Inhibitor Of Apoptosis Protein Family Research Articles

Cationic Metal-Organic Layer Delivers siRNAs to Overcome Radioresistance and Potentiate Cancer Radiotherapy.

Radiotherapy plays an important role in modern oncology, but its treatment efficacy is limited by the radioresistance of tumor cells. As a member of the inhibitor of apoptosis protein family, survivin plays a key role in developing radioresistance by mediating apoptosis evasion, promoting epithelial-mesenchymal transition, and modulating cell cycle dynamics. Efficient downregulation of survivin expression presents a promising strategy to enhance the antitumor effects of radiotherapy. Herein, we report the design of a hafnium-porphyrin-based cationic metal-organic layer (CMOL) with quaternary ammonium capping groups to deliver small interfering RNAs (siRNAs) for enhanced radiotherapy. The CMOL@siRNA nanoplatform not only increased energy deposition from X-rays and reactive oxygen species generation via a unique radiotherapy-radiodynamic therapy process, but also effectively delivered siRNAs to downregulate survivin expression and ameliorate radioresistance of cancer cells. Consequently, CMOL@siRNA in combination with low-dose X-ray irradiation demonstrated remarkable antitumor efficacy with 96.9% and 91.4% tumor growth inhibition in murine colorectal carcinoma and triple-negative breast cancer models, respectively.

Cationic Metal‐Organic Layer Delivers siRNAs to Overcome Radioresistance and Potentiate Cancer Radiotherapy

Radiotherapy plays an important role in modern oncology, but its treatment efficacy is limited by the radioresistance of tumor cells. As a member of the inhibitor of apoptosis protein family, survivin plays a key role in developing radioresistance by mediating apoptosis evasion, promoting epithelial‐mesenchymal transition, and modulating cell cycle dynamics. Efficient downregulation of survivin expression presents a promising strategy to enhance the antitumor effects of radiotherapy. Herein, we report the design of a hafnium‐porphyrin‐based cationic metal‐organic layer (CMOL) with quaternary ammonium capping groups to deliver small interfering RNAs (siRNAs) for enhanced radiotherapy. The CMOL@siRNA nanoplatform not only increased energy deposition from X‐rays and reactive oxygen species generation via a unique radiotherapy‐radiodynamic therapy process, but also effectively delivered siRNAs to downregulate survivin expression and ameliorate radioresistance of cancer cells. Consequently, CMOL@siRNA in combination with low‐dose X‐ray irradiation demonstrated remarkable antitumor efficacy with 96.9% and 91.4% tumor growth inhibition in murine colorectal carcinoma and triple‐negative breast cancer models, respectively.

High TNF and NF-κB Pathway Dependency Are Associated with AZD5582 Sensitivity in OSCC via CASP8-Dependent Apoptosis.

Mechanistically guided drug repurposing has been made possible by systematically integrating pharmacologic and CRISPR-Cas9 screen data. Our study discovers the biomarker and cell death mechanisms underpinning sensitivity toward AZD5582, an antagonist of the inhibitor of apoptosis family protein. Our findings have important implications for improving future trial design for patients with OSCC using this emerging drug class.

Inflammasome protein scaffolds the DNA damage complex during tumor development.

Inflammasome sensors activate cellular signaling machineries to drive inflammation and cell death processes. Inflammasomes also control the development of certain diseases independently of canonical functions. Here, we show that the inflammasome protein NLR family CARD domain-containing protein 4 (NLRC4) attenuated the development of tumors in the Apcmin/+ mouse model. This response was independent of inflammasome signaling by NLRP3, NLRP6, NLR family apoptosis inhibitory proteins, absent in melanoma 2, apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1 and caspase-11. NLRC4 interacted with the DNA-damage-sensing ataxia telangiectasia and Rad3-related (ATR)-ATR-interacting protein (ATRIP)-Ewing tumor-associated antigen 1 (ETAA1) complex to promote the recruitment of the checkpoint adapter protein claspin, licensing the activation of the kinase checkpoint kinase-1 (CHK1). Genotoxicity-induced activation of the NLRC4-ATR-ATRIP-ETAA1 complex drove the tumor-suppressing DNA damage response and CHK1 activation, and further attenuated the accumulation of DNA damage. These findings demonstrate a noninflammatory function of an inflammasome protein in promoting the DNA damage response and mediating protection against cancer.

