Glycans in melanoma: Drivers of tumour progression but sweet targets to exploit for immunotherapy.

Aberrant glycosylation recently emerged as an unmissable hallmark of cancer progression in many cancers. In melanoma, there is growing evidence that the tumour 'glycocode' plays a major role in promoting cell proliferation, invasion, migration, but also dictates the nature of the immune infiltrate, which strongly affects immune cell function, and clinical outcome. Aberrant glycosylation patterns dismantle anti-tumour defence through interactions with lectins on immune cells, which are crucial to shape anti-tumour immunity but also to trigger immune evasion. The glycan/lectin axis represents a new immune subversion pathway that is exploited by melanoma to hijack immune cells and escape from immune control. In this review, we describe the glycosylation features of melanoma tumour cells, and further gather findings related to the role of glycosylation in melanoma tumour progression, deciphering in detail its impact on immunity. We also depict glycan-based strategies aiming at restoring a functional anti-tumour response in melanoma patients. Glycans/lectins emerge as key immune checkpoints with promising translational properties. Exploitation of these pathways could reshape potent anti-tumour immunity while impeding immunosuppressive circuits triggered by aberrant tumour glycosylation patterns, holding great promise for cancer therapy.

Melanoma tumour-derived glycans hijack dendritic cell subsets through C-type lectin receptor binding.

Dendritic cell (DC) subsets play a crucial role in shaping anti-tumour immunity. Cancer escapes from the control immune system by hijacking DC functions. Yet, bases for such subversion are only partially understood. Tumour cells display aberrant glycan motifs on surface glycoproteins and glycolipids. Such carbohydrate patterns can be sensed by DCs through C-type lectin receptors (CLRs) that are critical to shape and orientate immune responses. We recently demonstrated that melanoma tumour cells harboured an aberrant 'glyco-code,' and that circulating and tumour-infiltrating DCs from melanoma patients displayed major perturbations in their CLR profiles. To decipher whether melanoma, through aberrant glycan patterns, may exploit CLR pathways to mislead DCs and evade immune control, we explored the impact of glycan motifs aberrantly found in melanoma (neoglycoproteins [NeoGP] functionalised with Gal, Man, GalNAc, s-Tn, fucose [Fuc] and GlcNAc residues) on features of human DC subsets (cDC2s, cDC1s and pDCs). We examined the ability of glycans to bind to purified DCs, and assessed their impact on DC basal properties and functional features using flow cytometry, confocal microscopy and multiplex secreted protein analysis. DC subsets differentially bound and internalised NeoGP depending on the nature of the glycan. Strikingly, Fuc directly remodelled the expression of activation markers and immune checkpoints, as well as the cytokine/chemokine secretion profile of DC subsets. NeoGP interfered with Toll like receptor (TLR)-signalling and pre-conditioned DCs to exhibit an altered response to subsequent TLR stimulation, dampening antitumor mediators while triggering pro-tumoral factors. We further demonstrated that DC subsets can bind NeoGP through CLRs, and identified GalNAc/MGL and s-Tn/ C-type lectin-like receptor 2 (CLEC2) as potential candidates. Moreover, DC dysfunction induced by tumour-associated carbohydrate molecules may be reversed by interfering with the glycan/CLR axis. These findings revealed the glycan/CLR axis as a promising checkpoint to exploit in order to reshape potent antitumor immunity while impeding immunosuppressive pathways triggered by aberrant tumour glycosylation patterns. This may rescue DCs from tumour hijacking and improve clinical success in cancer patients.

Harnessing Immune Cell Metabolism to Modulate Alloresponse in Transplantation.

Immune cell metabolism plays a pivotal role in shaping and modulating immune responses. The metabolic state of immune cells influences their development, activation, differentiation, and overall function, impacting both innate and adaptive immunity. While glycolysis is crucial for activation and effector function of CD8 T cells, regulatory T cells mainly use oxidative phosphorylation and fatty acid oxidation, highlighting how different metabolic programs shape immune cells. Modification of cell metabolism may provide new therapeutic approaches to prevent rejection and avoid immunosuppressive toxicities. In particular, the distinct metabolic patterns of effector and suppressive cell subsets offer promising opportunities to target metabolic pathways that influence immune responses and graft outcomes. Herein, we review the main metabolic pathways used by immune cells, the techniques available to assay immune metabolism, and evidence supporting the possibility of shifting the immune response towards a tolerogenic profile by modifying energetic metabolism.

