Deficiency in X-linked inhibitor of apoptosis protein promotes susceptibility to microbial triggers of intestinal inflammation.

Inflammatory bowel disease (IBD) is characterized by inappropriate immune responses to the microbiota in genetically susceptible hosts, but little is known about the pathways that link individual genetic alterations to microbiota-dependent inflammation. Here, we demonstrated that the loss of X-linked inhibitor of apoptosis protein (XIAP), a gene associated with Mendelian IBD, rendered Paneth cells sensitive to microbiota-, tumor necrosis factor (TNF)­, receptor-interacting protein kinase 1 (RIPK1)­, and RIPK3-dependent cell death. This was associated with deficiency in Paneth cell­derived antimicrobial peptides and alterations in the stratification and composition of the microbiota. Loss of XIAP was not sufficient to elicit intestinal inflammation but provided susceptibility to pathobionts able to promote granulomatous ileitis, which could be prevented by administration of a Paneth cell­derived antimicrobial peptide. These data reveal a pathway critical for host-microbial cross-talk, which is required for intestinal homeostasis and the prevention of inflammation and which is amenable to therapeutic targeting.

The reduction of XIAP is associated with inflammasome activation in RPE: implications for AMD pathogenesis.

BACKGROUND: Age-related macular degeneration (AMD) is a multifactorial chronic disease of the eye. Several candidate pathways have been hypothesized to play a role in AMD pathogenesis. Our work and those of others suggests inflammasome activity as a mechanism associated with retinal pigment epithelial (RPE) cell demise. X-linked inhibitor of apoptosis protein (XIAP), an anti-apoptosis factor, has recently been shown to regulate inflammasome activity in non-ocular cells. The purpose of this study is to characterize XIAP's regulatory role in RPE. METHODS: Protein lysates of eye tissues from rats (vinpocetine- or aurin tricarboxylic acid complex-treated, ATAC, vs naïve) and mice (wild type vs Caspase-4-/-) were utilized to analyze XIAP protein levels. Immunohistochemistry was used to detect NLRP3 levels in the RPE layer. In vitro inflammasome activation on RPE cells was achieved with L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) stimulation. Levels of XIAP mRNA and 18S RNA were quantified by RT-PCR. Cell culture supernatants were tested directly for secreted IL-1ß by ELISA or concentrated for the detection of secreted IL-18 by western blot. Protein lysates from RPE in cell culture were collected for the measurement of cleaved caspase-1 p20, XIAP, and GAPDH. Data are presented as Mean ± SD. p < 0.05 is considered statistically significant. RESULTS: The XIAP protein level was significantly increased when the inflammasome was inhibited at the "activation" step by ATAC, but not the "priming" step, in vivo. Concomitantly, NLRP3 immunoreactivity was lower in the RPE layer of animals fed with ATAC. In mice where caspase-1 cleavage was impaired by the genetic deficiency in caspase-4, the XIAP protein level increased in eye tissues. In RPE cell culture, Leu-Leu-OMe stimulation led to caspase-1 cleavage, cytokine secretion, and XIAP reduction, which can be abolished by Z-YVAD-FMK. When XIAP siRNA was given as a pre-treatment to RPE in vitro, Leu-Leu-OMe induced IL-1ß/IL-18 secretion was enhanced, whereas overexpressing XIAP reduced IL-1ß secretion under inflammasome activation, both compared to controls cells. CONCLUSIONS: Together, these data suggest XIAP-mediated inhibition of inflammasome activity in RPE may provide insights into the biological consequences of inflammasome activation in RPE and reveals the caspase-1/XIAP/IL-1ß/IL-18 axis as a target for broader applications in AMD biology and treatment design.

Targeted ablation of the cellular inhibitor of apoptosis 1 (cIAP1) attenuates denervation-induced skeletal muscle atrophy.

