Cellular FLICE-inhibitory Protein Research Articles

HnRNPK inhibits GSK3β Ser9 phosphorylation, thereby stabilizing c-FLIP and contributes to TRAIL resistance in H1299 lung adenocarcinoma cells.

c-FLIP (cellular FLICE-inhibitory protein) is the pivotal regulator of TRAIL resistance in cancer cells, It is a short-lived protein degraded through the ubiquitin/proteasome pathway. The discovery of factors and mechanisms regulating its protein stability is important for the comprehension of TRAIL resistance by tumor cells. In this study, we show that, when H1299 lung adenocarcinoma cells are treated with TRAIL, hnRNPK is translocated from nucleus to cytoplasm where it interacts and co-localizes with GSK3β. We find that hnRNPK is able to inhibit the Ser9 phosphorylation of GSK3β by PKC. This has the effect of activating GSK3β and thereby stabilizing c-FLIP protein which contributes to the resistance to TRAIL in H1299 cells. Our immunohistochemical analysis using tissue microarray provides the clinical evidence of this finding by establishing a negative correlation between the level of hnRNPK expression and the Ser9 phosphorylation of GSK3β in both lung adenocarcinoma tissues and normal tissues. Moreover, in all cancer tissues examined, hnRNPK was found in the cytoplasm whereas it is exclusively nuclear in the normal tissues. Our study sheds new insights on the molecular mechanisms governing the resistance to TRAIL in tumor cells, and provides new clues for the combinatorial chemotherapeutic interventions with TRAIL.

A novel derivative of tetrandrine (H1) induces endoplasmic reticulum stress-mediated apoptosis and prosurvival autophagy in human non-small cell lung cancer cells.

H1, a bromized derivative of tetrandrine, has been reported to induce apoptosis in human cancer cells. But, the underlying mechanism of apoptosis triggered by H1 is unclear. In the present study, we found that H1 triggered death receptor 5 (DR5)-dependent apoptosis in non-small cell lung cancer (NSCLC) cells. Further study showed that H1 activated ER stress through enforcing the expression of Bip/GRP78, IRE1α, p-eIF2α, and CHOP. Moreover, abrogating CHOP expression blocked DR5 upregulation and subsequent apoptosis, indicating that CHOP was essential for DR5-dependent apoptosis induced by H1. In addition, H1 greatly downregulated cellular FLICE-inhibitory protein (c-FLIP), and enhanced expression of c-FLIP protected cancer cells from apoptosis in spite of H1 therapy. Furthermore, we discovered that H1 induced autophagy in human NSCLC cells. Interestingly, the autophagy induced by H1 played a protective function in NSCLC cells and effectively weakened caspase-mediated apoptosis. In summary, these findings suggest that H1 induces DR5-dependent apoptosis in human NSCLC cells via stimulating ER stress signaling pathway, and pharmacologically inhibiting autophagy will be an efficient approach to synergize H1-caused apoptosis in lung cancer cells.

Modulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis by Helicobacter pylori in immune pathogenesis of gastric mucosal damage.

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer, gastric carcinoma, and gastric mucosa-associated lymphoid tissue lymphomas. Apoptosis induced by microbial infections is implicated in the pathogenesis of H. pylori infection. Enhanced gastric epithelial cell apoptosis during H. pylori infection was suggested to play an important role in the pathogenesis of chronic gastritis and gastric pathology. In addition to directly triggering apoptosis, H. pylori induces sensitivity to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in gastric epithelial cells. Human gastric epithelial cells sensitized to H. pylori confer susceptibility to TRAIL-mediated apoptosis via modulation of death-receptor signaling. The induction of TRAIL sensitivity by H. pylori is dependent upon the activation of caspase-8 and its downstream pathway. H. pylori induces caspase-8 activation via enhanced assembly of the TRAIL death-inducing signaling complex through downregulation of cellular FLICE-inhibitory protein. Moreover, H. pylori infection induces infiltration of T lymphocytes and triggers inflammation to augment apoptosis. In H. pylori infection, significant increases in CCR6+ CD3+ Tcell infiltration in the gastric mucosa was observed, and the CCR6 ligand, CCL20 chemokine, was selectively expressed in inflamed gastric tissues. These mechanisms initiate chemokine-mediated T lymphocyte trafficking into inflamed epithelium and induce mucosal injury during Helicobacter infection. This article will review recent findings on the interactions of H. pylori with host-epithelial signaling pathways and events involved in the initiation of gastric pathology, including gastric inflammation and mucosal damage.

