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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

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.

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.

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

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.

The IKKalpha and IKKbeta catalytic subunits of IkappaB kinase (IKK) share 51% amino-acid identity and similar biochemical activities: they both phosphorylate IkappaB proteins at serines that trigger their degradation. IKKalpha and IKKbeta differ, however, in their physiological functions. IKKbeta and the IKKgamma/NEMO regulatory subunit are required for activating NF-kappaB by pro-inflammatory stimuli and preventing apoptosis induced by tumour necrosis factor-alpha (refs 5,6,7,8,9,10,11). IKKalpha is dispensable for these functions, but is essential for developing the epidermis and its derivatives. The mammalian epidermis is composed of the basal, spinous, granular and cornified layers. Only basal keratinocytes can proliferate and give rise to differentiated derivatives, which on full maturation undergo enucleation to generate the cornified layer. Curiously, keratinocyte-specific inhibition of NF-kappaB, as in Ikkalpha-/- mice, results in epidermal thickening but does not block terminal differentiation. It has been proposed that the epidermal defect in Ikkalpha-/- mice may be due to the failed activation of NF-kappaB. Here we show that the unique function of IKKalpha in control of keratinocyte differentiation is not exerted through its IkappaB kinase activity or through NF-kappaB. Instead, IKKalpha controls production of a soluble factor that induces keratinocyte differentiation.

Cells respond to stress by activating cytoplasmic mechanisms as well as transcriptional programs that can lead to adaptation or death. Autophagy represents an important cytoprotective response that is regulated by both transcriptional and transcription-independent pathways. NFkappaB is perhaps the transcription factor most frequently activated by stress and has been ascribed with either pro- or anti-autophagic functions, depending on the cellular context. Our results demonstrate that activation of the IKK (IkappaB kinase) complex, which is critical for the stress-elicited activation of NFkappaB, is sufficient to promote autophagy independent of NFkappaB, and that IKK is required for the optimal induction of autophagy by both physiological and pharmacological autophagic triggers.

Monogenic interleukin-10 (IL-10) and IL-10 receptor (IL-10R) deficiencies cause very early onset severe inflammatory bowel disease. Here, we report that 5 patients with an IL-10R1 (n = 1) or IL-10R2 (n = 4) deficiency developed B-cell non-Hodgkin lymphoma between the ages of 5 and 6 years (which was recurrent in 1 patient). These lymphomas had some of the characteristics of diffuse large B-cell lymphomas and contained monoclonal, Epstein-Barr virus-negative germinal center B cells. The tumors displayed a remarkably homogeneous signature, with original activation of the nuclear factor κB pathway and a decrease in intratumor T-cell infiltration. Hence, IL-10R deficiency is associated with a high risk of developing B-cell lymphoma. Our results revealed an unexpected role of the IL-10R pathway in lymphomagenesis.

Interleukin-1 (IL-1) and tumor necrosis factor (TNF-alpha) stimulate transcription factors AP-1 and NF-kappaB through activation of the MAP kinases JNK and p38 and the IkappaB kinase (IKK), respectively. The TNF-alpha and IL-1 signals are transduced through TRAF2 and TRAF6, respectively. Overexpressed TRAF2 or TRAF6 activate JNK, p38, or IKK in the absence of extracellular stimulation. By replacing the carboxy-terminal TRAF domain of TRAF2 and TRAF6 with repeats of the immunophilin FKBP12, we demonstrate that their effector domains are composed of their amino-terminal Zn and RING fingers. Oligomerization of the TRAF2 effector domain results in specific binding to MEKK1, a protein kinase capable of JNK, p38, and IKK activation, and induction of TNF-alpha and IL-1 responsive genes. TNF-alpha also enhances the binding of native TRAF2 to MEKK1 and stimulates the kinase activity of the latter. Thus, TNF-alpha and IL-1 signaling is based on oligomerization of TRAF2 and TRAF6 leading to activation of effector kinases.

