Skin dendritic cells in melanoma are key for successful checkpoint blockade therapy

FLT3LG modulates the infiltration of immune cells and enhances the efficacy of anti-PD-1 therapy in lung adenocarcinoma

BACKGROUND

Immunotherapy, particularly anti-PD-1 therapy, has assumed a progressively significant position in the management of non-small cell lung cancer (NSCLC), especially in lung adenocarcinoma (LUAD). Nevertheless, a subset of patients exhibit resistance to anti-PD-1 therapy, and the exploration of biomarkers for evaluating the responsiveness to anti-PD-1 therapy necessitates further investigation. FLT3LG is regarded as being associated with tumor diagnosis and immunotherapy in a variety of tumor types, but its function in LUAD is uncertain.

METHODS

Bioinformatics analysis was conducted to evaluate the clinical value, functional enrichment, genetic correlation, and immune infiltration of FLT3LG in LUAD. We then used a mouse model to detect immune cell infiltration and relevant protein expression by flow cytometry and immunohistochemistry under anti-PD-1 treatment after overexpression of FLT3LG. The serum FLT3LG expression in LUAD patients was detected via ELISA, and PD-L1 expression in tumor samples was detected by immunohistochemistry.

RESULTS

In LUAD patients, a better prognosis is associated with elevated FLT3LG expression. Among the genes strongly associated with FLT3LG, the majority were involved in immune-related processes and were enriched predominantly in immune-related pathways. Moreover, high expression of FLT3LG was significantly positively correlated with increased infiltration of multiple immune cells, including T cells and natural killer (NK) cells, in lung adenocarcinomas, as well as the expression of several immune cell markers, such as CD4 and CD8a. In a mouse model, overexpression of FLT3LG in mice subjected to subcutaneous graft tumor elicited a pronounced immune response and could enhance the efficacy of anti-PD-1 therapy.

CONCLUSION

FLT3LG could be considered as a diagnostic and prognostic marker for LUAD and might play a role in enhancing the therapeutic response to immunotherapy in patients with LUAD.

Immunomodulation on tumor immune microenvironment in acquired targeted therapy resistance and implication for immunotherapy resistance

The emergence of molecularly targeted therapies and immunotherapies has revolutionized cancer treatment, yet the optimal sequencing of these modalities remains debated. While targeted therapies often induce initial immunostimulatory effects, the development of resistance is accompanied by dynamic alterations in the tumor-immune microenvironment. These changes can promote tumor growth, hinder immune surveillance, and contribute to subsequent immunotherapy resistance. This review focuses on solid tumors and summarizes the immunomodulatory effects arising in the context of targeted therapy resistance, highlighting the challenges they pose for the subsequent immunotherapy efficacy.

Tissue-specific properties of type 1 dendritic cells in lung cancer: implications for immunotherapy

Checkpoint inhibitors have led to remarkable benefits in non-small cell lung cancer (NSCLC), yet response rates remain below expectations. High-dimensional analysis and mechanistic experiments in clinical samples and relevant NSCLC models uncovered the immune composition of lung cancer tissues, providing invaluable insights into the functional properties of tumor-infiltrating T cells and myeloid cells. Among myeloid cells, type 1 conventional dendritic cells (cDC1s) stand out for their unique ability to induce effector CD8 T cells against neoantigens and coordinate antitumoral immunity. Notably, lung resident cDC1 are particularly abundant and long-lived and express a unique tissue-specific gene program, underscoring their central role in lung immunity. Here, we discuss recent insights on the induction and regulation of antitumoral T cell responses in lung cancer, separating it from the tissue-agnostic knowledge generated from heterogeneous tumor models. We focus on the most recent studies dissecting functional states and spatial distribution of lung cDC1 across tumor stages and their impact on T cell responses to neoantigens. Finally, we highlight relevant gaps and emerging strategies to harness lung cDC1 immunostimulatory potential.

Guidelines for preparation and flow cytometry analysis of human nonlymphoid tissue DC

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs, and various nonlymphoid tissues. Within this article, detailed protocols are presented that allow for the generation of single-cell suspensions from human nonlymphoid tissues including lung, skin, gingiva, intestine as well as from tumors and tumor-draining lymph nodes with a subsequent analysis of dendritic cells by flow cytometry. Further, prepared single-cell suspensions can be subjected to other applications including cellular enrichment procedures, RNA sequencing, functional assays, etc. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists.

