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Supplementary Table S1

Immune resistance may arise from both genetic instability and tumor heterogeneity. Microenvironmental stresses such as hypoxia and various resistance mechanisms promote carcinoma cell plasticity. AXL, a member of the TAM (Tyro3, Axl, and Mer) receptor tyrosine kinase family, is widely expressed in human cancers and increasingly recognized for its role in cell plasticity and drug resistance. To investigate mechanisms of immune resistance, we studied multiple human lung cancer clones derived from a model of hypoxia-induced tumor plasticity that exhibited mesenchymal or epithelial features. We demonstrate that AXL expression is increased in mesenchymal lung cancer clones. Expression of AXL in the cells correlated with increased cancer cell–intrinsic resistance to both natural killer (NK)– and cytotoxic T lymphocyte (CTL)–mediated killing. A small-molecule targeting AXL sensitized mesenchymal lung cancer cells to cytotoxic lymphocyte–mediated killing. Mechanistically, we showed that attenuation of AXL-dependent immune resistance involved a molecular network comprising NF-κB activation, increased ICAM1 expression, and upregulation of ULBP1 expression coupled with MAPK inhibition. Higher ICAM1 and ULBP1 tumor expression correlated with improved patient survival in two non–small cell lung cancer (NSCLC) cohorts. These results reveal an AXL-mediated immune-escape regulatory pathway, suggest AXL as a candidate biomarker for tumor resistance to NK and CTL immunity, and support AXL targeting to optimize immune response in NSCLC.

This file contains supplementary Figures

Supplemental video 1. 786-0 cells described in Figure 3B were recorded by time-lapse video microscopy

Supplementary Figures S1-S5. Figure S1. Differential susceptibility of 786-0, PRC3, and WT7 cell lines to NK-mediated lysis. Figure S2. Role of ANGPTL4 and ADM in RCC cell susceptibility to NK-mediated lysis. Figure S3. VHL and NK ligand expression in RCC cells. Figure S4. Silencing of HIF-2α and NK ligand expression in 786-0 cells. Figure S5. VHL status, targeting of HIF-2α or silencing of ITPR1 does not regulate autophagy in 786-0 cells.

Supplemental video 2. 786-0 cells described in Figure 3B were recorded by time-lapse video microscopy

Ultrahigh-resolution NMR has recently attracted considerable attention in the field of complex samples analysis. Indeed, the implementation of broadband homonuclear decoupling techniques has allowed us to greatly simplify crowded

Cancer cells outgrowing in distant organs of metastasis rewire their metabolism to fuel on the available nutrients. While this is often considered an adaptive pressure limiting metastasis formation, some nutrients available at the metastatic site naturally or through changes in organ physiology may inherently promote metastatic growth. We find that the lung, a frequent site of metastasis, is a lipid-rich environment. Moreover, we observe that pathological conditions such as pre-metastatic niche formation and obesity further increase the availability of the fatty acid palmitate in the lung. We find that targeting palmitate processing inhibits spheroid growthin vitroand metastasis formation in lean and obese mice. Mechanistically, we discover that breast cancer cells use palmitate to synthesize acetyl-CoA in a carnitine palmitoyltransferase 1a (CPT1a)-dependent manner. Lysine acetyltransferase 2a (KAT2a), whose expression is promoted by palmitate availability, relies on the available acetyl-CoA to acetylate the NF-κB subunit p65. This favors nuclear location of p65 and activates a pro-metastatic transcriptional program. Accordingly, deletion of KAT2a phenocopies CPT1a silencingin vitroas well asin vivoand patients with breast cancer show co-expression of both proteins in metastases across palmitate-rich metastatic sites. In conclusion, we find that palmitate-rich environments foster metastasis growth by increasing p65 acetylation resulting in elevated NF-κB signaling.

