The inhibition of Bid expression by Akt leads to resistance to TRAIL-induced apoptosis in ovarian cancer cells

TRIAL-based combination therapies in cancers

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) shows promising therapeutic potential in cancer treatment as it is able to trigger extrinsic apoptotic pathways by binding to the cognate death receptor, causing broad-spectrum apoptosis in cancer cells with negligible toxicity to normal cells. However, the majority of cancers display resistance to TRAIL, limiting its clinical utility. Overcoming resistance to TRAIL therapies remains a challenge in the development of effective anti-cancer strategies. To address the limitations of TRAIL therapy, a viable alternative approach involves combining TRAIL with more potent drugs compared to monotherapy. This combination strategy aims to induce synergistic effects or sensitize drug-resistant cancer cells. This review provides an overview of relevant modalities of TRAIL combination therapy, highlighting different drug classes. The findings demonstrate that combining TRAIL with other agents can effectively counteract resistance observed with TRAIL therapies in cancer. These findings lay a foundation for future advancements in TRAIL-based therapies for treating various cancers.

An Update on Physiopathological Roles of Akt in the ReprodAKTive Mammalian Ovary

The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian microenvironment. The optimal finetuning of this pathway is essential for physiological processes concerning oogenesis, folliculogenesis, oocyte maturation, and embryo development. The dysregulation of PI3K/Akt can impair molecular and structural mechanisms that will lead to follicle atresia, or the inability of embryos to reach later stages of development. Due to its pivotal role in the control of cell proliferation, apoptosis, and survival mechanisms, the dysregulation of this molecular pathway can trigger the onset of pathological conditions. Among these, we will focus on diseases that can harm female fertility, such as polycystic ovary syndrome and premature ovarian failure, or women's general health, such as ovarian cancer. In this review, we report the functions of the PI3K/Akt pathway in both its physiological and pathological roles, and we address the existing application of inhibitors and activators for the balancing of the molecular cascade in ovarian pathological environments.

GRP94 is an IGF-1R chaperone and regulates beta cell death in diabetes

High workload-induced cellular stress can cause pancreatic islet β cell death and dysfunction, or β cell failure, a hallmark of type 2 diabetes mellitus. Thus, activation of molecular chaperones and other stress-response genes prevents β cell failure. To this end, we have shown that deletion of the glucose-regulated protein 94 (GRP94) in Pdx1+ pancreatic progenitor cells led to pancreas hypoplasia and reduced β cell mass during pancreas development in mice. Here, we show that GRP94 was involved in β cell adaption and compensation (or failure) in islets from leptin receptor-deficient (db/db) mice in an age-dependent manner. GRP94-deficient cells were more susceptible to cell death induced by various diabetogenic stress conditions. We also identified a new client of GRP94, insulin-like growth factor-1 receptor (IGF-1R), a critical factor for β cell survival and function that may mediate the effect of GRP94 in the pathogenesis of diabetes. This study has identified essential functions of GRP94 in β cell failure related to diabetes.

MTCH2 stimulates cellular proliferation and cycles via PI3K/Akt pathway in breast cancer

The MTCH2 protein is located on the mitochondrial outer membrane and regulates mitochondria-related cell death. This study set out to investigate the role of MTCH2 in the underlying pathophysiological mechanisms of breast cancer (BC). MTCH2 expression levels in BC were analyzed using bioinformatics prior to verification by cell lines in vitro. Experiments of over-expression and siRNA-mediated knockdown of MTCH2 were conducted to assess its biological functions, including its effects on cellular proliferation and cycle progression. Xenografts were utilised for in vivo study and signaling pathway alterations were examined to identify the mechanisms driven by MTCH2 in BC proliferation and cell-cycle regulation. MTCH2 was up-regulated in BC and correlated with patients' overall survival. Over-expression of MTCH2 promoted cellular proliferation and cycle progression, while silencing MTCH2 had the opposite effect. Xenograft experiments were utilised to confirm the in vitro cellular findings and it was identified that the PI3K/Akt signaling pathway was activated by MTCH2 over-expression and suppressed by its silencing. Moreover, the activation of IGF-1R rescued cellular growth and cycle arrest induced by MTCH2-silencing. Overall, this study reveals that expression of MTCH2 in BC is upregulated and potentiates cellular proliferation and cycle progression via the PI3K/Akt pathway.

Nano-TRAIL: a promising path to cancer therapy

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand, also called apo-2 ligand (TRAIL/Apo-2L), is a cytokine that triggers apoptosis by binding to TRAIL-R1 (DR4) and TRAIL-R2 (DR5) death receptors. Apoptosis occurs through either the extrinsic or intrinsic pathway. The administration of recombinant human TRAIL (rhTRAIL) or TRAIL-receptor (TRAIL-R) agonists promotes apoptosis preferentially in cancerous cells over normal cells in vitro; this phenomenon has also been observed in clinical studies. The limited efficacy of rhTRAIL in clinical trials could be attributed to drug resistance, short half-life, targeted delivery issues, and off-target toxicities. Nanoparticles are excellent drug and gene delivery systems characterized by improved permeability and retention, increased stability and biocompatibility, and precision targeting. In this review, we discuss resistance mechanisms to TRAIL and methods to overcome TRAIL resistance by using nanoparticle-based formulations developed for the delivery of TRAIL peptides, TRAIL-R agonists, and TRAIL genes to cancer cells. We also discuss combinatorial approaches of chemotherapeutic drugs with TRAIL. These studies demonstrate TRAIL's potential as an anticancer agent.

Harnessing TRAIL-induced cell death for cancer therapy: a long walk with thrilling discoveries

Tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) can induce apoptosis in a wide variety of cancer cells, both in vitro and in vivo, importantly without killing any essential normal cells. These findings formed the basis for the development of TRAIL-receptor agonists (TRAs) for cancer therapy. However, clinical trials conducted with different types of TRAs have, thus far, afforded only limited therapeutic benefit, as either the respectively chosen agonist showed insufficient anticancer activity or signs of toxicity, or the right TRAIL-comprising combination therapy was not employed. Therefore, in this review we will discuss molecular determinants of TRAIL resistance, the most promising TRAIL-sensitizing agents discovered to date and, importantly, whether any of these could also prove therapeutically efficacious upon cancer relapse following conventional first-line therapies. We will also discuss the more recent progress made with regards to the clinical development of highly active non-immunogenic next generation TRAs. Based thereupon, we next propose how TRAIL resistance might be successfully overcome, leading to the possible future development of highly potent, cancer-selective combination therapies that are based on our current understanding of biology TRAIL-induced cell death. It is possible that such therapies may offer the opportunity to tackle one of the major current obstacles to effective cancer therapy, namely overcoming chemo- and/or targeted-therapy resistance. Even if this were achievable only for certain types of therapy resistance and only for particular types of cancer, this would be a significant and meaningful achievement.

Regulation of CyR61 expression and release by 3-mercaptopyruvate sulfurtransferase in colon cancer cells

Cysteine-rich angiogenic inducer 61 (CYR61, also termed CCN family member 1 or CCN1), is a matricellular protein encoded by the CYR61 gene. This protein has been implicated in the regulation of various cancer-associated processes including tumor growth, angiogenesis, tumor cell adhesion, migration, and invasion as well as the regulation of anticancer drug resistance. Hydrogen sulfide (H₂S) is a gaseous endogenous biological mediator, involved in the regulation of cellular bioenergetics, angiogenesis, invasion, and chemotherapeutic resistance in several types of cancer. H₂S is produced by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current studies were set up to investigate if CBS or 3-MST regulates CyR61 in colon cancer cells in the context of the regulation of proliferation, migration, and survival. The study mainly utilized HCT116 cells, in which two of the principal H₂S-producing enzymes, CBS and 3-MST, are highly expressed. The H₂S donor GYY4137 and the polysulfide donor Na₂S₃ activated the CyR61 promoter in a concentration-dependent fashion. Aminooxyacetic acid (AOAA), a pharmacological inhibitor of CBS as well as HMPSNE: 2-[(4-hydroxy-6- methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one, a pharmacological inhibitor of 3-MST inhibited CyR61 mRNA expression. This effect was more pronounced in response to HMPSNE than to AOAA and occurred through the modulation of S1PR via ATF1 and CREB. CyR61 was found to play an active, but relatively minor role in maintaining colon cell proliferation. HMPSNE markedly suppressed the secretion/release of CyR61 from the colon cancer cells. Moreover, HMPSNE promoted colon cancer cell apoptosis; endogenously produced CyR61 was found to counteract this effect, at least in part via RhoA activation. Taken together, we conclude that the upregulation of 3-MST in cancer cells exerts cytoprotective effects and confers the cancer cells a more aggressive phenotype - at least in part via the modulation of CyR61 expression and release.

