XIAP promotes melanoma growth by inducing tumour neutrophil infiltration.

Elevated expression of the X-linked inhibitor of apoptosis protein (XIAP) has been frequently reported in malignant melanoma suggesting that XIAP renders apoptosis resistance and thereby supports melanoma progression. Independent of its anti-apoptotic function, XIAP mediates cellular inflammatory signalling and promotes immunity against bacterial infection. The pro-inflammatory function of XIAP has not yet been considered in cancer. By providing detailed in vitro analyses, utilising two independent mouse melanoma models and including human melanoma samples, we show here that XIAP is an important mediator of melanoma neutrophil infiltration. Neutrophils represent a major driver of melanoma progression and are increasingly considered as a valuable therapeutic target in solid cancer. Our data reveal that XIAP ubiquitylates RIPK2, involve TAB1/RIPK2 complex and induce the transcriptional up-regulation and secretion of chemokines such as IL8, that are responsible for intra-tumour neutrophil accumulation. Alteration of the XIAP-RIPK2-TAB1 inflammatory axis or the depletion of neutrophils in mice reduced melanoma growth. Our data shed new light on how XIAP contributes to tumour growth and provides important insights for novel XIAP targeting strategies in cancer.

XIAP restrains TNF-driven intestinal inflammation and dysbiosis by promoting innate immune responses of Paneth and dendritic cells.

Deficiency in X-linked inhibitor of apoptosis protein (XIAP) is the cause for X-linked lymphoproliferative syndrome 2 (XLP2). About one-third of these patients suffer from severe and therapy-refractory inflammatory bowel disease (IBD), but the exact cause of this pathogenesis remains undefined. Here, we used XIAP-deficient mice to characterize the mechanisms underlying intestinal inflammation. In Xiap−/− mice, we observed spontaneous terminal ileitis and microbial dysbiosis characterized by a reduction of Clostridia species. We showed that in inflamed mice, both TNF receptor 1 and 2 (TNFR1/2) cooperated in promoting ileitis by targeting TLR5-expressing Paneth cells (PCs) or dendritic cells (DCs). Using intestinal organoids and in vivo modeling, we demonstrated that TLR5 signaling triggered TNF production, which induced PC dysfunction mediated by TNFR1. TNFR2 acted upon lamina propria immune cells. scRNA-seq identified a DC population expressing TLR5, in which Tnfr2 expression was also elevated. Thus, the combined activity of TLR5 and TNFR2 signaling may be responsible for DC loss in lamina propria of Xiap−/− mice. Consequently, both Tnfr1−/−Xiap−/− and Tnfr2−/−Xiap−/− mice were rescued from dysbiosis and intestinal inflammation. Furthermore, RNA-seq of ileal crypts revealed that in inflamed Xiap−/− mice, TLR5 signaling was abrogated, linking aberrant TNF responses with the development of a dysbiosis. Evidence for TNFR2 signaling driving intestinal inflammation was detected in XLP2 patient samples. Together, these data point toward a key role of XIAP in mediating resilience of TLR5-expressing PCs and intestinal DCs, allowing them to maintain tissue integrity and microbiota homeostasis.

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.

Immunity to X-linked inhibitor of apoptosis protein (XIAP) in malignant melanoma and check-point blockade.

Expression of inhibitors of apoptosis protein (IAP) family members is associated with poor prognosis in cancer patients. Immunity to ML-IAP (livin) and survivin has been well studied in patients with a variety of tumors. XIAP, the most potent inhibitor of apoptosis, is widely expressed in melanoma. To better define its potential role as an immunogenic target, cellular and humoral responses to XIAP were investigated in patients with advanced melanoma. An overlapping peptide library covering the full length of the XIAP protein was used to screen T cell responses of peripheral blood mononuclear cells (PBMC) from stage-IV melanoma patients treated with or without anti-CTLA4 (ipilimumab). The screen identified an array of peptides that predominantly induced CD4+ T cell responses. XIAP epitope-specific CD4+ T cells revealed proliferative responses to melanoma cells that express XIAP. Humoral responses to XIAP were also explored. Cellular and humoral responses to XIAP were associated with beneficial clinical outcomes after ipilimumab-based treatment, supporting XIAP as a potential therapeutic target.

X-linked inhibitor of apoptosis protein mediates tumor cell resistance to antibody-dependent cellular cytotoxicity.