A New Plasmacytoid Dendritic Cell-Based Vaccine in Combination with Anti-PD-1 Expands the Tumor-Specific CD8+ T Cells of Lung Cancer Patients.

The purpose of immune checkpoint inhibitor (ICI)-based therapies is to help the patient's immune system to combat tumors by restoring the immune response mediated by CD8+ cytotoxic T cells. Despite impressive clinical responses, most patients do not respond to ICIs. Therapeutic vaccines with autologous professional antigen-presenting cells, including dendritic cells, do not show yet significant clinical benefit. To improve these approaches, we have developed a new therapeutic vaccine based on an allogeneic plasmacytoid dendritic cell line (PDC*line), which efficiently activates the CD8+ T-cell response in the context of melanoma. The goal of the study is to demonstrate the potential of this platform to activate circulating tumor-specific CD8+ T cells in patients with lung cancer, specifically non-small-cell lung cancer (NSCLC). PDC*line cells loaded with peptides derived from tumor antigens are used to stimulate the peripheral blood mononuclear cells of NSCLC patients. Very interestingly, we demonstrate an efficient activation of specific T cells for at least two tumor antigens in 69% of patients irrespective of tumor antigen mRNA overexpression and NSCLC subtype. We also show, for the first time, that the antitumor CD8+ T-cell expansion is considerably improved by clinical-grade anti-PD-1 antibodies. Using PDC*line cells as an antigen presentation platform, we show that circulating antitumor CD8+ T cells from lung cancer patients can be activated, and we demonstrate the synergistic effect of anti-PD-1 on this expansion. These results are encouraging for the development of a PDC*line-based vaccine in NSCLC patients, especially in combination with ICIs.

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model.

Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin αvß3, which is a well-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5 µM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]4-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.

X-Chromosome complement and estrogen receptor signaling independently contribute to the enhanced TLR7-mediated IFN-α production of plasmacytoid dendritic cells from women.

Human plasmacytoid dendritic cells (pDCs) play a major role in innate immunity through the production of type I IFNs after TLR engagement by pathogens. Sex-based differences in the innate function of human pDCs have been established, with pDCs from women exhibiting enhanced TLR7-mediated IFN-α production as compared with pDCs from males. In mice, we recently provided evidence for a role of estrogens as a positive regulator of pDC innate functions through cell-intrinsic estrogen receptor α signaling, but did not exclude a role for other X-linked factors, particularly in human pDCs. In this study, we investigated the respective contribution of X chromosome dosage and sex hormones using a humanized mouse model in which male or female NOD-SCID-ß2m(-/-) were transplanted with human progenitor cells purified from either male or female cord blood cells. We showed that, in response to TLR7 ligands, the frequency of IFN-α- and TNF-α-producing pDCs from either sex was greater in female than in male host mice, suggesting a positive role for estrogens. Indeed, blockade of estrogen receptor signaling during pDC development in vitro inhibited TLR7-mediated IFN-α production by human pDCs, which expressed both ESR1 and ESR2 genes. Interestingly, we also found that X chromosome dosage contributed to this sex bias as female pDCs have an enhanced TLR7-mediated IFN-α response as compared with male ones, irrespective of the sex of the recipient mice. Together, these results indicate that female sex hormones, estrogens, and X chromosome complement independently contribute to the enhanced TLR7-mediated IFN-α response of pDCs in women.

pDCs efficiently process synthetic long peptides to induce functional virus- and tumour-specific T-cell responses.

Robust cell-mediated immunity is required for immune control of tumours and protection from viral infections, with both CD4(+) and CD8(+) T cells playing a pivotal role. Synthetic long peptides (SLPs) represent an attractive way to induce such combined responses, as they contain both class I and class II epitopes. The ability of plasmacytoid dendritic cells (pDCs) to cross-present SLPs has not yet been investigated; yet, pDCs play a critical role in shaping immune responses and have emerged as novel vectors for immunotherapy. Using overlapping 15-mer peptide pools covering the entire sequence of CMVpp65 and MelA, representing a viral disease (cytomegalovirus, CMV) and a tumour (melanoma), respectively, we showed that human pDCs can effectively process SLPs. Our results demonstrated that pDCs potently cross-present virus- and tumour-derived SLPs and cross-prime broad-ranging, effective and long-lived CD4(+) and CD8(+) T-cell responses, triggering more efficient immune responses than short peptide loaded pDCs. This ability required intracellular processing by the proteasome and was enhanced by co-exposure to TLR7/9-L. Combining SLPs with pDCs represents a powerful immunotherapeutic strategy to elicit potent immune responses, which are required for clinical success in cancers and viral infections.

