Therapeutic regulation of myeloid-derived suppressor cells and immune response to cancer vaccine in patients with extensive stage small cell lung cancer

Toll-like receptor agonists as cancer vaccine adjuvants

Cancer immunotherapy has emerged as a promising strategy to treat cancer patients. Among the wide range of immunological approaches, cancer vaccines have been investigated to activate and expand tumor-reactive T cells. However, most cancer vaccines have not shown significant clinical benefit as monotherapies. This is likely due to the antigen targets of vaccines, "self" proteins to which there is tolerance, as well as to the immunosuppressive tumor microenvironment. To help circumvent immune tolerance and generate effective immune responses, adjuvants for cancer vaccines are necessary. One representative adjuvant family is Toll-Like receptor (TLR) agonists, synthetic molecules that stimulate TLRs. TLRs are the largest family of pattern recognition receptors (PRRs) that serve as the sensors of pathogens or cellular damage. They recognize conserved foreign molecules from pathogens or internal molecules from cellular damage and propel innate immune responses. When used with vaccines, activation of TLRs signals an innate damage response that can facilitate the development of a strong adaptive immune response against the target antigen. The ability of TLR agonists to modulate innate immune responses has positioned them to serve as adjuvants for vaccines targeting infectious diseases and cancers. This review provides a summary of various TLRs, including their expression patterns, their functions in the immune system, as well as their ligands and synthetic molecules developed as TLR agonists. In addition, it presents a comprehensive overview of recent strategies employing different TLR agonists as adjuvants in cancer vaccine development, both in pre-clinical models and ongoing clinical trials.

The interplay between the tumor microenvironment and tumor-derived small extracellular vesicles in cancer development and therapeutic response

The tumor microenvironment (TME) plays an essential role in tumor cell survival by profoundly influencing their proliferation, metastasis, immune evasion, and resistance to treatment. Extracellular vesicles (EVs) are small particles released by all cell types and often reflect the state of their parental cells and modulate other cells' functions through the various cargo they transport. Tumor-derived small EVs (TDSEVs) can transport specific proteins, nucleic acids and lipids tailored to propagate tumor signals and establish a favorable TME. Thus, the TME's biological characteristics can affect TDSEV heterogeneity, and this interplay can amplify tumor growth, dissemination, and resistance to therapy. This review discusses the interplay between TME and TDSEVs based on their biological characteristics and summarizes strategies for targeting cancer cells. Additionally, it reviews the current issues and challenges in this field to offer fresh insights into comprehending tumor development mechanisms and exploring innovative clinical applications.

Myeloid‑derived suppressor cells as targets of emerging therapies and nanotherapies (Review)

Breast cancer (BC) is the leading cause of cancer-related mortality among women worldwide. Immunotherapies are a promising approach in cancer treatment, particularly for aggressive forms of BC with high mortality rates. However, the current eligibility for immunotherapy remains limited to a limited fraction of patients with BC. Myeloid-derived suppressor cells (MDSCs), originating from myeloid cells, are known for their dual role in immunosuppression and tumor promotion, significantly affecting patient outcomes by fostering the formation of premetastatic niches. Consequently, targeting MDSCs has emerged as a promising avenue for further exploration in therapeutic interventions. Leveraging nanotechnology-based drug delivery systems, which excel in accumulating drugs within tumors via passive or active targeting mechanisms, are a promising strategy for the use of MDSCs in the treatment of BC. The present review discusses the immunosuppressive functions of MDSCs, their role in BC, and the diverse strategies for targeting them in cancer therapy. Additionally, the present review discusses future advancements in BC treatments focusing on MDSCs. Furthermore, it elucidates the mechanisms underlying MDSC activation, recruitment and differentiation in BC progression, highlighting the clinical characteristics that render MDSCs suitable candidates for the therapy and targeted nanotherapy of BC.