SAT-360 - Loss of Cellular Flice-Inhibitory Protein Promotes Cholestasis-Induced Hepatocellular Injury and Inflammation in Bile Duct Ligated Mice

SAT-360 - Loss of Cellular Flice-Inhibitory Protein Promotes Cholestasis-Induced Hepatocellular Injury and Inflammation in Bile Duct Ligated Mice

TWEAK/Fn14 activation induces keratinocyte proliferation under psoriatic inflammation.

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) has been reported to induce keratinocyte apoptosis in vitro by engaging its sole receptor of fibroblast growth factor-inducible 14 (Fn14). In this study, we explored the role of TWEAK/Fn14 pathway in the growth of psoriatic keratinocytes that is, however, characterized by suppressed apoptotic cell death. Skin tissues from the patients with psoriasis or healthy donors were determined for TWEAK and Fn14 expression, and primary keratinocytes were evaluated under the stimulation of psoriatic proinflammatory cytokines or plus TWEAK. The results showed that both TWEAK and Fn14 were highly expressed in psoriatic skins. Moreover, the stimulation of psoriatic cytokines enhanced Fn14 expression by keratinocytes in vitro, which expressed TNF receptor 2 predominantly and proliferated increasingly with the addition of TWEAK. Furthermore, TWEAK stimulation enhanced the synthesis of survivin, inhibitor of apoptosis protein 2 and cellular FLICE-inhibitory protein in lesional keratinocytes. Therefore, TWEAK/Fn14 interaction prefers to enhance proliferation but not apoptosis of keratinocytes under psoriatic inflammation. The activation of nuclear factor-κB signalling-dependent anti-apoptotic proteins and biased expression of TNF receptors may be responsible for such a novel principle in keratinocytes under psoriatic inflammation.

Prognostic significance of TRAIL signalling molecules in cervical squamous cell carcinoma

AimTumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that preferentially induces apoptosis in cancer cells while exhibiting little or no toxicity in normal cells....

TNF Apoptosis Protection Fraction (TAPF) prevents apoptosis induced by TNF, but not by Fas or TRAIL, via NF-κB-induced increase in cFLIP

Tumor Necrosis Factor α (TNFα) induces both the apoptotic pathway and anti-apoptotic factors. Incubation of human dermal fibroblasts with TAPF (TNF Apoptosis Protection Fraction) protects them from apoptosis induced by the subsequent addition of TNF and cycloheximide (CHX). TAPF does not protect against apoptosis induced by CHX in combination with either TRAIL (TNF related apoptosis inducing ligand) or an agonistic Fas antibody, or against apoptosis induced by the chemotherapeutic agent doxorubicin. Incubation with TAPF does not affect the quantity of TNF that binds to the cell. TAPF prevents TNF-induced cleavage of caspases 8, 9, 3 and 7 and the apoptotic substrate PARP (poly-ADP ribose polymerase), but has no effect when these molecules are induced by an agonistic Fas antibody. TAPF induces rapid phosphorylation of the NF-κB/p65 (nuclear factor-κB) transcription factor at serine 536 which is indicative of its activation. TAPF increases the expression of cFLIP (cellular FLICE-inhibitory protein) which is a potent inhibitor of apoptosis that acts by preventing the cleavage of caspase 8. This increase in cFLIP is coincident with protection from TNF-induced apoptosis. Decreasing cFLIP levels using shRNA (short hairpin RNA) decreases protection by TAPF. TAPF also induced the anti-apoptotic A20 protein. These data indicate that TAPF protects human dermal fibroblasts from TNF-induced apoptosis by induction of cFLIP and subsequent inhibition of caspase 8 cleavage.

