Reduction of decoy receptor 3 enhances TRAIL-mediated apoptosis in pancreatic cancer

Gemcitabine-Lipid Conjugate and ONC201 Combination Therapy Effectively Treats Orthotopic Pancreatic Tumor-Bearing Mice

Gemcitabine (GEM) is a nucleoside analogue approved as a first line of therapy for pancreatic ductal adenocarcinoma (PDAC). However, rapid metabolism by plasma cytidine deaminase leading to the short half-life, intricate intracellular metabolism, ineffective cell uptake, and swift development of chemoresistance downgrades the clinical efficacy of GEM. ONC201 is a small molecule that inhibits the Akt and ERK pathways and upregulates the TNF-related apoptosis-inducing ligand (TRAIL), which leads to the reversal of both intrinsic and acquired GEM resistance in PDAC treatment. Moreover, the pancreatic cancer cells that were able to bypass apoptosis after treatment of ONC201 get arrested in the G1-phase, which makes them highly sensitive to GEM. To enhance the in vivo stability of GEM, we first synthesized a disulfide bond containing stearate conjugated GEM (lipid-GEM), which makes it sensitive to the redox tumor microenvironment (TME) comprising high glutathione levels. In addition, with the help of colipids 1,2-dioleoyl-glycero-3-phosphocholine (DOPC), cholesterol, and 1,2-distearoyl-glycero-3-phosphoethanolamine-poly(ethylene glycol)-2000 (DSPE-PEG 2000), we were able to synthesize the lipid-GEM conjugate and ONC201 releasing liposomes. A cumulative drug release study confirmed that both ONC201 and GEM showed sustained release from the formulation. Since MUC1 is highly expressed in 70-90% PDAC, we conjugated a MUC1 binding peptide in the liposomes which showed higher cytotoxicity, apoptosis, and cellular internalization by MIA PaCa-2 cells. A biodistribution study further confirmed that the systemic delivery of the liposomes through the tail vein resulted in a higher accumulation of drugs in orthotopic PDAC tumors in NSG mice. The IHC of the excised tumor grafts further confirmed the higher apoptosis and lower metastasis and cell proliferation. Thus, our MUC1 targeting binary drug-releasing liposomal formulation showed higher drug payload, enhanced plasma stability, and accumulation of drugs in the pancreatic orthotopic tumor and thus is a promising therapeutic alternative for the treatment of PDAC.

TNF-Related Apoptosis-Inducing Ligand: Non-Apoptotic Signalling

TNF-related apoptosis-inducing ligand (TRAIL or Apo2 or TNFSF10) belongs to the TNF superfamily. When bound to its agonistic receptors, TRAIL can induce apoptosis in tumour cells, while sparing healthy cells. Over the last three decades, this tumour selectivity has prompted many studies aiming at evaluating the anti-tumoral potential of TRAIL or its derivatives. Although most of these attempts have failed, so far, novel formulations are still being evaluated. However, emerging evidence indicates that TRAIL can also trigger a non-canonical signal transduction pathway that is likely to be detrimental for its use in oncology. Likewise, an increasing number of studies suggest that in some circumstances TRAIL can induce, via Death receptor 5 (DR5), tumour cell motility, potentially leading to and contributing to tumour metastasis. While the pro-apoptotic signal transduction machinery of TRAIL is well known from a mechanistic point of view, that of the non-canonical pathway is less understood. In this study, we the current state of knowledge of TRAIL non-canonical signalling.

The Role of Decoy Receptor DcR3 in Gastrointestinal Malignancy

Malignancies are among the leading causes of mortality worldwide. Early detection and treatment are the primary targets of clinical and translational research, and may be facilitated by the recognition of novel diagnostic and prognostic biomarkers. Decoy receptor 3 (DcR3) is a soluble receptor of the tumor necrosis factor receptor superfamily of proteins (TNFRSF), which associates with its respective TNF-like ligands, Fas-L, LIGHT, and TL1A. DcR3 has been recognised as a significant anti-apoptotic factor with prominent involvement in various inflammatory and neoplastic conditions. Increased intratumor expression of DcR3 and elevated soluble DcR3 protein content in the sera of patients has been reported for various malignancies. Recent published work has suggested that monitoring of local and systemic DcR3 may provide an attractive biomarker, mainly for defining subgroups of patients with aggressive tumor behaviour and poor prognosis. The aim of the present review is to summarize and critically present existing evidence regarding the potential clinical importance of monitoring DcR3 expression in patients with malignancies of the gastrointestinal tract, as well as liver and pancreatic cancer. We also present a detailed description of the pathophysiological basis that may underlie the involvement of DcR3 in gastrointestinal carcinogenesis. Based on these data, we comment on the potential applicability of DcR3 monitoring in the diagnosis and, most importantly, the prognostic stratification of patients.