Emerging advances in defining the molecular and therapeutic landscape of small-cell lung cancer

Small-cell lung cancer (SCLC) has traditionally been considered a recalcitrant cancer with a dismal prognosis, with only modest advances in therapeutic strategies over the past several decades. Comprehensive genomic assessments of SCLC have revealed that most of these tumours harbour deletions of the tumour-suppressor genes TP53 and RB1 but, in contrast to non-small-cell lung cancer, have failed to identify targetable alterations. The expression status of four transcription factors with key roles in SCLC pathogenesis defines distinct molecular subtypes of the disease, potentially enabling specific therapeutic approaches. Overexpression and amplification of MYC paralogues also affect the biology and therapeutic vulnerabilities of SCLC. Several other attractive targets have emerged in the past few years, including inhibitors of DNA-damage-response pathways, epigenetic modifiers, antibody-drug conjugates and chimeric antigen receptor T cells. However, the rapid development of therapeutic resistance and lack of biomarkers for effective selection of patients with SCLC are ongoing challenges. Emerging single-cell RNA sequencing data are providing insights into the plasticity and intratumoural and intertumoural heterogeneity of SCLC that might be associated with therapeutic resistance. In this Review, we provide a comprehensive overview of the latest advances in genomic and transcriptomic characterization of SCLC with a particular focus on opportunities for translation into new therapeutic approaches to improve patient outcomes.

Polydopamine nanoparticles cross-linked hyaluronic acid photothermal hydrogel with cascading immunoinducible effects for in situ antitumor vaccination

Tumor vaccine, which can effectively prevent tumor recurrence and metastasis, is a promising tool in tumor immunotherapy. However, heterogeneity of tumors and the inability to achieve a cascade effect limit the therapeutic effects of most developing tumor vaccine. We have developed a cascading immunoinducible in-situ mannose-functionalized polydopamine loaded with imiquimod phenylboronic hyaluronic acid nanocomposite gel vaccine (M/P-PDA@IQ PHA) through a boronic ester-based reaction. This reaction utilizes mannose-functionalized polydopamine loaded with imiquimod (M/P-PDA@IQ NAs) as a cross-linking agent to react with phenylboronic-grafted hyaluronic acid. Under near-infrared light irradiation, the M/P-PDA@IQ PHA caused local hyperthermia to trigger immunogenic cell death of tumor cells and tumor-associated antigens (TAAs) releasing. Subsequently, the M/P-PDA@IQ NAs which were gradually released by the pH/ROS/GSH-triggered degradation of M/P-PDA@IQ PHA, could capture and deliver these TAAs to lymph nodes. Finally, the M/P-PDA@IQ NAs facilitated maturation and cross-presentation of dendritic cells, as well as activation of cytotoxic T lymphocytes. Overall, the M/P-PDA@IQ PHA could serve as a novel in situ vaccine to stimulate several key nodes including TAAs release and capture, targeting lymph nodes and enhanced dendritic cells uptake and maturation as well as T cells activation. This cascading immune activation strategy can effectively elicit antitumor immune response.

Neoantigen Identification and Dendritic Cell-Based Vaccines for Lung Cancer Immunotherapy

Immunotherapies can treat many cancers, including difficult-to-treat cases such as lung cancer. Due to its tolerability, long-lasting therapeutic responses, and efficacy in a wide spectrum of patients, immunotherapy can also help to treat lung cancer, which has few treatment choices. Tumor-specific antigens (TSAs) for cancer vaccinations and T-cell therapies are difficult to discover. Neoantigens (NeoAgs) from genetic mutations, irregular RNA splicing, protein changes, or viral genetic sequences in tumor cells provide a solution. NeoAgs, unlike TSAs, are non-self and can cause an immunological response. Next-generation sequencing (NGS) and bioinformatics can swiftly detect and forecast tumor-specific NeoAgs. Highly immunogenic NeoAgs provide personalized or generalized cancer immunotherapies. Dendritic cells (DCs), which originate and regulate T-cell responses, are widely studied potential immunotherapeutic therapies for lung cancer and other cancers. DC vaccines are stable, reliable, and safe in clinical trials. The purpose of this article is to evaluate the current status, limitations, and prospective clinical applications of DC vaccines, as well as the identification and selection of major histocompatibility complex (MHC) class I and II genes for NeoAgs. Our goal is to explain DC biology and activate DC manipulation to help researchers create extremely potent cancer vaccines for patients.