Gastric cancer (GC) is one of the major causes of cancer-related mortality worldwide. The vast majority of GC cases are adenocarcinomas including intestinal and diffuse GC. The incidence of diffuse GCs, often associated with poor overall survival, has constantly increased in USA and Europe The molecular basis of diffuse GC aggressivity remains unclear. Using mRNA from diffuse and intestinal GC tumor samples of a Western cohort, this study reports the expression level of the immunomodulatory aryl-hydrocarbon receptor (AhR), and genes involved in immune suppression (PD1, PD-L1, PD-L2) and the early steps of tryptophan metabolism (IDO1, IDO2, TDO2). Strongly increased expression of IDO1 (p < 0.001) and PD1 (p < 0.003) was observed in the intestinal sub-type. The highest expression of IDO1 and PDL1 correlated with early clinical stage and absence of lymphatic invasion (×25 p = 0.004, ×3 p = 0.04, respectively). Our results suggest that kynurenine, produced by tryptophan catabolism, and AhR activation play a central role in creating an immunosuppressive environment. Correspondingly, as compared to intestinal GCs, expression levels of IDO1-TDO2 and PD-L1 were less prominent in diffuse GCs which also had less infiltration of immune cells, suggesting an inactive immune response in the advanced diffuse GC. Confirmation of these patterns of gene expression will require a larger cohort of early and advanced stages of diffuse GC samples.

Diffuse large B-cell lymphoma (DLBCL) is the most frequent lymphoid malignancy affecting adults. The NF-κB transcription factor family is activated by 2 main pathways, the canonical and the alternative NF-κB activation pathway, with different functions. The alternative NF-κB pathway leads to activation of the transcriptionally active RelB NF-κB subunit. Alternative NF-κB activation status and its role in DLBCL pathogenesis remain undefined. Here, we reveal a frequent activation of RelB in a large cohort of DLBCL patients and cell lines, independently of their activated B-cell–like or germinal center B-cell–like subtype. RelB activity defines a new subset of patients with DLBCL and a peculiar gene expression profile and mutational pattern. Importantly, RelB activation does not correlate with the MCD genetic subtype, enriched for activated B-cell–like tumors carrying MYD88L265P and CD79B mutations that cooperatively activate canonical NF-κB, thus indicating that current genetic tools to evaluate NF-κB activity in DLBCL do not provide information on the alternative NF-κB activation. Furthermore, the newly defined RelB-positive subgroup of patients with DLBCL exhibits a dismal outcome after immunochemotherapy. Functional studies revealed that RelB confers DLBCL cell resistance to DNA damage–induced apoptosis in response to doxorubicin, a genotoxic agent used in the front-line treatment of DLBCL. We also show that RelB positivity is associated with high expression of cellular inhibitor of apoptosis protein 2 (cIAP2). Altogether, RelB activation can be used to refine the prognostic stratification of DLBCL and may contribute to subvert the therapeutic DNA damage response in a segment of patients with DLBCL.

Although mortality rates have declined in recent years, the majority of cancers remain incurable and the medical challenge is evident. Recent progress in cancer genetics and genomics along with the identification of a novel generation of cancer hallmarks, that is, reprogramming of energy metabolism and evasion from immune surveillance, have led to the discovery of novel NF-κB-dependent cancer vulnerabilities. These discoveries have led to better patient stratification, and new drug combinations using cutting-edge therapies. This review aims to give an up-to-date view on the therapeutic potential of NF-κB transcription factors and the signaling pathways that control their activity in the new era of cancer therapy.

Objective The pathophysiology of giant cell arteritis (GCA) and the mechanisms underlying vascular remodeling, are poorly understood. We aimed to compare vascular smooth muscle cells (VSMCs) from patients with GCA and controls by a proteomic and gene expression profile approach and to identify the signaling pathways involved in proliferation. Methods VSMCs were cultured from temporal artery biopsies (TABs) from patients with biopsy-proven GCA (TAB+-GCA), biopsy-negative GCA (TAB−-GCA), and diagnosis other than GCA (GCA-control). VSMCs from normal human aorta (HAoSMC) were used as controls. 2D-differential in-gel electrophoresis and Affymetrix chips were used to compare proteomes and gene expression profiles of VSMCs. Proliferation was assessed by BrdU incorporation assay. TAB+-GCA and GCA-control TABs underwent immunohistochemistry staining for endothelin-1 (ET-1) and receptors ETAR and ETBR. Results We identified 16, 30 and 2 protein spots differentially expressed between TAB+-GCA and GCA-control VSMCs, TAB+-GCA and TAB−-GCA VSMCs and TAB−-GCA and GCA-control VSMCs, respectively (fold change ≥ 1.5 and p ≤ 0.05). Among the 153 proteins differentially expressed between TAB+-GCA and HAoSMC VSMCs, many were linked with ET-1. Genes differentially expressed between TAB+-GCA and GCA-control VSMCs were involved in proliferation. ET-1 was identified as a link between genes of interest. Proliferation was reduced for TAB+-GCA VSMCs on treatment with the endothelin antagonist macitentan and its active metabolite. Patients showing transmural expression of ET-1 in temporal artery lesions received a significantly higher glucocorticoid daily dose after 6-month follow-up. Conclusion Inhibiting the proliferation with macitentan, combined with glucocorticoids, might be a promising therapeutic approach for patients with GCA.