Decoy Receptor 3 Suppresses T-Cell Priming and Promotes Apoptosis of Effector T-Cells in Acute Cell-Mediated Rejection: The Role of Reverse Signaling

Background

Decoy receptor 3 (DcR3) belongs to the tumor necrosis factor (TNF) receptor superfamily and neutralizes TNF ligands, including FasL and TRAIL, to prevent T activation during T-cell priming. However, the cellular mechanisms underlying acute cell-mediated rejection (ACMR) remain unknown.

Methods

We generated DcR3 transgenic (Tg) mice and mice with high DcR3 expression (HDE) to study both in vivo and in vitro. FasR RNA knockdown in immortalized CD4⁺CD8⁺ T-cells was used to survey the role of DcR3 on FasR/Fas-associated protein with death domain (FADD)/caspase 8 pathway and its cross-link to TNF receptor-associated factor 1 (TNFR1)-associated death domain protein (TRADD) in suppressing TNFR1. TNF/TRADD knockout mice were used to show the importance of TNF adaptor protein.

Results

DcR3.Fc suppressed C57BL/6 female T-cell activation and transformation into CD4⁺CD69⁺, CD4⁺CD44⁺, and CD4⁺CD25⁺Foxp3⁺ when compared with isotype IgG1 and its co-treatment with FasL/TRAIL after exposing to bone marrow-derived dendritic cells (BMDCs) that carried alloantigen with male H-Y and minor antigenic determinant. Interleukin-17 and interferon-γ productions by BMDC-activated T-cells were lowered after co-treating with DcR3.Fc. DcR3.Fc induced effector T-cells (Teffs) and was susceptible to FasR-mediated apoptosis through the FADD/TRADD/caspase 8 pathway. After exposing to DcR3.Fc, TRADD was silenced, likely turning down the inflammatory response. The systemic effects of DcR3 Tg mice and HDE phenotype induced by the promoter of cytomegalovirus not only attenuated ACMR severity but also ameliorated the high serum creatinine and blood urea nitrogen levels even with high T-cell exposure frequencies. Besides this, DcR3 has minor biological effects on both MHC-matched and MHC-mismatched models.

Conclusions

High DcR3 doses protect renal tubular epithelial cells from acute T-cell attack during the T-cell priming stage via interfering with TNF ligand-mediated reverse signaling and possibly promoting Teff apoptosis through FasR upregulation. Our findings supported that the decoy receptor is involved in T-cell modulation in kidney transplant rejection.

The Role of Feedback Loops in Targeted Therapy for Pancreatic Cancer

Pancreatic cancer is the leading cause of cancer-related deaths worldwide, with limited treatment options and low long-term survival rates. The complex and variable signal regulation networks are one of the important reasons why it is difficult for pancreatic cancer to develop precise targeted therapy drugs. Numerous studies have associated feedback loop regulation with the development and therapeutic response of cancers including pancreatic cancer. Therefore, we review researches on the role of feedback loops in the progression of pancreatic cancer, and summarize the connection between feedback loops and several signaling pathways in pancreatic cancer, as well as recent advances in the intervention of feedback loops in pancreatic cancer treatment, highlighting the potential of capitalizing on feedback loops modulation in targeted therapy for pancreatic cancer.

Integrative analysis of TNFRSF6B as a potential therapeutic target for pancreatic cancer

Background

Pancreatic cancer is one of the most lethal malignant tumors worldwide with poor outcomes. Previous studies have shown that tumor necrosis factor receptor superfamily member 6b (TNFRSF6B) plays an important role in cancer progression and immunosuppression. However, the mechanisms by which TNFRSF6B influence pancreatic cancer, and the regulatory networks involved remain to be further studied.