Signature Construction and Disulfidptosis-Related Molecular Cluster Identification for Better Prediction of Prognosis in Glioma

Disulfidptosis is a newly discovered form of regulatory cell death. However, the identification of disulfidptosis-related molecular subtypes and potential biomarkers in gliomas and their prognostic predictive potential need to be further elucidated. RNA sequencing profiles and the relevant clinical data were obtained from the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA). Disulfidptosis-related clusters were identified by unsupervised clustering analysis. Immune cell infiltration analysis and drug sensitivity analysis were used to explore the differences between clusters. Gene set enrichment analysis (GSEA) of differential genes between clusters was performed to explore the potential biological functions and signaling. A disulfidptosis-related scoring system (DRSS) was constructed based on a combined COX and LASSO analysis. Mendelian randomization (MR) analyses were used to further explore the causal relationship between levels of genes in DRSS and an increased risk of glioma. A prognosis nomogram was constructed based on the DRSS and 3 clinical features (age, WHO stage, and IDH status). The accuracy and stability of the prognosis nomogram were also validated in different cohorts. We identified two clusters that exhibited different prognoses, drug sensitivity profiles, and tumor microenvironment infiltration profiles. The overall survival (OS) of Cluster2 was significantly better than Cluster1. Cluster1 had an overall greater infiltration of immune cells compared to Cluster2. However, the Monocytes, activated B cells had higher infiltration abundance in Cluster2. GSEA results showed significant enrichment of immune-related biological processes in Cluster1, while Cluster2 was more enriched for functions related to neurotransmission and regulation. PER3, RAB34, NKX3-2, GPX7, FRA10AC1, and TGIF1 were finally included to construct DRSS. DRSS was independently related to prognosis. There was a significant difference in overall survival between the low-risk score group and the high-risk score group. Among six genes in DRSS, GPX7 levels were demonstrated to have a causal relationship with an increased risk of glioma. GPX7 may become a more promising biomarker for gliomas. The prognosis nomogram constructed based on the DRSS and three clinical features has considerable potential for predicting the prognosis of patients with glioma. Free online software for implementing this nomogram was established:  https://yekun-zhuang.shinyapps.io/DynNomapp/ . Our study established a novel glioma classification based on the disulfidptosis-related molecular subtypes. We constructed the DRSS and the prognosis nomogram to accurately stratify the prognosis of glioma patients. GPX7 was identified as a more promising biomarker for glioma. We provide important insights into the treatment and prognosis of gliomas.

Cellular and micro-environmental responses influencing the antitumor activity of all-trans retinoic acid in breast cancer

All-trans retinoic acid (ATRA) is the most relevant and functionally active metabolite of Vitamin-A. From a therapeutic standpoint, ATRA is the first example of pharmacological agent exerting its anti-tumor activity via a cell differentiating action. In the clinics, ATRA is used in the treatment of Acute Promyelocytic Leukemia, a rare form of myeloid leukemia with unprecedented therapeutic results. The extraordinary effectiveness of ATRA in the treatment of Acute Promyelocytic Leukemia patients has raised interest in evaluating the potential of this natural retinoid in the treatment of other types of neoplasias, with particular reference to solid tumors.The present article provides an overview of the available pre-clinical and clinical studies focussing on ATRA as a therapeutic agent in the context of breast cancer from a holistic point of view. In detail, we focus on the direct effects of ATRA in breast cancer cells as well as the underlying molecular mechanisms of action. In addition, we summarize the available information on the action exerted by ATRA on the breast cancer micro-environment, an emerging determinant of the progression and invasive behaviour of solid tumors. In particular we discuss the recent evidences of ATRA activity on the immune system. Finally, we analyse and discuss the results obtained with the few ATRA-based clinical trials conducted in the context of breast cancer.