Emerging evidence suggests a link between tumor hypoxia and immune suppression. In this study, we investigated the role of hypoxia-induced Nanog, a stemness-associated transcription factor, in immune suppression. We observed that hypoxia-induced Nanog correlated with the acquisition of stem cell–like properties in B16-F10 cells. We further show that Nanog was selectively induced in hypoxic areas of B16-F10 tumors. Stable short hairpin RNA–mediated depletion of Nanog, combined with melanocyte differentiation Ag tyrosinase-related protein-2 peptide-based vaccination, resulted in complete inhibition of B16-F10 tumor growth. Nanog targeting significantly reduced immunosuppressive cells (regulatory T cells and macrophages) and increased CD8+ T effector cells in tumor bed in part by modulating TGF-β1 production. Additionally, Nanog regulated TGF-β1 under hypoxia by directly binding the TGF-β1 proximal promoter. Collectively, our data establish a novel functional link between hypoxia-induced Nanog and TGF-β1 regulation and point to a major role of Nanog in hypoxia-driven immunosuppression.

Hypoxia upregulates the core pluripotency factors NANOG, SOX2, and OCT4, associated with tumor aggressiveness and resistance to conventional anticancer treatments. We have previously reported that hypoxia-induced NANOG contributed in vitro to tumor cell resistance to autologous-specific CTL and in vivo to the in situ recruitment of immune-suppressive cells. In this study, we investigated the mechanisms underlying NANOG-mediated tumor cell resistance to specific lysis under hypoxia. We demonstrated the tumor-promoting effect of hypoxia on tumor initiation into immunodeficient mice using human non–small lung carcinoma cells. We next showed a link between NANOG and autophagy activation under hypoxia because inhibition of NANOG decreased autophagy in tumor cells. Chromatin immunoprecipitation and luciferase reporter assays revealed a direct binding of NANOG to a transcriptionally active site in a BNIP3L enhancer sequence. These data establish a new link between the pluripotency factor NANOG and autophagy involved in resistance to CTL under hypoxia.

The family of NF-κB transcription factors plays a key role in diverse biological processes, such as inflammatory and immune responses, cell survival and tumor development. Beyond the classical NF-κB activation pathway, a second NF-κB pathway has more recently been uncovered, the so-called alternative NF-κB activation pathway. It has been shown that this pathway mainly controls the activity of RelB, a member of the NF-κB family. Post-translational modifications, such as phosphorylation, acetylation, methylation, ubiquitination and SUMOylation, have recently emerged as a strategy for the fine-tuned regulation of NF-κB. Our review discusses recent progress in the understanding of RelB regulation by post-translational modifications and the associated functions in normal and pathological conditions.

It is well-established that the activation of the inhibitor of NFκB (IκBα) kinase (IKK) complex is required for autophagy induction by multiple stimuli. Here, we show that in autophagy-competent mouse embryonic fibroblasts (MEFs), distinct autophagic triggers, including starvation, mTOR inhibition with rapamycin and p53 inhibition with cyclic pifithrin α lead to the activation of IKK, followed by the phosphorylation-dependent degradation of IκBα and nuclear translocation of NFκB. Remarkably, the NFκB signaling pathway was blocked in MEFs lacking either the essential autophagy genes Atg5 or Atg7. In addition, we found that tumor necrosis factor α (TNFα)-induced NFκB nuclear translocation is abolished in both Atg5- and Atg7-deficient MEFs. Similarly, the depletion of essential autophagy modulators, including ATG5, ATG7, Beclin 1 and VPS34, by RNA interference inhibited TNFα-driven NFκB activation in two human cancer cell lines. In conclusion, it appears that, at least in some instances, autophagy is required for NFκB activation, highlighting an intimate crosstalk between these two stress response signaling pathways.