Methods

This study analyzed the mRNA information and clinical data of patients from The Cancer Genome Atlas (TCGA) and the ONCOMINE databases. The gene co-expression data regarding TNFRSF6B was obtained from the c-BioPortal and used to explore the functional network of TNFRSF6B in pancreatic cancer, as well as its function in tumor immunity. Short hairpin (sh) RNA knock-down experiments were performed to examine the functional roles of TNFRSF6B in pancreatic cancer cell lines.

Results

The expression of TNFRSF6B was elevated in pancreatic cancer tissues compared to normal pancreatic tissues, and its high expression was associated with poor prognosis of patients with pancreatic cancer. TNFRSF6B was found to be widely involved in cell cycle processes, apoptosis, apoptosis signaling pathways, immune responses, and responses to interferon. Knock-down of TNFRSF6B expression inhibited pancreatic cancer cell proliferation and invasion in vitro. Moreover, carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) was found to be co-expressed with TNFRSF6B, and there was a positive correlation between these molecules in pancreatic cancer cells.

Conclusions

This report suggested that TNFRSF6B has a critical role in the progression and metastasis of pancreatic cancer. These findings provide novel insights into the role of TNFRSF6B in the functional network of pancreatic cancer, and suggest that TNFRSF6B may be a potential therapeutic target.

Chemotherapeutic Agents Sensitize Resistant Cancer Cells to the DR5-Specific Variant DR5-B more Efficiently than to TRAIL by Modulating the Surface Expression of Death and Decoy Receptors

TRAIL is considered a promising antitumor agent because it causes apoptosis of transformed cells without affecting normal cells. However, many types of tumors are cytokine resistant, and combination therapy with various chemotherapeutic drugs is being developed to overcome the resistance. We have demonstrated that the combination of TRAIL with doxorubicin, bortezomib, and panobinostat dramatically reduced the viability of TRAIL-resistant A549 and HT-29 cells. Chemotherapy even more efficiently sensitized cells to the DR5-specific mutant variant of TRAIL DR5-B, which does not have an affinity for decoy receptors. Bortezomib and doxorubicin greatly enhanced the surface expression of the death receptors DR5 and DR4, while panobinostat increased expression of DR5 and suppressed expression of DR4 in both cell lines. All drugs increased surface expression of the decoy receptors DcR1 and DcR2. Unlike the combined treatment, if the cells were pretreated with chemotherapy for 24 h, the cytotoxic activity of TRAIL was less pronounced, while sequential treatment of cells enhanced the effectiveness of DR5-B. The same results were obtained with agonistic anti-DR5 antibodies. Thus, the effectiveness of TRAIL was rather limited due to changes in the ratio of death and decoy receptors and DR5-specific agonists may be preferred in combination antitumor therapy regimens.

DcR3 promotes proliferation and invasion of pancreatic cancer via a DcR3/STAT1/IRF1 feedback loop

Pancreatic cancer (PC) is one of the most common gastrointestinal malignancies that are highly aggressive with a low 5-year survival rate. Accumulated evidence has indicated that decoy receptor 3 (DcR3) is involved in several pathologic processes and various cancers. However, the mechanisms underlying dysregulated DcR3 expression and activation in PC remain to be fully established. In this study, we investigate the function and regulatory network of DcR3 in PC. We found that DcR3 was upregulated in PC tissues and serum. High DcR3 expression was associated with aggressive clinicopathological features and poor prognosis. Functionally, DcR3 not only increased cell migration and invasion in vitro but also promoted tumour growth both in vitro and in vivo by loss-of-function and gain-of-function experiments. Mechanistically, DcR3 promoted the phosphorylation of signal transducers and activators of transcription 1 (STAT1), leading to a dramatic increase in interferon regulatory factor 1 (IRF1). IRF1 then increased the transcriptional activity of DcR3, forming a positive feedback loop to reinforce DcR3 expression. In addition, DcR3 promoted carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) expression through activated IRF1. In conclusion, our findings provided novel insights into the function and mechanism of DcR3 in the pathogenesis of PC, which may be a potential therapeutic target for PC.