Identification of immune-related ferroptosis prognostic marker and in-depth bioinformatics exploration of multi-omics mechanisms in thyroid cancer

Background: Factors such as variations in thyroid carcinoma (THCA) gene characteristics could influence the clinical outcome. Ferroptosis and immunity have been verified to play an essential role in various cancers, and could affect the cancer patients' prognosis. However, their relationship to the progression and prognosis of many types of THCA remains unclear. Methods: First, we extracted prognosis-related immune-related genes and ferroptosis-related genes from 2 databases for co-expression analysis to obtain prognosis-related differentially expressed immune-related ferroptosis genes (PR-DE-IRFeGs), and screened BID and CDKN2A for building a prognostic model. Subsequently, multiple validation methods were used to test the model's performance and compare its performance with other 4 external models. Then, we explored the mechanism of immunity and ferroptosis in the occurrence, development and prognosis of THCA from the perspectives of anti-tumor immunity, CDKN2A-related competitive endogenous RNA regulatory, copy number variations and high frequency gene mutation. Finally, we evaluated this model's clinical practice value. Results: BID and CDKN2A were identified as prognostic risk and protective factors, respectively. External data and qRT-PCR experiment also validated their differential expression. The model's excellent performance has been repeatedly verified and outperformed other models. Risk scores were significantly associated with most immune cells/functions. Risk score/2 PR-DE-IRFeGs expression was strongly associated with BRAF/NRAS/HRAS mutation. Single copy number deletion of CDKN2A is associated with upregulation of CDKN2A expression and worse prognosis. The predicted regulatory network consisting of CYTOR, hsa-miRNA-873-5p and CDKN2A was shown to significantly affect prognosis. The model and corresponding nomogram have been shown to have excellent clinical practice value. Conclusion: The model can effectively predict the THCA patients' prognosis and guide clinical treatment. Ferroptosis and immunity may be involved in the THCA's progression through antitumor immunity and BRAF/NRAS/HRAS mutation. CYTOR-hsa-miRNA-873-5p-CDKN2A regulatory networks and single copy number deletion of CDKN2A may also affect THCA' progression and prognosis.

BidSi6 and BidEL isoforms as a potential marker for predicting colorectal adenomatous polyps

Background

As a well-known protein, Bid links the extrinsic and intrinsic apoptotic pathways and plays important roles in cell proliferation. In this study, we evaluated the expression of two isoforms of the Bid gene (BidSi6 and BidEL) in colorectal adenomatous polyps as a biomarker and investigated the relationship between their expression levels with clinicopathological factors.

Methods

The expression of BidSi6 and BidEL isoforms in 22 pairs of Adenomatous polyps and adjust non-polyp tissues was measured by qReal-Time PCR and compared with 10 normal colon tissues. ROC curve was performed to examine the diagnostic capacity. Also, sequencing was performed for molecular identification of BidSi6 isoform in adenomatous polyp.

Results

Our results showed that BidSi6 and BidEL isoforms were significantly overexpressed in Adenomatous polyps and non-polyp adjacent tissues from the same patients compared to that in normal colon tissues, but there was no significant expression between polyps and adjust non-polyp tissues. There were no significant correlations between the expression of two isoforms and other features of clinicopathology. The area under the curve of BidSi6 and BidEL isoforms indicated powerful diagnostic capability. The phylogenetic tree was constructed based on the sequence of idSi6 isoform, and the results showed that adenomatous polyp tissue and adjust non-polyp tissue were separated from healthy colorectal tissue and reference sequence (EU678292).

Conclusions

These findings suggest that BidSi6 and BidEL isoforms can be used as new potential biomarkers in adenomatous polyps.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01282-0.

The anti-ovarian carcinoma activity of L-amino acid oxidase from Crotalus adamanteus venom in vivo and in vitro

Snake venom L-Amino-acid oxidase (svLAAO) has become a critical research target in molecular biology and medical science since its widespread presence and diverse biological roles, including antitumor application. Our research confirmed that Crotalus adamanteus (C. adamanteus) venom LAAO exhibited potential anti-ovarian cancer activity both in vivo and in vitro. C. adamanteus venom LAAO significantly reduced viability of ovarian cancer cells and caused morphological changes that preceded cell death. The results of molecular biology experiments showed that C. adamanteus venom LAAO caused expression changes of genes related to apoptotic pathways either intrinsically or extrinsically in ovarian cancer cells. Animal experiments and histological analysis also proved that C. adamanteus venom LAAO could effectively inhibit the tissue damage caused by ovarian cancer, and animals treated with C. adamanteus venom LAAO showed higher survival time. Catalase blocked the major apoptosis induction of C. adamanteus venom LAAO on ovarian cancer cells, suggesting that the cytotoxicity of C. adamanteus venom LAAO on ovarian cancer cells was mainly mediated by H₂O₂. These results infer that C. adamanteus venom LAAO will have some advantages in new drug research and antitumor drug development in future.

Identification of a Novel Defined Immune-Autophagy-Related Gene Signature Associated With Clinical and Prognostic Features of Kidney Renal Clear Cell Carcinoma

Background: As a common cancer of the urinary system in adults, renal clear cell carcinoma is metastatic in 30% of patients, and 1-2 years after diagnosis, 60% of patients die. At present, the rapid development of tumor immunology and autophagy had brought new directions to the treatment of renal cancer. Therefore, it was extremely urgent to find potential targets and prognostic biomarkers for immunotherapy combined with autophagy. Methods: Through GSE168845, immune-related genes, autophagy-related genes, and immune-autophagy-related differentially expressed genes (IAR-DEGs) were identified. Independent prognostic value of IAR-DEGs was determined by differential expression analysis, prognostic analysis, and univariate and multivariate Cox regression analyses. Then, the lasso Cox regression model was established to evaluate the correlation of IAR-DEGs with the immune score, immune checkpoint, iron death, methylation, and one-class logistic regression (OCLR) score. Results: In this study, it was found that CANX, BID, NAMPT, and BIRC5 were immune-autophagy-related genes with independent prognostic value, and the risk prognostic model based on them was well constructed. Further analysis showed that CANX, BID, NAMPT, and BIRC5 were significantly correlated with the immune score, immune checkpoint, iron death, methylation, and OCLR score. Further experimental results were consistent with the bioinformatics analysis. Conclusion: CANX, BID, NAMPT, and BIRC5 were potential targets and effective prognostic biomarkers for immunotherapy combined with autophagy in kidney renal clear cell carcinoma.

OSMI-1 Enhances TRAIL-Induced Apoptosis through ER Stress and NF-κB Signaling in Colon Cancer Cells

Levels of O-GlcNAc transferase (OGT) and hyper-O-GlcNAcylation expression levels are associated with cancer pathogenesis. This study aimed to find conditions that maximize the therapeutic effect of cancer and minimize tissue damage by combining an OGT inhibitor (OSMI-1) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We found that OSMI-1 treatment in HCT116 human colon cancer cells has a potent synergistic effect on TRAIL-induced apoptosis signaling. Interestingly, OSMI-1 significantly increased TRAIL-mediated apoptosis by increasing the expression of the cell surface receptor DR5. ROS-induced endoplasmic reticulum (ER) stress by OSMI-1 not only upregulated CHOP-DR5 signaling but also activated Jun-N-terminal kinase (JNK), resulting in a decrease in Bcl2 and the release of cytochrome c from mitochondria. TRAIL induced the activation of NF-κB and played a role in resistance as an antiapoptotic factor. During this process, O-GlcNAcylation of IκB kinase (IKK) and IκBα degradation occurred, followed by translocation of p65 into the nucleus. However, combination treatment with OSMI-1 counteracted the effect of TRAIL-mediated NF-κB signaling, resulting in a more synergistic effect on apoptosis. Therefore, the combined treatment of OSMI-1 and TRAIL synergistically increased TRAIL-induced apoptosis through caspase-8 activation. Conclusively, OSMI-1 potentially sensitizes TRAIL-induced cell death in HCT116 cells through the blockade of NF-κB signaling and activation of apoptosis through ER stress response.

