Involvement of Bid in the crosstalk between ferroptotic agent-induced ER stress and TRAIL-induced apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces death receptor-mediated extrinsic apoptosis, specifically in cancer cells, and Bid (BH3-interacting domain death agonist) plays an important role in TRAIL-induced apoptosis. Ferroptosis is a newly defined form of regulated cell death known to be distinct from other forms of cell death. However, our previous studies have shown that ferroptosis shares common pathways with other types of programmed cell death such as apoptosis. In this study, we investigated the role of Bid in the crosstalk between the ferroptotic agent-induced endoplasmic reticulum (ER) stress response and TRAIL-induced apoptosis. When human colorectal carcinoma HCT116 cells were treated with the ferroptosis-inducing agents artesunate and erastin in combination with TRAIL, TRAIL-induced activation of caspase-8 was enhanced, and subsequently, the truncation of Bid was increased. Similar results were observed when ovarian adenocarcinoma OVCAR-3 cells were treated with the ferroptotic agents in combination with TRAIL. Results from studies with Bid mutants reveal that the truncation of Bid and the presence of intact BH3 domains are critical for synergistic apoptosis. Nonfunctional Bid mutants were not able to activate the mitochondria-dependent apoptosis pathway, which is required for the conversion of p19 to p17, the active form of caspase-3. These results indicate that Bid plays a critical role in the crosstalk between the ferroptotic agent-induced ER stress response and TRAIL-induced apoptosis.

The emerging role of selenium metabolic pathways in cancer: New therapeutic targets for cancer.

Selenium (Se) is incorporated into the body via the selenocysteine (Sec) biosynthesis pathway, which is critical in the synthesis of selenoproteins, such as glutathione peroxidases and thioredoxin reductases. Selenoproteins, which play a key role in several biological processes, including ferroptosis, drug resistance, endoplasmic reticulum stress, and epigenetic processes, are guided by Se uptake. In this review, we critically analyze the molecular mechanisms of Se metabolism and its potential as a therapeutic target for cancer. Sec insertion sequence binding protein 2 (SECISBP2), which is a positive regulator for the expression of selenoproteins, would be a novel prognostic predictor and an alternate target for cancer. We highlight strategies that attempt to develop a novel Se metabolism-based approach to uncover a new metabolic drug target for cancer therapy. Moreover, we expect extensive clinical use of SECISBP2 as a specific biomarker in cancer therapy in the near future. Of note, scientists face additional challenges in conducting successful research, including investigations on anticancer peptides to target SECISBP2 intracellular protein.

Glucose deprivation-induced endoplasmic reticulum stress response plays a pivotal role in enhancement of TRAIL cytotoxicity.

Abnormalities of the tumor vasculature result in insufficient blood supply and development of a tumor microenvironment that is characterized by low glucose concentrations, low extracellular pH, and low oxygen tensions. We previously reported that glucose-deprived conditions induce metabolic stress and promote tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cytotoxicity. In this study, we examined whether the metabolic stress-associated endoplasmic reticulum (ER) stress response pathway plays a pivotal role in the enhancement of TRAIL cytotoxicity. We observed no significant cytotoxicity when human colorectal cancer SW48 cells were treated with various doses of TRAIL (2-100 ng/ml) for 4 h or glucose (0-25 mM) for 24 h. However, a combination of TRAIL and low glucose-induced dose-dependent apoptosis through activation of caspases (-8, -9, and -3). Studies with activating transcription factor 4 (ATF4), C/EBP-homologous protein (CHOP), p53 upregulated modulator of apoptosis (PUMA), or death receptor 5 (DR5)-deficient mouse embryonic fibroblasts or HCT116 cells suggest that the ATF4-CHOP-PUMA axis and the ATF4-CHOP-DR5 axis are involved in the combined treatment-induced apoptosis. Moreover, the combined treatment-induced apoptosis was completely suppressed in BH3 interacting-domain death agonist (Bid)- or Bcl-2-associated X protein (Bax)-deficient HCT116 cells, but not Bak-deficient HCT116 cells. Interestingly, the combined treatment-induced Bax oligomerization was suppressed in PUMA-deficient HCT116 cells. These results suggest that glucose deprivation enhances TRAIL-induced apoptosis by integrating the ATF4-CHOP-PUMA axis and the ATF4-CHOP-DR5 axis, consequently amplifying the Bid-Bax-associated mitochondria-dependent pathway.

