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Fibroblastic reticular cells (FRC) are immunologically specialized myofibroblasts that control the elasticity of the lymph node, in part through their contractile properties. Swelling of tumor-draining lymph nodes is a hallmark of lymphophilic cancers such as cutaneous melanoma. Melanoma displays high intratumoral heterogeneity with the coexistence of melanoma cells with variable differentiation phenotypes from melanocytic to dedifferentiated states. Factors secreted by melanoma cells promote premetastatic lymph node reprograming and tumor spreading. Elucidating the impact of the melanoma secretome on FRC could help identify approaches to prevent metastasis. Here we show that melanocytic and dedifferentiated melanoma cells differentially impact the FRC contractile phenotype. Factors secreted by dedifferentiated cells, but not by melanocytic cells, strongly inhibited actomyosin-dependent contractile forces of FRC by decreasing the activity of the RHOA–RHO–kinase (ROCK) pathway and the mechano-responsive transcriptional coactivator Yes1 associated transcriptional regulator (YAP). Transcriptional profiling and biochemical analyses indicated that actomyosin cytoskeleton relaxation in FRC is driven by inhibition of the JAK1-STAT3 pathway. This FRC relaxation was associated with increased FRC proliferation and activation and with elevated tumor invasion in vitro. The secretome of dedifferentiated melanoma cells also modulated the biomechanical properties of distant lymph node in premetastatic mouse models. Finally, IL1 produced by dedifferentiated cells was involved in the inhibition of FRC contractility. These data highlight the role of the JAK1-STAT3 and YAP pathways in spontaneous contractility of resting FRC. They also suggest that dedifferentiated melanoma cells specifically target FRC biomechanical properties to favor tumor spreading in the premetastatic lymph node niche. Targeting this remote communication could be an effective strategy to prevent metastatic spread of the disease.Significance:Communication between dedifferentiated melanoma cells and lymph node fibroblasts reprograms the biomechanical properties of the premetastatic lymph node niche to promote tumor invasion.See related commentary by Lund, p. 1692

The table displays MS analysis of the matrisome between parental and BRAFi resistant melanoma cells

Mesenchymal signature of BRAFi resistant melanoma cells

BRAF and MEK inhibition induces F-actin remodeling, YAP/MRTF activation and focal adhesion assembly in BRAF-mutant melanoma cells

Supplementary Data from Secretion of IL1 by Dedifferentiated Melanoma Cells Inhibits JAK1-STAT3–Driven Actomyosin Contractility of Lymph Node Fibroblastic Reticular Cells

Aberrant extracellular matrix (ECM) deposition and stiffening is a physical hallmark of several solid cancers and is associated with therapy failure. BRAF-mutant melanomas treated with BRAF and MEK inhibitors almost invariably develop resistance that is frequently associated with transcriptional reprogramming and a de-differentiated cell state. Melanoma cells secrete their own ECM proteins, an event that is promoted by oncogenic BRAF inhibition. Yet, the contribution of cancer cell–derived ECM and tumor mechanics to drug adaptation and therapy resistance remains poorly understood. Here, we show that melanoma cells can adapt to targeted therapies through a mechanosignaling loop involving the autocrine remodeling of a drug-protective ECM. Analyses revealed that therapy-resistant cells associated with a mesenchymal dedifferentiated state displayed elevated responsiveness to collagen stiffening and force-mediated ECM remodeling through activation of actin-dependent mechanosensors Yes-associated protein (YAP) and myocardin-related transcription factor (MRTF). Short-term inhibition of MAPK pathway also induced mechanosignaling associated with deposition and remodeling of an aligned fibrillar matrix. This provided a favored ECM reorganization that promoted tolerance to BRAF inhibition in a YAP- and MRTF-dependent manner. Matrix remodeling and tumor stiffening were also observed in vivo upon exposure of BRAF-mutant melanoma cell lines or patient-derived xenograft models to MAPK pathway inhibition. Importantly, pharmacologic targeting of YAP reversed treatment-induced excessive collagen deposition, leading to enhancement of BRAF inhibitor efficacy. We conclude that MAPK pathway targeting therapies mechanically reprogram melanoma cells to confer a drug-protective matrix environment. Preventing melanoma cell mechanical reprogramming might be a promising therapeutic strategy for patients on targeted therapies.Significance:These findings reveal a biomechanical adaptation of melanoma cells to oncogenic BRAF pathway inhibition, which fuels a YAP/MRTF-dependent feed-forward loop associated with tumor stiffening, mechanosensing, and therapy resistance.