Mice Hepatic Organoids for Modeling Nonalcoholic Fatty Liver Disease and Drug Response.

Nonalcoholic fatty liver disease (NAFLD) is a serious disease. There are no specific drugs for it, in part because of the lack of effective models to aid drug development. However, it has been shown that three-dimensional organoid culture systems can reproduce the organ structure and maintain the gene expression profile of the original tissue. Therefore, we aimed to construct NAFLD models from liver organoids for pharmacological and mechanism studies. We successfully observed morphological changes in normal liver tissue in mouse liver organoids with positive albumin (ALB) expression and potential for differentiation toward hepatocyte-like cells. The mRNA expression of the hepatocyte markers ALB and hepatocyte nuclear factor 4 alpha increased after liver organoid differentiation. We observed free fatty acid (FFA)-induced lipid accumulation in organoids with significant increases in alanine aminotransferase, aspartate aminotransferase, total bilirubin, and triglyceride levels. Moreover, FFA-induced inflammatory cytokines (interleukin-6, tumor necrosis factor-α, and nitric oxide) and fibrosis indicators (collagen type I α1 and laminin α1) were also increased. In addition, RNA sequencing results showed that the expression of key genes [nucleotide oligomerization domain-like receptor (NLR) family apoptosis inhibitory protein, interferon regulatory factor (IRF) 3, and IRF7] involved in NAFLD metabolic abnormalities and insulin resistance in the NLR signaling pathway was altered after FFA induction of the liver organoids. Finally, we found that JC2-11 and lanifibranor limited the FFA-induced increase in oil-red lipid droplets, liver damage, inflammation, and liver fibrosis. In conclusion, tissue structure, gene expression, and the response of mouse liver organoids to drugs can partially mimic invivo liver tissue. Liver organoids can successfully construct NAFLD models for drug discovery research.

Abstract 3132: Examining The Role Of The Lung Endothelial Cell Anti-apoptotic Protein C-iap2 In Schistosomiasis-associated Pulmonary Hypertension

Introduction: Schistosomiasis-associated Pulmonary Hypertension (Sch-PH) is the most common form of group I PH worldwide and remains with no targeted therapy. Previously, we observed that the loss of the anti-inflammatory protein caveolin-1 (Cav-1) in lung endothelial cells (EC) contributed to the survival of the abnormal EC phenotype in Sch-PH. Abnormal cell survival has been associated with some members of the inhibitor of apoptosis protein (IAP) family, but their role in Sch-PH is unknown. Hypothesis: The major etiological agent of Sch-PH, i.e., S. mansoni , may contribute to the abnormal lung EC phenotype via altered IAP family expression, specifically the inducible member c-IAP2. Methods/Methods: To test this hypothesis, we first quantified constitutive c-IAP1 and inducible c-IAP2 expression on lung samples from male and female control and pre-clinical S. mansoni egg-exposed mice (240 eggs/gram body weight intraperitoneally followed by intravenous injection of 175 eggs/gram body weight). Then, the specific contribution of EC-c-IAP2 expression to the progression of the disease was evaluated in our new mouse model ( Cdh5.CreERT2;cIAP1 -/- ,cIAP2 fl/fl - Cdh5.CreERT2;cIAP1 +/- ,cIAP2 +/fl ). EC- Cav1 -/- mice were also evaluated to test the contribution of EC-Cav-1 to lung c-IAP2 expression. Results/Discussion: Western blot and immunohistochemistry analysis revealed a reduction in c-IAP2 expression in the whole lung tissue of S. mansoni egg-exposed mice compared to controls (1.21 ± 0.12; 0.88 ± 0.06, control and egg-exposed mice respectively; p<0.05; n=6). No difference was observed in c-IAP1 expression. Preliminary data indicate that genetic ablation of c-IAP2 in EC heterozygous mice promoted a mild increase in microvascular thickness and area in Masson’s Trichrome -stained lung sections. Consistent with our previous findings, c-IAP2 expression was also significantly impaired when Cav-1 expression was absent in lung ECs, suggesting that EC-Cav-1 may contribute to reduced lung c-IAP2 expression, leading to the severe vascular remodeling that underlies the development of Sch-PH. Conclusion: Our data is uncovering whether c-IAP2 expression is a novel and specific molecular target for future therapeutic approaches against chronic Sch-PH.