BACKGROUND: Skeletal muscle atrophy is a pathological condition that contributes to morbidity in a variety of conditions including denervation, cachexia, and aging. Muscle atrophy is characterized as decreased muscle fiber cross-sectional area and protein content due, in part, to the proteolytic activities of two muscle-specific E3 ubiquitin ligases: muscle RING-finger 1 (MuRF1) and muscle atrophy F-box (MAFbx or Atrogin-1). The nuclear factor-kappa B (NF-κB) pathway has emerged as a critical signaling network in skeletal muscle atrophy and has become a prime therapeutic target for the treatment of muscle diseases. Unfortunately, none of the NF-κB targeting drugs are currently being used to treat these diseases, likely because of our limited knowledge and specificity, for muscle biology and disease. The cellular inhibitor of apoptosis 1 (cIAP1) protein is a positive regulator of tumor necrosis factor alpha (TNFα)-mediated classical NF-κB signaling, and cIAP1 loss has been shown to enhance muscle regeneration during acute and chronic injury. METHODS: Sciatic nerve transection in wild-type, cIAP1-null and Smac mimetic compound (SMC)-treated mice was performed to investigate the role of cIAP1 in denervation-induced atrophy. Genetic in vitro models of C2C12 myoblasts and primary myoblasts were also used to examine the role of classical NF-κB activity in cIAP1-induced myotube atrophy. RESULTS: We found that cIAP1 expression was upregulated in denervated muscles compared to non-denervated controls 14 days after denervation. Genetic and pharmacological loss of cIAP1 attenuated denervation-induced muscle atrophy and overexpression of cIAP1 in myotubes was sufficient to induce atrophy. The induction of myotube atrophy by cIAP1 was attenuated when the classical NF-κB signaling pathway was inhibited. CONCLUSIONS: These results demonstrate the cIAP1 is an important mediator of NF-κB/MuRF1 signaling in skeletal muscle atrophy and is a promising therapeutic target for muscle wasting diseases.

XIAP deficiency in hematopoietic recipient cells drives donor T-cell activation and GvHD in mice.

Patients with X-linked lymphoproliferative syndrome type 2 (XLP-2) (BIRC4 deficiency) suffer from hyperinflammation often observed during the conditioning regimen prior to allogeneic bone marrow transplant. This article shows that in mice hematopoietic recipient cells contribute to graft-versus-host disease by the secretion of elevated levels of proinflammatory cytokines during engraftment when BIRC4 is absent.

cIAP1 regulates the EGFR/Snai2 axis in triple-negative breast cancer cells.

Inhibitor of apoptosis (IAP) proteins constitute a family of conserved molecules that regulate both apoptosis and receptor signaling. They are often deregulated in cancer cells and represent potential targets for therapy. In our work, we investigated the effect of IAP inhibition in vivo to identify novel downstream genes expressed in an IAP-dependent manner that could contribute to cancer aggressiveness. To this end, immunocompromised mice engrafted subcutaneously with the triple-negative breast cancer MDA-MB231 cell line were treated with SM83, a Smac mimetic that acts as a pan-IAP inhibitor, and tumor nodules were profiled for gene expression. SM83 reduced the expression of Snai2, an epithelial-to-mesenchymal transition factor often associated with increased stem-like properties and metastatic potential especially in breast cancer cells. By testing several breast cancer cell lines, we demonstrated that Snai2 downregulation prevents cell motility and that its expression is promoted by cIAP1. In fact, the chemical or genetic inhibition of cIAP1 blocked epidermal growth factor receptor (EGFR)-dependent activation of the mitogen-activated protein kinase (MAPK) pathway and caused the reduction of Snai2 transcription levels. In a number of breast cancer cell lines, cIAP1 depletion also resulted in a reduction of EGFR protein levels which derived from the decrease of its gene transcription, though, paradoxically, the silencing of cIAP1 promoted EGFR protein stability rather than its degradation. Finally, we provided evidence that IAP inhibition displays an anti-tumor and anti-metastasis effect in vivo. In conclusion, our work indicates that IAP-targeted therapy could contribute to EGFR inhibition and to the reduction of its downstream mediators. This approach could be particularly effective in tumors characterized by high levels of EGFR and Snai2, such as triple-negative breast cancer.

Human Parvovirus Infection of Human Airway Epithelia Induces Pyroptotic Cell Death by Inhibiting Apoptosis.