Supplementary Methods

Supplementary Figure from Secretion of IL1 by Dedifferentiated Melanoma Cells Inhibits JAK1-STAT3–Driven Actomyosin Contractility of Lymph Node Fibroblastic Reticular Cells

International audience; Cutaneous melanoma is one of the most aggressive cancers characterized by a high plasticity, a propensity for metastasis, and drug resistance. Melanomas are composed of phenotypically diverse subpopulations of tumor cells with heterogeneous molecular profiles that reflect intrinsic invasive abilities. In an attempt to identify novel factors of the melanoma invasive cell state, we previously investigated the nature of the invasive secretome by using a comparative proteomic approach. Here, we have extended this analysis to show that PTX3, an acute phase inflammatory glycoprotein, is one such factor secreted by invasive melanoma to promote tumor cell invasiveness. Elevated PTX3 production was observed in the population of MITFlow invasive cells but not in the population of MITFhigh differentiated melanoma cells. Consistently, MITF knockdown increased PTX3 expression in MITFhigh proliferative and poorly invasive cells. High levels of PTX3 were found in tissues and blood of metastatic melanoma patients, and in BRAF inhibitor-resistant melanoma cells displaying a mesenchymal invasive MITFlow phenotype. Genetic silencing of PTX3 in invasive melanoma cells dramatically impaired migration and invasion in vitro and in experimental lung extravasation assay in xenografted mice. In contrast, addition of melanoma-derived or recombinant PTX3, or expression of PTX3 enhanced motility of low migratory cells. Mechanistically, autocrine production of PTX3 by melanoma cells triggered an IKK/NFκB signaling pathway that promotes migration, invasion, and expression of the EMT factor TWIST1. Finally, we found that TLR4 and MYD88 knockdown inhibited PTX3-induced melanoma cell migration, suggesting that PTX3 functions through a TLR4-dependent pathway. Our work reveals that tumor-derived PTX3 contributes to melanoma cell invasion via targetable inflammation-related pathways. In addition to providing new insights into the biology of melanoma invasive behavior, this study underscores the notion that secreted PTX3 represents a potential biomarker and therapeutic target in a subpopulation of MITFlow invasive and/or refractory melanoma.

Fibroblastic reticular cells (FRC) are immunologically specialized myofibroblasts that control the elasticity of the lymph node, in part through their contractile properties. Swelling of tumor-draining lymph nodes is a hallmark of lymphophilic cancers such as cutaneous melanoma. Melanoma displays high intratumoral heterogeneity with the coexistence of melanoma cells with variable differentiation phenotypes from melanocytic to dedifferentiated states. Factors secreted by melanoma cells promote premetastatic lymph node reprograming and tumor spreading. Elucidating the impact of the melanoma secretome on FRC could help identify approaches to prevent metastasis. Here we show that melanocytic and dedifferentiated melanoma cells differentially impact the FRC contractile phenotype. Factors secreted by dedifferentiated cells, but not by melanocytic cells, strongly inhibited actomyosin-dependent contractile forces of FRC by decreasing the activity of the RHOA–RHO–kinase (ROCK) pathway and the mechano-responsive transcriptional coactivator Yes1 associated transcriptional regulator (YAP). Transcriptional profiling and biochemical analyses indicated that actomyosin cytoskeleton relaxation in FRC is driven by inhibition of the JAK1-STAT3 pathway. This FRC relaxation was associated with increased FRC proliferation and activation and with elevated tumor invasion in vitro. The secretome of dedifferentiated melanoma cells also modulated the biomechanical properties of distant lymph node in premetastatic mouse models. Finally, IL1 produced by dedifferentiated cells was involved in the inhibition of FRC contractility. These data highlight the role of the JAK1-STAT3 and YAP pathways in spontaneous contractility of resting FRC. They also suggest that dedifferentiated melanoma cells specifically target FRC biomechanical properties to favor tumor spreading in the premetastatic lymph node niche. Targeting this remote communication could be an effective strategy to prevent metastatic spread of the disease.Significance:Communication between dedifferentiated melanoma cells and lymph node fibroblasts reprograms the biomechanical properties of the premetastatic lymph node niche to promote tumor invasion.See related commentary by Lund, p. 1692