Inflammatory breast cancer (IBC) is the deadliest, distinct subtype of breast cancer. High expression of epidermal growth factor receptors [EGFR or human epidermal growth factor receptor 2 (HER2)] in IBC tumors has prompted trials of anti-EGFR/HER2 monoclonal antibodies to inhibit oncogenic signaling; however, de novo and acquired therapeutic resistance is common. Another critical function of these antibodies is to mediate antibody-dependent cellular cytotoxicity (ADCC), which enables immune effector cells to engage tumors and deliver granzymes, activating executioner caspases. We hypothesized that high expression of anti-apoptotic molecules in tumors would render them resistant to ADCC. Herein, we demonstrate that the most potent caspase inhibitor, X-linked inhibitor of apoptosis protein (XIAP), overexpressed in IBC, drives resistance to ADCC mediated by cetuximab (anti-EGFR) and trastuzumab (anti-HER2). Overexpression of XIAP in parental IBC cell lines enhances resistance to ADCC; conversely, targeted downregulation of XIAP in ADCC-resistant IBC cells renders them sensitive. As hypothesized, this ADCC resistance is in part a result of the ability of XIAP to inhibit caspase activity; however, we also unexpectedly found that resistance was dependent on XIAP-mediated, caspase-independent suppression of reactive oxygen species (ROS) accumulation, which otherwise occurs during ADCC. Transcriptome analysis supported these observations by revealing modulation of genes involved in immunosuppression and oxidative stress response in XIAP-overexpressing, ADCC-resistant cells. We conclude that XIAP is a critical modulator of ADCC responsiveness, operating through both caspase-dependent and -independent mechanisms. These results suggest that strategies targeting the effects of XIAP on caspase activation and ROS suppression have the potential to enhance the activity of monoclonal antibody-based immunotherapy.

CD1a+ survivin+ dendritic cell infiltration in dermal lesions of systemic sclerosis.

INTRODUCTION: Proto-oncogene survivin is a member of the inhibitor of apoptosis (IAP) family of proteins. The presence of serous antibodies against survivin in patients with systemic sclerosis has been previously reported; however, there are few reports regarding the pathophysiological relationship between survivin and systemic sclerosis. We herein investigated the expression and function of survivin in SSc patients. METHODS: We performed immunohistochemistry analyses to determine the expression of XIAP, cIAP and survivin in skin lesions from patients with SSc and non-SSc. The expression levels of survivin in peripheral blood mononuclear cells (PBMCs) obtained from SSc patients and healthy controls were evaluated using RT-PCR and flow cytometry. Additionally, the function of survivin was verified with overexpression experiments using monocyte-derived dendritic cells (Mo-DCs). RESULTS: The expression patterns of both XIAP and cIAP were similar, while only the survivin expression differed between the SSc and non-SSc skin lesions. Survivin-overexpressing cells were detected in the SSc dermis frequently. The positive rate of survivin in SSc dermis (64.3%, 9/14) was higher than that in non-SSc dermis (11.2%, 1/9). Furthermore, survivin+ cells expressed CD1a, one of the DC markers. Real-time PCR and FACS analyses revealed that the survivin-WT (wild type) expression levels in PBMCs, in particular CD14+ monocytes, from SSc patients were higher than that from healthy controls. Additionally, the overexpression experiments showed that survivin-WT-overexpressing CD1a+ Mo-DCs have the characteristics of promoting cell cycle progression and decreasing apoptotic cells. CONCLUSIONS: These findings suggest that dermal survivin+ CD1a+ cell infiltration may be a potential biomarker of SSc skin lesions. PBMCs and monocytes from SSc patients also overexpressed survivin; therefore, dermal survivin+ DC may be derived from peripheral blood monocytes. Additionally, survivin may be involved in dermal CD1a+ DC proliferation through cell cycle activation and resistance to apoptosis. Survivin may be an important molecule for the pathogenesis of SSc.

Inhibitors of apoptosis proteins (IAPs) are required for effective T-cell expansion/survival during antiviral immunity in mice.