DcR3 induces epithelial-mesenchymal transition through activation of the TGF-β3/SMAD signaling pathway in CRC

Decoy receptor 3 (DcR3), a novel member of the tumor necrosis factor receptor (TNFR) family, was recently reported to be associated with tumorigenesis and metastasis. However, the role of DcR3 in human colorectal cancer (CRC) has not been fully elucidated. In this study, we found that DcR3 expression was significantly higher in human colorectal cancer tissues than in paired normal tissues, and that DcR3 expression was strongly correlated with tumor invasion, lymph node metastases and poor prognoses. Moreover, DcR3 overexpression significantly enhanced CRC cell proliferation and migration in vitro and tumorigenesis in vivo. Conversely, DcR3 knockdown significantly repressed CRC cell proliferation and migration in vitro, and DcR3 deficiency also attenuated CRC tumorigenesis and metastasis in vivo. Functionally, DcR3 was essential for TGF-β3/SMAD-mediated epithelial-mesenchymal transition (EMT) of CRC cells. Importantly, cooperation between DcR3 and TGF-β3/SMAD-EMT signaling-related protein expression was correlated with survival and survival time in CRC patients. In conclusion, our results demonstrate that DcR3 may be a prognostic biomarker for CRC and that this receptor facilitates CRC development and metastasis by participating in TGF-β3/SMAD-mediated EMT of CRC cells.

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.

Decoy receptor 3: an endogenous immunomodulator in cancer growth and inflammatory reactions

Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor (TNFR) superfamily member 6b (TNFRSF6B), is a soluble decoy receptor which can neutralize the biological functions of three members of tumor necrosis factor superfamily (TNFSF): Fas ligand (FasL), LIGHT, and TL1A. In addition to ‘decoy’ function, recombinant DcR3.Fc is able to modulate the activation and differentiation of dendritic cells (DCs) and macrophages via ‘non-decoy’ action. DcR3-treated DCs skew T cell differentiation into Th2 phenotype, while DcR3-treated macrophages behave M2 phenotype. DcR3 is upregulated in various cancer cells and several inflammatory tissues, and is regarded as a potential biomarker to predict inflammatory disease progression and cancer metastasis. However, whether DcR3 is a pathogenic factor or a suppressor to attenuate inflammatory reactions, has not been discussed comprehensively yet. Because mouse genome does not have DcR3, it is not feasible to investigate its physiological functions by gene-knockout approach. However, DcR3-mediated effects in vitro are determined via overexpressing DcR3 or addition of recombinant DcR3.Fc fusion protein. Moreover, CD68-driven DcR3 transgenic mice are used to investigate DcR3-mediated systemic effects in vivo. Upregulation of DcR3 during inflammatory reactions exerts negative-feedback to suppress inflammation, while tumor cells hijack DcR3 to prevent apoptosis and promote tumor growth and invasion. Thus, ‘switch-on’ of DcR3 expression may be feasible for the treatment of inflammatory diseases and enhance tissue repairing, while ‘switch-off’ of DcR3 expression can enhance tumor apoptosis and suppress tumor growth in vivo.

DKK3 attenuates the cytotoxic effect of natural killer cells on CD133+ gastric cancer cells

Cancer stem cell (CSCs) has started a new era in cancer research. CD133 is a widely used marker for identification of CSCs. More and more studies showed that NK cells preferentially target cancer stem-like cells. However, the deeper mechanism of the susceptibility of cancer stem cells to NK cells remains unclear. In this study, we isolated CD133 positive population of a gastric cancer cell line, BGC823 cells, and cultured with NK cells. We found that CD133 could efficiently active NK cells in an NKG2D-dependent manner. DKK3 has been demonstrated as a suppressor in many cancers. Interestingly, we found that DKK3 suppressed CD133-induced activation in NK cells by inhibiting Erk pathway and immunological synapse (IS) formation. NK cells-based CSCs immunotherapy may be a novel approach for cancer therapy.

Dendritic cells engineered to secrete anti-DcR3 antibody augment cytotoxic T lymphocyte response against pancreatic cancer in vitro

AIM

To investigate the enhanced cytotoxic T lymphocyte responses against pancreatic cancer (PC) in vitro induced by dendritic cells (DCs) engineered to secrete anti-DcR3 monoclonal antibody (mAb).

METHODS

DCs, T lymphocytes and primary PC cells were obtained from PC patients. DCs were transfected with a designed humanized anti-DcR3 monoclonal antibody heavy and light chain mRNA and/or total tumor RNA (DC-tumor-anti-DcR3 RNA or DC-total tumor RNA) by using electroporation technology. The identification, concentration and function of anti-DcR3 mAb secreted by DC-tumor-anti-DcR3 RNA were determined by western blotting and enzyme-linked immunosorbent assay. After co-culturing of autologous isolated PC cells with target DCs, the effects of secreting anti-DcR3 mAb on RNA-DCs’ viability and apoptosis were assessed by MTT assay and flow cytometry. Analysis of enhanced antigen-specific immune response against PC induced by anti-DcR3 mAb secreting DCs was performed using a ⁵¹Cr releasing test. T cell responses induced by RNA-loaded DCs were analyzed by measuring cytokine levels, including IFN-γ, IL-10, IL4, TNF-α and IL-12.