Molluscum contagiosum virus (MCV) is a common cause of benign skin lesions in young children and currently the only endemic human poxvirus. Following the infection of primary keratinocytes in the epidermis, MCV induces the proliferation of infected cells and this results in the production of wart-like growths. Full productive infection is observed only after the infected cells differentiate. During this prolonged replication cycle the virus must avoid elimination by the host immune system. We therefore sought to investigate the function of the two major histocompatibility complex class-I-related genes encoded by the MCV genes mc033 and mc080. Following insertion into a replication-deficient adenovirus vector, codon-optimized versions of mc033 and mc080 were expressed as endoglycosidase-sensitive glycoproteins that localized primarily in the endoplasmic reticulum. MC080, but not MC033, downregulated cell-surface expression of endogenous classical human leucocyte antigen (HLA) class I and non-classical HLA-E by a transporter associated with antigen processing (TAP)-independent mechanism. MC080 exhibited a capacity to inhibit or activate NK cells in autologous assays in a donor-specific manner. MC080 consistently inhibited antigen-specific T cells being activated by peptide-pulsed targets. We therefore propose that MC080 acts to promote evasion of HLA-I-restricted cytotoxic T cells.

Molluscum contagiosum virus (MCV) is a common cause of benign skin lesions in young children and currently the only endemic human poxvirus. Following the infection of primary keratinocytes in the epidermis, MCV induces the proliferation of infected cells and this results in the production of wart-like growths. Full productive infection is observed only after the infected cells differentiate. During this prolonged replication cycle the virus must avoid elimination by the host immune system. We therefore sought to investigate the function of the two major histocompatibility complex class-I-related genes encoded by the MCV genes mc033 and mc080. Following insertion into a replication-deficient adenovirus vector, codon-optimized versions of mc033 and mc080 were expressed as endoglycosidase-sensitive glycoproteins that localized primarily in the endoplasmic reticulum. MC080, but not MC033, downregulated cell-surface expression of endogenous classical human leucocyte antigen (HLA) class I and non-classical HLA-E by a transporter associated with antigen processing (TAP)-independent mechanism. MC080 exhibited a capacity to inhibit or activate NK cells in autologous assays in a donor-specific manner. MC080 consistently inhibited antigen-specific T cells being activated by peptide-pulsed targets. We therefore propose that MC080 acts to promote evasion of HLA-I-restricted cytotoxic T cells.

Aberrant extracellular matrix (ECM) deposition and stiffening is a physical hallmark of several solid cancers and is associated with therapy failure. BRAF-mutant melanomas treated with BRAF and MEK inhibitors almost invariably develop resistance that is frequently associated with transcriptional reprogramming and a de-differentiated cell state. Melanoma cells secrete their own ECM proteins, an event that is promoted by oncogenic BRAF inhibition. Yet, the contribution of cancer cell–derived ECM and tumor mechanics to drug adaptation and therapy resistance remains poorly understood. Here, we show that melanoma cells can adapt to targeted therapies through a mechanosignaling loop involving the autocrine remodeling of a drug-protective ECM. Analyses revealed that therapy-resistant cells associated with a mesenchymal dedifferentiated state displayed elevated responsiveness to collagen stiffening and force-mediated ECM remodeling through activation of actin-dependent mechanosensors Yes-associated protein (YAP) and myocardin-related transcription factor (MRTF). Short-term inhibition of MAPK pathway also induced mechanosignaling associated with deposition and remodeling of an aligned fibrillar matrix. This provided a favored ECM reorganization that promoted tolerance to BRAF inhibition in a YAP- and MRTF-dependent manner. Matrix remodeling and tumor stiffening were also observed in vivo upon exposure of BRAF-mutant melanoma cell lines or patient-derived xenograft models to MAPK pathway inhibition. Importantly, pharmacologic targeting of YAP reversed treatment-induced excessive collagen deposition, leading to enhancement of BRAF inhibitor efficacy. We conclude that MAPK pathway targeting therapies mechanically reprogram melanoma cells to confer a drug-protective matrix environment. Preventing melanoma cell mechanical reprogramming might be a promising therapeutic strategy for patients on targeted therapies. Significance: These findings reveal a biomechanical adaptation of melanoma cells to oncogenic BRAF pathway inhibition, which fuels a YAP/MRTF-dependent feed-forward loop associated with tumor stiffening, mechanosensing, and therapy resistance.

Human CMV (HCMV)-encoded NK cell-evasion functions include an MHC class I homolog (UL18) with high affinity for the leukocyte inhibitory receptor-1 (CD85j, ILT2, or LILRB1) and a signal peptide (SPUL40) that acts by upregulating cell surface expression of HLA-E. Detailed characterization of SPUL40 revealed that the N-terminal 14 aa residues bestowed TAP-independent upregulation of HLA-E, whereas C region sequences delayed processing of SPUL40 by a signal peptide peptidase-type intramembrane protease. Most significantly, the consensus HLA-E–binding epitope within SPUL40 was shown to promote cell surface expression of both HLA-E and gpUL18. UL40 was found to possess two transcription start sites, with utilization of the downstream site resulting in translation being initiated within the HLA-E–binding epitope (P2). Remarkably, this truncated SPUL40 was functional and retained the capacity to upregulate gpUL18 but not HLA-E. Thus, our findings identify an elegant mechanism by which an HCMV signal peptide differentially regulates two distinct NK cell-evasion pathways. Moreover, we describe a natural SPUL40 mutant that provides a clear example of an HCMV clinical virus with a defect in an NK cell-evasion function and exemplifies issues that confront the virus when adapting to immunogenetic diversity in the host.