Inhibitors of apoptosis proteins (IAPs) were originally described as regulating apoptosis by direct binding to caspases. More recently, IAPs have been identified as important modulators of canonical and noncanonical nuclear factor κB signaling via their ubiquitin-E3 ligase activity. IAPs are therefore, not only gatekeepers of cell death, but are probably also involved in the regulation of inflammation, as well as innate and adaptive immunity. In this study, we analyzed the role of IAPs in T-cell immunity during lymphocytic choriomeningitis virus (LCMV) infection by pharmacological targeting with an IAP antagonist/second mitochondria-derived activator of caspase-mimetic. Expansion of virus-specific CD8 T cells was drastically reduced in LCMV-infected mice exposed to IAP antagonists. Accordingly, virus control was substantially impaired, indicated by high virus titres in the spleen and the spread of LCMV to peripheral organs. The profound negative effect of IAP antagonists on T-cell immunity was partially linked to tumor necrosis factor-mediated cell death of activated T cells and required inhibition of X-linked inhibitor of apoptosis, as well as cellular IAP-1. Thus, IAPs play an important role in T-cell expansion and survival in the context of a highly inflammatory environment such as a virus infection, indicating that IAP antagonists may interfere with immune responses.

X-linked lymphoproliferative syndromes and related autosomal recessive disorders.

PURPOSE OF REVIEW: X-linked lymphoproliferative (XLP) syndromes and related autosomal disorders are severe primary immune deficiencies triggered by infection with Epstein-Barr virus (EBV), the causative agent of infectious mononucleosis. Recent findings reviewed herein provided key new insights into the genetic and immunological basis of these diseases. They also improved our comprehension of the immunological mechanisms controlling EBV infection. RECENT FINDINGS: Mutations of an X-linked gene, SH2D1A, which encodes the signaling lymphocytic activation molecule (SLAM)-associated protein (SAP), are responsible for most cases of XLP disorders. More recently, other genetic causes for XLP syndromes and autosomal recessive variants of this disease were elucidated. Mutations in genes such as XIAP, ITK, and CD27 were identified. The clinical manifestations and immunological defects seen in these patients were characterized. SUMMARY: The similarities and differences in immunological defects and clinical manifestations between XLP syndromes and related autosomal recessive disorders enabled important new insights into the pathogenesis of these diseases. They also helped our comprehension of the mechanisms implicated in the control of EBV infection. They suggested that CD8+ T cells, natural killer (NK) cells, and NKT cells are critically involved.

X-linked inhibitor of apoptosis (XIAP) deficiency: the spectrum of presenting manifestations beyond hemophagocytic lymphohistiocytosis.

X-linked inhibitor of apoptosis (XIAP) deficiency caused by mutations in BIRC4 was initially described in patients with X-linked lymphoproliferative syndrome (XLP) who had no mutations in SH2D1A. In the initial reports, EBV-associated hemophagocytic lymphohistiocytosis (HLH) was the predominant clinical phenotype. Among 25 symptomatic patients diagnosed with XIAP deficiency, we identified 17 patients who initially presented with manifestations other than HLH. These included Crohn-like bowel disease (n=6), severe infectious mononucleosis (n=4), isolated splenomegaly (n=3), uveitis (n=1), periodic fever (n=1), fistulating skin abscesses (n=1) and severe Giardia enteritis (n=1). Subsequent manifestations included celiac-like disease, antibody deficiency, splenomegaly and partial HLH. Screening by flow cytometry identified 14 of 17 patients in our cohort. However, neither genotype nor protein expression nor results from cell death studies were clearly associated with the clinical phenotype. Only mutation analysis can reliably identify affected patients. XIAP deficiency must be considered in a wide range of clinical presentations.

Tat-SmacN7 induces radiosensitization in cancer cells through the activation of caspases and induction of apoptosis.

A major concern in cancer therapy is resistance of tumors such as human non-small cell lung cancer and esophageal cancer to radiotherapy. Intrinsic radioresistance of these cancer cells limits therapeutic efficiency. Here, we determined in two cancer cell lines the potential radiosensitizing activity of Tat-SmacN7, a small molecule compound, which mimics the activity of Smac, a mitochondrial protein released during apoptosis. We found that Tat-SmacN7 can enter the cells and promote RNA expression and the activity of caspase-3, -8 and -9 and sensitized the cancer cells to radiation with a sensitization enhancement ratio (SER) of 1.5-1.6. Tat-SmacN7 radiosensitization was mediated by both extrinsic and intrinsic apoptosis pathways through activation of caspases. Consistently, blockage of caspase activation, through treatment with a caspase inhibitor, z-VAD-fmk, inhibited apoptosis and abrogated Tat-SmacN7 radiosensitization. Our study demonstrates that Tat-SmacN7 also has radiosensitization effects in vivo, so it could be further developed as a novel class of radiosensitizers for the treatment of radioresistant human non-small cell lung cancer and esophageal cancer.

Human iNKT and MAIT cells exhibit a PLZF-dependent proapoptotic propensity that is counterbalanced by XIAP.