Chronic lymphocytic leukemia (CLL) is characterized by a clonal accumulation of mature neoplastic B cells that are resistant to apoptosis. Aiolos, a member of the Ikaros family of zinc-finger transcription factors, plays an important role in the control of mature B lymphocyte differentiation and maturation. In this study, we showed that Aiolos expression is up-regulated in B-CLL cells. This overexpression does not implicate isoform imbalance or disturb Aiolos subcellular localization. The chromatin status at the Aiolos promoter in CLL is defined by the demethylation of DNA and an enrichment of euchromatin associated histone markers, such as the dimethylation of the lysine 4 on histone H3. These epigenetic modifications should allow its upstream effectors, such as nuclear factor-κB, constitutively activated in CLL, to gain access to promoter, resulting up-regulation of Aiolos. To determine the consequences of Aiolos deregulation in CLL, we analyzed the effects of Aiolos overexpression or down-regulation on apoptosis. Aiolos is involved in cell survival by regulating the expression of some Bcl-2 family members. Our results strongly suggest that Aiolos deregulation by epigenetic modifications may be a hallmark of CLL.

International audience; MPhi and DC are key elements in the control of tissue homeostasis and response to insult. In this work, we demonstrate that MPhi and DC are the major producers of the phenylalanine catabolizing enzyme IL-4-induced gene 1 (IL4I1) under inflammatory conditions. IL4I1 was first described in B cells, which indeed can produce IL4I1 in vitro, although at much lower levels. In vivo, IL4I1 is highly expressed by MPhi and DC of Th1 granulomas (sarcoidosis, tuberculosis) but poorly detected in Th2 granulomas (schistosomiasis). In vitro, expression of the enzyme is induced in mononuclear phagocytes by various pro-inflammatory stimuli through the activation of the transcription factors NF-kappaB and/or STAT1. B cells also express IL4I1 in response to NF-kappaB-activating stimuli such as CD40L; however, in contrast to myeloid cells, B cells are insensitive to IFN-gamma but respond to stimulation of the IL-4/STAT6 axis. As we show that the expression of IL4I1 by a monocytic cell line inhibits T-cell proliferation and production of IFN-gamma and inflammatory cytokines, we propose that IL4I1 participates in the downregulation of Th1 inflammation in vivo.

In response to stress, cells start transcriptional and transcription-independent programs that can lead to adaptation or death. Here, we show that multiple inducers of autophagy, including nutrient depletion, trigger the activation of the IKK (IkappaB kinase) complex that is best known for its essential role in the activation of the transcription factor NF-kappaB by stress. Constitutively active IKK subunits stimulated autophagy and transduced multiple signals that operate in starvation-induced autophagy, including the phosphorylation of AMPK and JNK1. Genetic inhibition of the nuclear translocation of NF-kappaB or ablation of the p65/RelA NF-kappaB subunit failed to suppress IKK-induced autophagy, indicating that IKK can promote the autophagic pathway in an NF-kappaB-independent manner. In murine and human cells, knockout and/or knockdown of IKK subunits (but not that of p65) prevented the induction of autophagy in response to multiple stimuli. Moreover, the knockout of IKK-beta suppressed the activation of autophagy by food deprivation or rapamycin injections in vivo, in mice. Altogether, these results indicate that IKK has a cardinal role in the stimulation of autophagy by physiological and pharmacological stimuli.

The family of NF-kappaB transcription factors plays a key role in diverse biological processes, such as inflammatory and immune responses, cell survival and tumor development. A new NF-kappaB activation pathway has been recently uncovered, the so-called alternative NF-kappaB activation pathway. It has been shown that this pathway mainly controls the activity of RelB, a member of the NF-kappaB family, and its activation requires IKKalpha, one of the two catalytic subunits of the IKK complex. Recent studies suggest that constitutive activation of the alternative pathway may be involved in tumor development, but most surprisingly it is also reported that IKKalpha exerts a protective function against uncontrolled cell proliferation and cancer development. This review discusses recent progresses in the understanding on how the alternative pathway may participate in cancer development, focusing more specifically on RelB and IKKalpha.