Human cytomegalovirus (HCMV) UL141 induces protection against natural killer cell-mediated cytolysis by downregulating cell surface expression of CD155 (nectin-like molecule 5; poliovirus receptor), a ligand for the activating receptor DNAM-1 (CD226). However, DNAM-1 is also recognized to bind a second ligand, CD112 (nectin-2). We now show that HCMV targets CD112 for proteasome-mediated degradation by 48 h post-infection, thus removing both activating ligands for DNAM-1 from the cell surface during productive infection. Significantly, cell surface expression of both CD112 and CD155 was restored when UL141 was deleted from the HCMV genome. While gpUL141 alone is sufficient to mediate retention of CD155 in the endoplasmic reticulum, UL141 requires assistance from additional HCMV-encoded functions to suppress expression of CD112.

Human cytomegalovirus (HCMV) causes lifelong, persistent infections and its survival is under intense, continuous selective pressure from the immune system. A key aspect of HCMV’s capacity for survival lies in immune avoidance. In this context, cells undergoing productive infection exhibit remarkable resistance to natural killer (NK) cell-mediated cytolysis in vitro. To date, six genes encoding proteins (UL16, UL18, UL40, UL83, UL141 and UL142) and one encoding a microRNA (miR-UL112) have been identified as capable of suppressing NK cell recognition. Even though HCMV infection efficiently activates expression of ligands for the NK cell activating receptor NKG2D, at least three functions (UL16, UL142 and miR-UL112) act in concert to suppress presentation of these ligands on the cell surface. Although HCMV downregulates expression of endogenous MHC-I, it encodes an MHC-I homologue (UL18) and also upregulates the expression of cellular HLA-E through the action of UL40. The disruption of normal intercellular connections exposes ligands for NK cell activating receptors on the cell surface, notably CD155. HCMV overcomes this vulnerability by encoding a function (UL141) that acts post-translationally to suppress cell surface expression of CD155. The mechanisms by which HCMV systematically evades (or, more properly, modulates) NK cell recognition constitutes an area of growing understanding that is enhancing our appreciation of the basic mechanisms of NK cell function in humans.

The inhibitory leukocyte Ig-like receptor 1 (LIR-1, also known as ILT2, CD85j, or LILRB1) was identified by its high affinity for the human CMV (HCMV) MHC class I homolog gpUL18. The role of this LIR-1-gpUL18 interaction in modulating NK recognition during HCMV infection has previously not been clearly defined. In this study, LIR-1+ NKL cell-mediated cytotoxicity was shown to be inhibited by transduction of targets with a replication-deficient adenovirus vector encoding UL18 (RAd-UL18). Fibroblasts infected with an HCMV UL18 mutant (ΔUL18) also exhibited enhanced susceptibility to NKL killing relative to cells infected with the parental virus. In additional cytolysis assays, UL18-mediated protection was also evident in the context of adenovirus vector transduction and HCMV infection of autologous fibroblast targets using IFN-α-activated NK bulk cultures derived from a donor with a high frequency of LIR-1+ NK cells. A single LIR-1high NK clone derived from this donor was inhibited by UL18, while 3 of 24 clones were activated. CD107 mobilization assays revealed that LIR-1+ NK cells were consistently inhibited by UL18 in all tested donors, but this effect was often masked in the global response by UL18-mediated activation of a subset of LIR-1− NK cells. Although Ab-blocking experiments support UL18 inhibition being induced by a direct interaction with LIR-1, the UL18-mediated activation is LIR-1 independent.

