Small-molecule SMAC mimetics as new cancer therapeutics

Multifaceted Evaluation of Inhibitors of Anti-Apoptotic Proteins in Head and Neck Cancer: Insights from In Vitro, In Vivo, and Clinical Studies (Review)

This paper presents a multifaceted assessment of inhibitors of anti-apoptotic proteins (IAPs) in the context of head and neck squamous cell carcinoma (HNSCC). The article discusses the results of in vitro, in vivo, and clinical studies, highlighting the significance of IAPs in the resistance of cancer cells to apoptosis, which is a key factor hindering effective treatment. The main apoptosis pathways, including the intrinsic and extrinsic pathways, and the role of IAPs in their regulation, are presented. The study's findings suggest that targeting IAPs with novel therapies may offer clinical benefits in the treatment of advanced HNSCC, especially in cases resistant to conventional treatment methods. These conclusions underscore the need for further research to develop more effective and safer therapeutic strategies.

E3 ubiquitin ligase gene BIRC3 modulates TNF-induced cell death pathways and promotes aberrant proliferation in rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by synovitis, degradation of articular cartilage, and bone destruction. Fibroblast-like synoviocytes (FLS) play a central role in RA, producing a significant amount of inflammatory mediators such as tumor necrosis factor(TNF)-α and IL-6, which promote inflammatory responses within the joints. Moreover, FLS exhibit tumor-like behavior, including aggressive proliferation and enhanced anti-apoptotic capabilities, which collectively drive chronic inflammation and joint damage in RA. TNF is a major pro-inflammatory cytokine that mediates a series of signaling pathways through its receptor TNFR1, including NF-κB and MAPK pathways, which are crucial for inflammation and cell survival in RA. The abnormal proliferation and anti-apoptotic characteristics of FLS in RA may result from dysregulation in TNF-mediated cell death pathways such as apoptosis and necroptosis. Ubiquitination is a critical post-translational modification regulating these signaling pathways. E3 ubiquitin ligases, such as cIAP1/2, promote the ubiquitination and degradation of target proteins within the TNF receptor complex, modulating the signaling proteins. The high expression of the BIRC3 gene and its encoded protein, cIAP2, in RA regulates various cellular processes, including apoptosis, inflammatory signaling, immune response, MAPK signaling, and cell proliferation, thereby promoting FLS survival and inflammatory responses. Inhibiting BIRC3 expression can reduce the secretion of inflammatory cytokines by RA-FLS under both basal and inflammatory conditions and inhibit their proliferation. Although BIRC3 inhibitors show potential in RA treatment, their possible side effects must be carefully considered. Further research into the specific mechanisms of BIRC3, including its roles in cell signaling, apoptosis regulation, and immune evasion, is crucial for identifying new therapeutic targets and strategies.

From Crypts to Cancer: A Holistic Perspective on Colorectal Carcinogenesis and Therapeutic Strategies

Colorectal cancer (CRC) represents a significant global health burden, with high incidence and mortality rates worldwide. Recent progress in research highlights the distinct clinical and molecular characteristics of colon versus rectal cancers, underscoring tumor location's importance in treatment approaches. This article provides a comprehensive review of our current understanding of CRC epidemiology, risk factors, molecular pathogenesis, and management strategies. We also present the intricate cellular architecture of colonic crypts and their roles in intestinal homeostasis. Colorectal carcinogenesis multistep processes are also described, covering the conventional adenoma-carcinoma sequence, alternative serrated pathways, and the influential Vogelstein model, which proposes sequential APC, KRAS, and TP53 alterations as drivers. The consensus molecular CRC subtypes (CMS1-CMS4) are examined, shedding light on disease heterogeneity and personalized therapy implications.

Overcoming Cancer Drug Resistance with Nanoparticle Strategies for Key Protein Inhibition

Drug resistance remains a critical barrier in cancer therapy, diminishing the effectiveness of chemotherapeutic, targeted, and immunotherapeutic agents. Overexpression of proteins such as B-cell lymphoma 2 (Bcl-2), inhibitor of apoptosis proteins (IAPs), protein kinase B (Akt), and P-glycoprotein (P-gp) in various cancers leads to resistance by inhibiting apoptosis, enhancing cell survival, and expelling drugs. Although several inhibitors targeting these proteins have been developed, their clinical use is often hampered by systemic toxicity, poor bioavailability, and resistance development. Nanoparticle-based drug delivery systems present a promising solution by improving drug solubility, stability, and targeted delivery. These systems leverage the Enhanced Permeation and Retention (EPR) effect to accumulate in tumor tissues, reducing off-target toxicity and increasing therapeutic efficacy. Co-encapsulation strategies involving anticancer drugs and resistance inhibitors within nanoparticles have shown potential in achieving coordinated pharmacokinetic and pharmacodynamic profiles. This review discusses the mechanisms of drug resistance, the limitations of current inhibitors, and the advantages of nanoparticle delivery systems in overcoming these challenges. By advancing these technologies, we can enhance treatment outcomes and move towards more effective cancer therapies.

Cell Electrokinetic Fingerprint: A Novel Approach Based on Optically Induced Dielectrophoresis (ODEP) for In-Flow Identification of Single Cells

A novel optically induced dielectrophoresis (ODEP) system that can operate under flow conditions is designed for automatic trapping of cells and subsequent induction of 2D multi-frequency cell trajectories. Like in a "ping-pong" match, two virtual electrode barriers operate in an alternate mode with varying frequencies of the input voltage. The so-derived cell motions are characterized via time-lapse microscopy, cell tracking, and state-of-the-art machine learning algorithms, like the wavelet scattering transform (WST). As a cell-electrokinetic fingerprint, the dynamic of variation of the cell displacements happening, over time, is quantified in response to different frequency values of the induced electric field. When tested on two biological scenarios in the cancer domain, the proposed approach discriminates cellular dielectric phenotypes obtained, respectively, at different early phases of drug-induced apoptosis in prostate cancer (PC3) cells and for differential expression of the lectine-like oxidized low-density lipoprotein receptor-1 (LOX-1) transcript levels in human colorectal adenocarcinoma (DLD-1) cells. The results demonstrate increased discrimination of the proposed system and pose an additional basis for making ODEP-based assays addressing cancer heterogeneity for precision medicine and pharmacological research.

Necroptosis in recurrent implantation failure: A bioinformatics analysis of key genes and therapeutic targets

Recurrent implantation failure (RIF), a major issue in assisted reproductive technology (ART), may be influenced by necroptosis, a form of cell death linked to several diseases. This study was aimed at investigating the involvement of necroptosis in RIF. Using RNA-sequencing data from the Gene Expression Omnibus database, we identified differentially expressed necroptosis-related genes (DENRGs) in RIF patients compared with those in controls. Functional enrichment, protein-protein interaction (PPI) networks, and transcription factor (TF) regulatory networks were analyzed to identify key genes. Immune cell infiltration was analyzed using the single-sample gene set enrichment analysis (ssGSEA) algorithm. Finally, potential therapeutic drugs targeting key genes were explored using a Drug Gene Interaction Database. In total, 20 DENRGs associated with RIF were identified, with a focus on 6 key genes (MLKL, FASLG, XIAP, CASP1, BIRC3, and TLR3) implicated in necroptosis and immune processes. These genes were used to develop a predictive model for RIF, which was validated in 2 datasets. The model and TF network analysis underscored the importance of TLR3. Immune infiltration analysis showed reduced levels of 16 immune cells in RIF patients, highlighting immune system alterations. Several drugs targeting CASP1, such as nivocasan and emricasan, were identified as potential treatments. The study sheds light on the role of necroptosis in RIF, identifying key genes and immune alterations that could serve as biomarkers and therapeutic targets. These findings pave the way for future experimental research and clinical applications targeting necroptosis in RIF treatment.