Mutations in the gene encoding the transcriptional modulator methyl-CpG binding protein 2 (MeCP2) are responsible for the neurodevelopmental disorder Rett syndrome which is one of the most frequent sources of intellectual disability in women. Recent studies showed that loss of Mecp2 in astrocytes contributes to Rett-like symptoms and restoration of Mecp2 can rescue some of these defects. The goal of this work is to compare gene expression profiles of wild-type and mutant astrocytes from Mecp2(308/y) mice (B6.129S-MeCP2tm1Heto/J) by using Affymetrix mouse 2.0 microarrays. Results were confirmed by quantitative real-time RT-PCR and by Western blot analysis. Gene set enrichment analysis utilizing Ingenuity Pathways was employed to identify pathways disrupted by Mecp2 deficiency. A total of 2152 genes were statistically differentially expressed between wild-type and mutated samples, including 1784 coding transcripts. However, only 257 showed fold changes1.2. We confirmed our data by replicative studies in independent primary cultures of cortical astrocytes from Mecp2-deficient mice. Interestingly, two genes known to encode secreted proteins, chromogranin B and lipocalin-2, showed significant dysregulation. These proteins secreted from Mecp2-deficient glia may exert negative non-cell autonomous effects on neuronal properties, including dendritic morphology. Moreover, transcriptional profiling revealed altered Nr2f2 expression which may explain down- and upregulation of several target genes in astrocytes such as Ccl2, Lcn2 and Chgb. Unraveling Nr2f2 involvement in Mecp2-deficient astrocytes could pave the way for a better understanding of Rett syndrome pathophysiology and offers new therapeutic perspectives.

Rapid childhood T-ALL growth in xenograft models correlates with mature phenotype and NF-κB pathway activation but not with poor prognosis

P100, which is encoded by NF-kappa B2, inhibits Rel dimers. It can also be processed into p52, one of the DNA binding sub-units of NF-kappa B/Rel factors. Several p100 C-terminal truncations that result from gene rearrangements are associated with lymphomagenesis. Here, we characterized a new p100 mutant that we termed p100HB. It originates from a point-mutation that generates a premature stop-codon, and thus the protein lacks the last 125 amino acids. We have detected p100HB in several human tumor cell lines. The truncated protein is mainly unprocessed, and although it still binds Rel dimers, it has reduced inhibitory potency compared to p100 and translocates into the nucleus. Thus, p100HB may be associated with deregulated NF-kappa B/Rel functions.

Tumor necrosis factor-α (TNF-α) and lymphotoxin-β receptor (LTβR) signaling both play important roles in inflammatory and immune responses through activation of NF-κB. Using various deficient mouse embryonic fibroblast cells, we have compared the signaling pathways leading to NF-κB induction in response to TNF-α and LTβR activation. We demonstrate that LTβR ligation induces not only RelA/p50 dimers but also RelB/p50 dimers, whereas TNF-α induces only RelA/p50 dimers. LTβR-induced binding of RelB/p50 requires processing of p100 that is mediated by IKKα but is independent of IKKβ, NEMO/IKKγ, and RelA. Moreover, we show that RelB, p50, and p100 can associate in the same complex and that TNF-α but not LTβ signaling increases the association of p100 with RelB/p50 dimers in the nucleus, leading to the specific inhibition of RelB DNA binding. These results suggest that the alternative NF-κB pathway based on p100 processing may account not only for the activation of RelB/p52 dimers but also for that of RelB/p50 dimers and that p100 regulates the binding activity of RelB/p50 dimers via at least two distinct mechanisms depending on the signaling pathway involved.

TNFα is a potent cytokine that plays a critical role in numerous cellular processes, particularly immune and inflammatory responses, programmed cell death, angiogenesis, and cell migration. Thus, understanding the molecular mechanisms that mediate TNFα-induced cellular responses is a crucial issue. It is generally accepted that global DNA binding activity of the NF-κB avian reticuloendotheliosis viral (v-rel) oncogene related B (RelB) subunit is not induced upon TNFα treatment in fibroblasts, despite its TNFα-induced nuclear accumulation. Here, we demonstrate that RelB plays a critical role in promoting fibroblast migration upon prolonged TNFα treatment. We identified the two kinases IκB kinase α (IKKα) and IκB kinase β (IKKβ) as RelB interacting partners whose activation by TNFα promotes RelB phosphorylation at serine 472. Once phosphorylated on serine 472, nuclear RelB dissociates from its interaction with the inhibitory protein IκBα and binds to the promoter of critical migration-associated genes, such as the matrix metallopeptidase 3 (MMP3). Further, we show that RelB serine 472 phosphorylation status controls MMP3 expression and promigration activity downstream of TNF receptors. Our findings provide new insights into the regulation of RelB activity and reveal a novel link between selective NF-κB target gene expression and cellular response in response to TNFα.