International audience; Des mutations de SH3BP2 à l'origine du chérubisme Le chérubisme est une dysplasie cra-nio-faciale rare, caractérisée par un élargissement symétrique de la partie inférieure du visage qui donne au patient une apparence semblable à celle des chérubins de la Renaissance. Cette maladie génétique est transmise de manière autosomique dominante. Les patients présentent une érosion importante des os de la mâchoire dans lesquels s'accumulent des kystes fibreux remplis de cel-lules multinucléées géantes de type ostéoclaste. Les lésions apparaissent dans la petite enfance, entre 2 et 5 ans, et progressent jusqu'à la puberté pour régresser presque complètement à l'âge adulte. Cette maladie reste bénigne mais engendre des troubles importants de la face et de la denti-tion, associés à des problèmes esthé-tiques et psychologiques qui néces-sitent une intervention chirurgicale dans les cas sévères. La majorité des mutations associées au chérubisme affectent l'exon 9 du gène SH3BP2 codant pour 3BP2 ou SH3BP2 (Abl SH3 binding protein 2). Ces mutations conduisent au changement d'un unique acide aminé dans la séquence R 415 SPPDG 420 de 3BP2 [1]. 3BP2 est une protéine adaptatrice que nous avions identifiée comme un partenaire de la protéine tyrosine kinase SYK [2] et d'autres molécules de signalisation comme les kinases SRC et les facteurs d'échange nucléotidique VAV. Ainsi, 3BP2 est impliquée dans l'activation de programmes transcriptionnels et cellulaires (comme le remodelage du réseau d'actine) via l'engagement de multiples récepteurs dans les réponses leucocytaires [3], la différenciation des ostéoclastes [4] et le remodelage osseux [1]. L'étiologie du chérubisme est longtemps restée inconnue, mais le développement de modèles chez la souris a permis d'importants pro-grès dans la compréhension des fac-teurs déclencheurs de cette maladie énigmatique. Le knock-in des mutations P416R et G418R (respective-ment P418R et G420R chez l'homme) dans le gène Sh3bp2 montre qu'un seul allèle mutant n'est pas suffisant pour déclencher la maladie chez la sou-ris. Les souris mutantes homozygotes développent cependant une ostéopo-rose sévère et une inflammation sys-témique, avec des niveaux élevés de TNF- (tumor necrosis factor) sérique, résultant d'une hyperactivation des voies de signalisation dépendantes des kinases SRC et SYK et du facteur de transcription NFATc1 (nuclear factor of activated T-cells) dans les macro-phages et les ostéoclastes. Ainsi, ces modèles définissent le chérubisme comme une maladie héréditaire auto-inflammatoire médiée par les cellules myéloïdes, et confèrent à la mutation du gène Sh3bp2 un rôle moteur dans cette maladie [5, 6]. Une avancée importante dans la compréhension du chérubisme est venue du laboratoire du Dr Rottapel, qui a identifié l'inter-action entre 3BP2 et la poly(ADP-ribosyl)polymérase tankyrase comme une étape clé dans la pathogenèse de la maladie [7]. La fixation de tankyrase sur le motif RSPPDG de la protéine 3BP2 sauvage, en catalysant la poly(ADP-ribosyl)ation (PARyla-tion) de 3BP2, entraîne sa polyubi-quitination par RNF146 (ring finger protein 146), une E3 ubiquitine ligase dépendante de la PARylation des protéines. Cette séquence de modifications post-traductionnelles est suivie de la dégradation de 3BP2 par le protéasome, assurant ainsi l'ho-méostasie protéique de 3BP2. Dans le chérubisme, ce mécanisme est défec-tueux car les mutations ponctuelles du motif RSPPDG de 3BP2 abolissent son interaction avec tankyrase, avec pour conséquence une accumulation des protéines 3BP2 mutantes à l'ori-gine du syndrome auto-inflamma-toire observé [6, 7].

International audience; Disruption of the endothelial barrier by tumour-derived secreted factors is a critical step in cancer cell extravasation and metastasis. Here, by comparative proteomic analysis of melanoma secretomes, we identify the matricellular protein SPARC as a novel tumour-derived vascular permeability factor. SPARC deficiency abrogates tumour-initiated permeability of lung capillaries and prevents extravasation, whereas SPARC overexpression enhances vascular leakiness, extravasation and lung metastasis. SPARC-induced paracellular permeability is dependent on the endothelial VCAM1 receptor and p38 MAPK signalling. Blocking VCAM1 impedes melanoma-induced endothelial permeability and extravasation. The clinical relevance of our findings is highlighted by high levels of SPARC detected in tumour from human pulmonary melanoma lesions. Our study establishes tumour-produced SPARC and VCAM1 as regulators of cancer extravasation, revealing a novel targetable interaction for prevention of metastasis.

