic factor, whereas SNAI3 mRNA was associated with positive prognosis in BC. Therefore, the assessment of SNAI1 and SNAI3 expression may be valuable for predicting prognosis in BC patients.

TRAIL therapy and prospective developments for cancer treatment

Tumor Necrosis Factor (TNF) Related Apoptosis-Inducing Ligand (TRAIL), an immune cytokine of TNF-family, has received much attention in late 1990s as a potential cancer therapeutics due to its selective ability to induce apoptosis in cancer cells. TRAIL binds to cell surface death receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5) and facilitates formation of death-inducing signaling complex (DISC), eventually activating the p53-independent apoptotic cascade. This unique mechanism makes the TRAIL a potential anticancer therapeutic especially for p53-mutated tumors. However, recombinant human TRAIL protein (rhTRAIL) and TRAIL-R agonist monoclonal antibodies (mAb) failed to exert robust anticancer activities due to inherent and/or acquired resistance, poor pharmacokinetics and weak potencies for apoptosis induction. To get TRAIL back on track as a cancer therapeutic, multiple strategies including protein modification, combinatorial approach and TRAIL gene therapy are being extensively explored. These strategies aim to enhance the half-life and bioavailability of TRAIL and synergize with TRAIL action ultimately sensitizing the resistant and non-responsive cells. We summarize emerging strategies for enhanced TRAIL therapy in this review and cover a wide range of recent technologies that will provide impetus to rejuvenate the TRAIL therapeutics in the clinical realm.

RMP/URI inhibits both intrinsic and extrinsic apoptosis through different signaling pathways

The evading apoptosis of tumor cells may result in chemotherapy resistance. Therefore, investigating what molecular events contribute to drug-induced apoptosis, and how tumors evade apoptotic death, provides a paradigm to explain the relationship between cancer genetics and treatment sensitivity. In this study, we focused on the role of RMP/URI both in cisplatin-induced endogenous apoptosis and in TRAIL-induced exogenous apoptosis in HCC cells. Although flow cytometric analysis indicated that RMP overexpression reduced the apoptosis rate of HCC cells treated with both cisplatin and TRAIL, there was a difference in mechanism between the two treatments. Western blot showed that in intrinsic apoptosis induced by cisplatin, the overexpression of RMP promoted the Bcl-xl expression both in vitro and in vivo. Besides, RMP activated NF-κB/p65(rel) through the phosphorylation of ATM. However, in TRAIL-induced extrinsic apoptosis, RMP significantly suppressed the transcription and expression of P53. Moreover, the forced expression of P53 could offset this inhibitory effect. In conclusion, we presumed that RMP inhibited both intrinsic and extrinsic apoptosis through different signaling pathways. NF-κB was distinctively involved in the RMP circumvention of intrinsic apoptosis, but not in the extrinsic apoptosis of HCC cells. RMP might play an important role in defects of apoptosis, hence the chemotherapeutic resistance in hepatocellular carcinoma. These studies are promising to shed light on a more rational approach to clinical anticancer drug design and therapy.

Effect of modulation of epithelial-mesenchymal transition regulators Snail1 and Snail2 on cancer cell radiosensitivity by targeting of the cell cycle, cell apoptosis and cell migration/invasion

Cancer is one of the leading causes of cancer-associated mortality worldwide. Several strategies of treatment, including radiotherapy, have been developed and used to treat this disease. However, post-treatment metastasis and resistance to treatment are two major causes for the limited effectiveness of radiotherapy in cancer patients. Epithelial-mesenchymal transition (EMT) is regulated by SNAIL family transcription factors, including Snail1 and Snail2 (Slug), and serves important roles in progression and cancer resistance to treatment. Snail1 and Slug also have been shown to be implicated in cancer treatment resistance. For resolving the resistance to treatment problems, combining the modulation of gene expression with radiotherapy is a novel strategy to treat patients with cancer. The present review focuses on the effect of Snail1 and Slug on cancer radiosensitivity by targeting cell apoptosis, the cell cycle and cell migration/invasion.

The mechanism study of lentiviral vector carrying methioninase enhances the sensitivity of drug-resistant gastric cancer cells to Cisplatin

Background

To investigate the mechanism of lentiviral vector carrying methioninase enhances the sensitivity of drug-resistant gastric cancer cells to Cisplatin.