Global siRNA Screen Reveals Critical Human Host Factors of SARS-CoV-2 Multicycle Replication

Defining the subset of cellular factors governing SARS-CoV-2 replication can provide critical insights into viral pathogenesis and identify targets for host-directed antiviral therapies. While a number of genetic screens have previously reported SARS-CoV-2 host dependency factors, these approaches relied on utilizing pooled genome-scale CRISPR libraries, which are biased towards the discovery of host proteins impacting early stages of viral replication. To identify host factors involved throughout the SARS-CoV-2 infectious cycle, we conducted an arrayed genome-scale siRNA screen. Resulting data were integrated with published datasets to reveal pathways supported by orthogonal datasets, including transcriptional regulation, epigenetic modifications, and MAPK signalling. The identified proviral host factors were mapped into the SARS-CoV-2 infectious cycle, including 27 proteins that were determined to impact assembly and release. Additionally, a subset of proteins were tested across other coronaviruses revealing 17 potential pan-coronavirus targets. Further studies illuminated a role for the heparan sulfate proteoglycan perlecan in SARS-CoV-2 viral entry, and found that inhibition of the non-canonical NF-kB pathway through targeting of BIRC2 restricts SARS-CoV-2 replication both in vitro and in vivo. These studies provide critical insight into the landscape of virus-host interactions driving SARS-CoV-2 replication as well as valuable targets for host-directed antivirals.

Regulation of RIPK1 Phosphorylation: Implications for Inflammation, Cell Death, and Therapeutic Interventions

Receptor-interacting protein kinase 1 (RIPK1) plays a crucial role in controlling inflammation and cell death. Its function is tightly controlled through post-translational modifications, enabling its dynamic switch between promoting cell survival and triggering cell death. Phosphorylation of RIPK1 at various sites serves as a critical mechanism for regulating its activity, exerting either activating or inhibitory effects. Perturbations in RIPK1 phosphorylation status have profound implications for the development of severe inflammatory diseases in humans. This review explores the intricate regulation of RIPK1 phosphorylation and dephosphorylation and highlights the potential of targeting RIPK1 phosphorylation as a promising therapeutic strategy for mitigating human diseases.

Pro-apoptotic gene BAX is a pan-cancer predictive biomarker for prognosis and immunotherapy efficacy

BACKGROUND

Apoptosis Regulator BCL2 Associated X (BAX) is a pro-apoptotic gene. Apoptosis is one of the important components of immune response and immune regulation. However, there is no systematic pan-cancer analysis of BAX.

METHODS

Original data of this study were downloaded from TCGA databases and GTEX databases. We conducted the gene expression analysis and survival analysis of BAX in 33 types of cancer via Gene Expression Profiling Interactive Analysis (GEPIA) database. Real-time PCR and immunohistochemistry (IHC) were further performed to examine the BAX expression in cancer cells and tissues. Moreover, the relationship between BAX and immune infiltration and gene alteration was studied by the Tumor Immune Estimation Resource (TIMER) and cBioPortal tools. Protein-protein interaction analysis was performed in the STRING database. Finally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were utilized to evaluate the enrichment analysis.

RESULTS

BAX was highly expressed in most cancers and was associated with poor prognosis in nine cancer types. In addition, BAX showed significant clinical relevance, and the mRNA expression of BAX was also strongly associated with drug sensitivity of many drugs. Furthermore, BAX may participate in proliferation and metastasis of many cancers and was associated with methylation. Importantly, BAX expression was positively correlated with most immune infiltrating cells.

CONCLUSION

Our findings suggested that BAX can function as an oncogene and may be used as a potential predictive biomarker for prognosis and immunotherapy efficacy of human cancer, which could provide a new approach for cancer therapy.

Ubiquitin: Not just a one-way ticket to the proteasome, but a therapeutic dial to fine-tune the molecular landscape of disease

Recently, there is a rise in studies that recognize the importance of targeting ubiquitin and related molecular machinery in various therapeutic contexts. Here we briefly discuss the history of ubiquitin, its biological roles in protein degradation and beyond, as well as the current state of ubiquitin-targeting therapeutics across diseases. We conclude that targeting ubiquitin machinery is approaching a renaissance, and tapping its full potential will require embracing a wholistic perspective of ubiquitin's multifaceted roles.

Interaction of SMAC with a survivin-derived peptide alters essential cancer hallmarks: Tumor growth, inflammation, and immunosuppression

Second mitochondrial-derived activator of caspase (SMAC), also known as direct inhibitor of apoptosis-binding proteins with low pI (Diablo), is known as a pro-apoptotic mitochondrial protein released into the cytosol in response to apoptotic signals. We recently reported SMAC overexpression in cancers as essential for cell proliferation and tumor growth due to non-apoptotic functions, including phospholipid synthesis regulation. These functions may be associated with its interactions with partner proteins. Using a peptide array with 768 peptides derived from 11 selected SMAC-interacting proteins, we identified SMAC-interacting sequences. These SMAC-binding sequences were produced as cell-penetrating peptides targeted to the cytosol, mitochondria, or nucleus, inhibiting cell proliferation and inducing apoptosis in several cell lines. For in vivo study, a survivin/baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5)-derived peptide was selected, due to its overexpression in many cancers and its involvement in mitosis, apoptosis, autophagy, cell proliferation, inflammation, and immune responses, as a target for cancer therapy. Specifically, a SMAC-targeting survivin/BIRC5-derived peptide, given intratumorally or intravenously, strongly inhibited lung tumor growth, cell proliferation, angiogenesis, and inflammation, induced apoptosis, and remodeled the tumor microenvironment. The peptide promoted tumor infiltration of CD-8+ cells and increased cell-intrinsic programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) expression, resulting in cancer cell self-destruction and increased tumor cell death, preserving immune cells. Thus, targeting the interaction between the multifunctional proteins SMAC and survivin represents an innovative therapeutic cancer paradigm.

BIRC3-HSP90B1 Interaction Inhibits Non-Small Cell Lung Cancer Progression through the Extracellular Signal-Regulated Kinase Pathway

The long-term prognosis of nonsmall cell lung cancer (NSCLC) remains unsatisfactory, which is a major challenge in lung cancer treatment. BIRC3 is an inhibitor of apoptosis (IAP) protein that contributes to tumor regulation. However, the underlying regulatory mechanisms of BIRC3 in NSCLC remains unknown. We initiated an analysis of BIRC3 expression data in NSCLC tumors and adjacent tissues using the TCGA and GEO databases and examined the variations in prognosis. Further, we conducted overexpression (OE) and knockdown (KD) studies on BIRC3 to evaluate its effects on NSCLC cell proliferation, migration, and invasion. Additionally, through utilization of a nude mouse model, the regulatory effects of BIRC3 on NSCLC were verified in vivo. Co-immunoprecipitation (Co-IP) assay served to pinpoint the proteins with which BIRC3 interacts. The results indicated that BIRC3 is down-regulated in NSCLC tissues and that patients with high BIRC3 expression demonstrate a better prognosis. BIRC3 is a tumor suppressor, inhibiting the proliferation and metastasis of NSCLC. Co-IP results revealed that BIRC3 interacts with HSP90B1, leading to a decrease in HSP90B1 expression and subsequent negative regulation of the ERK signaling pathway. BIRC3 may serve as a prognostic biomarker for NSCLC. It directly interacts with HSP90B1 to negatively regulate the ERK signaling pathway, thereby hindering the progression of NSCLC.

Birinapant Reshapes the Tumor Immunopeptidome and Enhances Antigen Presentation

Birinapant, an antagonist of the inhibitor of apoptosis proteins, upregulates MHCs in tumor cells and displays a better tumoricidal effect when used in combination with immune checkpoint inhibitors, indicating that Birinapant may affect the antigen presentation pathway; however, the mechanism remains elusive. Based on high-resolution mass spectrometry and in vitro and in vivo models, we adopted integrated genomics, proteomics, and immunopeptidomics strategies to study the mechanism underlying the regulation of tumor immunity by Birinapant from the perspective of antigen presentation. Firstly, in HT29 and MCF7 cells, Birinapant increased the number and abundance of immunopeptides and source proteins. Secondly, a greater number of cancer/testis antigen peptides with increased abundance and more neoantigens were identified following Birinapant treatment. Moreover, we demonstrate the existence and immunogenicity of a neoantigen derived from insertion/deletion mutation. Thirdly, in HT29 cell-derived xenograft models, Birinapant administration also reshaped the immunopeptidome, and the tumor exhibited better immunogenicity. These data suggest that Birinapant can reshape the tumor immunopeptidome with respect to quality and quantity, which improves the presentation of CTA peptides and neoantigens, thus enhancing the immunogenicity of tumor cells. Such changes may be vital to the effectiveness of combination therapy, which can be further transferred to the clinic or aid in the development of new immunotherapeutic strategies to improve the anti-tumor immune response.