Ca2+ influx-mediated dilation of the endoplasmic reticulum and c-FLIPL downregulation trigger CDDO-Me-induced apoptosis in breast cancer cells.

The synthetic triterpenoid 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-C28-methyl ester (CDDO-Me) is considered a promising anti-tumorigenic compound. In this study, we show that treatment with CDDO-Me induces progressive endoplasmic reticulum (ER)-derived vacuolation in various breast cancer cells and ultimately kills these cells by inducing apoptosis. We found that CDDO-Me-induced increases in intracellular Ca2+ levels, reflecting influx from the extracellular milieu, make a critical contribution to ER-derived vacuolation and subsequent cell death. In parallel with increasing Ca2+ levels, CDDO-Me markedly increased the generation of reactive oxygen species (ROS). Interestingly, there exists a reciprocal positive-regulatory loop between Ca2+ influx and ROS generation that triggers ER stress and ER dilation in response to CDDO-Me. In addition, CDDO-Me rapidly reduced the protein levels of c-FLIPL (cellular FLICE-inhibitory protein) and overexpression of c-FLIPL blocked CDDO-Me-induced cell death, but not vacuolation. These results suggest that c-FLIPL downregulation is a key contributor to CDDO-Me-induced apoptotic cell death, independent of ER-derived vacuolation. Taken together, our results show that ER-derived vacuolation via Ca2+ influx and ROS generation as well as caspase activation via c-FLIPL downregulation are responsible for the potent anticancer effects of CDDO-Me on breast cancer cells.

Lipopolysaccharide pretreatment inhibits LPS-induced human umbilical cord mesenchymal stem cell apoptosis via upregulating the expression of cellular FLICE-inhibitory protein.

Mesenchymal stem cell (MSC)-based regenerative therapy is currently regarded as a novel approach with which to repair damaged tissues. However, the efficiency of MSC transplantation is limited due to the low survival rate of engrafted MSCs. Lipopolysaccharide (LPS) production is increased in numerous diseases and serves an essential function in the regulation of apoptosis in a variety of cell types. Previous studies have indicated that low-dose LPS pretreatment contributes to cytoprotection. In the current study, LPS was demonstrated to induce apoptosis in human umbilical cord mesenchymal stem cells (hUCMSCs) via the activation of caspase, in a dose-dependent manner. Low-dose LPS pretreatment may protect hUCMSCs against apoptosis induced by high-dose LPS, by upregulating the expression of cellular FADD-like IL-1β-converting enzyme-inhibitory protein (c-FLIP). The results of the present study indicate that pretreatment with an appropriate concentration of LPS may alleviate high-dose LPS-induced apoptosis.

Inefficient Codon Usage Impairs mRNA Accumulation: the Case of the v-FLIP Gene of Kaposi's Sarcoma-Associated Herpesvirus.

Latent Kaposi's sarcoma-associated herpesvirus (KSHV) genomes encode a homolog of cellular FLICE-inhibitory proteins (termed v-FLIP) that activates NF-κB and can trigger important proinflammatory and antiapoptotic changes in latently infected cells. The protein is present at very low levels in infection and has generally been difficult to efficiently express in recombinant vectors. Here we show that codon usage in the v-FLIP gene is strikingly suboptimal. Optimization of codon use in expression vectors, as expected, restores efficient protein expression. Surprisingly, however, it also dramatically increases the steady-state level of v-FLIP mRNA, at least in part by increasing mRNA stability. When codon-optimized v-FLIP sequences are reintroduced into intact KSHV genomes, the resulting virus expresses readily detectable monocistronic v-FLIP mRNAs that are undetectable in wild-type (WT) infection by blot hybridization, suggesting that such RNAs are in fact transcribed in WT infection but fail to accumulate. The overexpression of v-FLIP by codon-optimized latent genomes results in a 5- to 7-fold decrement in virus production following lytic induction, indicating that maximizing NF-κB signaling is deleterious to induction. These studies provide a clear explanation for the evolution of inefficient codon usage in this gene and point to a strong connection between translational efficiency and RNA accumulation in mammalian cells. This study reports that inefficient codon usage in a herpesviral gene is strikingly correlated with the inability of its mRNA to accumulate in cells; correction of efficient translatability restores RNA abundance. A similar correlation has been reported in yeast species, but the mechanisms operating in mammalian cells appear substantially different.