Traditional Chinese medicines and their active ingredients sensitize cancer cells to TRAIL-induced apoptosis

The rapidly developing resistance of cancers to chemotherapy agents and the severe cytotoxicity of such agents to normal cells are major stumbling blocks in current cancer treatments. Most current chemotherapy agents have significant cytotoxicity, which leads to devastating adverse effects and results in a substandard quality of life, including increased daily morbidity and premature mortality. The death receptor of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can sidestep p53-dependent pathways to induce tumor cell apoptosis without damaging most normal cells. However, various cancer cells can develop resistance to TRAIL-induced apoptosis via different pathways. Therefore, it is critical to find an efficient TRAIL sensitizer to reverse the resistance of tumor cells to TRAIL, and to reinforce TRAIL's ability to induce tumor cell apoptosis. In recent years, traditional Chinese medicines and their active ingredients have shown great potential to trigger apoptotic cell death in TRAIL-resistant cancer cell lines. This review aims to collate information about Chinese medicines that can effectively reverse the resistance of tumor cells to TRAIL and enhance TRAIL's ability to induce apoptosis. We explore the therapeutic potential of TRAIL and provide new ideas for the development of TRAIL therapy and the generation of new anti-cancer drugs for human cancer treatment. This study involved an extensive review of studies obtained from literature searches of electronic databases such as Google Scholar and PubMed. "TRAIL sensitize" and "Chinese medicine" were the search keywords. We then isolated newly published studies on the mechanisms of TRAIL-induced apoptosis. The name of each plant was validated using certified databases such as The Plant List. This study indicates that TRAIL can be combined with different Chinese medicine components through intrinsic or extrinsic pathways to promote cancer cell apoptosis. It also demonstrates that the active ingredients of traditional Chinese medicines enhance the sensitivity of cancer cells to TRAIL-mediated apoptosis. This provides useful information regarding traditional Chinese medicine treatment, the development of TRAIL-based therapies, and the treatment of cancer.

Biomarkers predicting the response to chemotherapy and the prognosis in patients with esophageal squamous cell carcinoma

BACKGROUND

The prognosis of patients with esophageal squamous cell carcinoma (ESCC) has been improved by multidisciplinary therapy with chemoradiotherapy and surgery, but it remains poor. Advanced stage, malignant potential, and chemo-resistance contribute to the poor prognosis. Here, we attempted to identify predictive factors of the response to chemotherapy and the prognosis of ESCC patients.

PATIENTS AND METHODS

We examined 51 ESCC patients who were treated with chemotherapy followed by radical surgery, and 23 patients who were treated with chemotherapy alone. We conducted quantitative reverse transcription-polymerase chain reaction gene expression analysis using RNA extracted from 74 tumor tissue samples collected before chemotherapy and 67 tumor tissue samples collected after chemotherapy, focusing on PIK3CA, AKT-1, mTOR, 4E-BP1, p70S6K, PD-L1, and PD-L2.

RESULTS

The proportions of patients with high expressions of AKT-1 and PD-L1 before chemotherapy were significantly higher among the non-responders than among the responders (p = 0.034, p = 0.020, respectively). Multivariate analyses revealed that high PD-L1 expression before chemotherapy was associated with poor response to chemotherapy (odds ratio 2.998; 95% CI 1.043-8.619; p = 0.042) and high p70S6K expression before chemotherapy was a poor prognostic factor (hazard ratio 2.518; 95% CI 1.058-5.988; p = 0.037). In addition, the patients with high expression of PD-L1 and PD-L2 in the tumors after chemotherapy had significantly worse survival than those with low expression of these genes (p = 0.012, p = 0.007, respectively).

CONCLUSION

These results demonstrated that PD-L1 and p70S6K in the primary ESCC tissues were related to a poor response to chemotherapy and poor prognosis, respectively.

The multifaceted role of TRAIL signaling in cancer and immunity

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can lead to the induction of apoptosis in tumor or infected cells. However, activation of TRAIL signaling may also trigger nonapoptotic pathways in cancer and in nontransformed cells, that is, immune cells. Here, we review the current knowledge on noncanonical TRAIL signaling. The biological outcomes of TRAIL signaling in immune and malignant cells are presented and explained, with a focus on the role of TRAIL for natural killer (NK) cell function. Furthermore, we highlight the technical difficulties in dissecting the precise molecular mechanisms involved in the switch between apoptotic and nonapoptotic TRAIL signaling. Finally, we discuss the consequences thereof for a therapeutic manipulation of TRAIL in cancer and possible approaches to bypass these difficulties.

An unexpected turn of fortune: targeting TRAIL-Rs in KRAS-driven cancer

Twenty-one percent of all human cancers bear constitutively activating mutations in the proto-oncogene KRAS. This incidence is substantially higher in some of the most inherently therapy-resistant cancers including 30% of non-small cell lung cancers (NSCLC), 50% of colorectal cancers, and 95% of pancreatic ductal adenocarcinomas (PDAC). Importantly, survival of patients with KRAS-mutated PDAC and NSCLC has not significantly improved since the 1970s highlighting an urgent need to re-examine how oncogenic KRAS influences cell death signaling outputs. Interestingly, cancers expressing oncogenic KRAS manage to escape antitumor immunity via upregulation of programmed cell death 1 ligand 1 (PD-L1). Recently, the development of next-generation KRASG12C-selective inhibitors has shown therapeutic efficacy by triggering antitumor immunity. Yet, clinical trials testing immune checkpoint blockade in KRAS-mutated cancers have yielded disappointing results suggesting other, additional means endow these tumors with the capacity to escape immune recognition. Intriguingly, oncogenic KRAS reprograms regulated cell death pathways triggered by death receptors of the tumor necrosis factor (TNF) receptor superfamily. Perverting the course of their intended function, KRAS-mutated cancers use endogenous TNF-related apoptosis-inducing ligand (TRAIL) and its receptor(s) to promote tumor growth and metastases. Yet, endogenous TRAIL-TRAIL-receptor signaling can be therapeutically targeted and, excitingly, this may not only counteract oncogenic KRAS-driven cancer cell migration, invasion, and metastasis, but also the immunosuppressive reprogramming of the tumor microenvironment it causes. Here, we provide a concise summary of the current literature on oncogenic KRAS-mediated reprogramming of cell death signaling and antitumor immunity with the aim to open novel perspectives on combinatorial treatment strategies involving death receptor targeting.

Shikonin sensitizes A549 cells to TRAIL-induced apoptosis through the JNK, STAT3 and AKT pathways

BACKGROUND

TRAIL, tumor necrosis factor-related apoptosis-inducing ligand, can selectively kill cancer cells with little or no cytotoxicity toward normal human cells and is regarded as a potential relatively safe antitumor drug. However, some cancer cells are resistant to TRAIL-induced apoptosis. Thus, reagents that potentiate TRAIL-induced cytotoxicity are needed. Herein, we investigated whether shikonin, a natural compound from the root of Lithospermum erythrorhizon, can sensitize TRAIL-resistant cells to TRAIL-induced cytotoxicity.

RESULTS

The viability of A549 cells, which were resistant to TRAIL, was significantly decreased after treatment with TRAIL followed by shikonin. The underlying mechanisms by which shikonin sensitizes cells to TRAIL-induced cytotoxicity were also examined. Combined treatment with shikonin and TRAIL activated the caspase and JNK pathways, inhibited the STAT3 and AKT pathways, downregulated the expression of Mcl-1, Bcl-2, Bcl-xL, c-FLIP and XIAP and upregulated the expression of Bid.