E3 ubiquitin ligases in lung cancer: Emerging insights and therapeutic opportunities

Aim In this review, we have attempted to provide the readers with an updated account of the role of a family of proteins known as E3 ligases in different aspects of lung cancer progression, along with insights into the deregulation of expression of these proteins during lung cancer. A detailed account of the therapeutic strategies involving E3 ligases that have been developed or currently under development has also been provided in this review. MATERIALS AND METHODS: The review article employs extensive literature search, along with differential gene expression analysis of lung cancer associated E3 ligases using the DESeq2 package in R, and the Gene Expression Profiling Interactive Analysis (GEPIA) database (http://gepia.cancer-pku.cn/). Protein expression analysis of CPTAC lung cancer samples was carried out using the UALCAN webtool (https://ualcan.path.uab.edu/index.html). Assessment of patient overall survival (OS) in response to high and low expression of selected E3 ligases was performed using the online Kaplan-Meier plotter (https://kmplot.com/analysis/index.php?p=background). KEY FINDINGS: SIGNIFICANCE: The review provides an in-depth understanding of the role of E3 ligases in lung cancer progression and an up-to-date account of the different therapeutic strategies targeting oncogenic E3 ligases for improved lung cancer management.

SMAC Mimetics for the Treatment of Lung Carcinoma: Present Development and Future Prospects

BACKGROUND

Uncontrolled cell growth and proliferation, which originate from lung tissue often lead to lung carcinoma and are more likely due to smoking as well as inhaled environmental toxins. It is widely recognized that tumour cells evade the ability of natural programmed death (apoptosis) and facilitates tumour progression and metastasis. Therefore investigating and targeting the apoptosis pathway is being utilized as one of the best approaches for decades.

OBJECTIVE

This review describes the emergence of SMAC mimetic drugs as a treatment approach, its possibilities to synergize the response along with current limitations as well as future perspective therapy for lung cancer.

METHOD

Articles were analysed using search engines and databases namely Pubmed and Scopus.

RESULT

Under cancerous circumstances, the level of Inhibitor of Apoptosis Proteins (IAPs) gets elevated, which suppresses the pathway of programmed cell death, plus supports the proliferation of lung cancer. As it is a major apoptosis regulator, natural drugs that imitate the IAP antagonistic response like SMAC mimetic agents/Diablo have been identified to trigger cell death. SMAC i.e. second mitochondria activators of caspases is a molecule produced by mitochondria, stimulates apoptosis by neutralizing/inhibiting IAP and prevents its potential responsible for the activation of caspases. Various preclinical data have proven that these agents elicit the death of lung tumour cells. Apart from inducing apoptosis, these also sensitize the cancer cells toward other effective anticancer approaches like chemo, radio, or immunotherapies. There are many SMAC mimetic agents such as birinapant, BV-6, LCL161, and JP 1201, which have been identified for diagnosis as well as treatment purposes in lung cancer and are also under clinical investigation.

CONCLUSION

SMAC mimetics acts in a restorative way in the prevention of lung cancer.

Targeting survivin for cancer therapy: Strategies, small molecule inhibitors and vaccine based therapeutics in development

Survivin is a member of the family of inhibitors of apoptosis proteins (IAPs). It is involved in the normal mitotic process and acts as an anti-apoptotic molecule. While terminally differentiated normal tissues lack survivin, several human malignancies have significant protein levels. Resistance to chemotherapy and radiation in tumor cells is associated with survivin expression. Decreased tumor development, apoptosis, and increased sensitivity to chemotherapy and radiation are all effects of downregulating survivin expression or activity. As a prospective cancer treatment, small molecules targeting the transcription and translation of survivin and molecules that can directly bind with the survivin are being explored both in pre-clinical and clinics. Pre-clinical investigations have found and demonstrated the effectiveness of several small-molecule survivin inhibitors. Unfortunately, these inhibitors have also been shown to have off-target effects, which could limit their clinical utility. In addition to small molecules, several survivin peptide vaccines are currently under development. These vaccines are designed to elicit a cytotoxic T-cell response against survivin, which could lead to the destruction of tumor cells expressing survivin. Some survivin-based vaccines are advancing through Phase II clinical studies. Overall, survivin is a promising cancer drug target. However, challenges still need to be addressed before the survivin targeted therapies can be widely used in the clinics.

Quaternary Benzophenanthridine Alkaloids Act as Smac Mimetics and Overcome Resistance to Apoptosis

Defects in cell death signaling pathways are one of the hallmarks of cancer and can lead to resistance to conventional therapy. Natural products are promising compounds that can overcome this resistance. In the present study we studied the effect of six quaternary benzophenanthridine alkaloids (QBAs), sanguinarine, chelerythrine, sanguirubine, chelirubine, sanguilutine, and chelilutine, on Jurkat leukemia cells, WT, and cell death deficient lines derived from them, CASP3/7/6-/- and FADD-/-, and on solid tumor, human malignant melanoma, A375 cells. We demonstrated the ability of QBAs to overcome the resistance of these deficient cells and identified a novel mechanism for their action. Sanguinarine and sanguirubine completely and chelerythrine, sanguilutine, and chelilutine partially overcame the resistance of CASP3/7/6-/- and FADD-/- cells. By detection of cPARP, a marker of apoptosis, and pMLKL, a marker of necroptosis, we proved the ability of QBAs to induce both these cell deaths (bimodal cell death) with apoptosis preceding necroptosis. We identified the new mechanism of the cell death induction by QBAs, the downregulation of the apoptosis inhibitors cIAP1 and cIAP2, i.e., an effect similar to that of Smac mimetics.

AREL1 resists the apoptosis induced by TGF-β by inhibiting SMAC in vascular endothelial cells

Abnormal apoptosis of vascular endothelial cells is an important feature of arteriosclerosis (AS). Here, we induced apoptosis in human umbilical vein endothelial cells (HUVECs) using transforming growth factor-β (TGF-β), and investigated the role of antiapoptotic E3 ubiquitin ligase (AREL1) in the apoptosis of vascular endothelial cells. We proved that AREL1 is downregulated in TGF-β treated HUVECs. The overexpression of AREL1 inhibits the activation of Caspase-3 and Caspase-9 and attenuates cell apoptosis induced by TGF-β. According to the result of coimmunoprecipitation, AREL1 interacts with the proapoptotic proteins the second mitochondria-derived activator of caspases (SMAC) in TGF-β treated HUVECs. In addition, miR-320b inhibits the expression of AREL1, and the overexpression of AREL1 attenuates the apoptosis induced by miR-320b mimics in HUVECs. In conclusion, AREL1 is downregulated by miR-320b. AREL1 overexpression inhibits TGF-β induced apoptosis through downregulating SMAC in vascular endothelial cells. Our study explores pathogenesis regulation mechanism and new biological therapeutic targets for vascular disease.

Small molecules targeting protein-protein interactions for cancer therapy

Protein-protein interactions (PPIs) are fundamental to many biological processes that play an important role in the occurrence and development of a variety of diseases. Targeting the interaction between tumour-related proteins with emerging small molecule drugs has become an attractive approach for treatment of human diseases, especially tumours. Encouragingly, selective PPI-based therapeutic agents have been rapidly advancing over the past decade, providing promising perspectives for novel therapies for patients with cancer. In this review we comprehensively clarify the discovery and development of small molecule modulators of PPIs from multiple aspects, focusing on PPIs in disease, drug design and discovery strategies, structure-activity relationships, inherent dilemmas, and future directions.