Cherubism is a rare autoinflammatory bone disorder that is associated with point mutations in the SH3-domain binding protein 2 (SH3BP2) gene, which encodes the adapter protein 3BP2. Individuals with cherubism present with symmetrical fibro-osseous lesions of the jaw, which are attributed to exacerbated osteoclast activation and defective osteoblast differentiation. Although it is a dominant trait in humans, cherubism appears to be recessively transmitted in mice, suggesting the existence of additional factors in the pathogenesis of cherubism. Here, we report that macrophages from 3BP2-deficient mice exhibited dramatically reduced inflammatory responses to microbial challenge and reduced phagocytosis. 3BP2 was necessary for LPS-induced activation of signaling pathways involved in macrophage function, including SRC, VAV1, p38MAPK, IKKα/β, RAC, and actin polymerization pathways. Conversely, we demonstrated that the presence of a single Sh3bp2 cherubic allele and pathogen-associated molecular pattern (PAMP) stimulation had a strong cooperative effect on macrophage activation and inflammatory responses in mice. Together, the results from our study in murine genetic models support the notion that infection may represent a driver event in the etiology of cherubism in humans and suggest limiting inflammation in affected individuals may reduce manifestation of cherubic lesions.

Cytotoxic T lymphocytes play a central role in the control of persistent human CMV (HCMV) infection and reactivation. In healthy virus carriers, the specific CD8+ CTL response is almost entirely directed against the virion tegument protein pp65 and/or the 72-kDa major immediate early protein, IE1. Studies that included a large panel of HCMV+ donors suggested that immunorelevance of pp65 and IE1 was directly related with individual HLA haplotype difference. Nevertheless, there are no data on the incidence of HCMV natural polymorphism on virus-specific CTL responses. To assess the impact of IE1 polymorphism on CTL response, we have sequenced in 103 clinical isolates the DNA region corresponding to IE1315–324, an immunodominant epitope presented by HLA-A*0201 molecules. Seven peptidic variants were found with extensive difference in their frequencies. The response of four HLA-A*0201-restricted anti-IE1 T lymphocyte clones, which were previously generated from one donor against autologous B lymphoblastoid cells expressing a recombinant clinical variant of IE1, was then evaluated using target cells loaded with mutant synthetic peptides or expressing rIE1 variants. One of four clones, which have been sorted 19 times among 22 clones targeted against IE1315–324, recognized six of the seven tested variant epitopes. All three other clones showed distinct reactivity patterns to target cells loaded with the different mutant peptides or expressing IE1 variants. Therefore, in the HLA-A2 context, clonal expansions of anti-IE1 memory CTLs may confer a protection against HCMV successive infections and reactivations by killing cells presenting most of the naturally occurring IE1315–324 epitope variants.

Cytotoxic T lymphocytes (CTLs) play a central role in the control of persistent human cytomegalovirus (HCMV) infection in healthy virus carriers. Previous analyses of the specificity of HCMV-reactive CD8+CTLs drawn from in vitro models in which antigen-presenting cells were autologous fibroblasts infected with laboratory HCMV strains have shown focusing of CTL responses against the major tegument protein, pp65. By contrast, the 72-kDa major immediate-early protein (IE1) was identified as a minor target for this response. Here we have studied the fine specificity and T-cell-receptor features of T-cell clones generated against autologous B lymphoblastoid cell lines stably transfected with HCMV cDNA coding for either pp65 or a natural variant of IE1. This strategy allowed efficient generation of T-cell clones against IE1 and pp65 and led to the identification of several new IE1 and pp65 epitopes, including some located in polymorphic regions of IE1. Such an approach may provide relevant information about the characteristics of the CTL response to IE1 and the effect of viral polymorphism on the immune response against HCMV.

The adapter protein 3BP2 (also known as SH3BP2 and Abl SH3-binding protein 2) has been involved in leukocyte signaling and activation downstream immunoreceptors. Genetic studies have further associated 3BP2 mutations to the human disease cherubism and to inflammation and bone dysfunction in mouse. However, how wild type 3BP2 functions in macrophage differentiation remains poorly understood. In this study, using small interfering RNA-mediated silencing of 3BP2 in the RAW264.7 monocytic cell line, we show that 3BP2 was required for receptor activator of NFkappaB ligand (RANKL)-induced differentiation of RAW264.7 cells into multinucleated mature osteoclasts but not for granulocyte macrophage-colony stimulating factor/interleukin-4-induced differentiation into dendritic cells. 3BP2 silencing was associated with impaired activation of multiple signaling events downstream of RANK, including actin reorganization; Src, ERK, and JNK phosphorylation; and up-regulation of osteoclastogenic factors. In addition, 3BP2 knockdown cells induced to osteoclast by RANKL displayed a reduced increase of Src and nuclear factor of activated T cells (NFATc1) mRNA and protein expression. Importantly, 3BP2 interacted with Src, Syk, Vav, and Cbl in monocytic cells, and the introduction of constitutively active mutants of Src and NFATc1 in 3BP2-deficient cells restored osteoclast differentiation. Finally, the expression of a 3BP2 cherubism mutant was found to promote increased Src activity and NFAT-dependent osteoclast formation. Together, this study demonstrates that wild type 3BP2 is a key regulator of RANK-mediated macrophage differentiation into osteoclast through Src and NFATc1 activation.