Invariant natural killer (iNKT) T cells and mucosal-associated invariant T (MAIT) cells represent peculiar T-lymphocyte subpopulations with innate-like properties that differ from conventional T cells. iNKT are reduced in the primary immunodeficiency caused by mutations in the X-linked inhibitor of apoptosis (XIAP). By studying the mechanism of this depletion, we herein report that iNKT cells exhibit a high susceptibility to apoptosis that is not observed with conventional T cells. Elevated expression of caspases 3 and 7 accounts for the proapoptotic phenotype of iNKT cells, which is inhibited by XIAP although it exerts a moderate effect in conventional T cells. Similarly, MAIT cells exhibit a proapoptotic propensity with elevated expression of activated caspases and are decreased in XIAP-deficient individuals. Knockdown of the transcription factor PLZF/ZBTB-16, which is involved in the effector program of iNKT cells, diminishes their proapoptotic phenotype. Conversely, overexpression of PLZF/ZBTB-16 in conventional T cells leads to a proapoptotic phenotype. Our findings identify a previously unknown pathway of regulation of innate-like T-cell homeostasis depending on XIAP and PLZF. The proapoptotic feature of iNKT cells also gives a reliable explanation of their exhaustion observed in different human conditions including the XIAP immunodeficiency.

Modulation of inflammatory immune reactions by low-dose ionizing radiation: molecular mechanisms and clinical application.

During the last decade, a multitude of experimental evidence has accumulated showing that low-dose radiation therapy (single dose 0.5-1 Gy) functionally modulates a variety of inflammatory processes and cellular compounds including endothelial (EC), mononuclear (PBMC) and polymorphonuclear (PMN) cells, respectively. These modulations comprise a hampered leukocyte adhesion to EC, induction of apoptosis, a reduced activity of the inducible nitric oxide synthase, and a lowered oxidative burst in macrophages. Moreover, irradiation with a single dose between 0.5-0.7 Gy has been shown to induce the expression of X-chromosome linked inhibitor of apoptosis and transforming growth factor beta 1, to reduce the expression of E-selectin and L-selectin from EC and PBMC, and to hamper secretion of Interleukin-1, or chemokine CCL20 from macrophages and PMN. Notably, a common feature of most of these responses is that they display discontinuous or biphasic dose dependencies, shared with "non-targeted" effects of low-dose irradiation exposure like the bystander response and hyper-radiosensitivity. Thus, the purpose of the present review is to discuss recent developments in the understanding of low-dose irradiation immune modulating properties with special emphasis on discontinuous dose response relationships.

Effects of Epstein-Barr virus on the development of dendritic cells derived from cord blood monocytes: an essential role for apoptosis.

OBJECTIVE: Epstein-Barr virus (EBV) is a ubiquitous human γ-herpes virus, which can adapt and evade host immune defense. Dendritic cells (DCs) play a pivotal role in the initiation and maintenance of immune responses. This study investigated the effects of EBV on cord blood monocytes derived DCs (CBDC). METHODS: Monocytes were isolated from cord blood and cultured in medium containing recombinant IL-4 and GM-CSF to induce DCs development. B95-8 supernatant was added in monocytes culture medium for EBV infection at day 0. Phenotypic characterization of DCs, apoptotic cells, and mitochondrial membrane potential (MMP) were detected by flow cytometry. The morphology was observed by Hoechst 33258 staining and TUNEL staining, the expression of X-linked inhibitor of apoptosis protein (XIAP) was detected by Western blotting assay and caspase 3, 8 and 9 activity was measured. RESULTS: Phenotypic characterization of DCs was changed in EBV-treated group. Chromatin condensation and DNA fragmentation were observed in EBV induced CBDC apoptosis. In addition, caspase 3, caspase 8, and caspase 9 activation were enhanced in the EBV-treated group. This was accompanied by the loss of MMP. Furthermore, XIAP expression was down-regulated in the EBV-treated group and compared to mock-infected group. CONCLUSION: These results suggested that EBV could inhibit CBDC phenotypic differentiation, and induce CBDC apoptosis in caspase-dependent manner with involvement of the mitochondrial pathway. This might help EBV to evade host immune responses to establish persistent infection.