Clear cell renal cell carcinomas (RCC) frequently display inactivation of von Hippel-Lindau (VHL) gene leading to increased level of hypoxia-inducible factors (HIF). In this study, we investigated the potential role of HIF2α in regulating RCC susceptibility to natural killer (NK) cell–mediated killing. We demonstrated that the RCC cell line 786-0 with mutated VHL was resistant to NK-mediated lysis as compared with the VHL-corrected cell line (WT7). This resistance was found to require HIF2α stabilization. On the basis of global gene expression profiling and chromatin immunoprecipitation assay, we found ITPR1 (inositol 1,4,5-trisphosphate receptor, type 1) as a direct novel target of HIF2α and that targeting ITPR1 significantly increased susceptibility of 786-0 cells to NK-mediated lysis. Mechanistically, HIF2α in 786-0 cells lead to overexpression of ITPR1, which subsequently regulated the NK-mediated killing through the activation of autophagy in target cells by NK-derived signal. Interestingly, both ITPR1 and Beclin-1 silencing in 786-0 cells inhibited NK-induced autophagy and subsequently increased granzyme B activity in target cells. Finally, in vivo ITPR1 targeting significantly enhanced the NK-mediated tumor regression. Our data provide insight into the link between HIF2α, the ITPR1-related pathway, and natural immunity and strongly suggest a role for the HIF2α/ITPR1 axis in regulating RCC cell survival. Cancer Res; 74(23); 6820–32. ©2014 AACR.

International audience; Development of novel therapies is critical for T-cell acute leukae-mia (T-ALL). Here, we investigated the effect of inhibiting the MAPK/MEK/ERK pathway on T-ALL cell growth. Unexpectedly, MEK inhibitors (MEKi) enhanced growth of 70% of human T-ALL cell samples cultured on stromal cells independently of NOTCH activa-tion and maintained their ability to propagate in vivo. Similar results were obtained when T-ALL cells were cultured with ERK1/ 2-knockdown stromal cells or with conditioned medium from MEKi-treated stromal cells. Microarray analysis identified interleu-kin 18 (IL-18) as transcriptionally up-regulated in MEKi-treated MS5 cells. Recombinant IL-18 promoted T-ALL growth in vitro, whereas the loss of function of IL-18 receptor in T-ALL blast cells decreased blast proliferation in vitro and in NSG mice. The NFKB pathway that is downstream to IL-18R was activated by IL-18 in blast cells. IL-18 circulating levels were increased in T-ALL-xeno-grafted mice and also in T-ALL patients in comparison with controls. This study uncovers a novel role of the pro-inflammatory cytokine IL-18 and outlines the microenvironment involvement in human T-ALL development.

Loss of hematopoietic stem cell (HSC) function and increased risk of developing hematopoietic malignancies are severe and concerning complications of anticancer radiotherapy and chemotherapy. We have previously shown that thrombopoietin (TPO), a critical HSC regulator, ensures HSC chromosomal integrity and function in response to γ-irradiation by regulating their DNA-damage response. TPO directly affects the double-strand break (DSB) repair machinery through increased DNA-protein kinase (DNA-PK) phosphorylation and nonhomologous end-joining (NHEJ) repair efficiency and fidelity. This effect is not shared by other HSC growth factors, suggesting that TPO triggers a specific signal in HSCs facilitating DNA-PK activation upon DNA damage. The discovery of these unique signaling pathways will provide a means of enhancing TPO-desirable effects on HSCs and improving the safety of anticancer DNA agents. We show here that TPO specifically triggers Erk and nuclear factor κB (NF-κB) pathways in mouse hematopoietic stem and progenitor cells (HSPCs). Both of these pathways are required for a TPO-mediated increase in DSB repair. They cooperate to induce and activate the early stress-response gene, Iex-1 (ier3), upon DNA damage. Iex-1 forms a complex with pERK and the catalytic subunit of DNA-PK, which is necessary and sufficient to promote TPO-increased DNA-PK activation and NHEJ DSB repair in both mouse and human HSPCs.

Tumor necrosis factor alpha (TNFalpha) is a potent proinflammatory cytokine that plays an important role in immunity and inflammation, and in the control of cell proliferation, differentiation and apoptosis. TNFalpha is also the founding member of a still growing family of cytokines with diverse bioregulatory functions. Considerable progress has been made in understanding the molecular mechanisms that mediate TNFalpha-induced cellular responses. Binding of TNFalpha to its two receptors, TNFR1 and TNFR2, results in recruitment of signal transducers that activate at least three distinct effectors. Through complex signaling cascades and networks, these effectors lead to the activation of caspases and two transcription factors, AP-1 and NF-kappaB. Similar signaling mechanisms are likely to be used by other members of the TNF family. This review focuses on proteins that transduce the signals generated at TNF receptors to nuclear targets such as AP-1 and NF-kappaB.