The GTPases Rac and Cdc42Hs control diverse cellular functions. In addition to being mediators of intracellular signaling cascades, they have important roles in cell morphogenesis and mitogenesis. We have identified a novel PAK-related kinase, PAK4, as a new effector molecule for Cdc42Hs. PAK4 interacts only with the activated form of Cdc42Hs through its GTPase-binding domain (GBD). Co-expression of PAK4 and the constitutively active Cdc42HsV12 causes the redistribution of PAK4 to the brefeldin A-sensitive compartment of the Golgi membrane and the subsequent induction of filopodia and actin polymerization. Importantly, the reorganization of the actin cytoskeleton is dependent on PAK4 kinase activity and on its interaction with Cdc42Hs. Thus, unlike other members of the PAK family, PAK4 provides a novel link between Cdc42Hs and the actin cytoskeleton. The cellular locations of PAK4 and Cdc42Hs suggest a role for the Golgi in cell morphogenesis.

The NF-κB family of transcription factors has emerged as a key player in the pathogenesis of multiple myeloma (MM). NF-κB is activated by at least two major signaling pathways. The classical pathway results in the activation of mainly RelA containing dimers, whereas the alternative pathway leads to the activation of RelB/p52 and RelB/p50 heterodimers. Activating mutations in regulators of the alternative pathway have been identified in 17% of MM patients. However, the status of RelB activation per se and its role in the regulation of cell survival in MM has not been investigated. Here, we reveal that 40% of newly diagnosed MM patients have a constitutive RelB DNA-binding activity in CD138(+) tumor cells, and we show an association with increased expression of a subset of anti-apoptotic NF-κB target genes, such as cIAP2. Furthermore, we demonstrate that RelB exerts a crucial anti-apoptotic activity in MM cells. Our findings indicate that RelB activation is key for promoting MM cell survival through the upregulation of anti-apoptotic proteins. Altogether, our study provides the framework for the development of new molecules targeting RelB in the treatment of MM.

Proteins with seven transmembrane segments (7TM) define a superfamily of receptors (7TM receptors) sharing the same topology: an extracellular N-terminus, three extramembranous loops on either side of the plasma membrane, and a cytoplasmic C-terminal tail. Upon ligand binding, cytoplasmic portions of the activated receptor interact with heterotrimeric G-coupled proteins to induce various second messengers. A small group, recently recognized on the basis of homologous primary amino acid sequences, comprises receptors to hormones of the secretin/vasoactive intestinal peptide/glucagon family, parathyroid hormone and parathyroid hormone-related peptides, growth hormone-releasing factor, corticotropin-releasing factor, and calcitonin. A cDNA, extracted from a neuroectodermal cDNA library, was predicted to encode a new 886-amino-acid protein with three distinct domains. The C-terminal third contains the seven hydrophobic segments and characteristic residues that allow the protein to be readily aligned with the various hormone receptors in the family. Six egf-like modules, at the N-terminus of the predicted mature protein, are separated from the transmembrane segments by a serine/threonine-rich domain, a feature reminiscent of mucin-like, single-span, integral membrane glycoproteins with adhesive properties. Because of its unique characteristics, this putative egf module-containing, mucin-like hormone receptor has been named EMR1. Southern analysis of a panel of somatic cell hybrids and fluorescence in situ hybridization have assigned the EMR1 gene to human chromosome 19p13.3.

International audience; The alternative nuclear factor-kappaB (NF-κB) -activation pathway proceeds via inducible p100 processing, leading to the activation of RelB-containing dimers. This pathway is aberrantly activated in several types of tumors; however, a direct role for RelB in the control of cell proliferation is still largely unexplored. Here, we demonstrate that RelB provides cell proliferation-inhibitory signals in murine fibroblasts. In agreement with these results, RelB ectopic expression inhibits xenograft tumor growth in vivo, whereas RelB knockdown enhances it. Significantly, we show that RelB inhibits cell proliferation and tumor growth in a p53-dependent manner. Mechanistic studies indicate that RelB regulates the transcription of the p53 tumor-suppressor gene through direct recruitment to the p53 promoter, thus increasing both p53 protein levels and expression of p53 target genes such as p21. Our findings define a novel link between NF-κB and growth-inhibitory pathways involving the RelB-dependent transcriptional upregulation of p53. Furthermore, they suggest that inhibition of RelB in some tumor types that retain wild-type p53 may diminish rather than improve therapeutic responses.