ASK1-mediated Apoptosis in Human Lung Fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a chronic, devastating lung disease characterized by progressive fibrosis and dysregulated wound repair that negatively affect lung function. Although lung fibroblasts are important in repair mechanisms following lung injury, differentiation into myofibroblasts in the presence of TGF-β and resistance to apoptosis can promote the progression of pulmonary fibrosis. Apoptosis signal regulating kinase 1 (ASK1) is a member of the mitogen activated protein (MAP) kinase family that is known to promote apoptosis. The objective of this study was to test the hypothesis that ASK1 is an important mediator of apoptosis in lung fibroblasts. Normal human lung fibroblasts were obtained from five donors and cultured in the presence or absence of TGF-β (1ng/mL) for 72h. Apoptosis was assessed by a Caspase-Glo® 3/7 assay following treatment with a combination of cycloheximide and Fas ligand antibody with or without the ASK1 inhibitor, selonsertib. Expression of α-smooth muscle actin (α-SMA), collagen, ASK1, and survivin (a member of the inhibitor of apoptosis protein family) were determined by western blot. Apoptosis was induced in three of the five donor lines, and selonsertib treatment reduced caspase-3/7 activity. These donor lines expressed lower levels of survivin compared with the non-responding lines. TGF-β did not significantly affect these results. As expected, TGF-β stimulated expression of collagen and α-SMA in all donor lines, but this was reduced by treatment with selonsertib. Interestingly, TGF-β caused a reduction in the expression of ASK1 which is consistent with the idea that myofibroblasts in IPF are resistant to apoptosis. These results suggest that ASK1 can promote apoptosis in normal lung fibroblasts, but this is dependent upon the expression of survivin. Supported by VA Merit Award BX005889 (CMW) and NIH grant HL131526 (CMW). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Structural basis of the human NAIP/NLRC4 inflammasome assembly and pathogen sensing.

The NLR family caspase activation and recruitment domain-containing 4 (NLRC4) inflammasome is a critical cytosolic innate immune machine formed upon the direct sensing of bacterial infection and in response to cell stress during sterile chronic inflammation. Despite its major role in instigating the subsequent host immune response, a more complete understanding of the molecular events in the formation of the NLRC4 inflammasome in humans is lacking. Here we identify Bacillus thailandensis type III secretion system needle protein (Needle) as a potent trigger of the human NLR family apoptosis inhibitory protein (NAIP)/NLRC4 inflammasome complex formation and determine its structural features by cryogenic electron microscopy. We also provide a detailed understanding of how type III secretion system pathogen components are sensed by human NAIP to form a cascade of NLRC4 protomer through a critical lasso-like motif, a 'lock-key' activation model and large structural rearrangement, ultimately forming the full human NLRC4 inflammasome. These results shed light on key regulatory mechanisms specific to the NLRC4 inflammasome assembly, and the innate immune modalities of pathogen sensing in humans.

Caffeic acid phenethyl ester: Unveiling its potential as a potent apoptosis inducer for combating hypopharyngeal squamous cell carcinoma.

Hypopharyngeal squamous cell carcinoma (HSCC) is a relatively rare form of head and neck cancer that is notorious for its poor prognosis and low overall survival rate. This highlights the need for new therapeutic options for this malignancy. The objective of the present study was to examine the ability of caffeic acid phenethyl ester (CAPE), which is an active compound found in propolis, to combat HSCC tumor growth. CAPE exerted its tumor‑suppressive activity in HSCC cell lines through the induction of apoptosis. Mechanistically, the CAPE‑mediated apoptotic process was attributed to the perturbation of the mitochondrial membrane potential and the activation of caspase‑9. CAPE also modulated survivin and X‑linked inhibitor of apoptosis, which are potent members of the inhibitors of apoptosis protein family, either through transcriptional or post‑translational regulation, leading to HSCC cell line death. Therefore, the findings of the present study suggested that CAPE is an effective treatment alternative for HSCC via the stimulation of mitochondria‑dependent apoptosis.