Identification of a novel DEC-205 binding peptide to develop dendritic cell-targeting nanovaccine for cancer immunotherapy

Cancer vaccine is regarded as an effective immunotherapy approach mediated by dendritic cells (DCs) which are crucial for antigen presentation and the initiation of adaptive immune responses. However, lack of DC-targeting properties significantly hampers the efficacy of cancer vaccines. Here, by using the phage display technique, peptides targeting the endocytic receptor DEC-205 primarily found on cDC1s were initially screened. An optimized hydrolysis-resistant peptide, hr-8, was identified and conjugated to PLGA-loaded antigen (Ag) and CpG adjuvant nanoparticles, resulting in a DC-targeting nanovaccine. The nanovaccine hr-8-PLGA@Ag/CpG facilitates dendritic cell maturation and improves antigen cross-presentation. The nanovaccine can enhance the antitumor immune response mediated by CD8+ T cells by encapsulating the nanovaccine with either exogenous OVA protein antigen or endogenous gp100/E7 antigenic peptide. As a result, strong antitumor effects are observed in both anti-PD-1 responsive B16-OVA and anti-PD-1 non-responsive B16 and TC1 immunocompetent tumor models. In summary, this study presents the initial documentation of a nanovaccine that targets dendritic cells via the novel DEC-205 binding peptide. This approach offers a new method for developing cancer vaccines that can potentially improve the effectiveness of cancer immunotherapy.

Innate Immune Cells in Melanoma: Implications for Immunotherapy

The innate immune system, composed of neutrophils, basophils, eosinophils, myeloid-derived suppressor cells (MDSCs), macrophages, dendritic cells (DCs), mast cells (MCs), and innate lymphoid cells (ILCs), is the first line of defense. Growing evidence demonstrates the crucial role of innate immunity in tumor initiation and progression. Several studies support the idea that innate immunity, through the release of pro- and/or anti-inflammatory cytokines and tumor growth factors, plays a significant role in the pathogenesis, progression, and prognosis of cutaneous malignant melanoma (MM). Cutaneous melanoma is the most common skin cancer, with an incidence that rapidly increased in recent decades. Melanoma is a highly immunogenic tumor, due to its high mutational burden. The metastatic form retains a high mortality. The advent of immunotherapy revolutionized the therapeutic approach to this tumor and significantly ameliorated the patients' clinical outcome. In this review, we will recapitulate the multiple roles of innate immune cells in melanoma and the related implications for immunotherapy.

Genomics and proteomics to determine novel molecular subtypes and predict the response to immunotherapy and the effect of bevacizumab in glioblastoma

Glioblastoma (GBM) is a highly aggressive, infiltrative malignancy that cannot be completely cured by current treatment modalities, and therefore requires more precise molecular subtype signatures to predict treatment response for personalized precision therapy. Expression subtypes of GBM samples from the Cancer Genome Atlas (TCGA) were identified using BayesNM and compared with existing molecular subtypes of GBM. Biological features of the subtypes were determined by single-sample gene set enrichment analysis. Genomic and proteomic data from GBM samples were combined and Genomic Identification of Significant Targets in Cancer analysis was used to screen genes with recurrent somatic copy-number alterations phenomenon. The immune environment among subtypes was compared by assessing the expression of immune molecules and the infiltration of immune cells. Molecular subtypes adapted to immunotherapy were identified based on Tumor Immune Dysfunction and Exclusion (TIDE) score. Finally, least absolute shrinkage and selection operator (LASSO) logistic regression was performed on the expression profiles of S2, S3 and S4 in TCGA-GBM and RPPA to determine the respective corresponding best predictive model. Four novel molecular subtypes were classified. Specifically, S1 exhibited a low proliferative profile; S2 exhibited the profile of high proliferation, IDH1 mutation, TP53 mutation and deletion; S3 was characterized by high immune scores, innate immunity and adaptive immune infiltration scores, with the lowest TIDE score and was most likely to benefit from immunotherapy; S4 was characterized by high proliferation, EGFR amplification, and high protein abundance, and was the most suitable subtype for bevacizumab. LASSO analysis constructed the best prediction model composed of 13 genes in S2 with an accuracy of 96.7%, and the prediction model consisting of 17 genes in S3 with an accuracy of 86.7%, and screened 14 genes as components of the best prediction model in S4 with an accuracy of 93%. To conclude, our study classified reproducible and robust molecular subtypes of GBM, and these findings might contribute to the identification of patients responding to immunotherapy, thereby improving GBM prognosis.

Development of Personalized Strategies for Precisely Battling Malignant Melanoma

Melanoma is the most severe and fatal form of skin cancer, resulting from multiple gene mutations with high intra-tumor and inter-tumor molecular heterogeneity. Treatment options for patients whose disease has progressed beyond the ability for surgical resection rely on currently accepted standard therapies, notably immune checkpoint inhibitors and targeted therapies. Acquired resistance to these therapies and treatment-associated toxicity necessitate exploring novel strategies, especially those that can be personalized for specific patients and/or populations. Here, we review the current landscape and progress of standard therapies and explore what personalized oncology techniques may entail in the scope of melanoma. Our purpose is to provide an up-to-date summary of the tools at our disposal that work to circumvent the common barriers faced when battling melanoma.