Identification of tumor heterogeneity associated with KRAS/TP53 co-mutation status in lung adenocarcinoma based on single-cell RNA sequencing

Lung cancer stands as the predominant cause of cancer-related mortality globally. Lung adenocarcinoma (LUAD), being the most prevalent subtype, garners extensive attention due to its notable heterogeneity, which significantly influences tumor development and treatment approaches. This research leverages single-cell RNA sequencing (scRNA-seq) datasets to delve into the impact of KRAS/TP53 co-mutation status on LUAD. Moreover, utilizing the TCGA-LUAD dataset, we formulated a novel predictive risk model, comprising seven prognostic genes, through LASSO regression, and subjected it to both internal and external validation sets. The study underscores the profound impact of KRAS/TP53 co-mutational status on the tumor microenvironment (TME) of LUAD. Crucially, KRAS/TP53 co-mutation markedly influences the extent of B cell infiltration and various immune-related pathways within the TME. The newly developed predictive risk model exhibited robust performance across both internal and external validation sets, establishing itself as a viable independent prognostic factor. Additionally, in vitro experiments indicate that MELTF and PLEK2 can modulate the invasion and proliferation of human non-small cell lung cancer cells. In conclusion, we elucidated that KRAS/TP53 co-mutations may modulate TME and patient prognosis by orchestrating B cells and affiliated pathways. Furthermore, we spotlight that MELTF and PLEK2 not only function as prognostic indicators for LUAD, but also lay the foundation for the exploration of innovative therapeutic approaches.

Cell membrane-coated biomimetic nanomedicines: productive cancer theranostic tools

As the second-leading cause of human death, cancer has drawn attention in the area of biomedical research and therapy from all around the world. Certainly, the development of nanotechnology has made it possible for nanoparticles (NPs) to be used as a carrier for delivery systems in the treatment of tumors. This is a biomimetic approach established to craft remedial strategies comprising NPs cloaked with membrane obtained from various natural cells like blood cells, bacterial cells, cancer cells, etc. Here we conduct an in-depth exploration of cell membrane-coated NPs (CMNPs) and their extensive array of applications including drug delivery, vaccination, phototherapy, immunotherapy, MRI imaging, PET imaging, multimodal imaging, gene therapy and a combination of photothermal and chemotherapy. This review article provides a thorough summary of the most recent developments in the use of CMNPs for the diagnosis and treatment of cancer. It critically assesses the state of research while recognizing significant accomplishments and innovations. Additionally, it indicates ongoing problems in clinical translation and associated queries that warrant deeper research. By doing so, this study encourages creative thinking for future projects in the field of tumor therapy using CMNPs while also educating academics on the present status of CMNP research.

Tretinoin improves the anti-cancer response to cyclophosphamide, in a model-selective manner

BACKGROUND

Chemotherapy is included in treatment regimens for many solid cancers, but when administered as a single agent it is rarely curative. The addition of immune checkpoint therapy to standard chemotherapy regimens has improved response rates and increased survival in some cancers. However, most patients do not respond to treatment and immune checkpoint therapy can cause severe side effects. Therefore, there is a need for alternative immunomodulatory drugs that enhance chemotherapy.

METHODS

We used gene expression data from cyclophosphamide (CY) responders and non-responders to identify existing clinically approved drugs that could phenocopy a chemosensitive tumor microenvironment (TME), and tested combination treatments in multiple murine cancer models.

RESULTS

The vitamin A derivative tretinoin was the top predicted upstream regulator of response to CY. Tretinoin pre-treatment induced an inflammatory, interferon-associated TME, with increased infiltration of CD8 + T cells, sensitizing the tumor to subsequent chemotherapy. However, while combination treatment significantly improved survival and cure rate in a CD4+ and CD8+ T cell dependent manner in AB1-HA murine mesothelioma, this effect was model-selective, and could not be replicated using other cell lines.

CONCLUSIONS

Despite the promising data in one model, the inability to validate the efficacy of combination treatment in multiple cancer models deprioritizes tretinoin/cyclophosphamide combination therapy for clinical translation.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

A Photoactive Supramolecular Complex Targeting PD-L1 Reveals a Weak Correlation between Photoactivation Efficiency and Receptor Expression Levels in Non-Small-Cell Lung Cancer Tumor Models