Structural basis for flagellin-induced NAIP5 activation.

The NAIP (NLR family apoptosis inhibitory protein)/NLRC4 (NLR family CARD containing protein 4) inflammasome senses Gram-negative bacterial ligand. In the ligand-bound state, the winged helix domain of NAIP forms a steric clash with NLRC4 to open it up. However, how ligand binding activates NAIP is less clear. Here, we investigated the dynamics of the ligand-binding region of inactive NAIP5 and solved the cryo-EM structure of NAIP5 in complex with its specific ligand, FliC from flagellin, at 2.9-Å resolution. The structure revealed a "trap and lock" mechanism in FliC recognition, whereby FliC-D0C is first trapped by the hydrophobic pocket of NAIP5, then locked in the binding site by ID (insertion domain) and C-terminal tail of NAIP5. The FliC-D0N domain further inserts into ID to stabilize the complex. According to this mechanism, FliC triggers the conformational change of NAIP5 by bringing multiple flexible domains together.

Potentiating Tweezer Affinity to a Protein Interface with Sequence-Defined Macromolecules on Nanoparticles.

Survivin, a well-known member of the inhibitor of apoptosis protein family, is upregulated in many cancer cells, which is associated with resistance to chemotherapy. To circumvent this, inhibitors are currently being developed to interfere with the nuclear export of survivin by targeting its protein-protein interaction (PPI) with the export receptor CRM1. Here, we combine for the first time a supramolecular tweezer motif, sequence-defined macromolecular scaffolds, and ultrasmall Au nanoparticles (us-AuNPs) to tailor a high avidity inhibitor targeting the survivin-CRM1 interaction. A series of biophysical and biochemical experiments, including surface plasmon resonance measurements and their multivalent evaluation by EVILFIT, reveal that for divalent macromolecular constructs with increasing linker distance, the longest linkers show superior affinity, slower dissociation, as well as more efficient PPI inhibition. As a drawback, these macromolecular tweezer conjugates do not enter cells, a critical feature for potential applications. The problem is solved by immobilizing the tweezer conjugates onto us-AuNPs, which enables efficient transport into HeLa cells. On the nanoparticles, the tweezer valency rises from 2 to 16 and produces a 100-fold avidity increase. The hierarchical combination of different scaffolds and controlled multivalent presentation of supramolecular binders was the key to the development of highly efficient survivin-CRM1 competitors. This concept may also be useful for other PPIs.

P53 and survivin expression in renal cell carcinoma.

Mutation of p53 is detected in more than 50% of human cancers, expression of p53 has a potential prognostic value in patients with renal cell carcinoma (RCC). Survivin is a member of the inhibitor of apoptosis protein family, its overexpression is observed in many malignancies, including RCC. The aim of the study was to estimate a correlation between survivin and p53 expression in tumor samples and the histologic type of a tumor, tumor stage, tumor grade, and survival of patients. Tumor samples were collected from surgical specimens of 90 patients who underwent radical or partial nephrectomy for RCC between November 2017 and July 2020. Tumors were staged according to the UICC (The Union for International Cancer Control) TNM classification system and histopathologically graded according to Fuhrman nuclear grade system. Histopathological diagnosis was confirmed with standard light microscopic evaluation, using hematoxylin and eosin staining and standard p53 and survivin antibodies. Positive p53 staining was observed in 36.7% of tumor specimens and 24.4% were survivin positive. There was a statistically significant correlation between p53 or survivin expression and histologic subtype of clear cell RCC as well as Type I and II of papillary RCC. There was a statistically significant correlation between p53 expression and tumor size, stage, and grade. The p53 or survivin expression was related to lower overall survival. The results of this study suggest that p53 overexpression and survivin positivity in RCC patients could be associated with poor prognosis. Thus, these proteins could be used as prognostic markers in RCC.

Changes in expression levels of Nod-like receptors in the spleen of ewes.