Ferroptotic agent-induced endoplasmic reticulum stress response plays a pivotal role in the autophagic process outcome.

Ferroptosis has been reported as a unique form of cell death. However, in recent years, researchers have increasingly challenged the uniqueness of ferroptosis compared to other types of cell death. In this study, we examined whether ferroptosis shares cell death pathways with other types of cell death, especially autophagy, via the autophagic process. Here, we observed that ferroptosis inducers (artesunate [ART] and erastin [ERA]) and autophagy inducers (bortezomib [BOR] and XIE62-1004) led to autophagosome formation via the endoplasmic reticulum (ER) stress response. Unlike XIE62-1004, ART, ERA, and BOR, which affect glutathione production or utilization, induced oxidative stress responses-an increase in the levels of heme oxygenase-1 and lipid peroxidation. Oxidative stress responses were attenuated by deletion of autophagy-related gene-5 or treatment with autophagy inhibitors (bafilomycin and chloroquine). Our studies provide an overview of common death pathways-the ER stress response-associated autophagic process in ferroptosis and autophagy. We also highlight the role played by glutathione redox system in the outcome of the autophagic process.

Genomic profiling of the residual disease of advanced high-grade serous ovarian cancer after neoadjuvant chemotherapy.

The goal of our study was to demonstrate the spectrum of genomic alterations present in the residual disease of patients with advanced high-grade serous ovarian cancer (HGSOC) after neoadjuvant chemotherapy (NAC), including matched pretreatment biopsies. During the study period between 2006 and 2017, we collected pre-NAC and post-NAC tumor tissue samples from patients with advanced HGSOC. We performed combined next-generation sequencing and immunohistochemistry to identify actionable targets and pathway activation in post-NAC residual tumors. We also examined whether post-NAC profiling of residual HGSOC identified targetable molecular lesions in the chemotherapy-resistant component of tumors. Among 102 post-NAC samples, 41 (40%) of patients had mutations in homologous recombination repair (HRR) genes (HRR deficiency). Patients with HRR mutations had higher tumor mutation burdens (p < 0.001) and higher alterations in the PI3K-AKT-mTOR pathway (p = 0.004) than patients without these HRR mutations. Nevertheless, we found no significant differences in progression-free survival (p = 0.662) and overall survival (OS; p = 0.828) between the two groups. Most patients (91%) had alterations in at least one of the targetable pathways, and those patients with cell cycle (p = 0.004) and PI3K-AKT-mTOR signaling (p = 0.005) pathway alterations had poorer OS (Bonferroni-corrected threshold = 0.0083, 0.05/6). We showed the genomic landscape of tumor cells remaining in advanced HGSOC after NAC. Once validated, these data can help inform biomarker-driven adjuvant studies in targeting residual tumors to improve the outcomes of patients with advanced HGSOC after NAC.

BAX-dependent mitochondrial pathway mediates the crosstalk between ferroptosis and apoptosis.

Ferroptosis is considered a distinctive form of cell death compared to other types of death such as apoptosis. It is known to result from iron-dependent accumulation of lipid peroxides rather than caspase activation. However, we reported recently that ferroptosis interplays with apoptosis. In this study, we investigated a possible mechanism of this interplay between ferroptosis and apoptosis. Results from our studies reveal that combined treatment of the ferroptotic agent erastin and the apoptotic agent TRAIL effectively disrupted mitochondrial membrane potential (ΔΨm) and subsequently promoted caspase activation. The alterations of mitochondrial membrane potential are probably due to an increase in oligomerization of BAX and its accumulation at the mitochondria during treatment with erastin and TRAIL. Interestingly, the combined treatment-promoted apoptosis was effectively inhibited in BAX-deficient HCT116 cells, but not BAK-deficient cells. These results indicate that the BAX-associated mitochondria-dependent pathway plays a pivotal role in erastin-enhanced TRAIL-induced apoptosis.