RESULTS

The anti-DcR3 mAb secreted by DCs reacted with recombinant human DcR3 protein and generated a band with 35 kDa molecular weight. The secreting mAb was transient, peaking at 24 h and becoming undetectable after 72 h. After co-incubation with DC-tumor-anti-DcR3 RNA for designated times, the DcR3 level in the supernatant of autologous PC cells was significantly down-regulated (P < 0.05). DCs secreting anti-DcR3 mAb could improve cell viability and slow down the apoptosis of RNA-loaded DCs, compared with DC-total tumor RNA (P < 0.01). The anti-DcR3 mAb secreted by DC-tumor-anti-DcR3 RNA could enhance the induction of cytotoxic T lymphocytes (CTLs) activity toward RNA-transfected DCs, primary tumor cells, and PC cell lines, compared with CTLs stimulated by DC-total tumor RNA or control group (P < 0.05). Meanwhile, the antigen-specific CTL responses were MHC class I-restricted. The CD4+ T cells and CD8+ T cells incubated with anti-DcR3 mAb secreting DCs could produce extremely higher level IFN-γ and lower level IL4 than those incubated with DC-total tumor RNA or controls (P < 0.01).

CONCLUSION

DCs engineered to secrete anti-DcR3 antibody can augment CTL responses against PC in vitro, and the immune-enhancing effects may be partly due to their capability of down-regulating DC apoptosis and adjusting the Th1/Th2 cytokine network.

Effect of silencing decoy receptor 3 on biological features of hepatoma cells

AIM

To detect the expression of decoy receptor 3 (DcR3) in hepatoma cells, and to investigate its role in the biological features of hepatoma cells.

METHODS

Real-time PCR and Western blot were used to detect the expression of DcR3 mRNA and protein in human hepatoma cell lines HepG2 and Huh7 and normal hepatocytes (HL-7702 and Chang liver). ELISA was used to detect the level of DcR3 protein in the supernatant of these four cell lines. A lentiviral vector carrying shRNA against DcR3 (LV-shDcR3) was synthesized and used to infect HepG2 and Huh7 cells, with the empty lentiviral vector as a control. After infection, the interference effects were determined by Western blot, cell proliferation was assessed by CCK-8 assay and colony forming assay, cell apoptosis was examined by flow cytometry, and the expression of apoptosis related protein like PARP was detected by Western blot. The expression of TRAIL, FasL and LIGHT before and after infection was also detected by Western blot.

RESULTS

The expression of DcR3 was significantly increased in hepatoma cell lines HepG2 and Huh7 both at the mRNA and protein levels compared with normal hepatocytes. The levels of DcR3 in the supernatants of HepG2 and Huh7 cells were also increased. Compared with the mock group and empty lentiviral vector infected group, the LV-shDcR3 infected group showed reduced expression of DcR3, lower cell viability rate, and higher cell apoptosis rate. The expression of TRAIL and FasL was increased after infection with LV-shDcR3 in HepG2 and Huh7 cells.

CONCLUSION

The expression of DcR3 is elevated in hepatoma cells. Down-regulation of the expression of DcR3 inhibits cell proliferation and induces cell apoptosis in hepatoma cells, via mechanisms that may be related with the TRAIL and FasL apoptosis pathway.