Iron supplementation effectively suppresses gastrocnemius muscle lesions to improve exercise capacity in chronic heart failure rats with anemia

ObjectiveFor patients with chronic heart failure (CHF), exertional fatigue is one of the most common and debilitating symptoms. However, the poor relationship between heart dysfunction and exercise capacity has been ascribed to peripheral abnormalities. Several previous studies confirmed that iron supplementation could significantly improve the exercise capacity of patients with CHF, although they did not analyze effects in the musculoskeletal system. The aim of this study was to investigate the effect of iron treatment on gastrocnemius muscles of CHF rats with anemia. MethodsMale Sprague-Dawley rats were subjected to coronary ligation to induce heart failure. At the same time, blood (1–1.5 mL) was withdrawn from the retro-orbital plexus once every week to induce anemia. After 6 wk of this process, iron dextran was administered to the CHF rats with anemia (CHFa rats) at the dose of 8, 16, 32, or 64 mg/kg every 2 d for 2 wk. ResultsIron dextran (8 mg/kg every 2 d) effectively improved hemodynamic parameters (P < 0.05) compared with CHFa rats. Similarly, this dose of iron dextran significantly reduced the ratio of heart weight to body weight (P < 0.01), whereas it significantly increased the distance run (m) to exhaustion (P < 0.01). Iron dextran effectively inhibited sarcoplasmic vacuolation and muscle atrophy of gastrocnemius muscles in CHFa rats, as evaluated by pathologic examinations. Other iron treatments, however, were found to be ineffective on the same parameters, so particular focus was placed on the iron dextran (8 mg/kg every 2 d) group in subsequent analyses. Consistently, phospho-p38 in gastrocnemius muscles of CHFa rats was markedly suppressed by iron dextran. Additionally, iron dextran significantly decreased c-fos and c-jun and up-regulated cellular FLICE-inhibitory protein expression levels.

Modulation of SIV and HIV DNA vaccine immunity by Fas-FasL signaling.

Signaling through the Fas/Apo-1/CD95 death receptor is known to affect virus-specific cell-mediated immune (CMI) responses. We tested whether modulating the Fas-apoptotic pathway can enhance immune responses to DNA vaccination or lymphocytic choriomeningitis virus (LCMV) infection. Mice were electroporated with plasmids expressing a variety of pro- or anti-apoptotic molecules related to Fas signaling and then either LCMV-infected or injected with plasmid DNA expressing SIV or HIV antigens. Whereas Fas or FasL knockout mice had improved CMI, down-regulation of Fas or FasL by shRNA or antibody failed to improve CMI and was accompanied by increases in regulatory T cells (Treg). Two “adjuvant” plasmids were discovered that significantly enhanced plasmid immunizations. The adjuvant effects of Fas-associated death domain (FADD) and of cellular FLICE-inhibitory protein (cFLIP) were consistently accompanied by increased effector memory T lymphocytes and increased T cell proliferation. This adjuvant effect was also observed when comparing murine infections with LCMV-Armstrong and its persisting variant LCMV-Clone 13. LCMV-Armstrong was cleared in 100% of mice nine days after infection, while LCMV-Clone 13 persisted in all mice. However, half of the mice pre-electroporated with FADD or cFLIP plasmids were able to clear LCMV-Clone 13 by day nine, and, in the case of cFLIP, increased viral clearance was accompanied by higher CMI. Our studies imply that molecules in the Fas pathway are likely to affect a number of events in addition to the apoptosis of cells involved in immunity.

Aloperine executes antitumor effects against multiple myeloma through dual apoptotic mechanisms.