The adenovirus (Ad) early transcription unit 3 (E3) encodes multiple immunosubversive functions that are presumed to facilitate the establishment and persistence of infection. Indeed, the capacity of E3/19K to inhibit transport of HLA class I (HLA-I) to the cell surface, thereby preventing peptide presentation to CD8+T cells, has long been recognized as a paradigm for viral immune evasion. However, HLA-I downregulation has the potential to render Ad-infected cells vulnerable to natural killer (NK) cell recognition. Furthermore, expression of the immediate-early Ad gene E1A is associated with efficient induction of ligands for the key NK cell-activating receptor NKG2D. Here we show that while infection with wild-type Ad enhances synthesis of the NKG2D ligands, major histocompatibility complex class I chain-related proteins A and B (MICA and MICB), their expression on the cell surface is actively suppressed. Both MICA and MICB are retained within the endoplasmic reticulum as immature endoglycosidase H-sensitive forms. By analyzing a range of cell lines and viruses carrying mutated versions of the E3 gene region, E3/19K was identified as the gene responsible for this activity. The structural requirements within E3/19K necessary to sequester MICA/B and HLA-I are similar. In functional assays, deletion of E3/19K rendered Ad-infected cells more sensitive to NK cell recognition. We report the first NK evasion function in theAdenoviridaeand describe a novel function for E3/19K. Thus, E3/19K has a dual function: inhibition of T-cell recognition and NK cell activation.

Human NK cells and subsets of T cells or NKT cells express the orphan C-type lectin receptor CD161 (NKR-P1A) of unknown function. In contrast to rodents that possess several NKR-P1 genes coding for either activating or inhibitory receptors, the nature of signals delivered by the single human NKR-P1A receptor is still to be clarified. In this article, we show that the lectin-like transcript 1 (LLT1) molecule is a ligand for the CD161 receptor. Engagement of CD161 on NK cells with LLT1 expressed on target cells inhibited NK cell-mediated cytotoxicity and IFN-γ secretion. Conversely, LLT1/CD161 interaction in the presence of a TCR signal enhanced IFN-γ production by T cells. These findings identify a novel ligand/receptor pair that differentially regulate NK and T cell functions.

H2-deleted, HLA-A2, or HLA-B7 transgenic mice were used to identify new human cytomegalovirus (HCMV)-derived major histocompatibility complex class I-restricted epitopes. Three different approaches for mice immunization were compared for their ability to induce a cytotoxic CD8(+) T cell (CTL) response: (1). inoculation of infectious HCMV, (2). injection of immunogenic synthetic peptides, and (3). infection with a newly designed HIV-derived central DNA flap positive lentiviral vector encoding the chimeric IE1-pp65 protein (Trip-IE1-pp65). Targets pulsed with either known immunogenic peptides or computer predicted ones were used to characterize CTL. Most of the mice immunized with the pp65 (495-NLVPMVATV-503) immunodominant peptide responded after one injection whereas only two of six mice responded to two successive inoculations with HCMV. Infection of mice with Trip-IE1-pp65 induced activation and expansion of CTL directed against peptides from both pp65 and IE1 and allowed identification of new epitopes. We further demonstrated the high capacity of monocyte-macrophage cells transduced with Trip-IE1-pp65 to activate and expand CTL directed against pp65 from peripheral blood mononuclear cells of HCMV-seropositive donors. Altogether these results suggest that Trip-IE1-pp65 is a powerful construct both to characterize new epitopes in combination with human leukocyte antigen-transgenic mice immunization and to provide an alternative to the use of known infectious and noninfectious approaches to expand effector T cells for adoptive immunotherapy.

The impact of natural polymorphism in a cytomegalovirus-dominant HLA-B * 1801-restricted epitope, IE1 199-206 , on the specific responses of T-cell clones was assessed by measuring their cytolytic activity against target cells expressing mutated recombinant IE1 proteins. Our results suggest an in vivo selection of T lymphocytes that cross-react with multiple IE1 variants.