Downregulation of DcR3 sensitizes hepatocellular carcinoma cells to TRAIL-induced apoptosis

Decoy receptor 3 (DcR3) has been recently described as an antiapoptosis and prometastasis factor since it can competitively bind to FasL, TL1A, and LIGHT, and it is highly expressed in many malignant tumors. Downregulation of DcR3 can promote tumor cell apoptosis and inhibit metastasis. A previous study demonstrated that reduction of DcR3 could induce tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in pancreatic cancer cells. However, whether such an effect is seen in hepatocellular carcinoma (HCC) remains to be explored. This study was designed to investigate the sensitivity of HCC cells to TRAIL after silencing DcR3, and this was done by evaluating the expression of DcR3 in HCC cells and the effect on TRAIL-mediated apoptosis after downregulation of DcR3. Our data showed that DcR3 was highly expressed in HepG2, BEL-7402, Hep3B, Huh-7, MHCC97H, and SMCC7721 cell lines compared with normal liver cell line LO-2. Both HepG2 and BEL-7402 were tolerant to TRAIL-mediated apoptosis, and the tolerance was negatively correlated to the expression of DcR3. Silencing of DcR3 with shRNA and treatment with TRAIL induced obvious apoptosis in HepG2 and BEL-7402, with more cancer cells found in the G1 phase. SiDcR3 combined with TRAIL could induce activation of caspases-3, -8, and -9, raise the expression of the apoptotic protein Bax, and reduce the expression of antiapoptotic proteins (Bcl-2, Mcl-1, Bcl-XL, IAP-2, and survivin). Caspase-8 inhibitor Ac-IETD-CHO significantly decreased the activation of caspase cascade, indicating that the extrinsic pathway may have a vital role in the apoptotic events induced by SiDcR3/TRAIL. Furthermore, our results showed that the TRAIL death receptor 5 (DR5) was upregulated and that DR5 neutralizing antibody abrogated the effect of SiDcR3. Our results demonstrated that downregulation of DcR3 could enhance TRAIL-mediated apoptosis in HCC through the death receptor pathway. In the future, this might be useful as a clinical treatment method of liver cancer.

Recent progress in nanomedicine-based combination cancer therapy using a site-specific co-delivery strategy

This review article highlights the recent progresses in nanomedicine-based combination cancer therapy via site-specific co-delivery strategies.

Effect of DcR3-specific siRNA on cell growth suppression and apoptosis induction in glioma cells via affecting ERK and AKT

BACKGROUND

Previously, we found that the expression of decoy receptor 3 (DcR3) in gliomas was significantly upregulated compared to normal brain tissues. However, the effect of DcR3-specific small interfering RNA (siRNA) on cell biological function of glioma cells remains incompletely understood.

OBJECTIVE

The aim of this study was to explore the effect of DcR3 siRNA on cell growth and apoptosis of glioma cells and to investigate the potential downstream pathways affected by DcR3.

METHODS

DcR3-specific siRNA was transfected into three glioma cell lines (U251MG, LN-308, and U87MG) using combiMAGnetofection method. MTS tetrazolium assay and fluorimetric resorufin viability assay were used to assess the growth of glioma cells. Then, apoptosis was examined using the Hoechst 33342/propidium iodide double-staining assay and fluorescent caspase-3/7 assay. Meanwhile, Western blot was performed to explore the probable pathway by which DcR3-specific siRNA acts in glioma cells. Also, microarray dataset analysis was applied to analyze the potential function of DcR3 in glioma.

RESULTS

The DcR3-specific siRNA had a potent effect on cell growth and apoptosis of all three glioma cells tested, and the effects were time dependent. Among these three glioma cell lines, U251MG had the most significant effect with regard to growth inhibition and apoptosis induction. MTS assay showed that the proliferation rate at 72 and 96 hours after the transfection was 76.333%±5.131% (t=7.611, P=0.002) and 64.333%±5.859% (t=10.983, P<0.001), respectively. The viability rate of U251MG cells was 80.667%±2.309% (t=12.302, P<0.001) and 62.333%±2.082% (t=21.213, P<0.001) at 72 and 96 hours posttreatment, respectively. The caspase-3/7 activity of U251MG cells was 2.76 (t=-6.601, P=0.003) and 4.75 (t=-9.189, P=0.001) folds that of the mock control at 72 and 96 hours, respectively. The apoptosis rate was increased to 1.85 (t=-2.496, P=0.067) and 3.93 (t=-12.587, P<0.001) folds at 72 and 96 hours after transfection, respectively. Furthermore, the levels of phospho-ERK1/2 and phospho-AKT were significantly downregulated after DcR3 silencing.

CONCLUSION

The DcR3-specific siRNA could efficiently inhibit growth and induce apoptosis of cells via affecting ERK and AKT. Hence, DcR3-specific siRNA treatment could act as a supplementary targeted therapy strategy for gliomas.