CONCLUSIONS

In conclusion, the results indicated that shikonin sensitized resistant cancer cells to TRAIL-induced cytotoxicity via the modulation of the JNK, STAT3 and AKT pathways, the downregulation of antiapoptotic proteins and the upregulation of proapoptotic proteins.

Bcl-2 Inhibition to Overcome Resistance to Chemo- and Immunotherapy

Abstract: According to the World Health Organization (WHO), cancer is a leading cause of death worldwide. The identification of novel targets for cancer treatment is an area of intense work that has led Bcl-2 over-expression to be proposed as one of the hallmarks of cancer and Bcl-2 inhibition as a promising strategy for cancer treatment. In this review, we describe the different pathways related to programmed cell death, the role of Bcl-2 family members in apoptosis resistance to anti-cancer treatments, and the potential utility of Bcl-2 inhibitors to overcome resistance to chemo- and immunotherapy.

Improved cytotoxicity of novel TRAIL variants produced as recombinant fusion proteins

The TNF-Related Apoptosis Inducing Ligand (TRAIL) cytokine triggers apoptosis specifically in cancer cells. Susceptibility of a given cell to TRAIL depends on the activity of regulatory proteins, one of the most important of which is BID. The aim of this study was to increase the cytotoxic potential of TRAIL against cancer cells. TRAIL was fused to the BH3 domain of BID. Hence, TRAIL acted not only as an anticancer agent, but also as a specific carrier for the BID fragment. Two fusion protein variants were obtained by genetic engineering, harboring two different linker sequences. The short linker allowed both parts of the fusion protein to fold into their native structures. The long linker influenced the structure of the fused proteins but nonetheless resulted in their highest cytotoxic activity. Optimal buffer formulation was determined for all the analyzed TRAIL variants. Fusing the BH3 domain of BID to TRAIL improved the cytotoxic potential of TRAIL. Further, these findings may be useful for the optimization of other anticancer drugs based on TRAIL, since the appropriate formulation would secure their native structures during prolonged storage.

Bid-Induced Release of AIF/EndoG from Mitochondria Causes Apoptosis of Macrophages during Infection with Leptospira interrogans

Leptospirosis is a global zoonotic infectious disease caused by pathogenic Leptospira species. Leptospire-induced macrophage apoptosis through the Fas/FasL-caspase-8/3 pathway plays an important role in the survival and proliferation of the pathogen in hosts. Although, the release of mitochondrial apoptosis-inducing factor (AIF) and endonuclease G (EndoG) in leptospire-infected macrophages has been described, the mechanisms linking caspase and mitochondrion-related host-cell apoptosis has not been determined. Here, we demonstrated that leptospire-infection induced apoptosis through mitochondrial damages in macrophages. Apoptosis was caused by the mitochondrial release and nuclear translocation of AIF and/or EndoG, leading to nuclear DNA fragmentation. However, the mitochondrion-related CytC-caspase-9/3 pathway was not activated. Next, we found that the release and translocation of AIF and/or EndoG was preceded by the activation of the BH3-interacting domain death agonist (Bid). Furthermore, our data demonstrated that caspase-8 was activated during the infection and caused the activation of Bid. Meanwhile, high reactive oxygen species (ROS) trigged by the infection caused the dephosphorylation of Akt, which also activated Bid. In conclusion, Bid-mediated mitochondrial release of AIF and/or EndoG followed by nuclear translocation is a major mechanism of leptospire- induced apoptosis in macrophages, and this process is modulated by both caspase-8 and ROS-Akt signal pathways.

Aberrant splicing and drug resistance in AML

The advent of next-generation sequencing technologies has unveiled a new window into the heterogeneity of acute myeloid leukemia (AML). In particular, recurrent mutations in spliceosome machinery and genome-wide aberrant splicing events have been recognized as a prominent component of this disease. This review will focus on how these factors influence drug resistance through altered splicing of tumor suppressor and oncogenes and dysregulation of the apoptotic signaling network. A better understanding of these factors in disease progression is necessary to design appropriate therapeutic strategies recognizing specific alternatively spliced or mutated oncogenic targets.

Caspase-3 feedback loop enhances Bid-induced AIF/endoG and Bak activation in Bax and p53-independent manner

Chemoresistance in cancer has previously been attributed to gene mutations or deficiencies. Bax or p53 deficiency can lead to resistance to cancer drugs. We aimed to find an agent to overcome chemoresistance induced by Bax or p53 deficiency. Here, we used immunoblot, flow-cytometry analysis, gene interference, etc. to show that genistein, a major component of isoflavone that is known to have anti-tumor activities in a variety of models, induces Bax/p53-independent cell death in HCT116 Bax knockout (KO), HCT116 p53 KO, DU145 Bax KO, or DU145 p53 KO cells that express wild-type (WT) Bak. Bak knockdown (KD) only partially attenuated genistein-induced apoptosis. Further results indicated that the release of AIF and endoG also contributes to genistein-induced cell death, which is independent of Bak activation. Conversely, AIF and endoG knockdown had little effect on Bak activation. Knockdown of either AIF or endoG alone could not efficiently inhibit apoptosis in cells treated with genistein, whereas an AIF, endoG, and Bak triple knockdown almost completely attenuated apoptosis. Next, we found that the Akt-Bid pathway mediates Bak-induced caspase-dependent and AIF- and endoG-induced caspase-independent cell death. Moreover, downstream caspase-3 could enhance the release of AIF and endoG as well as Bak activation via a positive feedback loop. Taken together, our data elaborate the detailed mechanisms of genistein in Bax/p53-independent apoptosis and indicate that caspase-3-enhanced Bid activation initiates the cell death pathway. Our results also suggest that genistein may be an effective agent for overcoming chemoresistance in cancers with dysfunctional Bax and p53.

Suppression of esophageal tumor growth and chemoresistance by directly targeting the PI3K/AKT pathway

Esophageal cancer is the sixth most common cause of cancer-related deaths worldwide. Novel therapeutic intervention is urgently needed for this deadly disease. The functional role of PI3K/AKT pathway in esophageal cancer is little known. In this study, our results from 49 pairs of human esophageal tumor and normal specimens demonstrated that AKT was constitutively active in the majority (75.5%) of esophageal tumors compared with corresponding normal tissues. Inhibition of the PI3K/AKT pathway with specific inhibitors, wortmannin and LY294002, significantly reduced Bcl-xL expression, induced caspase-3-dependent apoptosis, and repressed cell proliferation and tumor growth in vitro and in vivo without obvious toxic effects. Moreover, significantly higher expression level of p-AKT was observed in fluorouracil (5-FU)-resistant esophageal cancer cells. Inactivation of PI3K/AKT pathway markedly increased the sensitivity and even reversed acquired resistance of esophageal cancer cells to chemotherapeutic drugs in vitro. More importantly, the resistance of tumor xenografts derived from esophageal cancer cells with acquired 5-FU resistance to chemotherapeutic drugs was significantly abrogated by wortmannin treatment in animals. In summary, our data support PI3K/AKT as a valid therapeutic target and strongly suggest that PI3K/AKT inhibitors used in conjunction with conventional chemotherapy may be a potentially useful therapeutic strategy in treating esophageal cancer patients.

Synergy of BID with doxorubicin in the killing of cancer cells

Overexpression of the BH3-interacting domain death agonist (BID) protein sensitizes certain cancer cell lines to apoptosis induced by anticancer agents, particularly by those acting through death receptors (e.g. TRAIL). Previously, we showed that recombinant BID fused with TAT cell penetrating peptide (TAT-BID) allowed for controlled delivery of BID to different cancer cell lines and moderately sensitized some of them to TRAIL or slightly to camptothecin. In the present study, we showed that TAT-BID delivered to HeLa cells strongly sensitized them to doxorubicin, as identified by cell viability and apoptosis assays. Another cell line sensitized to doxorubicin was PC3, whereas A549 and LNCaP cells were sensitized moderately or not at all, respectively. Sensitization was more pronounced at 1 μM doxorubicin administered for 48 h than for lower doses and shorter treatments. TAT-BID and doxorubicin may thus be considered as a potential therapeutic combination for cervical carcinoma and advanced prostate cancer treatment.