Photo-immunotherapy uses antibodies conjugated to photosensitizers to produce nanostructured constructs endowed with targeting properties and photo-inactivation capabilities towards tumor cells. The superficial receptor density on cancer cells is considered a determining factor for the efficacy of the photodynamic treatment. In this work, we propose the use of a photoactive conjugate that consists of the clinical grade PD-L1-binding monoclonal antibody Atezolizumab, covalently linked to either the well-known photosensitizer eosin or the fluorescent probe Alexa647. Using single-molecule localization microscopy (direct stochastic optical reconstruction microscopy, dSTORM), and an anti-PD-L1 monoclonal antibody labelled with Alexa647, we quantified the density of PD-L1 receptors exposed on the cell surface in two human non-small-cell lung cancer lines (H322 and A549) expressing PD-L1 to a different level. We then investigated if this value correlates with the effectiveness of the photodynamic treatment. The photodynamic treatment of H322 and A549 with the photo-immunoconjugate demonstrated its potential for PDT treatments, but the efficacy did not correlate with the PD-L1 expression levels. Our results provide additional evidence that receptor density does not determine a priori the level of photo-induced cell death.

Exploiting innate immunity for cancer immunotherapy

Immunotherapies have revolutionized the treatment paradigms of various types of cancers. However, most of these immunomodulatory strategies focus on harnessing adaptive immunity, mainly by inhibiting immunosuppressive signaling with immune checkpoint blockade, or enhancing immunostimulatory signaling with bispecific T cell engager and chimeric antigen receptor (CAR)-T cell. Although these agents have already achieved great success, only a tiny percentage of patients could benefit from immunotherapies. Actually, immunotherapy efficacy is determined by multiple components in the tumor microenvironment beyond adaptive immunity. Cells from the innate arm of the immune system, such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, natural killer cells, and unconventional T cells, also participate in cancer immune evasion and surveillance. Considering that the innate arm is the cornerstone of the antitumor immune response, utilizing innate immunity provides potential therapeutic options for cancer control. Up to now, strategies exploiting innate immunity, such as agonists of stimulator of interferon genes, CAR-macrophage or -natural killer cell therapies, metabolic regulators, and novel immune checkpoint blockade, have exhibited potent antitumor activities in preclinical and clinical studies. Here, we summarize the latest insights into the potential roles of innate cells in antitumor immunity and discuss the advances in innate arm-targeted therapeutic strategies.

Shaping the tumor immune microenvironment of SCLC: Mechanisms, and opportunities for immunotherapy

Small-cell lung cancer (SCLC) is a very aggressive neuroendocrine tumor with a poor prognosis. Whereas immunotherapy has emerged as a promising approach for treating SCLC, its unique tumor immune microenvironment (TIME) might limit patient responses. To fully characterize the TIME and understand the mechanism of its formation with respect to SCLC is crucial. The recent rapid development of multi-omics technologies has rapidly advanced knowledge of TIME features and the regulatory mechanisms associated with SCLC. This review summarizes the TIME features of SCLC as well as shaping the TIME according to the genomics, epigenomics, and metabolomics of tumors. Future opportunities and challenges for immunotherapy are also discussed.

Regulation of T cells by myeloid-derived suppressor cells: emerging immunosuppressor in lung cancer

Myeloid-derived suppressor cells (MDSCs), major components maintaining the immune suppressive microenvironment in lung cancer, are relevant to the invasion, metastasis, and poor prognosis of lung cancer, through the regulation of epithelial-mesenchymal transition, remodeling of the immune microenvironment, and regulation of angiogenesis. MDSCs regulate T-cell immune functions by maintaining a strong immunosuppressive microenvironment and promoting tumor invasion. This raises the question of whether reversing the immunosuppressive effect of MDSCs on T cells can improve lung cancer treatment. To understand this further, this review explores the interactions and specific mechanisms of different MDSCs subsets, including regulatory T cells, T helper cells, CD8 + T cells, natural killer T cells, and exhausted T cells, as part of the lung cancer immune microenvironment. Second, it focuses on the guiding significance confirmed via clinical liquid biopsy and tissue biopsy that different MDSC subsets improve the prognosis of lung cancer. Finally, we conclude that targeting MDSCs through action targets or signaling pathways can help regulate T-cell immune functions and suppress T-cell exhaustion. In addition, immune checkpoint inhibitors targeting MDSCs may serve as a new approach for enhancing the efficiency of immunotherapy and targeted therapy for lung cancer in the future, providing better comprehensive options for lung cancer treatment.