BackgroundAloperine, a natural alkaloid constituent isolated from the herb Sophora alopecuroides displays anti-inflammatory properties in vitro and in vivo. Our group previously demonstrated that aloperine significantly induced apoptosis in colon cancer SW480 and HCT116 cells. However, its specific target(s) remain to be discovered in multiple myeloma (MM) and have not been investigated.MethodsHuman myeloma cell lines (n = 8), primary myeloma cells (n = 12), drug-resistant myeloma cell lines (n = 2), and animal models were tested for their sensitivity to aloperine in terms of proliferation and apoptosis both in vitro and in vivo, respectively. We also examined the functional mechanisms underlying the apoptotic pathways triggered by aloperine.ResultsAloperine induced MM cell death in a dose- and time-dependent manner, even in the presence of the proliferative cytokines interleukin-6 and insulin-like growth factor I. Mechanistic studies revealed that aloperine not only activated caspase-8 and reduced the expression of FADD-like interleukin-1β-converting enzyme (FLICE)-like inhibitory protein long (FLIPL) and FLICE-inhibitory proteins (FLIPS) but also activated caspase-9 and decreased the expression of phosphorylated (p)-PTEN. Moreover, co-activation of the caspase-8/cellular FLICE-inhibitory protein (cFLIP)- and caspase-9/p-PTEN/p-AKT-dependent apoptotic pathways by aloperine caused irreversible inhibition of clonogenic survival. Aloperine induce more MM apoptosis with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or borterzomib. A U266 xenograft tumor model and 5T33 MM cells recapitulated the antitumor efficacy of aloperine, and the animals displayed excellent tolerance of the drug and few adverse effects.ConclusionsAloperine has multifaceted antitumor effects on MM cells. Our data support the clinical development of aloperine for MM therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-015-0120-x) contains supplementary material, which is available to authorized users.

Changes in cFLIP expression in the corpus luteum throughout the estrous cycle of Shibagoats.

Changes in the expression of the anti-apoptotic protein cFLIP (cellular FLICE inhibitory protein) were examined in the caprine corpus luteum (CL), during development and subsequent maintenance. Corpora lutea at four different stages were collected from Shiba goats, to measure the expression of cFLIP mRNA, protein and immunolocalization. Expression of short form cFLIP (cFLIPS) mRNA was highest at the early CL stage, and decreased during late and regressed stages (P < 0.05). In contrast, long form cFLIP (cFLIPL) mRNA expression was high during early, mid and late stages, and only decreased at the regressed stage (P< 0.01). Protein expression of cFLIPS was highest at the late CL stage, and decreased at the regressed stage (P < 0.01). Protein expression of cFLIPL was highest at the early and mid CL stages, and decreased by the late and regressed stages (P < 0.01). Further expression of cFLIPL was higher at the early CL stage than at the mid stage (P < 0.01). cFLIP protein expression was detectable by immunostaining in the early, mid and late CL stages, but not at the regressed CL stage. These results are consistent with the hypothesis that cFLIP acts as a survival factor in the maintenance of CL function in goats.

Expression levels of heat shock protein 27 and cellular FLICE-like inhibitory protein in prostate cancer correlate with Gleason score sum and pathologic stage.

PurposeHeat shock protein (HSP) 27 protects the cell by controlling apoptosis and immune reactions, and c-FLIP (cellular-FLICE inhibitory protein) inhibits apoptosis by inhibiting caspase-8 activity. We investigated the relationship of HSP27 and c-FLIP expression to prostate-specific antigen, Gleason score sum (GSS), and pathologic stage.Materials and MethodsSamples from 163 patients between May 2004 and April 2010 were analyzed: 83 from patients that had underwent a radical prostatectomy, and 80 from those that underwent transurethral resection of the prostate to alleviate urinary symptoms from benign prostate hyperplasia. c-FLIP and HSP27 expression were observed by immunohistochemistry staining. Samples with less than 5% expression-positive cells were scored as 1, with 5%-50% were scored as 2, and with more than 50% were scored as 3. Local reactions were identified as 0.5 and evaluated.ResultsBoth the presence of HSP27 within the tumor and the number of cancer cells positive for HSP27 were significantly correlated to GSS and pathologic stage (p<0.001, p=0.001, p<0.001, p<0.001). The same was true for c-FLIP expression (p<0.001). GSS was more highly correlated to HSP27 expression than to c-FLIP expression (r=0.814 for HSP27, r=0.776 for c-FLIP), as was pathologic stage (r=0.592 for HSP27, r=0.554 for c-FLIP).ConclusionsIn prostate cancer, higher GSS and a more advanced pathologic stage were associated with a higher likelihood of having a HSP27-positive tumor and more HSP27-positive tumor cells. HSP27 expression was correlated with GSS and prostate cancer stage. A more advanced pathologic stage corresponded to a higher likelihood of having a c-FLIP-positive tumor and more c-FLIP-positive tumor cells. HSP27 expression had a higher correlation with prostate cancer stage and GSS than c-FLIP expression did.