Ferroptosis-inducing agents enhance TRAIL-induced apoptosis through upregulation of death receptor 5.

Ferroptosis is considered genetically and biochemically distinct from other forms of cell death. In this study, we examined whether ferroptosis shares cell death pathways with other types of cell death. When human colon cancer HCT116, CX-1, and LS174T cells were treated with ferroptotic agents such as sorafenib (SRF), erastin, and artesunate, data from immunoblot assay showed that ferroptotic agents induced endoplasmic reticulum (ER) stress and the ER stress response-mediated expression of death receptor 5 (DR5), but not death receptor 4. An increase in the level of DR5, which is activated by binding to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and initiates apoptosis, was probably responsible for synergistic apoptosis when cells were treated with ferroptotic agent in combination with TRAIL. This collateral effect was suppressed in C/EBP (CCAAT-enhancer-binding protein)-homologous protein (CHOP)-deficient mouse embryonic fibroblasts or DR5 knockdown HCT116 cells, but not in p53-deficient HCT116 cells. The results from in vitro studies suggest the involvement of the p53-independent CHOP/DR5 axis in the synergistic apoptosis during the combinatorial treatment of ferroptotic agent and TRAIL. The synergistic apoptosis and regression of tumor growth were also observed in xenograft tumors when SRF and TRAIL were administered to tumor-bearing mice.

Glioma-derived cancer stem cells are hypersensitive to proteasomal inhibition.

Although proteasome inhibitors (PIs) are used as anticancer drugs to treat various cancers, their relative therapeutic efficacy on stem cells vs. bulk cancers remains unknown. Here, we show that stem cells derived from gliomas, GSCs, are up to 1,000-fold more sensitive to PIs (IC50, 27-70 nM) compared with their differentiated controls (IC50, 47 to ¼100 µM). The stemness of GSCs correlates to increased ubiquitination, whose misregulation readily triggers apoptosis. PI-induced apoptosis of GSCs is independent of NF-κB but involves the phosphorylation of c-Jun N-terminal kinase as well as the transcriptional activation of endoplasmic reticulum (ER) stress-associated proapoptotic mediators. In contrast to the general notion that ER stress-associated apoptosis is signaled by prolonged unfolded protein response (UPR), GSC-selective apoptosis is instead counteracted by the UPR ATF3 is a key mediator in GSC-selective apoptosis. Pharmaceutical uncoupling of the UPR from its downstream apoptosis sensitizes GSCs to PIs in vitro and during tumorigenesis in mice. Thus, a combinational treatment of a PI with an inhibitor of UPR-coupled apoptosis may enhance targeting of stem cells in gliomas.

Peripheral cannabinoid 1 receptor blockade mitigates adipose tissue inflammation via NLRP3 inflammasome in mouse models of obesity.

AIM: To analyze the metabolic parameters and adipose tissue inflammation via NLRP3 inflammasome following chronic treatment of mouse models of obesity with AJ5018 as the peripherally restricted cannabinoid 1 receptor (CB1R) antagonist. MATERIALS AND METHODS: The selectivity for CB1R over CB2R, brain/plasma concentration ratio, and centrally mediated neurobehavioural effects of AJ5018, were assessed. The long-term effects of AJ5018 and rimonabant on the metabolic parameters and adipose tissue inflammation were analyzed in diet-induced obese (DIO) mice and diabetic db/db mice. RESULTS: AJ5018 had a higher degree of selectivity for CB1R over CB2R and markedly reduced brain penetrance, as reflected by the lower brain/plasma concentration ratio and the attenuated centrally mediated neurobehavioural effects, compared with its brain-penetrant parent compound rimonabant. In DIO and db/db mice, AJ5018 exhibited comparable effects to rimonabant in improving metabolic abnormalities and suppressing macrophage infiltration into white adipose tissue, activation of the NLRP3 inflammasome, and production of proinflammatory cytokines. CONCLUSIONS: These results suggest that peripheral CB1R blockade improves obesity-induced insulin resistance by suppressing adipose tissue inflammation via the NLRP3 inflammasome.