Fibroblastic reticular cells (FRCs) are lymph node (LN) myofibroblasts controlling the size and architecture of the LN, partly through their contractile properties. LN swelling is a hallmark of tumor-draining LN in lymphophilic cancers such as melanoma, but the link between this phenomenon and tumor-derived cues is poorly understood. The secretion of multiple factors by tumor cells, such as extracellular vesicles (EVs), or soluble growth factors and proinflammatory cytokines, promotes tumorigenesis and LN metastasis. Melanomas are very plastic tumors and the melanogenesis process is associated with switches between a proliferative melanocytic phenotype, associated with MITF high AXL low gene expression, and an invasive dedifferentiated phenotype associated with a MITF low AXL high gene signature. We show that proteins secreted by invasive melanomas, but not proliferative melanomas, strongly inhibit FRC actomyosin contractility by decreasing the activity of the RHOA and RHO-kinase (ROCK) pathway and of the mechano-responsive transcriptional co-activator YAP, leading to a decrease in F-actin stress fibers and cell elongation. This is independent of the EVs secreted by invasive melanomas, is associated with the activation and proliferation of FRCs, and is driven by the inhibition of JAK1 and the downstream transcription factor STAT3 in FRCs. Our results suggest that melanoma-derived cues could modulate the biomechanical properties of distant LN before metastatic invasion, and identify that the spontaneous contractility of actomyosin in resting human FRCs is driven by the basal activity of JAK1-STAT3 sustaining activation of the RHOA-ROCK and YAP interconnected pathways.; Le mélanome est le cancer de la peau le plus agressif. Il est caractérisé par une progression rapide des métastases, et une forte plasticité des cellules tumorales. On distingue des cellules au phénotype prolifératif avec une signature MITFhigh AXLlow et des cellules au profil invasif dé-différencié AXLhigh MITFlow. Ces cellules peuvent transiter d’un phénotype à l’autre en fonction des signaux du microenvironnement. Le mélanome possède un fort tropisme pour le ganglion lymphatique. Il sécrète des vésicules extracellulaires et des facteurs solubles capables de migrer dans le ganglion drainant et de reprogrammer les cellules du ganglion pour créer une niche pré-métastatique favorable à l’implantation tumorale. Dans le ganglion lymphatique, les Cellules Réticulaires Fibroblastiques (FRC) sont des myofibroblastes qui contrôlent l’architecture du ganglion ainsi que sa dilatation lors des réponses immunitaires. Les FRC sécrètent également des chimiokines et des cytokines ainsi qu’un réseau matriciel de conduits qui régulent le recrutement, la survie, l’activation et la circulation des cellules immunitaires. La modification architecturale du ganglion pré-métastatique est une des caractéristiques des cancers lymphophiles, comme le mélanome, mais les liens entre les facteurs sécrétés par le mélanome et les propriétés contractiles des FRC ne sont pas connus.Au cours de ma thèse, j’ai étudié l’effet des facteurs sécrétés par le mélanome sur les propriétés contractiles des FRC. J’ai identifié que les protéines sécrétées par les cellules de mélanome invasives à signature AXLhigh MITFlow, mais pas par les cellules au phénotype prolifératif, inhibent la contractilité du squelette d'actomyosine des FRC en inhibant la voie RHOA et RHO-kinase (ROCK) et le co-activateur transcriptionnel mécanosensible YAP, ce qui conduit à une diminution des fibres de stress et à une modulation de la morphologie des FRC. Ces effets sont indépendants des vésicules extracellulaires sécrétées par les mélanomes invasifs, et sont induits par l'inhibition de JAK1 et du facteur de transcription en aval, STAT3. Mes résultats suggèrent donc que les facteurs sécrétés par les cellules de mélanome invasives pourraient moduler les propriétés biomécaniques du ganglion pré-métastatique. Ils montrent également que la contractilité spontanée de l'actomyosine dans les FRC humains est déterminée par l'activité basale de JAK1-STAT3 en amont des voies de signalisation RHOA-ROCK et YAP. Par ailleurs, j’ai montré que les facteurs sécrétés par les lignées de mélanome invasives induisent également l'activation et la prolifération des FRC, ainsi que la modification du profil de cytokines et chimiokines sécrétées par les FRC.Mes travaux de thèse démontrent que les facteurs sécrétés par les mélanomes invasifs reprogramment profondément les FRC dans le ganglion pré-métastatique. Ils participent à une meilleure compréhension des interactions entre le mélanome et le ganglion lymphatique qui pourrait aboutir à la mise au point de nouveaux biomarqueurs ou de nouvelles cibles thérapeutiques pour mieux identifier et traiter les patients présentant un risque de métastase ganglionnaire.