Expression and localization of cFLIP anti-apoptotic protein in the porcine corpus luteum and corpora albicans during the estrous cycle and pregnancy.

We determined expression and localization of the anti-apoptotic cellular FLICE inhibitory protein (cFLIP) in the porcine corpora lutea (CL) and corpus albicans (CA) during estrous and pregnancy. The CL and CA were collected at different stages of estrous to determine cFLIP immunolocalization, and mRNA and protein expression. The mRNA expression of the short cFLIP isoform (cFLIPS) was higher at the early and mid CL stages, and lower by the late CL stage (P < 0.01); mRNA expression of the long cFLIP isoform (cFLIPL) was higher at the mid CL stage, and lower at the early and late CL stages (P < 0.01). Levels of cFLIPS and cFLIPL were steady and high during the early and mid CL stages, and had significantly decreased (P < 0.01) by the late stage. The cFLIP protein was highly expressed in the early and mid CL stages of estrous, but weakly ex-pressed in the late stage. Expression of cFLIPS showed no significant difference between preovulatory corpus albicans (CA1) and corpus albicans (CA2) coexistent with the CL from the previous estrus, but cFLIPL mRNA expression was higher during CA1 than CA2. The expression of cFLIPS showed no significant difference between CA1 and CA2, but cFLIPL was not detected. The cFLIP protein was weak-ly expressed in the CA. Expression of cFLIPS and cFLIPL mRNA and proteins was observed in the CL, and the cFLIP protein was highly expressed during pregnancy. We propose that cFLIPS/L acts as a survival factor, and performs an anti-apoptotic function in the porcine CL.

The endogenous caspase-8 inhibitor c-FLIPL regulates ER morphology and crosstalk with mitochondria.

Components of the death receptor-mediated pathways like caspase-8 have been identified in complexes at intracellular membranes to spatially restrict the processing of local targets. In this study, we report that the long isoform of the cellular FLICE-inhibitory protein (c-FLIPL), a well-known inhibitor of the extrinsic cell death initiator caspase-8, localizes at the endoplasmic reticulum (ER) and mitochondria-associated membranes (MAMs). ER morphology was disrupted and ER Ca2+-release as well as ER-mitochondria tethering was decreased in c-FLIP−/− mouse embryonic fibroblasts (MEFs). Mechanistically, c-FLIP ablation resulted in enhanced basal caspase-8 activation and in caspase-mediated processing of the ER-shaping protein reticulon-4 (RTN4) that was corrected by re-introduction of c-FLIPL and caspase inhibition, resulting in the recovery of a normal ER morphology and ER-mitochondria juxtaposition. Thus, the caspase-8 inhibitor c-FLIPL emerges as a component of the MAMs signaling platforms, where caspases appear to regulate ER morphology and ER-mitochondria crosstalk by impinging on ER-shaping proteins like the RTN4.

C-FLIP is involved in tumor progression of peripheral T-cell lymphoma and targeted by histone deacetylase inhibitors.