TRAIL-Induced Caspase Activation Is a Prerequisite for Activation of the Endoplasmic Reticulum Stress-Induced Signal Transduction Pathways.

It is well known that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis can be initially triggered by surface death receptors (the extrinsic pathway) and subsequently amplified through mitochondrial dysfunction (the intrinsic pathway). However, little is known about signaling pathways activated by the TRAIL-induced endoplasmic reticulum (ER) stress response. In this study, we report that TRAIL-induced apoptosis is associated with the endoplasmic reticulum (ER) stress response. Human colorectal carcinoma HCT116 cells were treated with TRAIL and the ER stress-induced signal transduction pathway was investigated. During TRAIL treatment, expression of ER stress marker genes, in particular the BiP (binding immunoglobulin protein) gene, was increased and activation of the PERK (PKR-like ER kinase)-eIF2α (eukaryotic initiation factor 2α)-ATF4 (activating transcription factor 4)-CHOP (CCAAT-enhancer-binding protein homologous protein) apoptotic signal transduction pathway occurred. Experimental data from use of a siRNA (small interfering RNA) technique, caspase inhibitor, and caspase-3-deficient cell line revealed that TRAIL-induced caspase activation is a prerequisite for the TRAIL-induced ER stress response. TRAIL-induced ER stress was triggered by caspase-8-mediated cleavage of BAP31 (B cell receptor-associated protein 31). The involvement of the proapoptotic PERK-CHOP pathway in TRAIL-induced apoptosis was verified by using a PERK knockout (PERK(-/-)) mouse embryo fibroblast (MEF) cell line and a CHOP(-/-) MEF cell line. These results suggest that TRAIL-induced the activation of ER stress response plays a role in TRAIL-induced apoptotic death.

Cancer Stem Cells Protect Non-Stem Cells From Anoikis: Bystander Effects.

Cancer stem cells (CSCs) are capable of initiation and metastasis of tumors. Therefore, understanding the biology of CSCs and the interaction between CSCs and their counterpart non-stem cells is crucial for developing a novel cancer therapy. We used CSC-like and non-stem breast cancer MDA-MB-231 and MDA-MB-453 cells to investigate mammosphere formation. We investigated the role of the epithelial cadherin (E-cadherin)-extracellular signal-regulated kinase (Erk) axis in anoikis. Data from E-cadherin small hairpin RNA assay and mitogen-activated protein kinase kinase (MEK) inhibitor study show that activation of Erk, but not modulation of E-cadherin level, may play an important role in anoikis resistance. Next, the two cell subtypes were mixed and the interaction between them during mammosphere culture and xenograft tumor formation was investigated. Unlike CSC-like cells, increased secretion of interleukin-6 (IL-6) and growth-related oncogene (Gro) chemokines was detected during mammosphere culture in non-stem cells. Similar results were observed in mixed cells. Interestingly, CSC-like cells protected non-stem cells from anoikis and promoted tumor growth. Our results suggest bystander effects between CSC-like cells and non-stem cells. J. Cell. Biochem. 117: 2289-2301, 2016. © 2016 Wiley Periodicals, Inc.

Role of Bcl-xL/Beclin-1 in synergistic apoptotic effects of secretory TRAIL-armed adenovirus in combination with mitomycin C and hyperthermia on colon cancer cells.