Nucleotide-binding oligomerization domain receptors (NOD-like receptors, NLRs) have critical effects on interfaces of the immune and reproductive systems, and the spleen plays a key role in both innate and adaptive immune functions. It is hypothesized that NLR family participates in maternal splenic immune regulation during early pregnancy in sheep. In this study, maternal spleens were collected on day 16 of the estrous cycle, and days 13, 16 and 25 of gestation (n = 6 for each group) in ewes. Expression of NLR family, including NOD1, NOD2, class II transactivator (CIITA), NLR family apoptosis inhibitory protein (NAIP), nucleotide-binding oligomerization domain, Leucine rich repeat and Pyrin domain containing 1 (NLRP1), NLRP3 and NLRP7, was analyzed using quantitative real-time PCR, Western blot and immunohistochemistry analysis. The results revealed that expression levels of NOD1, NOD2, CIITA and NLRP3 were downregulated at days 13 and 16 of pregnancy, but expression of NLRP3 was increased at day 25 of pregnancy. In addition, expression values of NAIP and NLRP7 mRNA and proteins were improved at days 16 and 25 of pregnancy, and NLRP1 was peaked at days 13 and 16 of pregnancy in the maternal spleen. Furthermore, NOD2 and NLRP7 proteins were limited to the capsule, trabeculae and splenic cords. In summary, early pregnancy changes expression of NLR family in the maternal spleen, which may be related with the maternal splenic immunomodulation during early pregnancy in sheep.

Modulation of Nod-like Receptor Expression in the Thymus during Early Pregnancy in Ewes.

Nucleotide-binding oligomerization domain receptors (NOD-like receptors, NLRs) are involved in modulating the innate immune responses of the trophoblast and the placenta in normal pregnancy. The thymus participates in regulation of innate and adaptive immune responses. However, it is unclear whether expression of NLR is modulated in the maternal thymus during early pregnancy. In this study, thymuses were sampled at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation (n = 6 for each group) from ewes after slaughter. Different stages were chosen because the maternal thymus was under the different effects of interferon-tau and/or progesterone or not. RT-qPCR, Western blot and immunohistochemistry analysis were used to analyze the expression of the NLR family, including NOD1; NOD2; major histocompatibility complex class II transactivator (CIITA); NLR family apoptosis inhibitory protein (NAIP); nucleotide-binding oligomerization domain and Leucine-rich repeat and Pyrin domain containing protein 1 (NLRP1), NLRP3 and NLRP7. The results showed that expression level of NOD1 was changed with the pregnancy stages, and expression levels of NOD2, CIITA, NAIP, NLRP1, NLRP3 and NLRP7 mRNA and proteins were peaked at day 13 of pregnancy. The levels of NOD2 and CIITA were increased during early pregnancy. The stainings for NOD2 and NLRP7 proteins were located in epithelial reticular cells, capillaries and thymic corpuscles. In summary, pregnancy stages changed expression of NLR family in the maternal thymus, which may be related to the modulation of maternal thymic immune responses, and beneficial for normal pregnancy in sheep.

Association between septic patient mortality and blood survivin concentrations

ObjectiveSurvivin is a member of inhibitors of apoptosis proteins family. There are not data about the association between mortality of septic patients and blood survivin concentrations. Therefore, the objective of this study was to determine whether exist that association. DesignObservational and prospective study. SettingThree Spanish Intensive Care Units. PatientsPatients with sepsis or septic shock according to Sepsis-3 Consensus criteria. InterventionsSerum survivin concentrations were determined at moment of sepsis diagnosis. Main variable of interestMortality at 30 days. ResultsA total of 204 patients were included in the study, of which 75 (36.8%) died in the first 30 days. Lower age (p<0.001), serum lactic acid levels (p=0.001), rate of septic shock (p=0.001) and SOFA (p<0.001), and higher serum survivin levels (p=0.001) exhibited surviving (n=129) than non-surviving patients (n=75). We found in multiple logistic regression analysis an association between serum survivin concentrations and mortality independently of SOFA, lactic acid, age, INR, activated partial thromboplastin time (aPTT) and empiric antimicrobial treatment adequate (OR=0.968; 95% CI=0.946–0.990; p=0.005), and also independently of APACHE-II, lactic acid, platelet, INR, aPTT and empiric antimicrobial treatment adequate (OR=0.966; 95% CI=0.943–0.989; p=0.004). ConclusionsThere is an association between septic patient mortality and low blood survivin concentrations.