Methods

Death receptors, anti-apoptotic protein, NF-κB, and TRAIL pathway-related factors were detected. The influence of LV-METase transfection on cell viability and pathway-related proteins were assessed by MTT method and western blot, respectively. Different treatments (NF-κB or caspase-3 inhibitor induction, TRAIL supplement, etc.) were performed in gastric cancer cells and the above parameters were analysed. Moreover, the connection between miR-21 and NF-κB or caspase-8 was determined by Chip and luciferase assay, respectively. LV-METase transfection drug-resistant gastric cancer cells were injected subcutaneously into mice.

Results

The expression of free MET, miR-21-5p, MDR1, P-gp, and DR5 was significantly increased in drug-resistant gastric cancer cell lines. When cells were transfected with LV-METase, intracellular TRAIL signalling was activated while NF-κB pathway was inhibited. Besides, enhanced TRAIL signalling or repressed NF-κB pathway can promote the sensitivity of drug-resistant strains to Cisplatin, and the combination shows more sensitive to sensitisation. LV-METase promoted TRAIL expression by reducing NF-κB, thereby contributing to the downregulation of P-gp and enhancing the susceptibility of drug-resistant gastric cancer cells to Cisplatin. Furthermore, miR-21 regulated by NF-κB mediated the expression of P-gp protein via inhibiting caspase-8, thus regulating Cisplatin-induced cell death.

Conclusions

Our results suggest that LV-METase has potential as a therapeutic agent for gastric cancer treatment.

Bioinformatic analysis and prediction of the function and regulatory network of long non-coding RNAs in hepatocellular carcinoma

Computational analysis and bioinformatics have significantly advanced the ability of researchers to process and analyze biological data. Molecular data from human and model organisms may facilitate drug target validation and identification of biomarkers with increased predictive accuracy. The aim of the present study was to investigate the function of long non-coding RNAs (lncRNAs) in hepatocellular carcinoma (HCC) using online databases, and to predict their regulatory mechanism. HCC-associated lncRNAs, their downstream transcription factors and microRNAs (miRNAs/miRs), as well as the HCC-associated target genes, were identified using online databases. HCC-associated lncRNAs, including HOX antisense intergenic RNA (HOTAIR) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) were selected based on established databases of lncRNAs. The interaction between the HCC-associated lncRNAs and miRNAs (hsa-miR-1, hsa-miR-20a-5p) was predicted using starBase2.0. Signal transducer and activator of transcription 1, hepatocyte nuclear factor 4α (HNF4A), octamer-binding transcription factor 4, Nanog homeobox (NANOG), caudal type homeobox 2 (CDX2), DEAD-box helicase 5, brahma-related gene 1, MYC-associated factor X and MYC proto-oncogene, bHLH transcription factor have been identified as the transcription factors for HOTAIR and MALAT1 using ChIPBase. Additionally, CDX2, HNF4A, NANOG, ETS transcription factor, Jun proto-oncogene and forkhead box protein A1 were identified as the transcription factors for hsa-miR-1 and hsa-miR-20a-5p. CDX2, HNF4A and NANOG were the transcriptional factors in common between the lncRNAs and miRNAs. Cyclin D1, E2F transcription factor 1, epithelial growth factor receptor, MYC, MET proto-oncogene, receptor tyrosine kinase and vascular endothelial growth factor A were identified as target genes for the HCC progression, two of which were also the target genes of hsa-miR-1 and hsa-miR-20a-5p using the miRwalk and OncoDN. HCC databases. Additionally, these target genes may be involved in biological functions, including the regulation of cell growth, cell cycle progression and mitosis, and in disease progression, as demonstrated using DAVID clustering analysis. The present study aimed to predict a regulatory network of lncRNAs in HCC progression using bioinformatics analysis.

High expression of Snail and NF-κB predicts poor survival in Chinese hepatocellular carcinoma patients

In this study, we explored the roles of Snail and NF-κB in hepatocellular carcinoma (HCC). Samples of HCC tumor tissue were collected from 83 Chinese HCC patients. Snail and NF-κB expression was then examined based on immunohistochemical staining, and the relations between Snail and NF-κB expression and the clinical characteristics of the patients were assessed using Cox model analysis. Snail and NF-κB were both expressed in HCC tissue, and their levels were strongly correlated. In addition, levels of both Snail and NF-κB expression were negatively related to tumor differentiation, which was an independent factor predictive of survival in HCC patients. Snail and NF-κB may thus be useful markers of tumor differentiation and survival in HCC, and may also be useful for guiding treatment and exploring molecular mechanisms.