Dendritic Cell Vaccination in Non-Small Cell Lung Cancer: Remodeling the Tumor Immune Microenvironment

Non-small-cell lung cancer (NSCLC) remains one of the leading causes of death worldwide. While NSCLCs possess antigens that can potentially elicit T cell responses, defective tumor antigen presentation and T cell activation hinder host anti-tumor immune responses. The NSCLC tumor microenvironment (TME) is composed of cellular and soluble mediators that can promote or combat tumor growth. The composition of the TME plays a critical role in promoting tumorigenesis and dictating anti-tumor immune responses to immunotherapy. Dendritic cells (DCs) are critical immune cells that activate anti-tumor T cell responses and sustain effector responses. DC vaccination is a promising cellular immunotherapy that has the potential to facilitate anti-tumor immune responses and transform the composition of the NSCLC TME via tumor antigen presentation and cell-cell communication. Here, we will review the features of the NSCLC TME with an emphasis on the immune cell phenotypes that directly interact with DCs. Additionally, we will summarize the major preclinical and clinical approaches for DC vaccine generation and examine how effective DC vaccination can transform the NSCLC TME toward a state of sustained anti-tumor immune signaling.

YTHDF2 inhibition potentiates radiotherapy antitumor efficacy

RNA N6-methyladenosine (m6A) modification is implicated in cancer progression. However, the impact of m6A on the antitumor effects of radiotherapy and the related mechanisms are unknown. Here we show that ionizing radiation (IR) induces immunosuppressive myeloid-derived suppressor cell (MDSC) expansion and YTHDF2 expression in both murine models and humans. Following IR, loss of Ythdf2 in myeloid cells augments antitumor immunity and overcomes tumor radioresistance by altering MDSC differentiation and inhibiting MDSC infiltration and suppressive function. The remodeling of the landscape of MDSC populations by local IR is reversed by Ythdf2 deficiency. IR-induced YTHDF2 expression relies on NF-κB signaling; YTHDF2 in turn leads to NF-κB activation by directly binding and degrading transcripts encoding negative regulators of NF-κB signaling, resulting in an IR-YTHDF2-NF-κB circuit. Pharmacological inhibition of YTHDF2 overcomes MDSC-induced immunosuppression and improves combined IR and/or anti-PD-L1 treatment. Thus, YTHDF2 is a promising target to improve radiotherapy (RT) and RT/immunotherapy combinations.

Cancer immune exclusion: breaking the barricade for a successful immunotherapy

Immunotherapy has changed the course of cancer treatment. The initial steps were made through tumor-specific antibodies that guided the setup of an antitumor immune response. A new and successful generation of antibodies are designed to target immune checkpoint molecules aimed to reinvigorate the antitumor immune response. The cellular counterpart is the adoptive cell therapy, where specific immune cells are expanded or engineered to target cancer cells. In all cases, the key for achieving positive clinical resolutions rests upon the access of immune cells to the tumor. In this review, we focus on how the tumor microenvironment architecture, including stromal cells, immunosuppressive cells and extracellular matrix, protects tumor cells from an immune attack leading to immunotherapy resistance, and on the available strategies to tackle immune evasion.

Here, There, and Everywhere: Myeloid-Derived Suppressor Cells in Immunology

Myeloid-derived suppressor cells (MDSCs) were initially identified in humans and mice with cancer where they profoundly suppress T cell- and NK cell-mediated antitumor immunity. Inflammation is a central feature of many pathologies and normal physiological conditions and is the dominant driving force for the accumulation and function of MDSCs. Therefore, MDSCs are present in conditions where inflammation is present. Although MDSCs are detrimental in cancer and conditions where cellular immunity is desirable, they are beneficial in settings where cellular immunity is hyperactive. Because MDSCs can be generated ex vivo, they are being exploited as therapeutic agents to reduce damaging cellular immunity. In this review, we discuss the detrimental and beneficial roles of MDSCs in disease settings such as bacterial, viral, and parasitic infections, sepsis, obesity, trauma, stress, autoimmunity, transplantation and graft-versus-host disease, and normal physiological settings, including pregnancy and neonates as well as aging. The impact of MDSCs on vaccination is also discussed.