Effects of Epstein-Barr virus on the development of dendritic cells derived from cord blood monocytes: an essential role for apoptosis

OBJECTIVE: Epstein-Barr virus (EBV) is a ubiquitous human γ-herpes virus, which can adapt and evade host immune defense. Dendritic cells (DCs) play a pivotal role in the initiation and maintenance of immune responses. This study investigated the effects of EBV on cord blood monocytes derived DCs (CBDC). METHODS: Monocytes were isolated from cord blood and cultured in medium containing recombinant IL-4 and GM-CSF to induce DCs development. B95-8 supernatant was added in monocytes culture medium for EBV infection at day 0. Phenotypic characterization of DCs, apoptotic cells, and mitochondrial membrane potential (MMP) were detected by flow cytometry. The morphology was observed by Hoechst 33258 staining and TUNEL staining, the expression of X-linked inhibitor of apoptosis protein (XIAP) was detected by Western blotting assay and caspase 3, 8 and 9 activity was measured. RESULTS: Phenotypic characterization of DCs was changed in EBV-treated group. Chromatin condensation and DNA fragmentation were observed in EBV induced CBDC apoptosis. In addition, caspase 3, caspase 8, and caspase 9 activation were enhanced in the EBV-treated group. This was accompanied by the loss of MMP. Furthermore, XIAP expression was down-regulated in the EBV-treated group and compared to mock-infected group. CONCLUSION: These results suggested that EBV could inhibit CBDC phenotypic differentiation, and induce CBDC apoptosis in caspase-dependent manner with involvement of the mitochondrial pathway. This might help EBV to evade host immune responses to establish persistent infection.

Immunohistochemical localization of X-linked inhibitor of apoptosis protein in brainstem-type and cortical Lewy bodies.

X-linked inhibitor of apoptosis protein (XIAP) blocks the apoptosis by binding to and inhibiting caspases-3, 7, and 9. XIAP is negatively regulated by the mitochondrial serine protease, HtrA2/Omi. The aim of this study was to investigate the role of XIAP and the relationship between XIAP and HtrA2/Omi in patients with Parkinson's disease or dementia with Lewy bodies. We conducted immunohistochemical studies on XIAP in formalin-fixed, paraffin-embedded sections from eight normal participants, 10 patients with Parkinson's disease, five patients with dementia with Lewy bodies, and seven patients with Alzheimer's disease, and then double-labeling immunohistochemistry for XIAP and HtrA2/Omi in sections from the Parkinson's disease and dementia with Lewy bodies cases. Brainstem-type and cortical Lewy bodies were intensely immunostained for XIAP, and XIAP immunoreactivity was localized to the halos of brainstem-type Lewy bodies and to the entire bodies of cortical Lewy bodies. Double immunofluorescence analyses showed that XIAP and HtrA2/Omi immunoreactivities were colocalized to both types of Lewy bodies. Our results suggest that XIAP may be partially associated with the pathogenesis of Parkinson's disease and dementia with Lewy bodies.

Clinical and genetic characteristics of XIAP deficiency in Japan.

Deficiency of X-linked inhibitor of apoptosis (XIAP) caused by XIAP/BIRC4 gene mutations is an inherited immune defect recognized as X-linked lymphoproliferative syndrome type 2. This disease is mainly observed in patients with hemophagocytic lymphohistiocytosis (HLH) often associated with Epstein-Barr virus infection. We described nine Japanese patients from six unrelated families with XIAP deficiency and studied XIAP protein expression, XIAP gene analysis, invariant natural killer T (iNKT) cell counts, and the cytotoxic activity of CD8(+) alloantigen-specific cytotoxic T lymphocytes. Of the nine patients, eight patients presented with symptoms in infancy or early childhood. Five patients presented with recurrent HLH, one of whom had severe HLH and died after cord blood transplantation. One patient presented with colitis, as did another patient's maternal uncle, who died of colitis at 4 years of age prior to diagnosis with XIAP deficiency. Interestingly, a 17-year-old patient was asymptomatic, while his younger brother suffered from recurrent HLH and EBV infection. Seven out of eight patients showed decreased XIAP protein expression. iNKT cells from patients with XIAP deficiency were significantly decreased as compared with age-matched healthy controls. These results in our Japanese cohort are compatible with previous studies, confirming the clinical characteristics of XIAP deficiency.

Expression of X-linked inhibitor of apoptosis protein in neoplastic thyroid disorder.