Elevated pressure enhanced TRAIL-induced apoptosis in hepatocellular carcinoma cells via ERK1/2-inactivation

The high frequency of intrinsic resistance to TNF-related apoptosisinducing ligand (TRAIL) in tumor cell lines has necessitated the development of strategies to sensitize tumors to TRAIL-induced apoptosis. We previously showed that elevated pressure applied as a mechanical stressor enhanced TRAIL-mediated apoptosis in human lung carcinoma cells in vitro and in vivo. This study focused on the effect of elevated pressure on the sensitization of TRAIL-resistant cells and the underlying mechanism. We observed elevated pressure-induced sensitization to TRAIL-mediated apoptosis in Hep3B cells, accompanied by the activation of several caspases and the mitochondrial signaling pathway. Interestingly, the enhanced apoptosis induced by elevated pressure was correlated with suppression of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) phosphorylation and CREB without any change to other MAPKs. Phosphorylation of Bcl-2-associated death promoter (BAD) also decreased, leading to inhibition of the mitochondrial pathway. To confirm whether the activation of pERK1/2 plays a key role in the TRAIL-sensitizing effect of elevated pressure, Hep3B cells were pre-treated with the ERK1/2-specific inhibitor PD98059 instead of elevated pressure. Co-treatment with PD98059 and TRAIL augmented TRAIL-induced apoptosis and decreased BAD phosphorylation. The inhibition of ERK1/2 activation by elevated pressure and PD98059 also reduced BH3 interacting-domain death agonist (BID), thereby amplifying apoptotic stress at the mitochondrial level. Our results suggest that elevated pressure enhances TRAIL-induced apoptosis of Hep3B cells via specific suppression of ERK1/2 activation among MAPKs.

Controlled delivery of BID protein fused with TAT peptide sensitizes cancer cells to apoptosis

BACKGROUND

Low cellular level of BID is critical for viability of numerous cancer cells. Sensitization of cells to anticancer agents by BID overexpression from adenovirus or pcDNA vectors is a proposed strategy for cancer therapy; however it does not provide any stringent control of cellular level of BID. The aim of this work was to examine whether a fusion of BID with TAT cell penetrating peptide (TAT-BID) may be used for controlled sensitization of cancer cells to anticancer agents acting through death receptors (TRAIL) or DNA damage (camptothecin). Prostate cancer PC3 and LNCaP, non-small human lung cancer A549, and cervix carcinoma HeLa cells were used in the study.

METHODS

Uptake of TAT-BID protein by cells was studied by quantitative Western blot analysis of cells extracts. Cells viability was monitored by MTT test. Apoptosis was detected by flow cytometry and cytochrome c release assay.

RESULTS

TAT-BID was delivered to all cancer cells in amounts depending on time, dose and the cell line. Recombinant BID sensitized PC3 cells to TRAIL or, to lesser extent, to camptothecin. Out of remaining cells, TAT-BID sensitized A549, and only slightly HeLa cells to TRAIL. None of the latter cell lines were sensitized to camptothecin. In all cases the mutant not phosphorylable by CK2 (TAT-BIDT59AS76A) was similarly efficient in sensitization as the wild type TAT-BID.

CONCLUSIONS

TAT-BID may be delivered to cancer cells in controlled manner and efficiently sensitizes PC3 and A549 cells to TRAIL. Therefore, it may be considered as a potential therapeutic agent that enhances the efficacy of TRAIL for the treatment of prostate and non-small human lung cancer.

CXCL12/CXCR4 blockade by oncolytic virotherapy inhibits ovarian cancer growth by decreasing immunosuppression and targeting cancer-initiating cells

Signals mediated by the chemokine CXCL12 and its receptor CXCR4 are involved in the progression of ovarian cancer through enhancement of tumor angiogenesis and immunosuppressive networks that regulate dissemination of peritoneal metastasis and development of cancer-initiating cells (CICs). In this study, we investigated the antitumor efficacy of a CXCR4 antagonist expressed by oncolytic vaccinia virus (OVV) against an invasive variant of the murine epithelial ovarian cancer cell line ID8-T. This variant harbors a high frequency of CICs that form multilayered spheroid cells and express the hyaluronan receptor CD44, as well as stem cell factor receptor CD117 (c-kit). Using an orthotopic ID8-T tumor model, we observed that i.p. delivery of a CXCR4 antagonist-expressing OVV led to reduced metastatic spread of tumors and improved overall survival compared with oncolysis alone. Inhibition of tumor growth with the armed virus was associated with efficient killing of CICs, reduced expression of ascitic CXCL12 and vascular endothelial growth factor, and decreases in i.p. numbers of endothelial and myeloid cells, as well as plasmacytoid dendritic cells. These changes, together with reduced recruitment of T regulatory cells, were associated with higher ratios of IFN-γ(+)/IL-10(+) tumor-infiltrating T lymphocytes, as well as induction of spontaneous humoral and cellular antitumor responses. Similarly, the CXCR4 antagonist released from virally infected human CAOV2 ovarian carcinoma cells inhibited peritoneal dissemination of tumors in SCID mice, leading to improved tumor-free survival in a xenograft model. Our findings demonstrate that OVV armed with a CXCR4 antagonist represents a potent therapy for ovarian CICs with a broad antitumor repertoire.

Momordica charantia lectin exhibits antitumor activity towards hepatocellular carcinoma

BACKGROUND

The incidence and mortality of hepatocellular carcinoma (HCC) remain high worldwide. Drug screening from natural plants is one of the potential therapeutic approaches on HCC.

METHODS

The antitumor effect of momordica charantia lectin (MCL) was examined, using MTT, colony formation, AnnexinV/PI staining, western blot and animal model.

RESULTS

MCL treatment induced G2/M phase arrest, autophagy, DNA fragmentation, mitochondrial injury, and subsequently cell apoptosis in HCC cells. Activation of caspase and MAPK pathway was involved in MCL-induced apoptosis. In vitro and in vivo studies showed that up-regulation of truncated Bid (tBid) upon MCL treatment. Correlation analysis revealed that Bid expression was reversely associated with the IC50 of MCL. Bid suppression using Bid siRNA, BI-6C9 (Bid inhibitor) and Z-IETD-FMK (caspase 8 inhibitor) dramatically attenuated MCL-induced cell proliferation inhibition, caspase 3 activation, ΔΨm depolarization and apoptosis. In addition, combination of MCL and sorafenib exerted stronger lethal activity towards HCC in vitro and in vivo.

CONCLUSION

Our data show that the natural compound MCL manifests antitumor activities towards HCC and therefore suggest MCL as a promising chemotherapeutic agent.

TRAIL-R2-specific antibodies and recombinant TRAIL can synergise to kill cancer cells

TRAIL induces apoptosis in cancer cells whilst sparing normal tissues. Despite promising pre-clinical results, few patients responded to treatment with recombinant TRAIL (Apo2L/Dulanermin) or TRAIL-R2-specific antibodies, such as conatumumab (AMG655). It is unknown whether this was due to intrinsic TRAIL resistance within primary human cancers or insufficient agonistic activity of the TRAIL-R-targeting drugs. FcγR-mediated crosslinking increases the cancer-cell-killing activity of TRAIL-R2-specific antibodies in vivo. We tested this phenomenon using FcγR-expressing immune cells from patients with ovarian cancer. However, even in the presence of high numbers of FcγR-expressing immune cells, as found in ovarian cancer ascites, AMG655-induced apoptosis was not enabled to any significant degree, indicating that this concept may not translate into clinical use. On the basis of these results we next set out to determine whether AMG655 possibly interferes with apoptosis induction by endogenous TRAIL which could be expressed by immune cells. To do so, we tested how AMG655 affected apoptosis induction by recombinant TRAIL. This, however, resulted in the surprising discovery of a striking synergy between AMG655 and non-tagged TRAIL (Apo2L/TRAIL) in killing cancer cells. This combination was as effective in killing cancer cells as highly active recombinant isoleucine-zipper-tagged TRAIL (iz-TRAIL). The increased killing efficiency was due to enhanced formation of the TRAIL death-inducing signalling complex (DISC), enabled by concomitant binding of Apo2L/TRAIL and AMG655 to TRAIL-R2. The synergy of AMG655 with Apo2L/TRAIL extended to primary ovarian cancer cells and was further enhanced by combination with the proteasome inhibitor bortezomib or a SMAC mimetic. Importantly, primary human hepatocytes were not killed by the AMG655-Apo2L/TRAIL combination, also not when further combined with bortezomib or a SMAC mimetic. We therefore propose that clinical-grade non-tagged recombinant forms of TRAIL, such as dulanermin, could be combined with antibodies such as AMG655 to introduce a highly active TRAIL-R2-agonistic therapy into the cancer clinic.