ShDcR3 sensitizes TRAIL-resistant HCC cells by inducing caspase-dependent apoptosis while suppressing NF-κB dependent cFLIPL expression

Evidence has shown that most hepatocellular carcinoma (HCC) cells are resistant to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis. However, the molecular mechanisms underlying TRAIL-mediated apoptosis resistance are not well understood. In this study, we reported that downregulation of Decoy receptor 3 (DcR3) expression by lentiviral vectors carrying shRNA against DcR3 (LV-ShDcR3, shDcR3) in Huh7 both greatly enhanced TRAIL-mediated apoptosis and reduced cell proliferation capability. In addition, silencing DcR3 resulted in upregulation of the cell apoptotic regulators including Bid, caspase-3, and caspase-8. Caspase inhibitors inhibited shDcR3-mediated cell death, which indicated that downregulation of DcR3 expression in Huh7 cells increased TRAIL-induced caspase-dependent apoptotic cell death. Furthermore, although the knockdown of DcR3 altered the expression of some Bcl-2- and IAP-family proteins, this change was inhibited by pretreatment with a pancaspase inhibitor, which indicated the cytotoxic effect of shDcR3 was not due to the expression of these proteins. In contrast, shDcR3 significantly inhibited TRAIL-induced transcription factor nuclear κB (NF-κB) activation through the IκB kinase (IKK) pathway, as well as inhibited TRAIL-induced increases in FLICE-inhibitory protein long form (cFLIP_L) expression at the transcriptional level. Silencing cFLIP_L expression mimicked the cytotoxic effect of shDcR3 on TRAIL-mediated cell apoptosis. Moreover, overexpression of cFLIP_L effectively prevented the increase in cell apoptosis in Huh7 cells co-treated with TRAIL and shDcR3. Taken together, our findings indicated that silencing DcR3 sensitizes TRAIL-mediated apoptosis in HCC cells by inhibiting NF-κB.

CCL2/CCR2 axis induces hepatocellular carcinoma invasion and epithelial-mesenchymal transition in vitro through activation of the Hedgehog pathway

Chemokine (C-C motif) ligand 2 (CCL2) has been shown to play an important role in the regulation of tumor cell growth, metastasis and host immune response. CCL2 preferentially binds to the C-C chemokine receptor type 2 (CCR2), which is expressed in various tissues. However, the role of the CCL2/CCR2 axis in hepatocellular carcinoma (HCC) invasion and its molecular mechanisms remain unclear. The aim of this study was to elucidate this issue. The human HCC cell line MHCC-97H was treated with CCL2. Cyclopamine, a smoothened (SMO) antagonist, was used to inhibit SMO activity. CCR2 siRNA and Gli-1 siRNA were used to inhibit CCR2 and Gli-1 expression respectively. The effect of CCL2 and Hedgehog (Hh) signaling on cancer cell epithelial-mesenchymal transition (EMT) and invasion was evaluated by quantitative real-time PCR analysis, western blotting and Transwell invasion assay. Our results revealed that CCL2 induced HCC cell invasion and EMT. This effect was accompanied by the activation of Hh signaling, the upregulation of Snail and vimentin and the reduction of E-cadherin. Notably, prior silencing of CCR2 with siRNA abolished CCL2-induced Hh signaling activation, Snail and vimentin upregulation, E-cadherin reduction, as well as HCC cell invasion and EMT. Furthermore, pretreatment with cyclopamine or predepletion of Gli-1 by siRNA also eliminated the changes of Snail, vimentin and E-cadherin, and HCC invasion and EMT caused by CCL2. Collectively, our results revealed that the link between the CCL2/CCR2 axis and the Hh pathway plays an important role in HCC progression. Therefore, the CCL2/CCR2 axis may represent a promising therapeutic target to prevent HCC progression.

A molecular signature for anastasis, recovery from the brink of apoptotic cell death

Cells can survive executioner caspase activation following transient apoptotic stimuli, a process called anastasis. Using whole-transcriptome RNA sequencing, Sun et al. show that anastasis is an active, two-stage program and characterize the cell behaviors and molecular signature involved in the process.

During apoptosis, executioner caspase activity has been considered a point of no return. However, recent studies show that cells can survive caspase activation following transient apoptotic stimuli, a process called anastasis. To identify a molecular signature, we performed whole-transcriptome RNA sequencing of untreated, apoptotic, and recovering HeLa cells. We found that anastasis is an active, two-stage program. During the early stage, cells transition from growth-arrested to growing. In the late stage, HeLa cells change from proliferating to migratory. Recovering cells also exhibited prolonged elevation of proangiogenic factors. Strikingly, some early-recovery mRNAs, including Snail, were elevated first during apoptosis, implying that dying cells poise to recover, even while under apoptotic stress. Snail was also required for recovery. This study reveals similarities in the anastasis genes, pathways, and cell behaviors to those activated in wound healing and identifies a repertoire of potential targets for therapeutic manipulation.