Mycoplasma hyorhinis infection promotes TNF-α signaling and SMAC mimetic-mediated apoptosis in human prostate cancer

Growing evidence suggests an association between Mycoplasma infections and the development and progression of prostate cancer (PCa). In this study, we report that chronic and persistent M. hyorhinis infection induced robust TNF-α secretion from PCa cells. TNF-α secreted from M. hyorhinis-infected PCa cells subsequently led to activation of the NF-κB pathway. Chronic M. hyorhinis infection induced gene expression of pro-inflammatory cytokines and chemokines in a NF-κB-dependent manner and promoted cell proliferation, migration, and invasion in PCa cells. The elimination of M. hyorhinis in PCa cells significantly blocked TNF-α secretion, gene expression of cytokines and chemokines, migration, and invasion in PCa cells, suggesting M. hyorhinis-induced TNF-α plays an important role to promote malignant transformation of PCa. Furthermore, second mitochondria-derived activator of caspases (SMAC) mimetics potentiated caspase activation and cell death in M. hyorhinis-infected PCa by antagonizing inhibitor of apoptosis proteins (IAPs) activity. Tissue microarray analysis indicated that TNF-α is co-expressed in M. hyorhinis-infected human patient tissues. Findings from this study advance our understanding of the mycoplasma-oncogenesis process and suggest the potential for new approaches for preventions, diagnosis, and therapeutic approaches against prostate cancers.

Reinvestigation of Passerini and Ugi scaffolds as multistep apoptotic inducers via dual modulation of caspase 3/7 and P53-MDM2 signaling for halting breast cancer

Selective induction of breast cancer apoptosis is viewed as the mainstay of various ongoing oncology drug discovery programs. Passerini scaffolds have been recently exploited as selective apoptosis inducers via a caspase 3/7 dependent pathway. Herein, the optimized Passerini caspase activators were manipulated to synergistically induce P53-dependent apoptosis via modulating the closely related P53-MDM2 signaling axis. The adopted design rationale and synthetic routes relied on mimicking the general thematic features of lead MDM2 inhibitors incorporating multiple aromatic rings. Accordingly, the cyclization of representative Passerini derivatives and related Ugi compounds into the corresponding diphenylimidazolidine and spiro derivative was performed, resembling the nutlin-based and spiro MDM-2 inhibitors, respectively. The study was also extended to explore the apoptotic induction capacity of the scaffold after simplification and modifications. MTT assay on MCF-7 and MDA-MB231 breast cancer cells compared to normal fibroblasts (WI-38) revealed their promising cytotoxic activities. The flexible Ugi derivatives 3 and 4, cyclic analog 8, Passerini adduct 12, and the thiosemicarbazide derivative 17 were identified as the study hits regarding cytotoxic potency and selectivity, being over 10-folds more potent (IC50 = 0.065-0.096 μM) and safer (SI = 4.4-18.7) than doxorubicin (IC50 = 0.478 μM, SI = 0.569) on MCF-7 cells. They promoted apoptosis induction via caspase 3/7 activation (3.1-4.1 folds) and P53 induction (up to 4 folds). Further apoptosis studies revealed that these compounds enhanced gene expression of BAX by 2 folds and suppressed Bcl-2 expression by 4.29-7.75 folds in the treated MCF-7 cells. Docking simulations displayed their plausible binding modes with the molecular targets and highlighted their structural determinants of activities for further optimization studies. Finally, in silico prediction of the entire library was computationally performed, showing that most of them could be envisioned as drug-like candidates.

Molecular basis for nuclear accumulation and targeting of the inhibitor of apoptosis BIRC2

The inhibitor of apoptosis protein BIRC2 regulates fundamental cell death and survival signaling pathways. Here we show that BIRC2 accumulates in the nucleus via binding of its second and third BIR domains, BIRC2BIR2 and BIRC2BIR3, to the histone H3 tail and report the structure of the BIRC2BIR3-H3 complex. RNA-seq analysis reveals that the genes involved in interferon and defense response signaling and cell-cycle regulation are most affected by depletion of BIRC2. Overexpression of BIRC2 delays DNA damage repair and recovery of the cell-cycle progression. We describe the structural mechanism for targeting of BIRC2BIR3 by a potent but biochemically uncharacterized small molecule inhibitor LCL161 and demonstrate that LCL161 disrupts the association of endogenous BIRC2 with H3 and stimulates cell death in cancer cells. We further show that LCL161 mediates degradation of BIRC2 in human immunodeficiency virus type 1-infected human CD4+ T cells. Our findings provide mechanistic insights into the nuclear accumulation of and blocking BIRC2.

Ceramide Analog 5cc Overcomes TRAIL Resistance by Enhancing JNK Activation and Repressing XIAP Expression in Metastatic Colon Cancer Cells

INTRODUCTION

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be an effective apoptosis inducer due to its selectivity for tumor cells. However, many cancer cells, especially metastatic cancer cells, often exhibit resistance to TRAIL because their apoptotic pathway is impaired or their pro-survival pathway is overactivated. TRAIL resistance is the main obstacle to current TRAIL therapy. Nowadays, ceramide analogs represent a new class of potential anticancer agents. Therefore, we hypothesized that disrupting pro-survival signaling with ceramide analogs would increase TRAIL-mediated apoptosis.

METHODS

MTT assay and flow cytometry were conducted to evaluate the synergistic effect of ceramide analog 5cc on TRAIL in metastatic colon cancer cells. Western blot was used to detect signaling proteins affected by 5cc. RNA interference was performed to analyze the effects of specific gene on 5cc-enhanced apoptosis.

RESULTS

Ceramide analog 5cc markedly enhanced TRAIL-induced apoptosis evidenced by increased propidium iodide/annexin V double-positive cells and PARP cleavage in SW620 and LS411N cells. At the molecular level, 5cc significantly reduced the expression of anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP) through the activation of the c-Jun n-terminal kinase (JNK) pathway which is critically involved in sensitizing tumor cells to TRAIL/5cc combination. JNK-silenced cells exhibited a significant reversal of TRAIL/5cc-mediated apoptosis.

CONCLUSION

Our data demonstrated that ceramide analog 5cc overcomes TRAIL resistance by enhancing JNK activation and repressing XIAP expression in metastatic colon cancer cells.

The GSTP1/MAPKs/BIM/SMAC modulatory actions of nitazoxanide: Bioinformatics and experimental evidence in subcutaneous solid Ehrlich carcinoma-inoculated mice

AIMS

Ehrlich ascites carcinoma and its subcutaneous inoculated solid tumour form (SEC) are reliable models for chemotherapeutic molecular targets exploration. Novel chemotherapeutic approaches are identified as molecular targets for intrinsic apoptosis, like the modulation of the second mitochondria-derived activator of caspases (SMAC). SMAC is a physiological substrate of mitogen-activated protein kinases (MAPKs). Glutathione-S-transferase P1 (GSTP1) and its close association with MAPKs play an important role in malignant cell proliferation, metastasis, and resistance to chemotherapeutics. Nitazoxanide (NTZ) is an emerging cancer therapy and its targeted GSTP1 evidence remains a knowledge need.

MAIN METHODS

In the present mice-established SEC, the chemotherapeutic roles of oral NTZ (200 mg/kg/day) and 5-fluorouracil (5-FU; 20 mg/kg/day, intraperitoneally) regimens were evaluated by measuring changes in tumour mass, the tumour MAPKs, cytochrome c, Bcl-2 interacting mediator of cell death (BIM), and SMAC signalling pathway in addition to its molecular downstream; caspases 3 and 9.

KEY FINDINGS

Computational analysis for these target protein interactions showed direct-ordered interactions. After individual therapy with NTZ and 5-FU regimens, the histological architecture of the extracted tumour discs revealed decreases in viable tumour regions with significant necrosis surrounds. These findings were consistent with gross tumour sizes. Each separate regimen lowered the remarkable GSTP1 and elevated the low MAPKs expressions, cytochrome c, BIM, SMAC, and caspases 3, and 9 in EST tissues.