Human bocavirus 1 (HBoV1) is a human parvovirus that causes acute respiratory tract infections in young children. In this study, we confirmed that, when polarized/well-differentiated human airway epithelia are infected with HBoV1 in vitro, they develop damage characterized by barrier function disruption and cell hypotrophy. Cell death mechanism analyses indicated that the infection induced pyroptotic cell death characterized by caspase-1 activation. Unlike infections with other parvoviruses, HBoV1 infection did not activate the apoptotic or necroptotic cell death pathway. When the NLRP3-ASC-caspase-1 inflammasome-induced pathway was inhibited by short hairpin RNA (shRNA), HBoV1-induced cell death dropped significantly; thus, NLRP3 mediated by ASC appears to be the pattern recognition receptor driving HBoV1 infection-induced pyroptosis. HBoV1 infection induced steady increases in the expression of interleukin 1α (IL-1α) and IL-18. HBoV1 infection was also associated with the marked expression of the antiapoptotic genes BIRC5 and IFI6 When the expression of BIRC5 and/or IFI6 was inhibited by shRNA, the infected cells underwent apoptosis rather than pyroptosis, as indicated by increased cleaved caspase-3 levels and the absence of caspase-1. BIRC5 and/or IFI6 gene inhibition also significantly reduced HBoV1 replication. Thus, HBoV1 infection of human airway epithelial cells activates antiapoptotic proteins that suppress apoptosis and promote pyroptosis. This response may have evolved to confer a replicative advantage, thus allowing HBoV1 to establish a persistent airway epithelial infection. This is the first report of pyroptosis in airway epithelia infected by a respiratory virus.IMPORTANCE Microbial infection of immune cells often induces pyroptosis, which is mediated by a cytosolic protein complex called the inflammasome that senses microbial pathogens and then activates the proinflammatory cytokines IL-1 and IL-18. While virus-infected airway epithelia often activate NLRP3 inflammasomes, studies to date suggest that these viruses kill the airway epithelial cells via the apoptotic or necrotic pathway; involvement of the pyroptosis pathway has not been reported previously. Here, we show for the first time that virus infection of human airway epithelia can also induce pyroptosis. Human bocavirus 1 (HBoV1), a human parvovirus, causes lower respiratory tract infections in young children. This study indicates that HBoV1 kills airway epithelial cells by activating genes that suppress apoptosis and thereby promote pyroptosis. This strategy appears to promote HBoV1 replication and may have evolved to allow HBoV1 to establish persistent infection of human airway epithelia.

XIAP Loss Triggers RIPK3- and Caspase-8-Driven IL-1ß Activation and Cell Death as a Consequence of TLR-MyD88-Induced cIAP1-TRAF2 Degradation.

X-linked Inhibitor of Apoptosis (XIAP) deficiency predisposes people to pathogen-associated hyperinflammation. Upon XIAP loss, Toll-like receptor (TLR) ligation triggers RIPK3-caspase-8-mediated IL-1ß activation and death in myeloid cells. How XIAP suppresses these events remains unclear. Here, we show that TLR-MyD88 causes the proteasomal degradation of the related IAP, cIAP1, and its adaptor, TRAF2, by inducing TNF and TNF Receptor 2 (TNFR2) signaling. Genetically, we define that myeloid-specific cIAP1 loss promotes TLR-induced RIPK3-caspase-8 and IL-1ß activity in the absence of XIAP. Importantly, deletion of TNFR2 in XIAP-deficient cells limited TLR-MyD88-induced cIAP1-TRAF2 degradation, cell death, and IL-1ß activation. In contrast to TLR-MyD88, TLR-TRIF-induced interferon (IFN)ß inhibited cIAP1 loss and consequent cell death. These data reveal how, upon XIAP deficiency, a TLR-TNF-TNFR2 axis drives cIAP1-TRAF2 degradation to allow TLR or TNFR1 activation of RIPK3-caspase-8 and IL-1ß. This mechanism may explain why XIAP-deficient patients can exhibit symptoms reminiscent of patients with activating inflammasome mutations.