A safe bacterial microsyringe for in vivo antigen delivery and immunotherapy.

The industrial development of active immunotherapy based on live-attenuated bacterial vectors has matured. We developed a microsyringe for antigen delivery based on the type III secretion system (T3SS) of P. aeruginosa. We applied the "killed but metabolically active" (KBMA) attenuation strategy to make this bacterial vector suitable for human use. We demonstrate that attenuated P. aeruginosa has the potential to deliver antigens to human antigen-presenting cells in vitro via T3SS with considerable attenuated cytotoxicity as compared with the wild-type vector. In a mouse model of cancer, we demonstrate that this KBMA strain, which cannot replicate in its host, efficiently disseminates into lymphoid organs and delivers its heterologous antigen. The attenuated strain effectively induces a cellular immune response to the cancerous cells while lowering the systemic inflammatory response. Hence, a KBMA P. aeruginosa microsyringe is an efficient and safe tool for in vivo antigen delivery.

Breast cancer instructs dendritic cells to prime interleukin 13-secreting CD4+ T cells that facilitate tumor development.

We previously reported (Bell, D., P. Chomarat, D. Broyles, G. Netto, G.M. Harb, S. Lebecque, J. Valladeau, J. Davoust, K.A. Palucka, and J. Banchereau. 1999. J. Exp. Med. 190: 1417-1426) that breast cancer tumors are infiltrated with mature dendritic cells (DCs), which cluster with CD4(+) T cells. We now show that CD4(+) T cells infiltrating breast cancer tumors secrete type 1 (interferon gamma) as well as high levels of type 2 (interleukin [IL] 4 and IL-13) cytokines. Immunofluorescence staining of tissue sections revealed intense IL-13 staining on breast cancer cells. The expression of phosphorylated signal transducer and activator of transcription 6 in breast cancer cells suggests that IL-13 actually delivers signals to cancer cells. To determine the link between breast cancer, DCs, and CD4(+) T cells, we implanted human breast cancer cell lines in nonobese diabetic/LtSz-scid/scid beta2 microglobulin-deficient mice engrafted with human CD34(+) hematopoietic progenitor cells and autologous T cells. There, CD4(+) T cells promote early tumor development. This is dependent on DCs and can be partially prevented by administration of IL-13 antagonists. Thus, breast cancer targets DCs to facilitate its development.

Altered functions of plasmacytoid dendritic cells and reduced cytolytic activity of natural killer cells in patients with chronic HBV infection.

BACKGROUND & AIMS: Hepatitis B virus (HBV) modulates the immune system to escape clearance. Plasmacytoid dendritic cells (pDCs) initiate antiviral immunity and might determine outcomes of HBV infections. Functional defects in pDCs and natural killer (NK) cells have been reported in patients with chronic HBV infection. However, the mechanisms of these immune dysfunctions and the interactions between pDCs and NK cells have not been determined. We investigated features of pDCs from patients with chronic HBV infection and their interactions with NK cells. METHODS: We used flow cytometry and cytokine assays to analyze pDCs from patients with chronic HBV infection (118 aviremic and 67 viremic) and compared them with pDCs from uninfected individuals (controls). We performed coculture assays to analyze the ability of pDCs to activate heterologous NK cells. RESULTS: Circulating and hepatic pDCs from patients with chronic HBV infection had higher levels of activation than pDCs from controls and defective responses to stimulation with Toll-like receptor 9 ligand (TLR9-L), regardless of the patient's viral load. TLR9-L-activated pDCs from viremic patients with HBV did not induce cytolytic activity of NK cells. This altered function of pDCs was associated with reduced expression of OX40L and could be reproduced by incubating control pDCs with plasma from viremic patients with HBV. A high level of interferon-induced protein 10 (IP-10 or CXCL10) and hepatitis B surface and e antigens might induce these defective pDC functions. CONCLUSIONS: HBV escapes antiviral immunity by altering pDC functions, to disrupt interactions between pDC and NK cells. This could reduce immune control of HBV and lead to chronic infection.