Inhibition of eIF2α dephosphorylation enhances TRAIL-induced apoptosis in hepatoma cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an inducer of cancer cell death that holds promise in cancer therapy. Cancer cells are more susceptible than normal cells to the cell-death-inducing effects of TRAIL. However, a variety of cancer cells are resistant to TRAIL through complex mechanisms. Here, we investigate the effects of inhibition of eukaryotic initiation factor 2 subunit α (eIF2α) dephosphorylation on TRAIL-induced apoptosis in hepatoma cells. Treatment of hepatoma cells with salubrinal, an inhibitor of eIF2α dephosphorylation, enhances TRAIL-induced eIF2α phosphorylation, CCAAT/enhancer-binding protein homologous protein (CHOP) expression and caspase activation. Salubrinal enhances TRAIL-induced apoptosis, which could be abrogated by caspase inhibitor. Overexpression of phosphomimetic eIF2α (S51D) enhances TRAIL-induced CHOP expression, caspase 7 and PARP cleavage and apoptosis. By contrast, overexpression of phosphodeficient eIF2α (S51A) abrogates the stimulation of TRAIL-induced apoptosis by salubrinal. Moreover, knockdown of growth arrest and DNA damage-inducible protein 34 (GADD34), which recruits protein phosphatase 1 to dephosphorylate eIF2α, enhances TRAIL-induced eIF2α phosphorylation, CHOP expression, caspase activation and apoptosis. Furthermore, the sensitization of hepatoma cells to TRAIL by salubrinal is dependent on CHOP. Knockdown of CHOP abrogates the stimulation of TRAIL-induced caspase activation and apoptosis by salubrinal. Combination of salubrinal and TRAIL leads to increased expression of Bim, a CHOP-regulated proapoptotic protein. Bim knockdown blunts the stimulatory effect of salubrinal on TRAIL-induced apoptosis. Collectively, these findings suggest that inhibition of eIF2α dephosphorylation may lead to synthetic lethality in TRAIL-treated hepatoma cells.

Single CpG island methylation is not sufficient to maintain the silenced expression of CASPASE-8 apoptosis-related gene among women with epithelial ovarian cancer

Despite impressive research efforts, the biology of epithelial ovarian cancer (EOC) remains poorly understood and alterations in the expression of CASPASE-8 contribute to a worse tumor prognosis. This study assesses the methylation of the CpG island within the CASPASE-8 promoter and CASPASE-8 gene expression both in cystadenoma tumors and in primary and metastatic EOC. DNA and RNA were obtained from women with normal ovarian tissues (n=18), ovarian serous cystadenoma tumors (n=11) and EOC (n=16) using Trizol(®). The methylation frequency of the CpG island in the CASPASE-8 promoter was assessed using the methylation-specific PCR assay after DNA bisulfite conversion. Quantitative PCR was performed to quantify the relative levels of CASPASE-8 in each sample. The differences between samples with each group were evaluated using the Mann-Whitney U and Kruskal-Wallis tests as indicated. Hemimethylation of the CASPASE-8 promoter was found in 11.8% of the normal ovary samples, 20% of the cystadenoma tumors and 20% of the metastatic EOC, while methylation of the CASPASE-8 promoter was absent in the EOC primary tissues (P=0.047). An increased CASPASE-8 expression level was observed in all tumor groups. Significant differences were observed in the CASPASE-8 expression levels when compared with all ovarian tumor groups (P=0.0278). Promoter DNA methylation did not associate with expression levels of CASPASE-8, suggesting the presence of other mechanisms in relation to gene expression control in EOC; thus providing a better understanding of this complex disease.

Osteoprotegerin (OPG) activates integrin, focal adhesion kinase (FAK), and Akt signaling in ovarian cancer cells to attenuate TRAIL-induced apoptosis

BACKGROUND

Resistance to apoptosis is a major problem in ovarian cancer (OC) and correlates with poor prognosis. Osteoprotegerin (OPG) is a soluble secreted factor that acts as a decoy receptor for receptor activator of NF-κB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). OPG has been reported to attenuate TRAIL-induced apoptosis in a variety of cancer cells, including OC cells. OPG-mediated protection against TRAIL has been attributed to its decoy receptor function. However, OPG activates integrin/focal adhesion kinase (FAK) signaling in endothelial cells. In OC cells, activation of integrin/FAK signaling inhibits TRAIL-induced apoptosis. Based on these observations, we hypothesized that OPG could attenuate TRAIL-induced apoptosis in OC cells through integrin/FAK signaling.

METHODS

In vitro experiments including immunoblots, colony formation assays, and apoptosis measurements were used to assess the effect of OPG on TRAIL-induced apoptosis.

RESULTS

Exogenous OPG protected from TRAIL-induced apoptosis in a TRAIL binding-independent manner and OPG protection was αvβ3 and αvβ5 integrin/FAK signaling-dependent. Moreover, OPG-mediated activation of integrin/FAK signaling resulted in the activation of Akt. Inhibition of both integrin/FAK and Akt signaling significantly inhibited OPG-mediated attenuation of TRAIL-induced apoptosis. Although OPG also stimulated ERK1/2 phosphorylation, inhibition of ERK1/2 signaling did not significantly altered OPG protection.

CONCLUSIONS

Our studies provide evidence, for the first time, that OPG can attenuate TRAIL-induced apoptosis in a TRAIL binding-independent manner through the activation of integrin/FAK/Akt signaling in OC cells.

Immunomodulatory effects of interferons in malignancies

Investigation of the antitumor and immunomodulatory activities of interferon (IFN) began shortly after the cytokine was discovered in 1957. Early work showed a direct correlation between administration of IFN and inhibition of symptoms associated with virally induced leukemia in mice as well as an increase in their survival time. Subsequent studies with purified IFNs confirmed the direct and indirect stimulation of immune cells, resulting in antitumor activities of IFN. Clinically, IFN-alphas (αs) have been shown to have activity against a variety of tumors. Initially, the U.S. Food and Drug Administration licensed 2 recombinant IFN-αs for the treatment of hairy-cell leukemia and then later for several other cancers. The success rate seen with IFNs and certain tumors has been varied. Unfortunately, some neoplasms show no response to IFN. Monocytes/macrophages play an important role in cancer progression. Monocytes in combination with IFN may be an important therapy for several cancers. This article focuses on the role of IFN and monocytes alone or in combination in affecting malignancies.