Targeting MDSC Differentiation Using ATRA: A Phase I/II Clinical Trial Combining Pembrolizumab and All-Trans Retinoic Acid for Metastatic Melanoma

PURPOSE

A phase Ib/II clinical trial was conducted to evaluate the safety and efficacy of the combination of all-trans retinoic acid (ATRA) with pembrolizumab in patients with stage IV melanoma.

PATIENTS AND METHODS

Anti-PD-1 naïve patients with stage IV melanoma were treated with pembrolizumab plus supplemental ATRA for three days surrounding each of the first four pembrolizumab infusions. The primary objective was to establish the MTD and recommended phase II dose (RP2D) of the combination. The secondary objectives were to describe the safety and toxicity of the combined treatment and to assess antitumor activity in terms of (i) the reduction in circulating myeloid-derived suppressor cell (MDSC) frequency and (ii) progression-free survival (PFS).

RESULTS

Twenty-four patients were enrolled, 46% diagnosed with M1a and 29% with M1c stage disease at enrollment. All patients had an ECOG status ≤1, and 75% had received no prior therapies. The combination was well tolerated, with the most common ATRA-related adverse events being headache, fatigue, and nausea. The RP2D was established at 150 mg/m2 ATRA + 200 mg Q3W pembrolizumab. Median PFS was 20.3 months, and the overall response rate was 71%, with 50% of patients experiencing a complete response, and the 1-year overall survival was 80%. The combination effectively lowered the frequency of circulating MDSCs.

CONCLUSIONS

With a favorable tolerability and high response rate, this combination is a promising frontline treatment strategy for advanced melanoma. Targeting MDSCs remains an attractive mechanism to enhance the efficacy of immunotherapies, and this combination merits further investigation. See related commentary by Olson and Luke, p. 1167.

MDSCs in sepsis-induced immunosuppression and its potential therapeutic targets

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. In sepsis, a complicated immune response is initiated, which varies over time with sustained excessive inflammation and immunosuppression. Identifying a promising way to orchestrate sepsis-induced immunosuppression is a challenge. Myeloid-derived suppressor cells (MDSCs) comprise pathologically activated neutrophils and monocytes with potent immunosuppressive activity. They play an important part in inhibiting innate and adaptive immune responses, and have emerged as part of the immune response in sepsis. MDSCs numbers are persistently high in sepsis patients, and associated with nosocomial infections and other adverse clinical outcomes. However, their characteristics and functional mechanisms during sepsis have not been addressed fully. Our review sheds light on the features and suppressive mechanism of MDSCs. We also review the potential applications of MDSCs as biomarkers and targets for clinical treatment of sepsis.

The role of innate immune cells in the tumor microenvironment and research progress in anti-tumor therapy

Innate immune cells in the tumor microenvironment (TME) mainly include macrophages, neutrophils, natural killer cells, dendritic cells and bone marrow derived suppressor cells. They play an anti-tumor or pro-tumor role by secreting various cytokines, chemokines and other factors, and determine the occurrence and development of tumors. Comprehending the role of innate immune cells in tumorigenesis and progression can help improve therapeutic approaches targeting innate immune cells in the TME, increasing the likelihood of favorable prognosis. In this review, we discussed the cell biology of innate immune cells, their role in tumorigenesis and development, and the current status of innate immune cell-based immunotherapy, in order to provide an overview for future research lines and clinical trials.

Monitoring Blood Immune Cells in Patients with Advanced Small Cell Lung Cancer Undergoing a Combined Immune Checkpoint Inhibitor/Chemotherapy