Plasmacytoid dendritic cells induce efficient stimulation of antiviral immunity in the context of chronic hepatitis B virus infection.

UNLABELLED: The immune control of hepatitis B virus (HBV) infection is essential for viral clearance. Therefore, restoring functional anti-HBV immunity is a promising immunotherapeutic approach to treatment of chronic infection. Plasmacytoid dendritic cells (pDCs) play a crucial role in triggering antiviral immunity through their ability to capture and process viral antigens and subsequently induce adaptive immune responses. We investigated the potential of pDCs to trigger antiviral cellular immunity against HBV. We used a human leukocyte antigen A (HLA-A)*0201(+) pDC line loaded with HLA-A*0201-restricted peptides derived from hepatitis B core/hepatitis B surface (HBc/HBs) antigens to amplify specific CD8 T cells ex vivo from chronic HBV patients and established a Hepato-HuPBL mouse model to address the therapeutic potential of the strategy in vivo. Stimulation of PBMCs or liver-infiltrating lymphocytes from HLA-A*0201(+) chronic HBV patients by HBc peptide-loaded pDCs elicited up to 23.1% and 76.1% HBV-specific CD8 T cells in 45.8% of cases. The specific T cells from the "responder" group secreted interferon-γ, expressed CD107 upon restimulation, and efficiently lysed HBV antigen-expressing hepatocytes. Circulating hepatitis B e antigen (HBeAg) was found to distinguish the group of patients not responding to the pDC stimulation. The therapeutic efficacy of the pDC vaccine was evaluated in immunodeficient NOD-SCID ß(2) m(-/-) mice reconstituted with HBV patients' PBMCs and xenotransplanted with human HBV-transfected hepatocytes. Vaccination of Hepato-HuPBL mice with the HBc/HBs peptide-loaded pDCs elicited HBV-specific T cells able to specifically lyse the transfected hepatocytes and reduce the systemic viral load. CONCLUSION: pDCs loaded with HBV-derived peptides can elicit functional virus-specific T cells. HBeAg appears to be critical in determining the outcome of immunotherapies in chronic HBV patients. A pDC-based immunotherapeutic approach could be of interest in attempts to restore functional antiviral immunity, which is critical for the control of the virus in chronic HBV patients.

Dendritic Cell Subsets in Melanoma: Pathophysiology, Clinical Prognosis and Therapeutic Exploitation.

Evasion from immunity is a hallmark of cancer development. Dendritic cells (DCs) are strategic immune cells shaping anti-tumor immune responses, but tumor cells exploit DC versatility to subvert their functions. Unveiling the puzzling role of DCs in the control of tumor development and mechanisms of tumor-induced DC hijacking is critical to optimize current therapies and to design future efficient immunotherapies for melanoma. Dendritic cells, crucially positioned at the center of anti-tumor immunity, represent attractive targets to develop new therapeutic approaches. Harnessing the potencies of each DC subset to trigger appropriate immune responses while avoiding their subversion is a challenging yet promising step to achieve tumor immune control. This review focuses on advances regarding the diversity of DC subsets, their pathophysiology and impact on clinical outcome in melanoma patients. We provide insights into the regulation mechanisms of DCs by the tumor, and overview DC-based therapeutic developments for melanoma. Further insights into DCs' diversity, features, networking, regulation and shaping by the tumor microenvironment will allow designing novel effective cancer therapies. The DCs deserve to be positioned in the current melanoma immunotherapeutic landscape. Recent discoveries strongly motivate exploitation of the exceptional potential of DCs to drive robust anti-tumor immunity, offering promising tracks for clinical successes.

Immune checkpoints on T and NK cells in the context of HBV infection: Landscape, pathophysiology and therapeutic exploitation.