Journey of TRAIL from Bench to Bedside and its Potential Role in Immuno-Oncology

Induction of apoptosis in cancer cells has increasingly been the focus of many therapeutic approaches in oncology field. Since its identification as a TNF family member, TRAIL (TNF-related apoptosis-inducing ligand) paved a new path in apoptosis inducing cancer therapies. Its selective ability to activate extrinsic and intrinsic cell death pathways in cancer cells only, independently from p53 mutations responsible for conventional therapeutics resistance, spotted TRAIL as a potent cancer apoptotic agent. Many recombinant preparations of TRAIL and death receptor targeting monoclonal antibodies have been developed and being tested pre-clinically and clinically both as a single agent and in combinations. Of note, the monoclonal antibodies were not the only type of antibodies developed to target TRAIL receptors. Recent technology has brought forth several single chain variable domains (scFv) designs fused recombinantly to TRAIL as well. Also, it is becoming progressively more understandable that field of nanotechnology has revolutionized cancer diagnosis and therapy. The recent breakthroughs in materials science and protein engineering have helped considerably in strategically loading drugs into nanoparticles or conjugating drugs to their surface. In this review we aim to comprehensively highlight the molecular knowledge of TRAIL in the context of its pathway, receptors and resistance factors. We also aim to review the clinical trials that have been done using TRAIL based therapies and to review various scFv designs, the arsenal of nano-carriers and molecules available to selectively target tumor cells with TRAIL.

Snail represses the expression of human phospholipid scramblase 4 gene

Human phospholipid scramblases (hPLSCRs) are a group of transmembrane ATP independent lipid transporters mediating bi-directional transport of phospholipids. There are four homologues hPLSCR1-hPLSCR4 and hPLSCR1 is the extensively studied homologue among them. hPLSCR4 shares 48% homology with hPLSCR1 and mediates scrambling of PLs similar to hPLSCR1 in Ca(2+) dependent manner. Transcriptional regulation helps in better understanding of the function and the expression of a protein. Till date there are no reports suggesting the transcriptional regulation of hPLSCR4. In this study, we identified Snail to be a potent regulator of hPLSCR4. ConSite tool predicted the presence of a putative Snail binding site with a consensus sequence of (-1521)CAGGTG(-1516) on hPLSCR4 promoter. Luciferase assays depicted a dose dependent decrease in hPLSCR4 promoter activity with an increase in amount of Snail. Deletion analysis revealed that the region from -1380 to -2100 to be the regulatory region of hPLSCR4. Knock down studies further confirmed Snail mediated downregulation of hPLSCR4, as the mRNA and the protein levels of hPLSCR4 considerably increased under knock down conditions. The in vivo interaction of Snail with hPLSCR4 promoter was further confirmed by ChIP assay. This is the first report on the transcriptional regulation of hPLSCR4, where Snail was shown to downregulate the expression of hPLSCR4.

Paclitaxel enhances tumoricidal potential of TRAIL via inhibition of MAPK in resistant gastric cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) holds promise for cancer therapy due to its unique capacity to selectively trigger apoptosis in cancer cells. However, TRAIL therapy is greatly hampered by its resistance. A preclinical successful strategy is to identify combination treatments that sensitize resistant cancers to TRAIL. In the present study, we fully assessed TRAIL sensitivity in 9 gastric cancer cell lines. We found combined administration of paclitaxel (PTX) markedly enhanced TRAIL-induced apoptosis in resistant cancer cells both in vitro and in vivo. The sensitization to TRAIL was accompanied by activation of mitochondrial apoptotic pathway, upregulation of TRAIL receptors and downregulation of anti-apoptotic proteins including C-IAP1, C-IAP2, Livin and Mcl-1. Noticeably, we found PTX could suppress the activation of mitogen-activated protein kinases (MAPKs). Inhibition of MAPKs using specific inhibitors (ERK inhibitor U0126, JNK inhibitor SP600125 and P38 inhibitor SB202190) facilitated TRAIL-mediated apoptosis and cytotoxicity. Additionally, SP600125 upregulated TRAL receptors as well as downregulated C-IAP2 and Mcl-1 suggesting the anti-apoptotic role of JNK. Thus, PTX-induced suppression of MAPKs may contribute to restoring TRAIL senstitivity. Collectively, our comprehensive analyses gave new insight into the role of PTX on enhancing TRAIL sensitivity, and provided theoretical references on the development of combination treatment in TRAIL-resistant gastric cancer.