SIGNIFICANCE

The chemotherapeutic activity of NTZ in SEC was proven. Additionally, NTZ possesses a SMAC modulatory activity that, following thorough research, should be taken into consideration as a chemotherapeutic approach in solid tumours.

Structures of BIRC6-client complexes provide a mechanism of SMAC-mediated release of caspases

Tight regulation of apoptosis is essential for metazoan development and prevents diseases such as cancer and neurodegeneration. Caspase activation is central to apoptosis, and inhibitor of apoptosis proteins (IAPs) are the principal actors that restrain caspase activity and are therefore attractive therapeutic targets. IAPs, in turn, are regulated by mitochondria-derived proapoptotic factors such as SMAC and HTRA2. Through a series of cryo-electron microscopy structures of full-length human baculoviral IAP repeat-containing protein 6 (BIRC6) bound to SMAC, caspases, and HTRA2, we provide a molecular understanding for BIRC6-mediated caspase inhibition and its release by SMAC. The architecture of BIRC6, together with near-irreversible binding of SMAC, elucidates how the IAP inhibitor SMAC can effectively control a processive ubiquitin ligase to respond to apoptotic stimuli.

Targeting regulated cell death pathways in acute myeloid leukemia

The use of the BCL2 inhibitor venetoclax has transformed the management of patients with acute myeloid leukemia (AML) who are ineligible for intensive chemotherapy. By triggering intrinsic apoptosis, the drug is an excellent illustration of how our greater understanding of molecular cell death pathways can be translated into the clinic. Nevertheless, most venetoclax-treated patients will relapse, suggesting the need to target additional regulated cell death pathways. To highlight advances in this strategy, we review the recognized regulated cell death pathways, including apoptosis, necroptosis, ferroptosis and autophagy. Next, we detail the therapeutic opportunities to trigger regulated cell death in AML. Finally, we describe the main drug discovery challenges for regulated cell death inducers and their translation into clinical trials. A better knowledge of the molecular pathways regulating cell death represents a promising strategy to develop new drugs to cure resistant or refractory AML patients, particularly those resistant to intrinsic apoptosis.

E3 Ligases Meet Their Match: Fragment-Based Approaches to Discover New E3 Ligands and to Unravel E3 Biology

Ubiquitination is a key post-translational modification of proteins, affecting the regulation of multiple cellular processes. Cells are equipped with over 600 ubiquitin orchestrators, called E3 ubiquitin ligases, responsible for directing the covalent attachment of ubiquitin to substrate proteins. Due to their regulatory role in cells, significant efforts have been made to discover ligands for E3 ligases. The recent emergence of the proteolysis targeting chimera (PROTAC) and molecular glue degrader (MGD) modalities has further increased interest in E3 ligases as drug targets. This perspective focuses on how fragment based lead discovery (FBLD) methods have been used to discover new ligands for this important target class. In some cases these efforts have led to clinical candidates; in others, they have provided tools for deepening our understanding of E3 ligase biology. Recently, FBLD-derived ligands have inspired the design of PROTACs that are able to artificially modulate protein levels in cells.

Inhibitor of apoptosis proteins as therapeutic targets in bladder cancer

Evasion from apoptosis is a hallmark of cancer. Inhibitor of apoptosis proteins (IAPs) contribute to this hallmark by suppressing the induction of cell death. IAPs were found to be overexpressed in cancerous tissues and to contribute to therapeutic resistance. The present review focuses on the IAP members cIAP1, cIAP2, XIAP, Survivin and Livin and their importance as potential therapeutic targets in bladder cancer.

Advancements in Oncoproteomics Technologies: Treading toward Translation into Clinical Practice

Proteomics continues to forge significant strides in the discovery of essential biological processes, uncovering valuable information on the identity, global protein abundance, protein modifications, proteoform levels, and signal transduction pathways. Cancer is a complicated and heterogeneous disease, and the onset and progression involve multiple dysregulated proteoforms and their downstream signaling pathways. These are modulated by various factors such as molecular, genetic, tissue, cellular, ethnic/racial, socioeconomic status, environmental, and demographic differences that vary with time. The knowledge of cancer has improved the treatment and clinical management; however, the survival rates have not increased significantly, and cancer remains a major cause of mortality. Oncoproteomics studies help to develop and validate proteomics technologies for routine application in clinical laboratories for (1) diagnostic and prognostic categorization of cancer, (2) real-time monitoring of treatment, (3) assessing drug efficacy and toxicity, (4) therapeutic modulations based on the changes with prognosis and drug resistance, and (5) personalized medication. Investigation of tumor-specific proteomic profiles in conjunction with healthy controls provides crucial information in mechanistic studies on tumorigenesis, metastasis, and drug resistance. This review provides an overview of proteomics technologies that assist the discovery of novel drug targets, biomarkers for early detection, surveillance, prognosis, drug monitoring, and tailoring therapy to the cancer patient. The information gained from such technologies has drastically improved cancer research. We further provide exemplars from recent oncoproteomics applications in the discovery of biomarkers in various cancers, drug discovery, and clinical treatment. Overall, the future of oncoproteomics holds enormous potential for translating technologies from the bench to the bedside.

Towards a templated reaction that translates RNA in cells into a proaptotic peptide-PNA conjugate

Nucleic acid-templated chemistry opens the intriguing prospect of triggering the synthesis of drugs only in diseased cells. Herein, we explore the feasibility of using RNA-templated chemical reactions for the activation of a known Smac peptidomimetic compound (SMC), which has proapoptotic activity. Two peptide nucleic acid (PNA) conjugates were used to enable conditional activation of a masked SMC by reduction of an azide either by Staudinger reduction or catalytic photoreduction using a ruthenium complex. The latter provided ~135 nM SMC-PNA on as little as 10 nM (0.01 eq.) template. For the evaluation of the templated azido-SMC reduction system in cellulo, a stable HEK 293 cell line was generated, which overexpressed a truncated, non-functional form of the XIAP mRNA target. We furthermore describe the development of electroporation protocols that enable a robust delivery of PNA conjugates into HEK 293 cells. The action of the reactive PNA conjugates was evaluated by viability and flow cytometric apoptosis assays. In addition, electroporated probes were re-isolated and analyzed by ultra-high performance liquid chromatography (UPLC). Unfortunately, the ruthenium-PNA conjugate proved phototoxic, and treatment of cells with PNA-linked reducing agent and the azido-masked SMC conjugate did not result in a greater viability loss than treatment with scrambled sequence controls. Intracellular product formation was not detectable. A control experiment in total cellular RNA isolate indicated that the templated reaction can in principle proceed in a complex system. The results of this first-of-its-kind study reveal the numerous hurdles that must be overcome if RNA molecules are to trigger the synthesis of pro-apoptotic drugs inside cells.

Structure optimization of new tumor-selective Passerini α-acyloxy carboxamides as Caspase-3/7 activators

Selective elimination of tumors has always been the mainstay of oncology research. The on-going research underlying the cellular apoptotic mechanisms reveal caspases activation, especially the key effector caspase-3, as a personalized tumor-selective therapeutic strategy. Our continued research protocol has exploited new optimized Passerini α-acyloxy carboxamides as efficient apoptotic inducers via caspase-3/7 dependent mechanism with highly selective anticancer profiles. The adopted design rationale relied on excluding structural alerts of previous leads, while merging various pharmacophoric motifs of natural and synthetic caspase activators via optimized one-pot Passerini reaction conditions. The prepared compounds resulting from Passerini reaction were screened for their cytotoxic activities against colorectal Caco-2 and liver HepG-2 cancer cells compared to normal fibroblasts utilizing MTT assay. Notably, all compounds exhibited promising low-range submicromolar IC₅₀ against the studied cancer cell lines, with outstanding tumor selectivity (SI values up to 266). Hence, they were superior to 5-fluorouracil. Notably, 7a, 7g, and 7j conferred the highest potencies against Caco-2 and HepG-2 cells and were selected for further mechanistic studies. Caspas-3/7 activation assay of the hit compounds and flow cytometric analysis of the treated apoptotic cancer cells demonstrated their significant caspase activation potential (up to 4.2 folds) and apoptotic induction capacities (up to 58.7%). Further assessment of Bcl2 expression was performed being a physiological caspase-3 substrate. Herein, the three studied Passerini adducts were able to downregulate Bcl2 in the treated Caco-2 cells. Importantly, the mechanistic studies results of the three hits echoed their preliminary MTT antiproliferative potencies data highlighting their caspase-3 dependent apoptotic induction. Finally, the in silico predicted physicochemical and pharmacokinetic profiles, as well as ligand efficiency metrics were drug-like.