In hepatitis B virus (HBV) infection, the interplay between the virus and the host immune system is crucial in determining the pathogenesis of the disease. Patients who fail to mount a sufficient and sustained anti-viral immune response develop chronic hepatitis B (CHB). T cells and natural killer (NK) cells play decisive role in viral clearance, but they are defective in chronic HBV infection. The activation of immune cells is tightly controlled by a combination of activating and inhibitory receptors, called immune checkpoints (ICs), allowing the maintenance of immune homeostasis. Chronic exposure to viral antigens and the subsequent dysregulation of ICs actively contribute to the exhaustion of effector cells and viral persistence. The present review aims to summarize the function of various ICs and their expression in T lymphocytes and NK cells in the course of HBV infection as well as the use of immunotherapeutic strategies targeting ICs in chronic HBV infection.

Stimulation of the immune system by a tumor antigen-bearing adenovirus-inspired VLP allows control of melanoma growth.

Virus-like particles (VLPs) are versatile protein-based platforms that can be used as a vaccine platform mainly in infectiology. In the present work, we compared a previously designed, non-infectious, adenovirus-inspired 60-mer dodecahedric VLP to display short epitopes or a large tumor model antigen. To validate these two kinds of platforms as a potential immuno-stimulating approach, we evaluated their ability to control melanoma B16-ovalbumin (OVA) growth in mice. A set of adjuvants was screened, showing that polyinosinic-polycytidylic acid (poly(I:C)) was well suited to generate a homogeneous cellular and humoral response against the desired epitopes. In a prophylactic setting, vaccination with the VLP displaying these epitopes resulted in total inhibition of tumor growth 1 month after vaccination. A therapeutic vaccination strategy showed a delay in grafted tumor growth or its total rejection. If the "simple" epitope display on the VLP is sufficient to prevent tumor growth, then an improved engineered platform enabling display of a large antigen is a tool to overcome the barrier of immune allele restriction, broadening the immune response, and paving the way for its potential utilization in humans as an off-the-shelf vaccine.

The melanoma tumor glyco-code impacts human dendritic cells' functionality and dictates clinical outcomes.

Subversion of immunity is a hallmark of cancer development. Dendritic cells (DCs) are strategic immune cells triggering anti-tumor immune responses, but tumor cells exploit their versatility to subvert their functions. Tumor cells harbor unusual glycosylation patterns, which can be sensed through glycan-binding receptors (lectins) expressed by immune cells that are crucial for DCs to shape and orientate antitumor immunity. Yet, the global tumor glyco-code and its impact on immunity has not been explored in melanoma. To decrypt the potential link between aberrant glycosylation patterns and immune evasion in melanoma, we investigated the melanoma tumor glyco-code through the GLYcoPROFILE™ methodology (lectin arrays), and depicted its impact on patients' clinical outcome and DC subsets' functionality. Specific glycan patterns correlated with clinical outcome of melanoma patients, GlcNAc, NeuAc, TF-Ag and Fuc motifs being associated with poor outcome, whereas Man and Glc residues elicited better survival. Strikingly, tumor cells differentially impacting cytokine production by DCs harbored distinct glyco-profiles. GlcNAc exhibited a negative influence on cDC2s, whereas Fuc and Gal displayed inhibitory impacts on cDC1s and pDCs. We further identified potential booster glycans for cDC1s and pDCs. Targeting specific glycans on melanoma tumor cells restored DCs' functionality. The tumor glyco-code was also linked to the nature of the immune infiltrate. This study unveils the impact of melanoma glycan patterns on immunity, and paves the way for innovative therapeutic options. Glycans/lectins interactions arise as promising immune checkpoints to rescue DCs from tumor' hijacking to reshape antitumor immunity and inhibit immunosuppressive circuits triggered by aberrant tumor glycosylation.

Impaired Antitumor Immune Response in MYCN-amplified Neuroblastoma Is Associated with Lack of CCL2 Secretion and Poor Dendritic Cell Recruitment.