Allogeneic NK cells induce the in vitro activation of monocyte-derived and conventional type-2 dendritic cells and trigger an inflammatory response under cancer-associated conditions

Natural killer (NK) cells are innate lymphocytes capable to recognize and kill virus-infected and cancer cells. In the past years, the use of allogeneic NK cells as anti-cancer therapy gained interest due to their ability to induce graft-versus-cancer responses without causing graft-versus-host disease and multiple protocols have been developed to produce high numbers of activated NK cells. While the ability of these cells to mediate tumor kill has been extensively studied, less is known about their capacity to influence the activity of other immune cells that may contribute to a concerted anti-tumor response in the tumor microenvironment (TME). In this study, we analyzed how an allogeneic off-the-shelf cord blood stem cell-derived NK-cell product influenced the activation of dendritic cells (DC). Crosstalk between NK cells and healthy donor monocyte-derived DC (MoDC) resulted in the release of IFNγ and TNF, MoDC activation, and the release of the T-cell-recruiting chemokines CXCL9 and CXCL10. Moreover, in the presence of prostaglandin-E2, NK cell/MoDC crosstalk antagonized the detrimental effect of IL-10 on MoDC maturation leading to higher expression of multiple (co-)stimulatory markers. The NK cells also induced activation of conventional DC2 (cDC2) and CD8+ T cells, and the release of TNF, GM-CSF, and CXCL9/10 in peripheral blood mononuclear cells of patients with metastatic colorectal cancer. The activated phenotype of MoDC/cDC2 and the increased release of pro-inflammatory cytokines and T-cell-recruiting chemokines resulting from NK cell/DC crosstalk should contribute to a more inflamed TME and may thus enhance the efficacy of T-cell-based therapies.

Tumor-targeted therapy with BRAF-inhibitor recruits activated dendritic cells to promote tumor immunity in melanoma

BACKGROUND

Tumor-targeted therapy causes impressive tumor regression, but the emergence of resistance limits long-term survival benefits in patients. Little information is available on the role of the myeloid cell network, especially dendritic cells (DC) during tumor-targeted therapy.

METHODS

Here, we investigated therapy-mediated immunological alterations in the tumor microenvironment (TME) and tumor-draining lymph nodes (LN) in the D4M.3A preclinical melanoma mouse model (harboring the V-Raf murine sarcoma viral oncogene homolog B (BRAF)V600E mutation) by using high-dimensional multicolor flow cytometry in combination with multiplex immunohistochemistry. This was complemented with RNA sequencing and cytokine quantification to characterize the immune status of the tumors. The importance of T cells during tumor-targeted therapy was investigated by depleting CD4+ or CD8+ T cells in tumor-bearing mice. Tumor antigen-specific T-cell responses were characterized by performing in vivo T-cell proliferation assays and the contribution of conventional type 1 DC (cDC1) to T-cell immunity during tumor-targeted therapy was assessed using Batf3-/- mice lacking cDC1.

RESULTS

Our findings reveal that BRAF-inhibitor therapy increased tumor immunogenicity, reflected by an upregulation of genes associated with immune activation. The T cell-inflamed TME contained higher numbers of activated cDC1 and cDC2 but also inflammatory CCR2-expressing monocytes. At the same time, tumor-targeted therapy enhanced the frequency of migratory, activated DC subsets in tumor-draining LN. Even more, we identified a cDC2 population expressing the Fc gamma receptor I (FcγRI)/CD64 in tumors and LN that displayed high levels of CD40 and CCR7 indicating involvement in T cell-mediated tumor immunity. The importance of cDC2 is underlined by just a partial loss of therapy response in a cDC1-deficient mouse model. Both CD4+ and CD8+ T cells were essential for therapy response as their respective depletion impaired therapy success. On resistance development, the tumors reverted to an immunologically inert state with a loss of DC and inflammatory monocytes together with the accumulation of regulatory T cells. Moreover, tumor antigen-specific CD8+ T cells were compromised in proliferation and interferon-γ-production.

CONCLUSION

Our results give novel insights into the remodeling of the myeloid landscape by tumor-targeted therapy. We demonstrate that the transient immunogenic tumor milieu contains more activated DC. This knowledge has important implications for the development of future combinatorial therapies.

Oncolytic alphavirus replicons mediated recruitment and activation of T cells

Oncolytic viruses show promise in enhancing tumor immunogenicity by releasing immunogenic signals during tumor cell infection and lysis. In this study, we improved the virus-induced tumor immunogenicity of recombinant Semliki Forest virus (rSFV)-based replicon particles by encoding immunogenic cytokines such as C-X-C motif chemokine ligand 10 (CXCL10), FMS-like tyrosine kinase 3 ligand (Flt3L), or interferon-gamma (IFN-ƴ). Real-time imaging and flow cytometry of human cancer cell-based monolayer and spheroid cultures, using LNCaP or PANC-1 cells, revealed effective infection and transgene expression in both models. LNCaP cells exhibited higher and earlier rSFV infection compared to PANC-1 cells. While infected LNCaP cells effectively triggered immune recruitment and T cell activation even without encoding cytokines, PANC-1 cells demonstrated improved immune responses only when infected with replicons encoding cytokines, particularly IFN-ƴ, which enhanced tumor immunogenicity irrespective of cancer cell susceptibility to infection. Our study demonstrates that despite innate phenotypic disparities in cancer cells, rSFV-based replicons encoding cytokines can potentially generate effective immune responses in the tumor.