Clinical Trial Development in TP53-Mutated Locally Advanced and Recurrent and/or Metastatic Head and Neck Squamous Cell Carcinoma

TP53 mutation is the most frequent genetic event in head and neck squamous cell carcinoma (HNSCC), found in more than 80% of patients with human papillomavirus-negative disease. As mutations in the TP53 gene are associated with worse outcomes in HNSCC, novel therapeutic approaches are needed for patients with TP53-mutated tumors. The National Cancer Institute sponsored a Clinical Trials Planning Meeting to address the issues of identifying and developing clinical trials for patients with TP53 mutations. Subcommittees, or breakout groups, were tasked with developing clinical studies in both the locally advanced and recurrent and/or metastatic (R/M) disease settings as well as considering signal-seeking trial designs. A fourth breakout group was focused on identifying and standardizing biomarker integration into trial design; this information was provided to the other breakout groups prior to the meeting to aid in study development. A total of 4 concepts were prioritized to move forward for further development and implementation. This article summarizes the proceedings of the Clinical Trials Planning Meeting with the goal of developing clinical trials for patients with TP53-mutant HNSCC that can be conducted within the National Clinical Trials Network.

TRIM56 promotes malignant progression of glioblastoma by stabilizing cIAP1 protein

BACKGROUND

The tripartite motif (TRIM) family of proteins plays a key role in the developmental growth and therapeutic resistance of many tumors. However, the regulatory mechanisms and biological functions of TRIM proteins in human glioblastoma (GBM) are not yet fully understood. In this study, we focused on TRIM56, which emerged as the most differentially expressed TRIM family member with increased expression in GBM.

METHODS

Western blot, real-time quantitative PCR (qRT-PCR), immunofluorescence (IF) and immunohistochemistry (IHC) were used to study the expression levels of TRIM56 and cIAP1 in GBM cell lines. Co-immunoprecipitation (co-IP) was used to explore the specific binding between target proteins and TRIM56. A xenograft animal model was used to verify the tumor promoting effect of TRIM56 on glioma in vivo.

RESULTS

We observed elevated expression of TRIM56 in malignant gliomas and revealed that TRIM56 promoted glioma progression in vitro and in a GBM xenograft model in nude mice. Analysis of the Human Ubiquitin Array and co-IPs showed that cIAP1 is a protein downstream of TRIM56. TRIM56 deubiquitinated cIAP1, mainly through the zinc finger domain (amino acids 21-205) of TRIM56, thereby reducing the degradation of cIAP1 and thus increasing its expression. TRIM56 also showed prognostic significance in overall survival of glioma patients.

CONCLUSIONS

TRIM56-regulated post-translational modifications may contribute to glioma development through stabilization of cIAP1. Furthermore, TRIM56 may serve as a novel prognostic indicator and therapeutic molecular target for GBM.

Mechanisms of EGFR-TKI-Induced Apoptosis and Strategies Targeting Apoptosis in EGFR-Mutated Non-Small Cell Lung Cancer

Homeostasis is achieved by balancing cell survival and death. In cancer cells, especially those carrying driver mutations, the processes and signals that promote apoptosis are inhibited, facilitating the survival and proliferation of these dysregulated cells. Apoptosis induction is an important mechanism underlying the therapeutic efficacy of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) for EGFR-mutated non-small cell lung cancer (NSCLC). However, the mechanisms by which EGFR-TKIs induce apoptosis have not been fully elucidated. A deeper understanding of the apoptotic pathways induced by EGFR-TKIs is essential for the developing novel strategies to overcome resistance to EGFR-TKIs or to enhance the initial efficacy through therapeutic synergistic combinations. Recently, therapeutic strategies targeting apoptosis have been developed for cancer. Here, we review the state of knowledge on EGFR-TKI-induced apoptotic pathways and discuss the therapeutic strategies for enhancing EGFR-TKI efficiency. We highlight the great progress achieved with third-generation EGFR-TKIs. In particular, combination therapies of EGFR-TKIs with anti-vascular endothelial growth factor/receptor inhibitors or chemotherapy have emerged as promising therapeutic strategies for patients with EGFR-mutated NSCLC. Nevertheless, further breakthroughs are needed to yield an appropriate standard care for patients with EGFR-mutated NSCLC, which requires gaining a deeper understanding of cancer cell dynamics in response to EGFR-TKIs.

Osteoblasts and osteoclasts: an important switch of tumour cell dormancy during bone metastasis

Bone metastasis occurs when tumour cells dissociate from primary tumours, enter the circulation (circulating tumour cells, CTCs), and colonize sites in bone (disseminated tumour cells, DTCs). The bone marrow seems to be a particularly dormancy-inducing environment for DTCs, yet the mechanisms of dormancy initiation, reactivation, and interaction within the bone marrow have to be elucidated. Intriguingly, some evidence has suggested that dormancy is a reversible state that is switched 'on' or 'off' depending on the presence of various bone marrow resident cells, particularly osteoclasts and osteoblasts. It has become clear that these two cells contribute to regulating dormant tumour cells in bone both directly (interaction) and indirectly (secreted factors). The involved mechanisms include TGFβ signalling, the Wnt signalling axis, the Notch2 pathway, etc. There is no detailed review that specifically focuses on ascertaining the dynamic interactions between tumour cell dormancy and bone remodelling. In addition, we highlighted the roles of inflammatory cytokines during this 'cell-to-cell' communication. We also discussed the potential clinical relevance of remodelling the bone marrow niche in controlling dormant tumour cells. Understanding the unique role of osteoclasts and osteoblasts in regulating tumour dormancy in bone marrow will provide new insight into preventing and treating tumour bone metastasis.

Targeting the apoptosis pathway to treat tumours of the paediatric nervous system

New, more effective therapeutics are required for the treatment of paediatric cancers. Current treatment protocols of cytotoxic treatments including chemotherapy trigger cancer-cell death by engaging the apoptosis pathway, and chemotherapy efficacy is frequently impeded by apoptosis dysregulation. Apoptosis dysregulation, through genetic or epigenetic mechanisms, is a feature of many cancer types, and contributes to reduced treatment response, disease progression and ultimately treatment resistance. Novel approaches are required to overcome dysregulated apoptosis signalling, increase the efficacy of cancer treatment and improve patient outcomes. Here, we provide an insight into current knowledge of how the apoptosis pathway is dysregulated in paediatric nervous system tumours, with a focus on TRAIL receptors, the BCL-2 proteins and the IAP family, and highlight preclinical evidence demonstrating that pharmacological manipulation of the apoptosis pathway can restore apoptosis signalling and sensitise cancer cells to treatment. Finally, we discuss the potential clinical implications of these findings.

BRCA mutations lead to XIAP overexpression and sensitise ovarian cancer to inhibitor of apoptosis (IAP) family inhibitors

Background

We tested the hypothesis that inhibitor of apoptosis family (IAP) proteins may be altered in BRCA1-mutated ovarian cancers and that could affect the sensitivity to IAP inhibitors.

Methods

The levels of IAP proteins were evaluated in human cancers and cell lines. Cell lines were used to determine the effects of IAP inhibitors. The in vivo effects of treatments were evaluated in PDX mouse models.