BACKGROUND:\ud Isolated limb perfusion with TNF-α and melphalan is used with remarkable efficiency to treat unresectable limb sarcomas. Here we tested the ability of TNF-α to directly induce apoptosis of sarcoma cells. In addition, we investigated the impact of p53 in the regulation of such effect.\ud \ud METHODOLOGY/PRINCIPAL FINDINGS:\ud We first analysed the ability of TNF-α to induce apoptosis in freshly isolated tumour cells. For this purpose, sarcoma tumours (n = 8) treated ex vivo with TNF-α were processed for TUNEL staining. It revealed substantial endothelial cell apoptosis and levels of tumour cell apoptosis that varied from low to high. In order to investigate the role of p53 in TNF-α-induced cell death, human sarcoma cell lines (n = 9) with different TP53 and MDM2 status were studied for their sensitivity to TNF-α. TP53(Wt) cell lines were sensitive to TNF-α unless MDM2 was over-expressed. However, TP53(Mut) and TP53(Null) cell lines were resistant. TP53 suppression in TP53(Wt) cell lines abrogated TNF-α sensitivity and TP53 overexpression in TP53(Null) cell lines restored it. The use of small molecules that restore p53 activity, such as CP-31398 or Nutlin-3a, in association with TNF-α, potentiated the cell death of respectively TP53(Mut) and TP53(Wt)/MDM2(Ampl). In particular, CP-31398 was able to induce p53 as well as some of its apoptotic target genes in TP53(Mut) cells. In TP53(Wt)/MDM2(Ampl) cells, Nutlin-3a effects were associated with a decrease of TNF-α-induced NF-κB-DNA binding and correlated with a differential regulation of pro- and anti-apoptotic genes such as TP53BP2, GADD45, TGF-β1 and FAIM.\ud \ud CONCLUSION/SIGNIFICANCE:\ud More effective therapeutic approaches are critically needed for the treatment of unresectable limb sarcomas. Our results show that restoring p53 activity in sarcoma cells correlated with increased sensitivity to TNF-α, suggesting that this strategy may be an important determinant of TNF-α-based sarcomas treatment.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Its pathogenesis is frequently linked to liver inflammation. Gain-of-function mutations in the gene encoding β-catenin are frequent genetic modifications found in human HCCs. Thus, we investigated whether inflammation was a component of β-catenin-induced tumorigenesis using genetically modified mouse models that recapitulated the stages of initiation and progression of this tumoral process. Oncogenic β-catenin signaling was found to induce an inflammatory program in hepatocytes that involved direct transcriptional control by β-catenin and activation of the NF-κB pathway. This led to a specific inflammatory response, the intensity of which determined the degree of tumor aggressiveness. The chemokine-like chemotactic factor leukocyte cell-derived chemotaxin 2 (LECT2) and invariant NKT (iNKT) cells were identified as key interconnected effectors of liver β-catenin-induced inflammation. In genetic deletion models lacking the gene encoding LECT2 or iNKT cells, hepatic β-catenin signaling triggered the formation of highly malignant HCCs with lung metastasis. Thus, our results identify inflammation as a key player in β-catenin-induced liver tumorigenesis. We provide strong evidence that, by activating pro- and antiinflammatory mediators, β-catenin signaling produces an inflammatory microenvironment that has an impact on tumoral development. Our data are consistent with the fact that most β-catenin-activated HCCs are of better prognosis.