Dendritic cell-targeted therapy expands CD8 T cell responses to bona-fide neoantigens in lung tumors

Cross-presentation by type 1 DCs (cDC1) is critical to induce and sustain antitumoral CD8 T cell responses to model antigens, in various tumor settings. However, the impact of cross-presenting cDC1 and the potential of DC-based therapies in tumors carrying varied levels of bona-fide neoantigens (neoAgs) remain unclear. Here we develop a hypermutated model of non-small cell lung cancer in female mice, encoding genuine MHC-I neoepitopes to study neoAgs-specific CD8 T cell responses in spontaneous settings and upon Flt3L + αCD40 (DC-therapy). We find that cDC1 are required to generate broad CD8 responses against a range of diverse neoAgs. DC-therapy promotes immunogenicity of weaker neoAgs and strongly inhibits the growth of high tumor-mutational burden (TMB) tumors. In contrast, low TMB tumors respond poorly to DC-therapy, generating mild CD8 T cell responses that are not sufficient to block progression. scRNA transcriptional analysis, immune profiling and functional assays unveil the changes induced by DC-therapy in lung tissues, which comprise accumulation of cDC1 with increased immunostimulatory properties and less exhausted effector CD8 T cells. We conclude that boosting cDC1 activity is critical to broaden the diversity of anti-tumoral CD8 T cell responses and to leverage neoAgs content for therapeutic advantage.

Conventional type 1 dendritic cells (cDC1) in cancer immunity

Cancer immunotherapy, alone or in combination with conventional therapies, has revolutionized the landscape of antineoplastic treatments, with dendritic cells (DC) emerging as key orchestrators of anti-tumor immune responses. Among the distinct DC subsets, conventional type 1 dendritic cells (cDC1) have gained prominence due to their unique ability to cross-present antigens and activate cytotoxic T lymphocytes. This review summarizes the distinctive characteristics of cDC1, their pivotal role in anticancer immunity, and the potential applications of cDC1-based strategies in immunotherapy.

Targeting the dendritic cell-T cell axis to develop effective immunotherapies for glioblastoma

Glioblastoma is an aggressive primary brain tumor that has seen few advances in treatments for over 20 years. In response to this desperate clinical need, multiple immunotherapy strategies are under development, including CAR-T cells, immune checkpoint inhibitors, oncolytic viruses and dendritic cell vaccines, although these approaches are yet to yield significant clinical benefit. Potential reasons for the lack of success so far include the immunosuppressive tumor microenvironment, the blood-brain barrier, and systemic changes to the immune system driven by both the tumor and its treatment. Furthermore, while T cells are essential effector cells for tumor control, dendritic cells play an equally important role in T cell activation, and emerging evidence suggests the dendritic cell compartment may be deeply compromised in glioblastoma patients. In this review, we describe the immunotherapy approaches currently under development for glioblastoma and the challenges faced, with a particular emphasis on the critical role of the dendritic cell-T cell axis. We suggest a number of strategies that could be used to boost dendritic cell number and function and propose that the use of these in combination with T cell-targeting strategies could lead to successful tumor control.

A Spontaneous Melanoma Mouse Model Applicable for a Longitudinal Chemotherapy and Immunotherapy Study

Mouse models that reflect human disorders provide invaluable tools for the translation of basic science discoveries to clinical therapies. However, many of these in vivo therapeutic studies are short term and do not accurately mimic patient conditions. In this study, we used a fully immunocompetent, transgenic mouse model, TGS, in which the spontaneous development of metastatic melanoma is driven by the ectopic expression of a normal neuronal receptor, mGluR1, as a model to assess longitudinal treatment response (up to 8 months) with an inhibitor of glutamatergic signaling, troriluzole, which is a prodrug of riluzole, plus an antibody against PD-1, an immune checkpoint inhibitor. Our results reveal a sex-biased treatment response that led to improved survival in troriluzole and/or anti-PD-1-treated male mice that correlated with differential CD8+ T cells and CD11b+ myeloid cell populations in the tumor-stromal interface, supporting the notion that this model is a responsive and tractable system for evaluating therapeutic regimens for melanoma in an immunocompetent setting.

Circulating extracellular vesicles are monitoring biomarkers of anti-PD1 response and enhancer of tumor progression and immunosuppression in metastatic melanoma

BACKGROUND

Clinical drawback in checkpoint inhibitors immunotherapy (ICI) of metastatic melanoma (MM) is monitoring clinical benefit. Soluble forms of PD1(sPD1) and PD-L1(sPD-L1) and extracellular vesicles (EVs) expressing PD1 and PD-L1 have recently emerged as predictive biomarkers of response. As factors released in the blood, EVs and soluble forms could be relevant in monitoring treatment efficacy and adaptive resistance to ICI.