Results

Expression of X-linked inhibitor of apoptosis (XIAP) is increased in BRCA1-mutated cancers and high levels are associated with improved patient outcomes after platinum chemotherapy. XIAP overexpression is mediated by NF-kB activation and is associated with an optimisation of PARP. BRCA1-mutated cell lines are particularly sensitive to IAP inhibitors due to an inhibitory effect on PARP. Both a BRCA1-mutated cell line with acquired resistance to PARP inhibitors and one with restored BRCA1 remain sensitive to IAP inhibitors. Treatment with IAP inhibitors restores the efficacy of PARP inhibition in these cell lines. The IAP inhibitor LCL161 alone and in combination with a PARP inhibitor, exhibited antitumour effects in PDX mouse models of resistant BRCA2 and 1-mutated ovarian cancer, respectively.

Conclusion

A clinical trial may be justified to further investigate the utility of IAP inhibitors.

Escaping Death: How Cancer Cells and Infected Cells Resist Cell-Mediated Cytotoxicity

Cytotoxic lymphocytes are critical in our immune defence against cancer and infection. Cytotoxic T lymphocytes and Natural Killer cells can directly lyse malignant or infected cells in at least two ways: granule-mediated cytotoxicity, involving perforin and granzyme B, or death receptor-mediated cytotoxicity, involving the death receptor ligands, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand (FasL). In either case, a multi-step pathway is triggered to facilitate lysis, relying on active pro-death processes and signalling within the target cell. Because of this reliance on an active response from the target cell, each mechanism of cell-mediated killing can be manipulated by malignant and infected cells to evade cytolytic death. Here, we review the mechanisms of cell-mediated cytotoxicity and examine how cells may evade these cytolytic processes. This includes resistance to perforin through degradation or reduced pore formation, resistance to granzyme B through inhibition or autophagy, and resistance to death receptors through inhibition of downstream signalling or changes in protein expression. We also consider the importance of tumour necrosis factor (TNF)-induced cytotoxicity and resistance mechanisms against this pathway. Altogether, it is clear that target cells are not passive bystanders to cell-mediated cytotoxicity and resistance mechanisms can significantly constrain immune cell-mediated killing. Understanding these processes of immune evasion may lead to novel ideas for medical intervention.

Structure-based identification of a new IAP-targeting compound that induces cancer cell death inducing NF-κB pathway

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Virtual docking vs type I BIRs of IAPs identified FC2 as a modulator of NF-kB.

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FC2 is active as a single agent with no toxicity in normal cells.

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The cytotoxic activity of FC2 is enhanced by TNF and by the Smac-mimetic SM83.

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FC2 stabilizes XIAP/TAB1 interaction, prolonging the activation of NF-κB.

Inhibitors of apoptosis proteins (IAPs) are validated onco-targets, as their overexpression correlates with cancer onset, progression, diffusion and chemoresistance. IAPs regulate cell death survival pathways, inflammation, and immunity. Targeting IAPs, by impairing their protein–protein interaction surfaces, can affect events occurring at different stages of cancer development.

To this purpose, we employed a rational virtual screening approach to identify compounds predicted to interfere with the assembly of pro-survival macromolecular complexes. One of the candidates, FC2, was shown to bind in vitro the BIR1 domains of both XIAP and cIAP2. Moreover, we demonstrated that FC2 can induce cancer cell death as a single agent and, more potently, in combination with the Smac-mimetic SM83 or with the cytokine TNF. FC2 determined a prolonged activation of the NF-κB pathway, accompanied to a stabilization of XIAP-TAB1 complex. This candidate molecule represents a valuable lead compound for the development of a new class of IAP-antagonists for cancer treatment.

SMAC Mimetics as Therapeutic Agents in HIV Infection

Although combination antiretroviral therapy is extremely effective in lowering HIV RNA to undetectable levels in the blood, HIV persists in latently infected CD4⁺ T-cells and persistently infected macrophages. In latently/persistently infected cells, HIV proteins have shown to affect the expression of proteins involved in the apoptosis pathway, notably the inhibitors of apoptosis proteins (IAPs), and thereby influence cell survival. IAPs, which are inhibited by endogenous second mitochondrial-derived activators of caspases (SMAC), can serve as targets for SMAC mimetics, synthetic compounds capable of inducing apoptosis. There is increasing evidence that SMAC mimetics can be used to reverse HIV latency and/or kill cells that are latently/persistently infected with HIV. Here, we review the current state of knowledge of SMAC mimetics as an approach to eliminate HIV infected cells and discuss the potential future use of SMAC mimetics as part of an HIV cure strategy.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

IAP and HDAC inhibitors interact synergistically in myeloma cells through noncanonical NF-κB- and caspase-8-dependent mechanisms

Interactions between the inhibitor of apoptosis protein antagonist LCL161 and the histone deacetylase inhibitor panobinostat (LBH589) were examined in human multiple myeloma (MM) cells. LCL161 and panobinostat interacted synergistically to induce apoptosis in diverse MM cell lines, including those resistant to bortezomib (PS-R). Similar interactions were observed with other histone deacetylase inhibitors (MS-275) or inhibitors of apoptosis protein antagonists (birinapant). These events were associated with downregulation of the noncanonical (but not the canonical) NF-κB pathway and activation of the extrinsic, caspase-8-related apoptotic cascade. Coexposure of MM cells to LCL161/LBH589 induced TRAF3 upregulation and led to TRAF2 and NIK downregulation, diminished expression of BCL-XL, and induction of γH2A.X. Ectopic expression of TRAF2, NIK, or BCL-XL, or short hairpin RNA TRAF3 knock-down, significantly reduced LCL161/LBH589 lethality, as did ectopic expression of dominant-negative FADD. Stromal/microenvironmental factors failed to diminish LCL161/LBH589-induced cell death. The LCL161/LBH589 regimen significantly increased cell killing in primary CD138+ cells (N = 31) and was particularly effective in diminishing the primitive progenitor cell-enriched CD138-/19+/20+/27+ population (N = 23) but was nontoxic to normal CD34+ cells. Finally, combined LCL161/LBH589 treatment significantly increased survival compared with single-agent treatment in an immunocompetent 5TGM1 murine MM model. Together, these findings argue that LCL161 interacts synergistically with LBH589 in MM cells through a process involving inactivation of the noncanonical NF-κB pathway and activation of the extrinsic apoptotic pathway, upregulation of TRAF3, and downregulation of TRAF2/BCL-XL. Notably, this regimen overcomes various forms of resistance, is active against primary MM cells, and displays significant in vivo activity. This strategy warrants further consideration in MM.

Identification of key potential targets for TNF-α/TNFR1-related intervertebral disc degeneration by bioinformatics analysis

BACKGROUND

Bioinformatics analysis was performed on gene expression profile microarray data to identify the key genes activated through the TNF-α/TNFR1 signaling pathway in intervertebral disc degeneration (IDD). The common differentially expressed genes (co-DEGs) were calculated in nucleus pulposus (NP) cells and annulus fibrosus (AF) cells under TNF-α treatment or TNFR1 knockdown, which reveals the potential mechanism of TNF-α involvement in IDD and may provide new therapeutic targets for IDD.

METHODS

Differentially expressed genes (DEGs) in TNF-α-treated or TNFR1-knockdown NP cells and AF cells were identified. Further analysis of the gene ontology (GO), signaling pathways and interaction networks of the DEGs or co-DEGs were conducted using the Database for Annotation, Visualization and Integrated Discovery, STRING Database, and Cytoscape software. The relationship between genes and musculoskeletal diseases, including IDD, was assessed with the Comparative Toxicogenomics Database. The predicted microRNAs corresponding to the co-DEGs were also identified by microRNA Data Integration Portal.

RESULTS

In NP cells, the DEGs (|log₂FoldChange|>2, adj.P < 0.01) were identified including 48 DEGs by TNF-α treatment and 74 DEGs by TNFR1 knockdown; in AF cells, correspondingly, 105 DEGs were identified. The co-DEGs between NP cells and AF cells were calculated including CXCL8, ICAM1, BIRC3, RELB, NFKBIA, and TNFAIP3. They may be the hub genes that were significantly associated with both NP cells and AF cells through the TNF-α/TNFR1 signaling pathway. The co-DEGs and corresponding predicted miRNAs may be potential therapeutic targets for IDD.