Novel insights into the synergistic interaction of a thioredoxin reductase inhibitor and TRAIL: the activation of the ASK1-ERK-Sp1 pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death in various types of cancer cells but has little or no effects on normal cells. Unfortunately, not all cancer cells respond to TRAIL; therefore, TRAIL sensitizing agents are currently being explored. Here, we reported that 6-(4-N,N-dimethylaminophenyltelluro)-6-deoxy-β-cyclodextrin (DTCD), a cyclodextrin-derived diorganyl telluride which has been identified as an excellent inhibitor of thioredoxin reductase (TrxR), could sensitize TRAIL resistant human ovarian cancer cells to undergo apoptosis. In vitro, DTCD enhanced TRAIL-induced cytotoxicity in human ovarian cancer cells through up-regulation of DR5. Luciferase analysis and CHIP assays showed that DTCD increased DR5 promoter activity via Sp1 activation. Additionally, DTCD stimulated extracellular signal-regulated kinase (ERK) activation, while the ERK inhibitor PD98059 blocked DTCD-induced DR5 expression and suppressed binding of Sp1 to the DR5 promoter. We further demonstrated that DTCD could induce the release of ASK1 from its complex with Trx-1, and recovered its kinase activity. Meanwhile, suppression of ASK1 by RNA interference led to decreased ERK phosphorylation induced by DTCD. The underlying mechanisms reveal that Trx-1 is heavily oxidized in response to DTCD treatment, in accordance with the fact that DTCD could inhibit the activity of TrxR that reduces oxidized Trx-1. Moreover, using an A2780 xenograft model, DTCD plus TRAIL significantly inhibited the growth of tumor in vivo. Our results suggest that Trx/TrxR system inhibition may play a critical role in apoptosis by combined treatment with DTCD and TRAIL, and raise the possibility that their combination may be a promising strategy for ovarian carcinoma treatment.

Mitochondria in relation to cancer metastasis

Mitochondria, also known as "Power House of cell," are crucial organelles, regulating energy metabolism. Recently, an involvement of mitochondria in cancer occurrence and metastasis has been proposed. The roles of mitochondria in cancer progression/metastasis include alteration of glycolysis, regulation of ROS and suppression of intrinsic apoptosis. This mini-review explains the specific mitochondrial characteristics during cancer metastasis with past and recent findings. It may contribute to understanding mitochondria-related mechanisms of cancer metastasis.

High expression of crystallin αB represents an independent molecular marker for unfavourable ovarian cancer patient outcome and impairs TRAIL- and cisplatin-induced apoptosis in human ovarian cancer cells

Dysregulated apoptotic pathways are regarded as major reasons for chemoresistance development as a particular challenge in ovarian cancer therapy. In search of molecular factors affecting human ovarian cancer cell apoptosis and, consequently, patient survival, we examined tumors of 103 platinum-/taxane-treated ovarian cancer patients by mRNA-array hybridization, qPCR, and immunohistochemistry. We identified high expression of crystallin αB (CRYAB), a proposed negative regulator of tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. By Kaplan Meier analysis, this factor turned out to be significantly associated with poor patient outcome [overall survival (OS) p = 0.001, recurrence-free survival (RFS) p = 0.003]. Elevated hazard ratios (HR) were estimated with regard to OS (HR = 2.11, 95% CI 1.10-4.06) and RFS (HR = 1.92, 95% CI 1.07-3.47) in multivariable analyses. These associations were confirmed in independent, publicly available mRNA data comprising 431 patients for OS (p < 0.001) and 413 for RFS (p < 0.001). Our findings were validated by studying apoptotic events in cultured human ovarian cancer cells which were stably transfected to express elevated CRYAB levels. These data emphasized the crucial role of CRYAB in human ovarian cancer biology since TRAIL- as well as cisplatin-induced apoptosis was significantly impaired as a function of enhanced CRYAB expression. Taken together, we identified CRYAB as an independent biomarker for unfavourable outcome of human ovarian cancer patients. Since TRAIL is currently tested as anti-cancer drug and large proportions of the present patient cohort displayed low CRYAB levels in their tumors, CRYAB may enable the selection of patient subgroups benefiting most from TRAIL-containing therapy.

Differential susceptibility of gastric cancer cells to TRAIL-induced apoptosis

Understanding the molecular basis of the differential sensitivity of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis is required to predict therapeutic outcomes and to improve the effectiveness of TRAIL-based therapy. This study aimed to compare the responsiveness of gastric cancer cells to TRAIL treatment and to investigate the molecular basis of the differential TRAIL sensitivity of four gastric cancer cell lines. The TRAIL sensitivity of the four cell lines was ranked in the following order: SNU-16 ≈ SNU-620 > SNU-5 >> SNU-1. The level of Annexin V binding and the activation profile of caspase-3, -8 and -9 corroborated the differential TRAIL susceptibility of the cell lines. To determine the molecular basis of the differential sensitivity to TRAIL, we examined the expression of signaling components involved in TRAIL-mediated apoptosis. The mRNA level and surface expression of death receptor 4 (DR4) were significantly decreased in the SNU-1 cells compared to the other cell lines. Bid cleavage and X-linked inhibitor of apoptosis (XIAP) degradation were significantly increased in the SNU-16 and SNU-620 cells compared to the SNU-5 and SNU-1 cells, although Bid and XIAP were expressed at similar levels across the four cell lines. The expression and degradation of FLICE-inhibitory protein (FLIP) upon TRAIL treatment was independent of TRAIL sensitivity. In conclusion, the differential susceptibility of the four gastric cancer cells to TRAIL may be ascribed to the differential expression of DR4 and the proper augmentation of the death signal by the truncation of Bid and degradation of XIAP.

Ovarian cancer ascites increase Mcl-1 expression in tumor cells through ERK1/2-Elk-1 signaling to attenuate TRAIL-induced apoptosis

Background

Ascites may affect the progression of ovarian cancer (OC). In particular, soluble factors present in OC ascites can create a protective environment for tumor cells that promote de novo resistance to drug- and death receptor-induced apoptosis. However, the underlying molecular mechanisms responsible for ascites-induced drug resistance are not well characterized.

Methods

Using human OC cell lines and tissues microarrays of human OC biopsies, we assessed the mechanism by which OC ascites increase Mcl-1 expression using Western blots, chemical inhibitors of ERK and small-inhibitory RNA treatments.

Results

In the present study, we found that both Mcl-1 mRNA and protein levels were upregulated within 2 h upon treatment of OC cells with ascites obtained from women with advanced OC. In contrast, the expression of other Bcl-2 family antiapoptotic members such as Bcl-2 and Bcl-X_L was not affected by ascites. An increase of Mcl-1 expression was consistently observed across different ascites from women with advanced serous OC. The knockdown of Mcl-1 significantly blocked ascites-induced Mcl-1 upregulation and ascites-mediated inhibition of TRAIL-induced apoptosis. Ascites induced a rapid phosphorylation of ERK1/2 and Elk-1 transcription factor. Furthermore, we found that ERK1/2 inhibition or Elk-1 knockdown was sufficient to block ascites-induced Mcl-1 expression. In high grade serous OC, we found a positive correlation between phosphorylated ERK1/2 and Mcl-1 expression.

Conclusions

These results indicate that ascites-induced ERK1/2/Elk-1 signaling is critical for Mcl-1 expression and for the ascites-mediated attenuation of TRAIL-induced apoptosis. The ERK1/2/Elk-1/Mcl-1 pathway represents a novel mechanism by which ascites induce de novo TRAIL resistance in OC cells.

Osteoprotegerin (OPG) protects ovarian cancer cells from TRAIL-induced apoptosis but does not contribute to malignant ascites-mediated attenuation of TRAIL-induced apoptosis

BACKGROUND

Resistance to apoptosis is a major problem in ovarian cancer and correlates with poor prognosis. Osteoprotegerin (OPG) is a secreted factor in malignant ascites and acts as a decoy receptor for receptor activator of NF-κB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL promotes apoptosis in ovarian cancer cells. Ovarian cancer ascites attenuate TRAIL-induced apoptosis raising the possibility that OPG contained in ascites may abrogate the anti-tumor activity of TRAIL.

METHODS

Determination of OPG levels in ascites was measured by ELISA. Effect of OPG on TRAIL-induced cell death was determined by XTT and colony forming assays in ovarian cancer cell lines and primary tumor cells. Apoptosis was assessed by ELISA.

RESULTS

We found that recombinant OPG and malignant ascites attenuates TRAIL-induced cell death and apoptosis in a dose-dependent manner in ovarian cancer cell lines and primary ovarian tumor cells. OPG is present at high levels in the ascites of patients with ovarian cancer. We found a positive correlation between the levels of OPG in ascites and the ability of the ascites to attenuate TRAIL-induced cell death. The anti-apoptotic effect of ascites was not reversed by co-incubation with an OPG blocking antibody.