A novel inhibitor of apoptosis protein (IAPs) from Crassostrea gigas is involved in anti-apoptosis and innate defense role under Vibrio alginolyticus stimulation

Apoptosis is an essential biological process in vertebrates and invertebrates for the development and maintenance of homeostasis. Inhibition of apoptosis can help some pathogens survive in host cells and escape from immune surveillance. Importantly, it also plays an important role in immune signaling regulation from insects to mammals. In this study, we identified a new inhibitor of the apoptosis protein gene (IAP), CgIAP3 from the Pacific oyster C. gigas, which contained one BIR domain and one RING domain. Blast analysis showed that CgIAP3 share the highest sequence identity of 65.68% with C. virginica IAP8, and clustered with other shellfish IAP in the phylogenetic tree, indicating that CgIAP3 belonged to a member of the IAPs family of shellfish. Homology comparison showed that the BIR domain of CgIAP3 was highly conserved with the BIR3 domain of human IAP. The tissue distribution of CgIAP3 in healthy C. gigas showed that CgIAP3 is ubiquitously expressed in all analyzed tissues, with the highest level of expression in the gills and digestive gland than the adductor muscle and was rapidly up-regulated after V. alginolyticus stimulation. Moreover, cell experiments showed CgIAP3 could inhibit apoptosis by maintaining cell morphology and cell viability. The result of subcellular localization showed that CgIAP3 is widely distributed in cytoplasm and nucleus and only expressed in A549 cells with damaged nucleus. Taken together, we speculated that CgIAP3 might be involved in the innate immune process of the Pacific oyster against V. alginolyticus through maintaining host cell morphology and viability.

Immunohistochemical expression of survivin in oral epithelial dysplasia and different grades of oral squamous cell carcinoma.

Survivin, a member of the inhibitor of apoptosis proteins family, is not detectable in most differentiated normal adult tissues but is expressed in a wide range of cancer tissues. Survivin expression in cancer has been associated with poor prognosis, cancer progression, and drug resistance, and the expression levels correlate with more aggressive disease and a poor clinical outcome. To evaluate and compare the immunoexpression of survivin in the normal oral epithelium (NOE), oral epithelial dysplasia (OED), and different grades of oral squamous cell carcinoma (OSCC). The patterns of survivin immunoexpression and immunoreactivity were assessed in previously diagnosed, paraffin-embedded sections of 10 tissues of NOE and 15 tissues each of OED and the three grades of OSCC (well-, moderately-, and poorly-differentiated). The pattern of survivin expression was recorded as cytoplasmic, nuclear, or both. Survivin immunoreactivity was assessed semi-quantitatively as the immunoreactive score (IRS). Analysis of variance and Tukey-HSD tests were employed for statistical analysis. No immunoreactivity for survivin was evident in the NOE tissues. In the OED tissues, the immunoexpression pattern of survivin was predominantly nuclear in the basal cells, and in the OSCC tissues, cytoplasmic and nuclear. IRS was highest among the moderately- differentiated OSCC, followed by poorly- and well-differentiated OSCC and OED, with a statistically significant difference in the IRS scores between the normal and the study groups. Survivin protein expression may be an important early event in oral carcinogenesis and may predict unfavorable prognosis in OSCC.

Vitamin D receptor enhances NLRC4 inflammasome activation by promoting NAIPs-NLRC4 association.