CONCLUSIONS

CXCL8, ICAM1, BIRC3, RELB, NFKBIA, and TNFAIP3 may have a synergistic effect on TNF-α-induced IDD development.Abbreviations: IDD: Intervertebral disc degeneration; NP: Nucleus pulposus; AF: Annulus fibrosus; co-DEG: Common differentially expressed gene; GO: Gene Ontology; KEGG: Kyoto Encyclopedia of Genes and Genomes; PPI: Protein-protein interaction.

CaBir1 functions as an inhibitor-of-apoptosis and affects caspase-like activitiy in Candida albicans

CaMca1 is the only metacaspase in Candida albicans, which shows structural homology to the mammalian caspases. CaMca1 consists of the caspase domain, the P20 and P10 regions, and the conserved catalytic histidine-cysteine dyad that is required for executing apoptosis in C. albicans. However, little is known about the proteolytic processing of CaMca1 or its activation under apoptosis-inducing conditions. To understand the regulation of this process, we characterized CaBir1 which is the single IAP (inhibitor-of-apoptosis protein) in C. albicans. IAPs are a family of proteins whose members all harbor a BIR (baculovirus IAP repeat) domain and negatively regulate apoptosis by inhibiting caspases. We found that the Cabir1/Cabir1 deletion mutant exhibited increased apoptotic phenotypes, such as ROS accumulation, nuclear segmentation, and cell survival, under apoptosis-inducing conditions. Examination of CaMca1 cleavage patterns in response to various apoptotic stresses revealed that these cleavages were stress-specific and dependent on the catalytic histidine-cysteine residues of CaMca1. The Cabir1/Cabir1 mutation was not associated with altered CaMca1 processing with or without apoptotic stimuli, but the Cabir1/Cabir1 mutant exhibited significantly increased caspase-like activities. These results suggest that CaBir1 acts as an apoptosis inhibitor by regulating caspase-like activity, but not CaMca1 processing.

Clinical stage drugs targeting inhibitor of apoptosis proteins purge episomal Hepatitis B viral genome in preclinical models

A major unmet clinical need is a therapeutic capable of removing hepatitis B virus (HBV) genome from the liver of infected individuals to reduce their risk of developing liver cancer. A strategy to deliver such a therapy could utilize the ability to target and promote apoptosis of infected hepatocytes. Presently there is no clinically relevant strategy that has been shown to effectively remove persistent episomal covalently closed circular HBV DNA (cccDNA) from the nucleus of hepatocytes. We used linearized single genome length HBV DNA of various genotypes to establish a cccDNA-like reservoir in immunocompetent mice and showed that clinical-stage orally administered drugs that antagonize the function of cellular inhibitor of apoptosis proteins can eliminate HBV replication and episomal HBV genome in the liver. Primary human liver organoid models were used to confirm the clinical relevance of these results. This study underscores a clinically tenable strategy for the potential elimination of chronic HBV reservoirs in patients.

CLDN1 regulates trophoblast apoptosis and proliferation in preeclampsia

Preeclampsia is a gestational hypertensive disease; however, preeclampsia remains poorly understood. Bioinformatics analysis was applied to find novel genes involved in the pathogenesis of preeclampsia and identified CLDN1 as one of the most differentially expressed genes when comparing patients with preeclampsia and healthy controls. The results of the qRT-PCR, Western blotting and immunohistochemistry experiments demonstrated that CLDN1 was significantly downregulated in the chorionic villi in samples from patients with preeclampsia. Furthermore, knockdown of CLDN1 in HTR-8/SVneo cells resulted in the inhibition of proliferation and induction of apoptosis, and overexpression of CLDN1 reversed these effects. In addition, RNA-seq assays demonstrated that the gene BIRC3 is potentially downstream of CLDN1 and is involved in the regulation of apoptosis. Knockdown of CLDN1 confirmed that the expression level of BIRC3 was obviously decreased and was associated with a significant increase in cleaved PARP. Interestingly, the apoptotic effect in CLDN1 knockdown cells was rescued after BIRC3 overexpression. Overall, these results indicate that a decrease in CLDN1 inhibits BIRC3 expression and increases cleaved PARP levels thus participating in the pathogenesis of preeclampsia.

Hyperbaric Oxygen Preconditioning Protects Against Cerebral Ischemia/Reperfusion Injury by Inhibiting Mitochondrial Apoptosis and Energy Metabolism Disturbance

Hyperbaric oxygen (HBO) therapy is considered a safe and feasible method that to provide neuroprotection against ischemic stroke. However, the therapy mechanisms of HBO have not been fully elucidated. We hypothesized that the mechanism underlying the protective effect of HBO preconditioning (HBO-PC) against cerebral ischemia/reperfusion injury was related to inhibition of mitochondrial apoptosis and energy metabolism disorder. To test this hypothesis, an ischemic stroke model was established by middle cerebral artery occlusion (MCAO) in rats. HBO-PC involved five consecutive days of pretreatment before MCAO. In additional experiments, X chromosome-linked inhibitor of apoptosis protein (XIAP) and second mitochondria-derived activator of caspases (SMAC) shRNA and NC plasmids were intraventricularly injected into rat brains after MCAO (2 h). After 24 h, all rats underwent motor function evaluation, which was assessed by modified Garcia scores. TTC staining for the cerebral infarct and cerebral edema, and TUNEL staining for cell apoptosis, were also analyzed. Reactive oxygen species and antioxidative enzymes in rat brains were detected, as well as mitochondrial complex enzyme activities, ATP levels, and Na+/K+ ATPase activity. Western blot was used to detect apoptotic proteins including Bcl-2, Bax, caspase-3, caspase-9, cyc-c, XIAP, and SMAC. HBO-PC remarkably reduced the infarct volume and improved neurological deficits. Furthermore, HBO-PC alleviated oxidative stress and regulated the expression of apoptosis-related proteins. Moreover, HBO-PC inhibited the decrease in ATP levels, mitochondrial complex enzyme activities, and Na+/K+ ATPase activity to maintain stable energy metabolism. XIAP knockdown weakened the protective effect of HBO, whereas SMAC knockdown strengthened its protective effect. The effects of HBO-PC can be attributed to inhibition of ischemia/hypoxia-induced mitochondrial apoptosis and energy metabolism disturbance. The action of HBO-PC is related to the XIAP and SMAC signaling pathways.

Induction of interferon-β and interferon signaling by TRAIL and Smac mimetics via caspase-8 in breast cancer cells

Breast cancer prognosis is frequently good but a substantial number of patients suffer from relapse. The death receptor ligand TRAIL can in combination with Smac mimetics induce apoptosis in some luminal-like ER-positive breast cancer cell lines, such as CAMA-1, but not in MCF-7 cells. Here we show that TRAIL and the Smac mimetic LCL161 induce non-canonical NF-κB and IFN signaling in ER-positive MCF-7 cells and in CAMA-1 breast cancer cells when apoptosis is blocked by caspase inhibition. Levels of p52 are increased and STAT1 gets phosphorylated. STAT1 phosphorylation is induced by TRAIL alone in MCF-7 cells and is independent of non-canonical NF-κB since downregulation of NIK has no effect. The phosphorylation of STAT1 is a rather late event, appearing after 24 hours of TRAIL stimulation. It is preceded by an increase in IFNB1 mRNA levels and can be blocked by siRNA targeting the type I IFN receptor IFNAR1 and by inhibition of Janus kinases by Ruxolitinib. Moreover, downregulation of caspase-8, but not inhibition of caspase activity, blocks TRAIL-mediated STAT1 phosphorylation and induction of IFN-related genes. The data suggest that TRAIL-induced IFNB1 expression in MCF-7 cells is dependent on a non-apoptotic role of caspase-8 and leads to autocrine interferon-β signaling.