In neuroblastoma, MYCN amplification is associated with sparse immune infiltrate and poor prognosis. Dendritic cells (DC) are crucial immune sentinels but their involvement in neuroblastoma pathogenesis is poorly understood. We observed that the migration of monocytes, myeloid and plasmacytoid DC induced by MYCN-nonamplified neuroblastoma supernatants was abrogated by the addition of anti-CCL2 antibodies, demonstrating the involvement of the CCR2/CCL2 axis in their recruitment by these tumors. Using public RNA sequencing and microarray datasets, we describe lower level of expression of CCL2 in MYCN-amplified neuroblastoma tumors, and we propose a working model for T-cell recruitment in neuroblastoma tumors in which CCL2 produced by neuroblastoma cells initiates the recruitment of monocytes, myeloid and plasmacytoid DCs. Among these cells, the CD1c+ subset may recruit T cells by means of CCL19/CCL22 secretion. In vitro, supernatants from DCs cocultured with neuroblastoma cell lines and activated contain CCL22 and CCL19, and are chemotactic for both CD4+ and CD8+ T cells. We also looked at immunomodulation induced by neuroblastoma cell lines, and found MYCN-nonamplified neuroblastoma cell lines were able to create a microenvironment where DC activation is enhanced. Overall, our findings highlight a major role for CCL2/CCR2 axis in monocytes, myeloid and plasmacytoid cells recruitment toward MYCN-nonamplified neuroblastoma, allowing further immune cell recruitment, and show that these tumors present a microenvironment that can favor DC responses. Significance: In MYCN-nonamplified neuroblastoma, CCL2 produced by neuroblastoma cells induces the recruitment of antigen-presenting cells (DCs and monocytes/macrophages), allowing infiltration by T cells, in link with CCL19 and CCL22 production, hence favoring immune responses.

Diversification of circulating and tumor-infiltrating plasmacytoid DCs towards the P3 (CD80+ PDL1-)-pDC subset negatively correlated with clinical outcomes in melanoma patients.

Objectives: Plasmacytoid DCs (pDCs) play a critical yet enigmatic role in antitumor immunity through their pleiotropic immunomodulatory functions. Despite proof of pDC diversity in several physiological or pathological contexts, pDCs have been studied as a whole population so far in cancer. The assessment of individual pDC subsets is needed to fully grasp their involvement in cancer immunity, especially in melanoma where pDC subsets are largely unknown and remain to be uncovered. Methods: We explored for the first time the features of diverse circulating and tumor-infiltrating pDC subsets in melanoma patients using multi-parametric flow cytometry, and assessed their clinical relevance. Based on CD80, PDL1, CD2, LAG3 and Axl markers, we provided an integrated overview of the frequency, basal activation status and functional features of pDC subsets in melanoma patients together with their relationship to clinical outcome. Results: Strikingly, we demonstrated that P3-pDCs (CD80+PDL1-) accumulated within the tumor of melanoma patients and negatively correlated with clinical outcomes. The basal activation status, diversification towards P1-/P2-/P3-pDCs and functionality of several pDC subsets upon TLR7/TLR9 triggering were perturbed in melanoma patients, and were differentially linked to clinical outcome. Conclusion: Our study shed light for the first time on the phenotypic and functional heterogeneity of pDCs in the blood and tumor of melanoma patients and their potential involvement in shaping clinical outcomes. Such novelty brightens our understanding of pDC complexity, and prompts the further deciphering of pDCs' features to better apprehend and exploit these potent immune players. It highlights the importance of considering pDC diversity when developing pDC-based therapeutic strategies to ensure optimal clinical success.

Adenovirus-Inspired Virus-Like-Particles Displaying Melanoma Tumor Antigen Specifically Target Human DC Subsets and Trigger Antigen-Specific Immune Responses.

Virus-like particles constitute versatile vectors that can be used as vaccine platforms in many fields from infectiology and more recently to oncology. We previously designed non-infectious adenovirus-inspired 60-mer dodecahedric virus-like particles named ADDomers displaying on their surface either a short epitope or a large tumor/viral antigen. In this work, we explored for the first time the immunogenicity of ADDomers exhibiting melanoma-derived tumor antigen/epitope and their impact on the features of human dendritic cell (DC) subsets. We first demonstrated that ADDomers displaying tumor epitope/antigen elicit a strong immune-stimulating potential of human DC subsets (cDC2s, cDC1s, pDCs), which were able to internalize and cross-present tumor antigen, and subsequently cross-prime antigen-specific T-cell responses. To further limit off-target effects and enhance DC targeting, we engineered specific motifs to de-target epithelial cells and improve DCs' addressing. The improved engineered platform making it possible to display large antigen represents a tool to overcome the barrier of immune allele restriction, broadening the immune response, and paving the way to its potential utilization in humans as an off-the-shelf vaccine.