Gene-silencing effects of anti-survivin siRNA delivered by RGDV-functionalized nanodiamond carrier in the breast carcinoma cell line MCF-7.

Nanodiamond (ND) is a renowned material in nonviral small interfering RNA (siRNA) carrier field due to its unique physical, chemical, and biological properties. In our previous work, it was proven that ND could deliver siRNA into cells efficiently and downregulate the expression of desired protein. However, synthesizing a high-efficient tumor-targeting carrier using ND is still a challenge. In this study, a novel carrier, NDCONH(CH2)2NH-VDGR, was synthesized for siRNA delivery, and its properties were characterized with methods including Fourier transform infrared spectrometry, transmission electron microscopy, scanning electron microscopy, gel retardation assay, differential scanning calorimetry, confocal microscopy, releasing test, real-time polymerase chain reaction (PCR) assay, enzyme-linked immunosorbent assay (ELISA), flow cytometry, cytotoxicity assay, and gene-silencing efficacy assay in vitro and in vivo. The mechanism of NDCONH(CH2)2NH-VDGR/survivin-siRNA-induced tumor apoptosis was evaluated via flow cytometer assay using Annexin V-fluorescein isothiocyanate/propidium iodide staining method. The NDCONH(CH2)2NH-VDGR/survivin-siRNA nanoparticle with 60-110 nm diameter and 35.65±3.90 mV zeta potential was prepared. For real-time PCR assay, the results showed that the expression of survivin mRNA was reduced to 46.77%±6.3%. The expression of survivin protein was downregulated to 48.49%±2.25%, as evaluated by ELISA assay. MTT assay showed that NDCONH(CH2)2NH-VDGR/survivin-siRNA had an inhibitory effect on MCF-7 cell proliferation. According to these results, the survivin-siRNA could be delivered, transported, and released stably, which benefits in increasing the gene-silencing effect. Therefore, as an siRNA carrier, NDCONH(CH2)2NH-VDGR was suggested to be used in siRNA delivery system and in cancer treatments.

TRAF2 exerts opposing effects on basal and TNFα-induced activation of the classic IKK complex in hematopoietic cells in mice.

The role of TRAF2 and TRAF5 in TNFα-induced NF-κB activation has become complicated owing to the accumulation of conflicting data. Here, we report that 7-day-old TRAF2-knockout (KO) and TRAF2 TRAF5 double KO (TRAF2/5-DKO) mice exhibit enhanced canonical IκB kinase (IKK) and caspase-8 activation in spleen and liver, and that subsequent knockout of TNFα suppresses the basal activity of caspase-8, but not of IKK. In primary TRAF2 KO and TRAF2/5-DKO cells, TNFα-induced immediate IKK activation is impaired, whereas delayed IKK activation occurs normally; as such, owing to elevated basal and TNFα-induced delayed IKK activation, TNFα stimulation leads to significantly increased induction of a subset of NF-κB-dependent genes in these cells. In line with this, both TRAF2 KO and TRAF2/5-DKO mice succumb to a sublethal dose of TNFα owing to increased expression of NF-κB target genes, diarrhea and bradypnea. Notably, depletion of IAP1 and IAP2 (also known as BIRC2 and BIRC3, respectively) also results in elevated basal IKK activation that is independent of autocrine TNFα production and that impairs TNFα-induced immediate IKK activation. These data reveal that TRAF2, IAP1 and IAP2, but not TRAF5, cooperatively regulate basal and TNFα-induced immediate IKK activation.

Loss of Survivin in Intestinal Epithelial Progenitor Cells Leads to Mitotic Catastrophe and Breakdown of Gut Immune Homeostasis.

A tightly regulated balance of proliferation and cell death of intestinal epithelial cells (IECs) is essential for maintenance of gut homeostasis. Survivin is highly expressed during embryogenesis and in several cancer types, but little is known about its role in adult gut tissue. Here, we show that Survivin is specifically expressed in transit-amplifying cells and Lgr5(+) stem cells. Genetic loss of Survivin in IECs resulted in destruction of intestinal integrity, mucosal inflammation, and death of the animals. Survivin deletion was associated with decreased epithelial proliferation due to defective chromosomal segregation. Moreover, Survivin-deficient animals showed induced phosphorylation of p53 and H2AX and increased levels of cell-intrinsic apoptosis in IECs. Consequently, induced deletion of Survivin in Lgr5(+) stem cells led to cell death. In summary, Survivin is a key regulator of gut tissue integrity by regulating epithelial homeostasis in the stem cell niche.