METHODS

We used pre-therapy plasma samples of 110 MM patients and longitudinal samples of 46 patients. Elisa assay and flow cytometry (FCM) were used to measure sPD-L1 and sPD1 concentrations and the percentage of PD1+ EVs and PD-L1+ EVs, released from tumor and immune cells in patients subsets. Transwell assays were conducted to investigate the impact of EVs of each patient subset on MM cells invasion and interaction between tumor cells and macrophages or dendritic cells. Viability assays were performed to assess EVs effect on MM cells and organoids sensitivity to anti-PD1. FCM was used to investigate immunosuppressive markers in EVs and immune cells.

RESULTS

The concentrations of sPD1 and sPD-L1 in pre-treatment and longitudinal samples did not correlate with anti-PD1 response, instead only tumor-derived PD1+ EVs decreased in long responders while increased during disease progression in responders. Notably, we observed reduction of T cell derived EVs expressing LAG3+ and PD1+ in long responders and their increase in responders experiencing progression. By investigating the impact of EVs on disease progression, we found that those isolated from non-responders and from patients with progression disease accelerated tumor cells invasiveness and migration towards macrophages, while EVs of long responders reduced the metastatic potential of MM cells and neo-angiogenesis. Additionally, the EVs of non-responders and of progression disease patients subset reduced the sensitivity of MM cells and organoids of responder to anti-PD1 and the recruitment of dendritic cells, while the EVs of progression disease subset skewed macrophages to express higher level of PDL-1.

CONCLUSION

Collectively, we suggest that the detection of tumor-derived PD1 + EVs may represent a useful tool for monitoring the response to anti-PD1 and a role for EVs shed by tumor and immune cells in promoting tumor progression and immune dysfunction.

The Current State of Neoadjuvant Therapy in Resectable Advanced Stage Melanoma

The advent of effective immunotherapy and targeted therapy has significantly improved outcomes in advanced-stage resectable melanoma. Currently, the mainstay of treatment of malignant melanoma is surgery followed by adjuvant systemic therapies. However, recent studies have shown a potential role for neoadjuvant therapy in the treatment of advanced-stage resectable melanoma. Mechanistically, neoadjuvant immunotherapy may yield a more robust response than adjuvant immunotherapy, as the primary tumor serves as an antigen in this setting rather than only micrometastatic disease after the index procedure. Additionally, targeted therapy has been shown to yield effective neoadjuvant cytoreduction, and oncolytic viruses may also increase the immunogenicity of primary tumors. Effective neoadjuvant therapy may serve to decrease tumor size and thus reduce the extent of required surgery and thus morbidity. It also allows for assessment of pathologic response, facilitating prognostication as well as tailoring future therapy. The current literature consistently supports that neoadjuvant therapy, even as little as one dose, is associated with improved outcomes and is well-tolerated. Some patients with a complete pathological response may even avoid surgery completely. These results challenge the current paradigm of a surgery-first approach and provide further evidence supporting neoadjuvant therapy in advanced-stage resectable melanoma. Further research into the optimal treatment schedule and dose timing is warranted, as is the continued investigation of novel therapies and combinations of therapies.

A 211At-labelled mGluR1 inhibitor induces cancer senescence to elicit long-lasting anti-tumor efficacy

Metabotropic glutamate receptor 1 (mGluR1), a key mediator of glutamatergic signaling, is frequently overexpressed in tumor cells and is an attractive drug target for most cancers. Here, we present a targeted radiopharmaceutical therapy strategy that antagonistically recognizes mGluR1 and eradicates mGluR1+ human tumors by harnessing a small-molecule alpha (α)-emitting radiopharmaceutical, 211At-AITM. A single dose of 211At-AITM (2.96 MBq) in mGluR1+ cancers exhibits long-lasting in vivo antitumor efficacy across seven subtypes of four of the most common tumors, namely, breast cancer, pancreatic cancer, melanoma, and colon cancers, with little toxicity. Moreover, complete regression of mGluR1+ breast cancer and pancreatic cancer is observed in approximate 50% of tumor-bearing mice. Mechanistically, the functions of 211At-AITM are uncovered in downregulating mGluR1 oncoprotein and inducing senescence of tumor cells with a reprogrammed senescence-associated secretory phenotype. Our findings suggest α-radiopharmaceutical therapy with 211At-AITM can be a useful strategy for mGluR1+ pan-cancers, regardless of their tissue of origin.