Unique CLR expression patterns on circulating and tumor-infiltrating DC subsets correlated with clinical outcome in melanoma patients.

Subversion of immunity by tumors is a crucial step for their development. Dendritic cells (DCs) are strategic immune cells that orchestrate anti-tumor immune responses but display altered functions in cancer. The bases for such DCs' hijacking are not fully understood. Tumor cells harbor unusual glycosylation patterns of surface glycoproteins and glycolipids. DCs express glycan-binding receptors, named C-type lectin receptors (CLR), allowing them to sense changes in glycan signature of their environment, and subsequently trigger a response. Recognition of tumor glycans by CLRs is crucial for DCs to shape antitumor immunity, and decisive in the orientation of the response. Yet the status of the CLR machinery on DCs in cancer, especially melanoma, remained largely unknown. We explored CLR expression patterns on circulating and tumor-infiltrating cDC1s, cDC2s, and pDCs of melanoma patients, assessed their clinical relevance, and further depicted the correlations between CLR expression profiles and DCs' features. For the first time, we highlighted that the CLR repertoire of circulating and tumor-infiltrating cDC1s, cDC2s, and pDCs was strongly perturbed in melanoma patients, with modulation of DCIR, CLEC-12α and NKp44 on circulating DCs, and perturbation of Dectin-1, CD206, DEC205, DC-SIGN and CLEC-9α on tumor-infiltrating DCs. Furthermore, melanoma tumor cells directly altered CLR expression profiles of healthy DC subsets, and this was associated with specific glycan patterns (Man, Fuc, GlcNAc) that may interact with DCs through CLR molecules. Notably, specific CLR expression profiles on DC subsets correlated with unique DCs' activation status and functionality and were associated with clinical outcome of melanoma patients. Higher proportions of DCIR-, DEC205-, CLEC-12α-expressing cDCs were linked with a better survival, whereas elevated proportions of CD206-, Dectin1-expressing cDCs and NKp44-expressing pDCs were associated with a poor outcome. Thus, melanoma tumor may shape DCs' features by exploiting the plasticity of the CLR machinery. Our study revealed that melanoma manipulates CLR pathways to hijack DC subsets and escape from immune control. It further paved the way to exploit glycan-lectin interactions for the design of innovative therapeutic strategies, which exploit DCs' potentialities while avoiding hijacking by tumor, to properly reshape anti-tumor immunity by manipulating the CLR machinery.

Dysfunctional BTN3A together with deregulated immune checkpoints and type I/II IFN dictate defective interplay between pDCs and γδ T cells in melanoma patients, which impacts clinical outcomes.

OBJECTIVES: pDCs and γδ T cells emerge as potent immune players participating in the pathophysiology of cancers, yet still remaining enigmatic while harbouring a promising potential for clinical translations. Despite strategic and closed missions, crosstalk between pDCs and γδ T cells has not been deciphered yet in cancers, especially in melanoma where the long-term control of the tumor still remains a challenge. METHODS: This prompted us to explore the interplay between pDCs and γδ T cells in the context of melanoma, investigating the reciprocal features of pDCs or γδ T cells, the underlying molecular mechanisms and its impact on clinical outcomes. RESULTS: TLRL-activated pDCs from the blood and tumor infiltrate of melanoma patients displayed an impaired ability to activate, to modulate immune checkpoints and trigger the functionality of γδ T cells. Conversely, γδ T cells from the blood or tumor infiltrate of melanoma patients activated by PAg were defective in triggering pDCs' activation and modulation of immune checkpoints, and failed to elicit the functionality of pDCs. Reversion of the dysfunctional cross-talks could be achieved by specific cytokine administration and immune checkpoint targeting. Strikingly, we revealed an increased expression of BTN3A on circulating and tumor-infiltrating pDCs and γδ T cells from melanoma patients, but stressed out the potential impairment of this molecule. CONCLUSION: Our study uncovered that melanoma hijacked the bidirectional interplay between pDCs and γδ T cells to escape from immune control, and revealed BTN3A dysfunction. Such understanding will help harness and synergise the power of these potent immune cells to design new therapeutic approaches exploiting their antitumor potential while counteracting their skewing by tumors to improve patient outcomes.