In this study, we attempted to develop a multimodality approach using chemotherapeutic agent mitomycin C, biologic agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo-2L), and mild hyperthermia to treat colon cancer. For this study, human colon cancer LS174T, LS180, HCT116 and CX-1 cells were infected with secretory TRAIL-armed adenovirus (Ad.TRAIL) and treated with chemotherapeutic agent mitomycin C and hyperthermia. The combinatorial treatment caused a synergistic induction of apoptosis which was mediated through an increase in caspase activation. The combinational treatment promoted the JNK-Bcl-xL-Bak pathway which transmitted the synergistic effect through the mitochondria-dependent apoptotic pathway. JNK signaling led to Bcl-xL phosphorylation at serine 62, dissociation of Bak from Bcl-xL, oligomerization of Bak, alteration of mitochondrial membrane potential, and subsequent cytochrome c release. Overexpression of dominant-negative mutant of Bcl-xL (S62A), but not dominant-positive mutant of Bcl-xL (S62D), suppressed the synergistic death effect. Interestingly, Beclin-1 was dissociated from Bcl-xL and overexpression of dominant-negative mutant of Bcl-xL (S62A), but not dominant-positive mutant of Bcl-xL (S62D), suppressed dissociation of Beclin-1 from Bcl-xL. A combinatorial treatment of mitomycin C, Ad.TRAIL and hyperthermia induced Beclin-1 cleavage, but the Beclin-1 cleavage was abolished in Beclin-1 double mutant (D133A/D146A) knock-in HCT116 cells, suppressing the apoptosis induced by the combination therapy. We believe that this study supports the application of the multimodality approach to colon cancer therapy.

Gingerol sensitizes TRAIL-induced apoptotic cell death of glioblastoma cells.

Glioblastoma multiforme (GBM) is the most lethal and aggressive astrocytoma of primary brain tumors in adults. Although there are many clinical trials to induce the cell death of glioblastoma cells, most glioblastoma cells have been reported to be resistant to TRAIL-induced apoptosis. Here, we showed that gingerol as a major component of ginger can induce TRAIL-mediated apoptosis of glioblastoma. Gingerol increased death receptor (DR) 5 levels in a p53-dependent manner. Furthermore, gingerol decreased the expression level of anti-apoptotic proteins (survivin, c-FLIP, Bcl-2, and XIAP) and increased pro-apoptotic protein, Bax and truncate Bid, by generating reactive oxygen species (ROS). We also found that the sensitizing effects of gingerol in TRAIL-induced cell death were blocked by scavenging ROS or overexpressing anti-apoptotic protein (Bcl-2). Therefore, we showed the functions of gingerol as a sensitizing agent to induce cell death of TRAIL-resistant glioblastoma cells. This study gives rise to the possibility of applying gingerol as an anti-tumor agent that can be used for the purpose of combination treatment with TRAIL in TRAIL-resistant glioblastoma tumor therapy.

AFM-based dual nano-mechanical phenotypes for cancer metastasis.

An enhanced mechanical compliance is considered to be a mechanical indicator for metastatic cancer cells. Our study using atomic force microscopy (AFM) revealed that breast cancer cells agreed well with this hypothesis. However, prostate cancer cells displayed a reverse correlation; less metastatic prostate cancer cells were more mechanically compliant. Two-dimensional AFM force spectroscopy was performed to characterize dual mechanical properties-the cell-substrate adhesion as well as the mechanical compliance. Interestingly, prostate cancer cells displayed a strong positive correlation between the cell-substrate adhesion and metastatic potential. However, there was no clearly observable correlation between the cell-substrate adhesion and the metastatic potential despite variations in mechanical compliance of breast cancer cells. These results suggest that the correlation between the dual mechanical signatures and metastatic potential be uniquely identified for cancer cells originating from different organs. We postulate that this correlation could reveal which step of cancer progression is favorable in terms of physical interaction between cancer cells and micro-environments. We expect that based on the "seed and soil hypothesis", the identification of the dual mechanical phenotypes, could provide a new insight for understanding how a dominant metastatic site is determined for cancer cells originating from specific organs.

Diverse functions of cytochrome c in cell death and disease.