Treatment of melanoma with dendritic cell vaccines and immune checkpoint inhibitors: A mathematical modeling study

Dendritic cell (DC) vaccines and immune checkpoint inhibitors (ICIs) play critical roles in shaping the immune responses of tumor cells (TCs) and are widely used in cancer immunotherapies. Quantitatively evaluating the effectiveness of these therapies are essential for the optimization of treatment strategies. Here, based on the combined therapy of melanoma with DC vaccines and ICIs, we formulated a mathematical model to investigate the dynamic interactions between TCs and the immune system and understand the underlying mechanisms of immunotherapy. First, we obtained a threshold parameter for the growth of TCs, which is given by the ratio of spontaneous proliferation to immune inhibition. Next, we proved the existence and locally asymptotic stability of steady states of tumor-free, tumor-dominant, and tumor-immune coexistent equilibrium, and identified the existence of Hopf bifurcation of the proposed model. Furthermore, global sensitivity analysis showed that the growth of TCs strongly correlates with the injection rate of DC vaccines, the activation rate of CTLs, and the killing rate of TCs. Finally, we tested the efficacy of multiple monotherapies and combined therapies with model simulations. Our results indicate that DC vaccines can decelerate the growth of TCs, and ICIs can inhibit the growth of TCs. Besides, both therapies can prolong the lifetime of patients, and the combined therapy of DC vaccines and ICIs can effectively eradicate TCs.

Programmed cell death-1 blockade therapy in melanoma: Resistance mechanisms and combination strategies

Melanoma is a highly aggressive tumor derived from melanocytes. In recent years, the incidence and mortality of melanoma have gradually increased, seriously threatening human health. Classic treatments like surgery, chemotherapy, and radiotherapy show very limited efficacy. Due to the high immunogenicity of melanoma cells, immune checkpoint inhibitors have received considerable attention as melanoma treatments. One such therapy is blockade of programmed cell death-1 (PD-1), which is one of the most important negative immune regulators and is mainly expressed on activated T cells. Disruption of the interactions between PD-1 and its ligands, programmed death-ligand 1 (PD-L1) or programmed death-ligand 2 (PD-L2) rejuvenates exhausted T cells and enhances antitumor immunity. Although PD-1 blockade therapy is widely used in melanoma, a substantial proportion of patients still show no response or short durations of remission. Recent researches have focused on revealing the underlying mechanisms for resistance to this treatment and improving its efficacy through combination therapy. Here, we will introduce the resistance mechanisms associated with PD-1 blockade therapy in melanoma and review the combination therapies available.

Acral Melanoma Is Infiltrated with cDC1s and Functional Exhausted CD8 T Cells Similar to the Cutaneous Melanoma of Sun-Exposed Skin

Acral melanoma (AM) is the most common melanoma in non-Caucasian populations, yet it remains largely understudied. As AM lacks the UV-radiation mutational signatures that characterize other cutaneous melanomas, it is considered devoid of immunogenicity and is rarely included in clinical trials assessing novel immunotherapeutic regimes aiming to recover the antitumor function of immune cells. We studied a Mexican cohort of melanoma patients from the Mexican Institute of Social Security (IMSS) (n = 38) and found an overrepresentation of AM (73.9%). We developed a multiparametric immunofluorescence technique coupled with a machine learning image analysis to evaluate the presence of conventional type 1 dendritic cells (cDC1) and CD8 T cells in the stroma of melanoma, two of the most relevant immune cell types for antitumor responses. We observed that both cell types infiltrate AM at similar and even higher levels than other cutaneous melanomas. Both melanoma types harbored programmed cell death protein 1 (PD-1+) CD8 T cells and PD-1 ligand (PD-L1+) cDC1s. Despite this, CD8 T cells appeared to preserve their effector function and expanding capacity as they expressed interferon-γ (IFN-γ) and KI-67. The density of cDC1s and CD8 T cells significantly decreased in advanced stage III and IV melanomas, supporting these cells' capacity to control tumor progression. These data also argue that AM could respond to anti-PD-1-PD-L1 immunotherapy.

Tissue Biomarkers Predicting Lymph Node Status in Cutaneous Melanoma

Cutaneous melanoma is a severe neoplasm that shows early invasiveness of the lymph nodes draining the primary site, with increased risk of distant metastases and recurrence. The tissue biomarker identification could be a new frontier to predict the risk of early lymph node invasiveness, especially in cases considered by current guidelines to be at low risk of lymph node involvement and not requiring evaluation of the sentinel lymph node (SLN). For this reason, we present a narrative review of the literature, seeking to provide an overview of current tissue biomarkers, particularly vascular endothelium growth factors (VEGF), Tetraspanin CD9, lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), D2-40, and gene expression profile test (31-GEP). Among these, 31-GEP seems to be able to provide a distinction between low or high risk for positive SLN classes. VEGF receptor-3 and CD9 expression may be independent predictors of positive SLN. Lastly, LYVE-1 and D2-40 allow an easier assessment of lymph vascular invasion, which can be considered a good predictor of SLN status. In conclusion, biomarkers to assess the lymph node status of cutaneous melanoma patients may play an important role in those cases where the clinician is in doubt whether or not to perform SLN biopsy.