Essential Role for Survivin in the Proliferative Expansion of Progenitor and Mature B Cells.

Survivin is a member of the inhibitor of apoptosis family of proteins and a biomarker of poor prognosis in aggressive B cell non-Hodgkin's lymphoma. In addition to its role in inhibition of apoptosis, survivin also regulates mitosis. In this article, we show that deletion of survivin during early B cell development results in a complete block at the cycling pre-B stage. In the periphery, B cell homeostasis is not affected, but survivin-deficient B cells are unable to mount humoral responses. Correspondingly, we show that survivin is required for cell division in response to mitogenic stimulation. Thus, survivin is essential for proliferation of B cell progenitors and activated mature B cells, but is dispensable for B cell survival. Moreover, a small-molecule inhibitor of survivin strongly impaired the growth of representative B lymphoma lines in vitro, supporting the validity of survivin as an attractive therapeutic target for high-grade B cell non-Hodgkin's lymphoma.

Intact Regulatory T-Cell Function but Defective Generation of IL-17A-Producing CD4+ T Cells in XIAP Deficiency.

OBJECTIVE: X-linked inhibitor of apoptosis (xIAP) deficiency is a primary immune deficiency disorder associated with hemophagocytic lymphohistiocytosis. About 17% of xIAP-deficient patients present with very early onset severe colitis with high mortality. We hypothesized that xIAP deficiency leads to defective generation and/or survival of T regulatory cells (Treg) through its involvement in transforming growth factor-ß signaling. METHODS AND RESULTS: We used a T-cell transfer model of chronic colitis and observed a mild increase in colitis severity induced by naïve CD4 T cells from xIAP mice compared with colitis induced by naïve CD4 T cells from WT mice. We did not observe any significant difference in the induction of Treg cells in these studies. We next tested whether xIAP is required for Treg cell function by co-transferring xIAP or WT Treg cells with naïve WT CD4 cells in this model. We demonstrate that XIAP-deficient Treg cells were able to prevent disease similarly to WT Treg cells. In these experiments we, however, found a significantly decreased percentage of IL-17A-producing CD4 T cells in mice receiving Tregs from xIAP mice. CONCLUSIONS: xIAP appears dispensable for the generation of induced Treg cells as well as function of natural Treg cells. There appeared to be a role of xIAP in generation of IL-17-producing cells from either naïve CD4 T cells or Treg cells. Further research is needed to explore the role of xIAP in generation of IL-17-producing cells.

A critical role for cellular inhibitor of protein 2 (cIAP2) in colitis-associated colorectal cancer and intestinal homeostasis mediated by the inflammasome and survival pathways.

Cellular inhibitors of apoptosis proteins (cIAPs) are critical arbiters of cell death and key mediators of inflammation and innate immunity. cIAP2 is frequently overexpressed in colorectal cancer and in regenerating crypts of ulcerative colitis patients. However, its corresponding functions in intestinal homeostasis and underlying mechanisms in disease pathogenesis are poorly understood. We found that mice deficient in cIAP2 exhibited reduced colitis-associated colorectal cancer tumor burden but, surprisingly, enhanced susceptibility to acute and chronic colitis. The exacerbated colitis phenotype of cIAP2-deficient mice was mediated by increased cell death and impaired activation of the regenerative inflammasome-interleukin-18 (IL-18) pathway required for tissue repair following injury. Accordingly, administration of recombinant IL-18 or pharmacological inhibition of caspases or the kinase RIPK1 protected cIAP2-deficient mice from colitis and restored intestinal epithelial barrier architecture. Thus, cIAP2 orchestrates intestinal homeostasis by exerting a dual function in suppressing cell death and promoting intestinal epithelial cell proliferation and crypt regeneration.