Inflammasomes are cytosolic multiprotein complexes that initiate host defense against bacterial pathogens. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family caspase-associated recruitment domain-containing protein 4 (NLRC4) inflammasomes plays a critical role in the inflammatory response against intracellular bacterial infection. The NLR family apoptosis inhibitory proteins (NAIPs) detect Flagellin or type III secretion system (T3SS) microbial components to activate NLRC4 inflammasome. However, the underlying mechanism of NLRC4 inflammasome activation is not completely understood. Here, we show that the vitamin D receptor (VDR) is an essential immunological regulator of the NLRC4 inflammasome. Conditional VDR knockout mice (VDRflox/flox lyz2-Cre) exhibited impaired clearance of pathogens after acute Salmonella Typhimurium infection leading to poor survival. In macrophages, VDR deficiency reduced caspase-1 activation and IL-1β secretion upon S. Typhimurium infection. For NAIPs act as upstream sensors for NLRC4 inflammasome assembly, the further study demonstrated that VDR promoted the NAIP-NLRC4 association and triggered NAIP-NLRC4 inflammasome activation, not NLRP3 activation. Moreover, Lys123 residue of VDR is identified as the critical amino acid for VDR-NLRC4 interaction, and the mutant VDR (K123A) effectively attenuates the NLRC4 inflammasome activation. Together, our findings suggest that VDR is a critical regulator of NAIPs-NLRC4 inflammasome activation, mediating innate immunity against bacterial infection.

A novel survivin dimerization inhibitor without a labile hydrazone linker induces spontaneous apoptosis and synergizes with docetaxel in prostate cancer cells

Survivin, a member of the inhibitor of apoptosis protein family, exists as a homodimer and is aberrantly upregulated in a wide spectrum of cancers. It was thought to be an ideal target due to its lack of expression in most adult normal tissues and importance in cancer cell survival. However, it has been challenging to target survivin due to its “undruggable” nature. We previously attempted to target its dimerization domain with a hypothesis that inhibiting survivin dimerization would promote its degradation in proteasome, which led to identification of a lead small-molecule inhibitor, LQZ-7F. LQZ-7F consists of a flat tetracyclic aromatic core with labile hydrazone linking a 1,2,5-oxadiazole moiety. In this study, we tested the hypothesis that LQZ-7F could be developed as a prodrug because the labile hydrazone linker could be hydrolyzed, releasing the tetracyclic aromatic core. To this end, we synthesized the tetracyclic aromatic core (LQZ-7F1) using reported procedure and tested LQZ-7F1 for its biological activities. Here we show that LQZ-7F1 has a significantly improved potency with submicromolar IC50’s and induces spontaneous apoptosis in prostate cancer cells. It also more effectively inhibits survivin dimerization and induces survivin degradation in a proteasome-dependent manner than LQZ-7F. We also show that the combination of LQZ-7F1 and docetaxel have strong synergism in inhibiting prostate cancer cell survival. Together, we conclude that the hydrazone linker with the oxadiazole tail is dispensable for survivin inhibition and the survivin dimerization inhibitor, LQZ-7F, may be developed as a prodrug for prostate cancer treatment and to overcome docetaxel resistance.

Targeting inhibitor of apoptosis proteins (IAPs) with IAP inhibitors sensitises malignant rhabdoid tumour cells to cisplatin

Malignant rhabdoid tumour (MRT) is a rare, aggressive paediatric malignancy most commonly diagnosed in those below the age of three. MRTs can arise in soft tissue but are more often associated with the central nervous system or kidney. Unfortunately, the prognosis upon diagnosis with MRT is poor. Given the resistance of MRT to current treatment protocols including cisplatin, and the vulnerability of this young patient population to aggressive therapies, there is a need for novel treatment options. Several members of the inhibitor of apoptosis protein (IAP) family including X‑linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/cIAP2), livin and survivin have been implicated in chemotherapy resistance in various malignancies. We have previously demonstrated expression of these IAP family members in a panel of MRT cell lines. In the present study, sensitivity of this same panel of MRT cell lines to small-molecule mediated inhibition of the IAPs via the survivin inhibitor YM155 and the XIAP/cIAP1/cIAP2 inhibitor BV6 was demonstrated. Additionally, both BV6 and the XIAP inhibitor embelin synergistically enhanced cisplatin mediated apoptotic cell death in MRT cell lines, with enhanced caspase-3 cleavage. Importantly, we have demonstrated, for the first time, expression of XIAP, its target caspase-3 and its endogenous inhibitor SMAC in rhabdoid tumour patient tissue. In conclusion, this study provides pre-clinical evidence that IAP inhibition may be a new therapeutic option in MRT.