The expression pattern of pyroptosis-related genes predicts the prognosis and drug response of melanoma

Cutaneous melanoma (CM, hereafter referred to as melanoma) is a highly malignant tumor that typically undergoes early metastasis. Pyroptosis, as a special programmed cell death process that releases inflammatory factors and has been widely studied in tumors, but its role in melanoma has not been fully elucidated. In this study, we examined the relationship between pyroptosis and the prognosis of melanoma through bioinformatic analysis of RNA-sequencing data. Our results demonstrated that pyroptosis is a protective factor associated with melanoma prognosis. A higher pyroptosis score was associated with a more favorable overall survival. We used weighted gene co-expression networks analysis (WGCNA) to establish an effective prognosis model based on 12 pyroptosis-related genes. We then validated it in two independent cohorts. Furthermore, a nomogram combining clinicopathological characteristics and a pyroptosis-related gene signature (PGS) score was designed to effectively evaluate the prognosis of melanoma. Additionally, we analyzed the potential roles of pyroptosis in the tumor immune microenvironment and drug response. Interestingly, we found that the elevated infiltration of multiple immune cells, such as CD4⁺ T cells, CD8⁺ T cells, dendritic cells, and M1 macrophages, may be associated with the occurrence of pyroptosis. Pyroptosis was also related to a better response of melanoma to interferon-α, paclitaxel, cisplatin and imatinib. Through Spearman correlation analysis of the 12 pyroptosis-related genes and 135 chemotherapeutic agents in the Genomics of Drug Sensitivity in Cancer database, we identified solute carrier family 31 member 2 (SLC31A2) and collagen type 4 alpha 5 chain (COL4A5) as being associated with resistance to most of these drugs. In conclusion, this PGS is an effective and novelty prognostic indicator in melanoma, and also has an association with the melanoma immune microenvironment and melanoma treatment decision-making.

Local delivery of low-dose anti–CTLA-4 to the melanoma lymphatic basin leads to systemic T reg reduction and effector T cell activation

Preclinical studies show that locoregional CTLA-4 blockade is equally effective in inducing tumor eradication as systemic delivery, without the added risk of immune-related side effects. This efficacy is related to access of the CTLA-4 blocking antibodies to tumor-draining lymph nodes (TDLNs). Local delivery of anti–CTLA-4 after surgical removal of primary melanoma, before sentinel lymph node biopsy (SLNB), provides a unique setting to clinically assess the role of TDLN in the biological efficacy of locoregional CTLA-4 blockade. Here, we have evaluated the safety, tolerability, and immunomodulatory effects in the SLN and peripheral blood of a single dose of tremelimumab [a fully human immunoglobulin gamma-2 (IgG2) mAb directed against CTLA-4] in a dose range of 2 to 20 mg, injected intradermally at the tumor excision site 1 week before SLNB in 13 patients with early-stage melanoma (phase 1 trial; NCT04274816). Intradermal delivery was safe and well tolerated and induced activation of migratory dendritic cell (DC) subsets in the SLN. It also induced profound and durable decreases in regulatory T cell (T reg ) frequencies and activation of effector T cells in both SLN and peripheral blood. Moreover, systemic T cell responses against NY-ESO-1 or MART-1 were primed or boosted ( N = 7), in association with T cell activation and central memory T cell differentiation. These findings indicate that local administration of anti–CTLA-4 may offer a safe and promising adjuvant treatment strategy for patients with early-stage melanoma. Moreover, our data demonstrate a central role for TDLN in the biological efficacy of CTLA-4 blockade and support TDLN-targeted delivery methods.

Tetraspanin CD9 Expression Predicts Sentinel Node Status in Patients with Cutaneous Melanoma

The tetraspanin CD9 is considered a metastasis suppressor in many cancers, however its role is highly debated. Currently, little is known about CD9 prognostic value in cutaneous melanoma. Our aim was to analyse CD9 expression in melanocytic nevi and primary cutaneous melanomas through immunohistochemistry and immunofluorescence approaches to determine its correlation with invasiveness and metastatic potential. CD9 displayed homogeneous staining in all melanocytic nevi. In contrast, it showed a complete loss of reactivity in all thin melanomas. Interestingly, CD9 was re-expressed in 46% of intermediate and thick melanomas in small tumor clusters predominantly located at sites of invasion near or inside the blood or lymphatic vessels. The most notable finding is that all CD9 stained melanomas presented sentinel node positivity. Additionally, a direct association between CD9 expression and presence of distant metastasis was reported. Finally, we confirm that CD9 expression is consistent with an early protective role against tumorigenesis, however, our data endorse in melanoma a specific function of CD9 in vascular dissemination during late tumor progression. The presence of CD9 hotspots could be essential for melanoma cell invasion in lymphatic and endothelial vessels. CD9 could be a valid prognostic factor for lymph node metastasis risk.