The redox-active protein cytochrome c is a highly positively charged hemoglobin that regulates cell fate decisions of life and death. Under normal physiological conditions, cytochrome c is localized in the mitochondrial intermembrane space, and its distribution can extend to the cytosol, nucleus, and extracellular space under specific pathological or stress-induced conditions. In the mitochondria, cytochrome c acts as an electron carrier in the electron transport chain, facilitating adenosine triphosphate synthesis, regulating cardiolipin peroxidation, and influencing reactive oxygen species dynamics. Upon cellular stress, it can be released into the cytosol, where it interacts with apoptotic peptidase activator 1 (APAF1) to form the apoptosome, initiating caspase-dependent apoptotic cell death. Additionally, following exposure to pro-apoptotic compounds, cytochrome c contributes to the survival of drug-tolerant persister cells. When translocated to the nucleus, it can induce chromatin condensation and disrupt nucleosome assembly. Upon its release into the extracellular space, cytochrome c may act as an immune mediator during cell death processes, highlighting its multifaceted role in cellular biology. In this review, we explore the diverse structural and functional aspects of cytochrome c in physiological and pathological responses. We summarize how posttranslational modifications of cytochrome c (e.g., phosphorylation, acetylation, tyrosine nitration, and oxidation), binding proteins (e.g., HIGD1A, CHCHD2, ITPR1, and nucleophosmin), and mutations (e.g., G41S, Y48H, and A51V) affect its function. Furthermore, we provide an overview of the latest advanced technologies utilized for detecting cytochrome c, along with potential therapeutic approaches related to this protein. These strategies hold tremendous promise in personalized health care, presenting opportunities for targeted interventions in a wide range of conditions, including neurodegenerative disorders, cardiovascular diseases, and cancer.

AFM nano-mechanics and calcium dynamics of prostate cancer cells with distinct metastatic potential.

BACKGROUND: Despite recent advances, it is not clear to correlate the mechanical compliances and the metastatic potential of cancer cells. In this study, we investigated combined signatures of mechanical compliances, adhesions, and calcium dynamics correlated with the metastatic potential of cancer cells. SCOPE OF REVIEW: We used the lowly (LNCaP) and highly (CL-1, CL-2) metastatic human prostate cancer cells. The AFM-based nanomechanics was performed to determine the elastic moduli and the cell-to-substrate adhesion. The intracellular calcium dynamics was evaluated by fluorescence spectroscopy. Cell migration and the distribution of cytoskeleton were evaluated using the wounded monolayer model and immunofluorescence, respectively. The elastic moduli, the calcium dynamics, and the migratory ability are greater in CL-1 and CL-2 than LNCaP. CL-1 and CL-2 also display a significantly larger area of cell-to-substrate adhesions while the LNCaP displays a limited adhesion. These properties were slightly reduced in CL-2 compared with CL-1 cells. The enhanced elastic moduli and calcium dynamics found in CL-1 and CL-2 can be consistently explained by the intensified tensile stress generated by actin cytoskeletons anchored at more focal adhesion sites. MAJOR CONCLUSIONS: Although the suppressed mechanical compliance of highly metastatic cells may not support the enhanced cancer metastasis, the enhanced adhesion and calcium dynamics are favorable for invasion and extra-vasation required for malignant progression. GENERAL SIGNIFICANCE: Our results suggest that the mechanical compliance alone may fail to indicate the metastatic progression, but the combined biomechanical signatures of mechanical compliance, adhesion, and calcium dynamics can provide critical clues to determine the metastatic potential of cells.

Synergistic interactions between heregulin and peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist in breast cancer cells.

Here, we demonstrate that troglitazone (Rezulin), a peroxisome proliferator-activated receptor agonist, acted in synergy with heregulin to induce massive cell death in breast cancer cells. Although the combination of heregulin and troglitazone (HRG/TGZ) induced both apoptosis and necrosis, the main mode of cell death was caspase-independent and occurred via necrosis. This combination increased generation of superoxide in mitochondria, which in turn destabilized mitochondria potential. Pretreatment with N-acetyl-l-cysteine and catalase expression ameliorated cell death induced by the combination treatment, indicating a role of oxidative stress in mediating HRG/TGZ-induced cell death. Notably, pretreatment with pyruvate significantly prevented the cell death, suggesting a potential mechanistic link between metabolic stress and HRG/TGZ-induced cell death. The activation of the HRG signaling axis has been considered as a poor prognostic factor in breast cancer and confers resistance to gefitinib (Iressa) and tamoxifen. However, our data presented here paradoxically suggest that HRG expression can actually be beneficial when it comes to treating breast cancer with peroxisome proliferator-activated receptor-γ ligands. Taken together, the combination of HRG and TGZ may provide a basis for the development of a novel strategy in the treatment of apoptosis-resistant and/or hormone-refractory breast cancer.