X-linked inhibitor of apoptosis protein (XIAP) is associated with tumor genesis, growth, progression and metastasis, and acts by blocking caspase-mediated apoptosis. In the present study, we sought to evaluate the expression patterns of XIAP in various neoplastic thyroid disorders and determine the association between XIAP expression and clinicopathologic factors. Expression of XIAP was evaluated with immunohistochemical staining using monoclonal anti-XIAP in 164 specimens of conventional papillary thyroid carcinoma (PTC) and 53 specimens of other malignant or benign thyroid tumors. XIAP positivity was observed in 128 (78%) of the 164 conventional PTC specimens. Positive rates of XIAP expression in follicular variant PTC, follicular, medullary, poorly differentiated, and anaplastic thyroid carcinoma specimens were 20%, 25%, 38%, 67%, and 38%, respectively. Six nodular hyperplasia specimens were negative and 1 of 7 follicular adenomas (8%) was positive for XIAP. Lateral neck lymph node metastases were more frequent in patients negative for XIAP expression (P = 0.01). Immunohistochemical staining for XIAP as a novel molecular marker may thus be helpful in the differential diagnosis of thyroid cancer. Moreover, high XIAP expression in conventional PTC is strongly associated with reduced risk of lateral neck lymph node metastasis.

Phosphatidylinositol 3-kinase signaling delays sendai virus-induced apoptosis by preventing XIAP degradation.

Sendai virus (SeV) infection causes apoptosis, which is manifested only late after infection; however, inhibition of phosphatidylinositol 3-kinase (PI3K) dramatically accelerates the process. We report here that rapid apoptosis uses the same mitochondrial apoptotic pathway as slow apoptosis. Cytoplasmic cytochrome c (cyt c) was released early in both cases, but the antiapoptotic protein XIAP prevented early activation of the caspases in cells with active PI3K. When the enzyme was inhibited, XIAP was degraded rapidly in infected cells, allowing cyt c to cause caspase activation and early apoptosis. Thus, SeV infection-mediated apoptosis is temporally regulated by the prevention of XIAP degradation by PI3K.

Differential expression of factors involved in the intrinsic and extrinsic apoptotic pathways in juvenile systemic lupus erythematosus.

Dysregulated neutrophil apoptosis may result in the development of autoimmune disease by contributing to nuclear autoantigen exposure, leading to autoantibody generation and a breakdown in immune tolerance. It has previously been shown that neutrophil apoptosis is increased in juvenile-onset systemic lupus erythematosus (JSLE). This study aims to investigate the pathways involved in JSLE serum-induced apoptosis. Caspases 3, 7-9, IAP1/2, XIAP and FADD mRNA levels and TRAIL R2, BID/tBID, caspase 8 and 9 protein expression were measured in neutrophils from JSLE patients (n = 14) and controls (n = 10). The mRNA levels of caspases 7-9 were significantly higher in JSLE neutrophils than in controls, whereas the mRNA levels of IAP1, IAP2 and XIAP were decreased (p < 0.05). A decrease in neutrophil apoptosis induced by JSLE serum was observed in the presence of caspase 8 and 9 inhibitors (p < 0.05), and the activity of caspases 8 and 9 increased over time. tBID protein expression increased following incubation with JSLE serum. These data focus specifically on the expression and activity of the main caspases in the intrinsic and extrinsic apoptotic pathways. Increased expression of factors involved in the downstream signalling of the extrinsic apoptotic pathway indicates a prominent involvement of this pathway in JSLE serum-induced apoptosis.

Expression of X-linked Inhibitor of Apoptosis Protein in Neoplastic Thyroid Disorder

X-linked inhibitor of apoptosis protein (XIAP) is associated with tumor genesis, growth, progression and metastasis, and acts by blocking caspase-mediated apoptosis. In the present study, we sought to evaluate the expression patterns of XIAP in various neoplastic thyroid disorders and determine the association between XIAP expression and clinicopathologic factors. Expression of XIAP was evaluated with immunohistochemical staining using monoclonal anti-XIAP in 164 specimens of conventional papillary thyroid carcinoma (PTC) and 53 specimens of other malignant or benign thyroid tumors. XIAP positivity was observed in 128 (78%) of the 164 conventional PTC specimens. Positive rates of XIAP expression in follicular variant PTC, follicular, medullary, poorly differentiated, and anaplastic thyroid carcinoma specimens were 20%, 25%, 38%, 67%, and 38%, respectively. Six nodular hyperplasia specimens were negative and 1 of 7 follicular adenomas (8%) was positive for XIAP. Lateral neck lymph node metastases were more frequent in patients negative for XIAP expression (P = 0.01). Immunohistochemical staining for XIAP as a novel molecular marker may thus be helpful in the differential diagnosis of thyroid cancer. Moreover, high XIAP expression in conventional PTC is strongly associated with reduced risk of lateral neck lymph node metastasis.