Integration of immune and hypoxia gene signatures improves the prediction of radiosensitivity in breast cancer

Immunity and hypoxia are two important factors that affect the response of cancer patients to radiotherapy. At the same time, considering the limited predictive value of a single predictive model and the uncertainty of grouping patients near the cutoff value, we developed and validated a combined model based on immune- and hypoxia-related gene expression profiles to predict the radiosensitivity of breast cancer patients. This study was based on breast cancer data from The Cancer Genome Atlas (TCGA). Spike-and-slab Lasso regression analysis was performed to select three immune-related genes and develop a radiosensitivity model. Lasso Cox regression modeling selected 11 hypoxia-related genes for development of radiosensitivity model. Three independent datasets (Molecular Taxonomy of Breast Cancer International Consortium [METABRIC], E-TABM-158, GSE103746) were used to validate the predictive value of radiosensitivity signatures. In the TCGA dataset, the 10-year survival probabilities of the immune radioresistant (IRR) and hypoxia radioresistant (HRR) groups were 0.189 (0.037, 0.973) and 0.477 (0.293, 0.776), respectively. The 10-year survival probabilities of the immune radiosensitive (IRS) and hypoxia radiosensitive (HRS) groups were 0.778 (0.676, 0.895) and 0.824 (0.723, 0.939), respectively. Based on these two gene signatures, we further constructed a combined model and divided all patients into three groups (IRS/HRS, mixed, IRR/HRR). We identified the IRS/HRS patients most likely to benefit from radiotherapy; the 10-year survival probability was 0.886 (0.806, 0.976). The 10-year survival probability of the IRR/HRR group was 0. In conclusion, a combined model integrating immune- and hypoxia-related gene signatures could effectively predict the radiosensitivity of breast cancer and more accurately identify radiosensitive and radioresistant patients than a single model.

New Therapeutic Approaches for Conjunctival Melanoma-What We Know So Far and Where Therapy Is Potentially Heading: Focus on Lymphatic Vessels and Dendritic Cells

Conjunctival melanoma (CM) accounts for 5% of all ocular melanomas and arises from malignantly transformed melanocytes in the conjunctival epithelium. Current therapies using surgical excision in combination with chemo- or cryotherapy still have high rates for recurrences and metastatic disease. Lately, novel signal transduction-targeted and immune checkpoint inhibitors like cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, programmed cell death protein-1 (PD-1) receptor inhibitors, BRAF- or MEK-inhibitors for systemic treatment of melanoma have improved the outcome even for unresectable cutaneous melanoma, improving patient survival dramatically. The use of these therapies is now also recommended for CM; however, the immunological background of CM is barely known, underlining the need for research to better understand the immunological basics when treating CM patients with immunomodulatory therapies. Immune checkpoint inhibitors activate tumor defense by interrupting inhibitory interactions between tumor cells and T lymphocytes at the so-called checkpoints. The tumor cells exploit these inhibitory targets on T-cells that are usually used by dendritic cells (DCs). DCs are antigen-presenting cells at the forefront of immune response induction. They contribute to immune tolerance and immune defense but in the case of tumor development, immune tolerance is often prevalent. Enhancing the immune response via DCs, interfering with the lymphatic pathways during immune cell migration and tumor development and specifically targeting tumor cells is a major therapeutic opportunity for many tumor entities including CM. This review summarizes the current knowledge on the function of lymphatic vessels in tumor growth and immune cell transport and continues to compare DC subsets in CM with related melanomas, such as cutaneous melanoma and mucosal melanoma.

The Microenvironment's Role in Mycosis Fungoides and Sézary Syndrome: From Progression to Therapeutic Implications

BACKGROUND

Mycosis fungoides (MF) and Sezary Syndrome (SS) are the most common cutaneous T-cell lymphomas. It has been hypothesized that the interaction between the immune system, cutaneous cells, and neoplastic elements may play a role in MF/SS pathogenesis and progression.

METHODS

This paper aims to revise in a narrative way our current knowledge of the microenvironment's role in MF/SS.

RESULTS AND CONCLUSIONS

Literature data support a possible implication of microenvironment cells in MF/SS pathogenesis and progression, opening up new therapeutic avenues.

Glutamatergic Signaling a Therapeutic Vulnerability in Melanoma

Like other cancers, melanomas are associated with the hyperactivation of two major cell signaling cascades, the MAPK and PI3K/AKT pathways. Both pathways are activated by numerous genes implicated in the development and progression of melanomas such as mutated BRAF, RAS, and NF1. Our lab was the first to identify yet another driver of melanoma, Metabotropic Glutamate Receptor 1 (protein: mGluR1, mouse gene: Grm1, human gene: GRM1), upstream of the MAPK and PI3K/AKT pathways. Binding of glutamate, the natural ligand of mGluR1, activates MAPK and PI3K/AKT pathways and sets in motion the deregulated cellular responses in cell growth, cell survival, and cell metastasis. In this review, we will assess the proposed modes of action that mediate the oncogenic properties of mGluR1 in melanoma and possible application of anti-glutamatergic signaling modulator(s) as therapeutic strategy for the treatment of melanomas.