Expression and clinicopathological implication of DcR3 in lung cancer tissues: a tissue microarray study with 365 cases

BACKGROUND

Decoy receptor 3 (DcR3) has been reported to be involved in different cancers. However, few related researches have been accomplished on the role of DcR3 in lung cancer.

OBJECTIVE

To explore the expression level and clinicopathological implication of DcR3 protein in lung cancer tissues.

MATERIALS AND METHODS

Immunohistochemistry was used to examine DcR3 protein expression in lung cancer (n=365) and normal lung tissues (n=26). The relationships between DcR3 expression and clinical parameters were further investigated. Furthermore, the diagnostic and clinicopathological value of DcR3 mRNA was analyzed based on The Cancer Genome Atlas database in lung cancer patients.

RESULTS

Compared to normal lung tissues, DcR3 expression was significantly higher in lung cancer (P=0.007) tissues, including small-cell lung cancer (P=0.001) and non-small-cell lung cancer (P=0.008). In addition, DcR3 expression was related to tumor-node-metastasis (TNM) stage (P<0.001), tumor diameter (P=0.007), distant metastasis (P<0.001), and lymph node metastasis (P<0.001) in lung cancers. When concerning non-small-cell lung cancer, consistent correlations between DcR3 expression and TNM stage (P<0.001), tumor diameter (P=0.019), distant metastasis (P<0.001), and lymph node metastasis (P<0.001) were found. Simultaneously, in small-cell lung cancer, TNM stage (P=0.004) and lymph node metastasis (P=0.005) were also associated with DcR3 expression. Additionally, receiver operator characteristic curve revealed that the area under curve (AUC) of DcR3 was 0.637 (95% confidence interval [CI] 0.531-0.742) for lung cancer. Furthermore, DcR3 was overexpressed in both adenocarcinoma and squamous cell carcinoma tissues than in noncancerous lung tissues (all P<0.0001) based on the data from The Cancer Genome Atlas. AUC of DcR3 was 0.726 (95% CI 0.644-0.788) for lung adenocarcinoma patients and 0.647 (95% CI 0.566-0.728) for squamous cell carcinoma patients. DcR3 expression was also related to the overall survival (P<0.001) and disease-free survival (P<0.001) of lung adenocarcinoma according to the data from The Cancer Genome Atlas.

CONCLUSION

Our study confirms that DcR3 might be involved in the tumorigenesis and deterioration of lung cancer. Therefore, the detection of DcR3 gains the potential to be applied in the clinic for screening and progression prediction of lung cancer.

Overexpression of DcR3 and its significance on tumor cell differentiation and proliferation in glioma

Background. Overexpression of decoy receptor 3 (DcR3) have been reported in various classes of malignancies. However, its expression and clinicopathological contribution in gliomas has not been fully elucidated. Objective. To explore the expression and clinical significance of DcR3 protein in relation to tumor cell differentiation and proliferation in glioma cell lines and tissues. Methods. One hundred and twenty-five samples of glioma patients and 18 cases of normal brain tissues were recruited. The expression of DcR3 protein was detected using immunohistochemistry. Tumor differentiation was assessed by histologic characters and the status of glial fibrillary acidic protein (GFAP). Tumor cell labeling indexes (LIs) of Ki-67 and PCNA were also obtained. The relationship between the DcR3 level and clinicopathological features was investigated, including tumor differentiation, LIs, and survival. Meanwhile, the expression of DcR3 protein was also measured in the supernatants of 8 glioma cell lines and glioma cells freshly prepared from 8 human glioblastoma specimens by using western blot. Results. The level of DcR3 protein in gliomas was significantly higher than that in normal brain tissues (P < 0.01). DcR3 expression showed positive correlations with tumor pathological grade (r = 0.621, P < 0.01) and negative with GFAP expression (r = −0.489, P < 0.01). Furthermore, there were positive correlations between DcR3 expression and Ki-67, PCNA LIs (r = 0.529, P < 0.01; r = 0.556, P < 0.01). The survival in the DcR3 negative group was 50 ± 1.79 months, longer than that of the DcR3 positive group (48.36 ± 2.90), however, without significance (P = 0.149). Different levels of DcR3 could also be detected in the culturing supernatants of all the 8 glioma cell lines and glioma cells freshly obtained from 8 human glioblastoma specimens. Conclusions. The overexpression of DcR3 might play a crucial role in the tumorigenesis, differentiation, and proliferation of glioma.