"Triple-punch" strategy for triple negative breast cancer therapy with minimized drug dosage and improved antitumor efficacy.

Effective therapeutics against triple negative breast cancer (TNBC), which has no standard-of-care therapy, needs to be developed urgently. Here we demonstrated a strategy of integrating indocyanine green (ICG), paclitaxel (PTX), and survivin siRNA into one thermosensitive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate)-co-2-(dimethylamino)ethyl methacrylate-b-poly(D,L-lactide-co-glycolide) (P (MEO2MA-co-OEGMA-co-DMAEMA)-b-PLGA) nanoparticle (NP-IPS) for triple-punch strategy against TNBC. The NP-IPS significantly enhanced the stability of ICG. Controlled release of the PTX in tumor regions was triggered by the hyperthermia produced by laser irradiated ICG. The NP-IPS exhibited remarkable antitumor efficacy (almost complete ablation of the tumor xenografts) due to the combinational effects of chemotherapy, photothermal therapy, and gene therapy with low drug dose (ICG, 0.32 µmol/kg; PTX, 0.54 µmol/kg; siRNA, 1.5 mg/kg) and minimal side effects. Taken together, our current study demonstrates a nanoplatform for triple-therapy, which reveals a promising strategy for TNBC treatment.

Survivin as a therapeutic target in Sonic hedgehog-driven medulloblastoma.

Medulloblastoma (MB) is a highly malignant brain tumor that occurs primarily in children. Although surgery, radiation and high-dose chemotherapy have led to increased survival, many MB patients still die from their disease, and patients who survive suffer severe long-term side effects as a consequence of treatment. Thus, more effective and less toxic therapies for MB are critically important. Development of such therapies depends in part on identification of genes that are necessary for growth and survival of tumor cells. Survivin is an inhibitor of apoptosis protein that regulates cell cycle progression and resistance to apoptosis, is frequently expressed in human MB and when expressed at high levels predicts poor clinical outcome. Therefore, we hypothesized that Survivin may have a critical role in growth and survival of MB cells and that targeting it may enhance MB therapy. Here we show that Survivin is overexpressed in tumors from patched (Ptch) mutant mice, a model of Sonic hedgehog (SHH)-driven MB. Genetic deletion of survivin in Ptch mutant tumor cells significantly inhibits proliferation and causes cell cycle arrest. Treatment with small-molecule antagonists of Survivin impairs proliferation and survival of both murine and human MB cells. Finally, Survivin antagonists impede growth of MB cells in vivo. These studies highlight the importance of Survivin in SHH-driven MB, and suggest that it may represent a novel therapeutic target in patients with this disease.

Survivin silencing enhances radiosensitivity in oral squamous cell carcinoma cell.

OBJECTIVE: Survivin is a member of the inhibitor of apoptosis protein (IAP) family. It is overexpressed in most cancer tissues and induces resistance to radiation therapy. In this study, we investigated whether knockdown of survivin by siRNA could induce apoptosis and enhance radiosensitivity in oral squamous cell carcinoma cells (OSCC). MATERIALS AND METHODS: Oral squamous cell carcinoma cell lines KB was subjected to radiotherapy, small interfering RNA (siRNA) targeting survivin was transfected into KB cells in vitro, then subjected to radiotherapy. After irradiation or/and siRNA transfection, viable and dead cells were counted to determine radiation sensitivity by MTT assay, proliferation by colony-forming ability and apoptosis was analyzed by flow cytometry. Tumor-bearing mice were irradiated with 6 Gy of 60 Co-γ radiator. RESULTS: The results showed knockdown of survivin in KB cells showed reduced cell proliferation and increased number of radiation-induced apoptosis. Apoptosis was increased by survivin silencing alone and increased further in combination with irradiation. Colony formation was significantly reduced by survivin silencing in combination with irradiation. CONCLUSIONS: Survivin silencing sensitizes KB cells toward irradiation. Survivin silencing in combination with radiation inhibits cell proliferation and colony formation significantly and increases apoptosis more than each single treatment alone. In addition, survivin silencing significantly enhanced inhibition of tumor growth and potentiated cell apoptosis by irradiation in KB xenografts. In conclusion, survivin silencing could enhance sensitivity of human KB cells to radiotherapy in vitro and in vivo.