CONCLUSIONS

OPG and malignant ascites protect ovarian cancer cells from TRAIL-induced apoptosis. Although malignant ascites contain high levels of OPG, OPG is not a critical component that contributes to ascites-mediated attenuation of TRAIL-induced apoptosis.

Targeted ovarian cancer treatment: the TRAILs of resistance

Ovarian cancer (OC) is the leading cause of death from gynecological malignancies. Although most patients respond to the initial therapy when presenting with advanced disease, only 10-15% maintain a complete response following first-line therapy. Recurrence defines incurable disease in most cases. Despite improvements with conventional chemotherapy combinations, the overall cure rate remained mostly stable over the years. Increased long-term survival in OC patients will only be achieved through a comprehensive understanding of the basic mechanisms of tumor cell resistance. Such knowledge will translate into the development of new targeted strategies. In addition, because OC is considered to be a heterogeneous group of diseases with distinct gene expression profiles, it is likely that different approaches to treatment for distinct sub-types will be required to optimize response. One of the new promising anti-cancer therapies is the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL has the ability to selectively induce apoptosis in tumor cells with little toxicity to normal cells. Death receptor ligands such as TRAIL rely on the activation of the apoptotic signaling pathway to destroy tumor cells. TRAIL induces the formation of a pro-apoptotic death-inducing signaling complex (DISC) via its death receptors, TRAIL receptor 1 (TRAIL R1) and TRAIL receptor 2 (TRAIL R2). The formation of the DISC activates caspase-8 which requires further signal amplification through the mitochondrial pathway for an efficient activation of effector caspases in OC cells. The initial enthusiasm for TRAIL has been hampered by accumulating data demonstrating TRAIL resistance in various tumor types including OC cells. There is, therefore, a need to identify markers of TRAIL resistance, which could represent new hits for targeted therapy that will enhance TRAIL efficacy. In addition, the identification of patients that are more likely to respond to TRAIL therapy would be highly desirable. In this review, we discuss the different molecular and cellular mechanisms leading to TRAIL resistance in OC. In particular, we address the mechanisms involved in intrinsic, acquired and environment-mediated TRAIL resistance, and their potential implication in the clinical outcome.

Knockdown of MADD and c-FLIP overcomes resistance to TRAIL-induced apoptosis in ovarian cancer cells

OBJECTIVE

The clinical utility of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in the treatment of established human malignancies is limited by the development of resistance to TRAIL. We hypothesized that knockdown of map-kinase activating death domain containing protein (MADD), a TRAIL-resistance factor, may overcome TRAIL resistance in ovarian cancer cells.

STUDY DESIGN

MADD expression in resected ovarian cancer specimens and cell lines was quantified with the use of polymerase chain reaction. Sensitivity of ovarian cancer cell lines to TRAIL, with or without MADD knockdown, was assessed.

RESULTS

MADD is expressed at relatively higher levels in human malignant ovarian cancer tissues and cell lines, compared with normal ovarian tissues. The cell lines OVCA429 and OVCAR3 were susceptible, and cell lines CAOV-3 and SKOV-3 were resistant to TRAIL. MADD knockdown in CAOV-3 cells, but not in SKOV-3 cells, conferred TRAIL sensitivity. Knockdown of cellular Fas-associated death domain-like interleukin-1 beta-converting enzyme-inhibitory protein (c-FLIP) in SKOV-3 cells increased spontaneous and TRAIL-induced apoptosis, which was further increased on MADD knockdown.

CONCLUSION

MADD/c-FLIP(L) knockdown can render TRAIL-resistant ovarian cancer cells susceptible to TRAIL.

Simultaneously targeting bcl-2 and Akt pathways sensitizes nasopharyngeal carcinoma to tumor necrosis factor-related apoptosis-inducing ligand

The 5-year survival rate of nasopharyngeal carcinoma (NPC) is disappointing despite the much improved technologies in its treatment. Thus, finding more effective treatment for NPC has become an urgent priority. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can selectively induce apoptosis in most tumor cells while sparing normal cells. However, its potential in the treatment of NPC has been limited by the eventual emergence of drug resistance. Bcl-2 and Akt contribute to TRAIL resistance in some cancer cells. In this study, CNE-2 was found to be the most resistant NPC cell line to TRAIL, and whether Bcl-2 small-interfering RNA (siRNA) and phosphatidylinositol 3-kinase (PI3-K) inhibitors (LY294002 and Wortmannin) could prevent TRAIL resistance in CNE-2 was also investigated. Results showed that both Bcl-2 siRNA and PI3-K inhibitors could prevent TRAIL resistance in CNE-2. Bcl-2 siRNA sensitized CNE-2 by activating the intrinsic apoptotic pathway and PI3-K inhibitors sensitized CNE-2 by activating both intrinsic and extrinsic pathways. Further, simultaneously targeting Bcl-2 and Akt was found to be a more efficient approach to prevent TRAIL resistance in CNE-2 and this synergistic effect happened at the level of Bid downstream. At last, the combinative treatments did not enhance toxicity of TRAIL in MRC5, a human benign fibroblast cell line. This study suggests that simultaneously targeting Bcl-2 and Akt pathway might be effective in preventing TRAIL resistance of NPC cells.

PTEN deletion prevents ischemic brain injury by activating the mTOR signaling pathway

It is increasingly clear that the tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a negative regulator of neuronal cell survival. However, its molecular mechanisms remain poorly understood. Here we found that PTEN/mTOR is critical for controlling neuronal cell death after ischemic brain injury. Male rats were subjected to MCAO (middle cerebral artery occlusion) followed by pretreating with bpv (pic), a potent inhibitor for PTEN, or by intra-cerebroventricular infusion of PTEN siRNA. bpv (pic) significantly decreased infarct volume and reduced the number of TUNEL-positive cells. We further demonstrated that although bpv (pic) did not affect brain injury-induced mTOR protein expression, bpv (pic) prevented decrease in phosphorylation of mTOR, and the subsequent decrease in S6. Similarly, down-regulation of PTEN expression also reduced the number of TUNEL-positive cells, and increased phospho-mTOR. These data suggest that PTEN deletion prevents neuronal cell death resulting from ischemic brain injury and that its neuroprotective effects are mediated by increasing the injury-induced mTOR phosphorylation.

ROS and CHOP are critical for dibenzylideneacetone to sensitize tumor cells to TRAIL through induction of death receptors and downregulation of cell survival proteins

Because tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) selectively kills tumor cells, it is being tested in cancer patients. Unfortunately, patients develop resistance to the cytokine, therefore, agents that can sensitize cells to TRAIL are urgently needed. In this study, we investigated whether dibenzylideneacetone (DBA) can sensitize cancer cells to TRAIL and potentiates TRAIL-induced apoptosis. As indicated by accumulation of the membrane phospholipid phosphatidylserine, DNA breaks, intracellular esterase activity, and activation of caspase-8, -9, and -3, we concluded that DBA potentiated TRAIL-induced apoptosis in colon cancer cells. DBA also converted TRAIL resistant-cells to TRAIL-sensitive. When examined for the mechanism, we found that DBA decreased the expression of antiapoptotic proteins and decoy receptor-2 and increased proapoptotic proteins. DBA also induced both death receptor (DR)-5 and DR4. Knockdown of DR5 and DR4 by small interfering RNA (SiRNA) reduced the sensitizing effect of DBA on TRAIL-induced apoptosis. In addition, DBA increased the expression of CHOP proteins. Knockdown of CHOP by siRNA decreased the induction of DBA-induced DR5 expression and apoptosis. Induction of receptors by DBA, however, was p53-independent, as deletion of p53 had no effect on receptor induction. We observed that DBA-induced induction of DR5 and DR4 was mediated through generation of reactive oxygen species (ROS), as N-acetylcysteine blocked the induction of death receptors and suppression of cell survival proteins by DBA. Overall, our results show that DBA potentiates TRAIL-induced apoptosis through downregulation of cell survival proteins and upregulation of death receptors via activation of ROS and CHOP mediated pathways.