BackgroundPeripheral T-cell lymphomas (PTCLs) are often aggressive tumors and resistant to conventional chemotherapy. Dysregulation of extrinsic apoptosis plays an important role on tumor cell sensitivity to chemotherapeutic agents. Cellular FLICE inhibitory protein (c-FLIP) is a key regulator of extrinsic apoptotic pathway.Methodsc-FLIP expression was assessed by real-time PCR and compared according to clinical parameters in patients with PTCLs. The relation of c-FLIP to tumor cell apoptosis mediated by histone deacetylases inhibitors (HDACIs) and the possible mechanism were examined in T-lymphoma cell lines and in a murine xenograft model.Resultsc-FLIP was overexpressed and associated with decreased tumor TRAIL/DR5 expression, elevated serum lactate dehydrogenase level and high-risk International Prognostic Index of the patients. In vitro, molecular silencing of c-FLIP by specific small-interfering RNA increased TRAIL/DR5 expression, enhanced T-lymphoma cell apoptosis and sensitized cells to chemotherapeutic agents. However, HDACIs valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA) could downregulate c-FLIP expression and triggered extrinsic apoptosis of T-lymphoma cells, through inhibiting NF-κB signaling and interrupting P50 interaction with c-FLIP promoter. As Class I HDACIs, both VPA and SAHA inhibited HDAC1, resulting in P50 inactivation and c-FLIP downregulation. In vivo, oral VPA treatment significantly retarded tumor growth and induced in situ apoptosis, consistent with inhibition of HDAC1/P50/c-FLIP axis and increase of TRAIL/DR5 expression.Conclusionsc-FLIP overexpression in PTCLs protected tumor cells from extrinsic apoptosis and contributed to tumor progression. Although linking to chemoresistance, c-FLIP indicated tumor cell sensitivity to HDACIs, providing a potential biomarker of targeting apoptosis in treating PTCLs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-014-0088-y) contains supplementary material, which is available to authorized users.

Carbon nanotubes induce apoptosis resistance of human lung epithelial cells through FLICE-inhibitory protein.

Chronic exposure to single-walled carbon nanotubes (SWCNT) has been reported to induce apoptosis resistance of human lung epithelial cells. As resistance to apoptosis is a foundation of neoplastic transformation and cancer development, we evaluated the apoptosis resistance characteristic of the exposed lung cells to understand the pathogenesis mechanism. Passage control and SWCNT-transformed human lung epithelial cells were treated with known inducers of apoptosis via the intrinsic (antimycin A and CDDP) or extrinsic (FasL and TNF-α) pathway and analyzed for apoptosis by DNA fragmentation, annexin-V expression, and caspase activation assays. Whole-genome microarray was performed to aid the analysis of apoptotic gene signaling network. The SWCNT-transformed cells exhibited defective death receptor pathway in association with cellular FLICE-inhibitory protein (c-FLIP) overexpression. Knockdown or chemical inhibition of c-FLIP abrogated the apoptosis resistance of SWCNT-transformed cells. Whole-genome expression signature analysis confirmed these findings. This study is the first to demonstrate carbon nanotube-induced defective death receptor pathway and the role of c-FLIP in the process.

Acute organ failure following the loss of anti-apoptotic cellular FLICE-inhibitory protein involves activation of innate immune receptors

Apoptosis signaling is involved in both physiological tissue homeostasis and acute and chronic diseases. The role of regulatory apoptosis signaling molecules and their organ-specific functions are less defined. Therefore, we investigated the loss of the anti-apoptotic cellular FLICE-inhibitory protein (cFLIP) and the mechanisms of the resulting lethal organ failure in vivo using inducible knockout mice. These were generated by crossing floxed cFLIP mice to a tamoxifen inducible Rosa26-creERT2 mouse strain. Death following global loss of cFLIP resulted from liver failure, accumulation of M1-polarized macrophages and accompanying hepatic cell death and inflammation. Apoptosis was also prominent in immune cells, the kidney and intestinal epithelial cells (IECs) but not in cardiomyocytes. Cellular injury led to the release of damage-associated molecular patterns (DAMPs) and the induction of innate immune receptors including toll-like receptors (TLRs) 4 and 9, and stimulator of interferon genes (STING). Transplantation of bone marrow with intact cFLIP or depletion of macrophages prevented the phenotype of acute liver failure. Interestingly, compound deletion of cFLIP in bone marrow-derived cells and hepatocytes did not promote organ failure. Thus, cFLIP exerts a critical role in tissue homeostasis by preventing the activation of monocytic cells and innate immunity, which causes cell death and inflammation in susceptible tissues. These results encourage the development of organ-specific anti-apoptotic and anti-inflammatory therapies in acute organ failure.