Inability to resolve specific infection generates innate immunodeficiency syndrome in Xiap-/- mice.

Emerging evidence indicates that innate immunodeficiency syndromes are linked to mutations in innate receptors and to specific infections. X-linked lymphoproliferative syndrome type-2 (XLP-2) is associated with deficiency in X-linked inhibitor of apoptosis protein (XIAP), with poorly understood molecular mechanisms. Here we showed that XIAP deficiency selectively impaired B-cell chronic lymphocytic leukemia/lymphoma 10 (BCL10)-mediated innate responses to dectin-1 ligands but did not affect responses to various Toll-like receptor agonists. Consequently, Xiap(-/-) mice became highly vulnerable on Candida albicans infection. The compromised early innate responses led to the persistent presence of C albicans and inflammatory cytokines in Xiap(-/-) mice. Furthermore, priming of Xiap(-/-) mice with the dectin-1 ligand curdlan alone resulted in XLP-2-like syndromes. Restoration of dectin-1-induced Rac1 activation and phagocytosis by resolvin D1, but not up-regulation of nuclear factor-κB, rescued Xiap(-/-) mice from C albicans lethal infection. Therefore, development of XLP-2 in XIAP-deficient patients could be partly due to sustained inflammation as a consequence of defective BCL10-dependent innate immunity toward specific pathogens. Importantly, our results suggest the potential therapeutic value of resolvin D1 in the treatment of XLP-2 and innate immunodeficiency syndromes.

Survivin depletion inhibits tumor growth and enhances chemosensitivity in hepatocellular carcinoma.

Survivin is a member of the inhibitor of apoptosis family, which has been suggested to be crucial in the control of cell division and inhibition of apoptosis. Expression of this protein has been observed in transformed cell lines and human tumor tissues, including those from colorectal cancer, but not in terminally differentiated adult tissues. Survivin mRNA expression has frequently been detected in hepatocellular carcinoma (HCC) and its protein expression has been demonstrated to be highly correlated with proliferation index rather than apoptotic index. The present study aimed to analyze the effect of survivin on the tumorigenicity and chemosensitivity of HCC via the establishment of an HCC cell line (PLC/PRF/5) with the stable knockdown of the survivin gene (PLC­k3). This cell line displayed significantly lower rates of survival and proliferation in assays of cell viability and proliferation, respectively, compared with those of the control cell line (PLC­v). In addition, PLC­k3 cells were more sensitive to cisplatin treatment, resulting in S phase arrest. These findings were further confirmed by an in vivo experiment. The data of the present study suggest that survivin is critical in promoting cell proliferation but not in inhibition of apoptosis, and enhances the chemosensitivity of HCC. Thus, the suppression of survivin expression in combination with cisplatin may contribute to the development of more effective treatments for HCC.

Cellular inhibitor of apoptosis protein cIAP2 protects against pulmonary tissue necrosis during influenza virus infection to promote host survival.

Cellular inhibitors of apoptosis proteins (cIAPs) are essential regulators of cell death and immunity. The corresponding contributions of IAPs to infectious disease outcomes are relatively unexplored. We find that mice deficient in cIAP2 exhibit increased susceptibility and mortality to influenza A virus infection. The lethality was not due to impaired antiviral immune functions, but rather because of death-receptor-induced programmed necrosis of airway epithelial cells that led to severe bronchiole epithelial degeneration, despite control of viral replication. Pharmacological inhibition of RIPK1 or genetic deletion of Ripk3, both kinases involved in programmed necrosis, rescued cIAP2-deficient mice from influenza-induced lethality. Genetic deletion of the death receptor agonists Fas ligand or TRAIL from the hematopoietic compartment also reversed the susceptibility of cIAP2-deficient mice. Thus, cIAP2-dependent antagonism of RIPK3-mediated programmed necrosis critically protects the host from influenza infection through maintenance of pulmonary tissue homeostasis rather than through pathogen control by the immune system.