In this exploratory prospective observational study on 40 small cell lung cancer (SCLC) patients treated with a combination of chemotherapy and immune checkpoint inhibitors, blood immune cells were characterized by multi-color flow cytometry at the baseline and at the third therapy cycle. The numbers of neutrophils and of T-, B-, and NK cells, as well as the frequency of HLA-DR^low monocytes, 6-SulfoLacNAc (slan)+ non-classical monocytes and circulating dendritic cell (DC) subtypes were determined. The prognostic value of the parameters was evaluated by the patient's survival analysis with overall survival (OS) as the primary endpoint. In addition, blood cell parameters from SCLC patients were compared to those from non-SCLC (NSCLC). The global median OS of patients was 10.4 ± 1.1 months. Disease progression (15% of patients) correlated with a higher baseline neutrophil/lymphocyte ratio (NLR), more HLA-DR^low monocytes, and lower NK cell and DC numbers. The risk factors for poor OS were the presence of brain/liver metastases, a baseline NLR ≥ 6.1, HLA-DR^low monocytes ≥ 21% of monocytes, slan+ non-classical monocytes < 0.12%, and/or CD1c+ myeloid DC < 0.05% of leukocytes. Lymphocytic subpopulations did not correlate with OS. When comparing biomarkers in SCLC versus NSCLC, SCLC had a higher frequency of brain/liver metastases, a higher NLR, the lowest DC frequencies, and lower NK cell numbers. Brain/liver metastases had a substantial impact on the survival of SCLC patients. At the baseline, 45% of SCLC patients, but only 24% of NSCLC patients, had between three and five risk factors. A high basal NLR, a high frequency of HLA-DR^low monocytes, and low levels of slan+ non-classical monocytes were associated with poor survival in all lung cancer histotypes. Thus, the blood immune cell signature might contribute to a better prediction of SCLC patient outcomes and may uncover the pathophysiological peculiarities of this tumor entity.

Understanding the squamous cell carcinoma immune microenvironment

Primary cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer with a rising incidence of about 1.8 million in the United States annually. Primary cSCC is usually curable by surgery; however, in some cases, cSCC eventuates in nodal metastasis and death from disease specific death. cSCC results in up to 15,000 deaths each year in the United States. Until recently, non-surgical options for treatment of locally advanced or metastatic cSCC were largely ineffective. With the advent of checkpoint inhibitor immunotherapy, including cemiplimab and pembrolizumab, response rates climbed to 50%, representing a vast improvement over chemotherapeutic agents used previously. Herein, we discuss the phenotype and function of SCC associated Langerhans cells, dendritic cells, macrophages, myeloid derived suppressor cells and T cells as well as SCC-associated lymphatics and blood vessels. Possible role(s) of SCC-associated cytokines in progression and invasion are reviewed. We also discuss the SCC immune microenvironment in the context of currently available and pipeline therapeutics.

LncRNAs has been identified as regulators of Myeloid-derived suppressor cells in lung cancer

Lung tumours are widespread pathological conditions that attract much attention due to their high incidence of death. The immune system contributes to the progression of these diseases, especially non-small cell lung cancer, resulting in the fast evolution of immune-targeted therapy. Myeloid-derived suppressor cells (MDSCs) have been suggested to promote the progression of cancer in the lungs by suppressing the immune response through various mechanisms. Herein, we summarized the clinical studies on lung cancer related to MDSCs. However, it is noteworthy to mention the discovery of long non-coding RNAs (lncRNAs) that had different phenotypes and could regulate MDSCs in lung cancer. Therefore, by reviewing the different phenotypes of lncRNAs and their regulation on MDSCs, we summarized the lncRNAs' impact on the progression of lung tumours. Data highlight LncRNAs as anti-cancer agents. Hence, we aim to discuss their possibilities to inhibit tumour growth and trigger the development of immunosuppressive factors such as MDSCs in lung cancer through the regulation of lncRNAs. The ultimate purpose is to propose novel and efficient therapy methods for curing patients with lung tumours.

Global research landscape and trends of lung cancer immunotherapy: A bibliometric analysis

​Background

Immunotherapy for lung cancer has been a hot research area for years. This bibliometric analysis aims to present the research trends on lung cancer immunotherapy.

Method

On 1 July, 2022, the authors identified 2,941 papers on lung cancer immunotherapy by the Web of Science and extracted their general information and the total number of citations. A bibliometric analysis was carried out to present the research landscape, demonstrate the research trends, and determine the most cited papers (top papers) as well as major journals on lung cancer immunotherapy. After that, recent research hotspots were analyzed based on the latest publications in major journals.

Results

These 2,941 papers were cited a total of 122,467 times. "Nivolumab vs. docetaxel in advanced non-squamous non-small-cell lung cancer" published in 2015 by Borghaei H et al. was the most cited paper (5,854 citations). Among the journals, New England Journal of Medicine was most influential. Corresponding authors represented China took part in most articles (904) and papers with corresponding authors from the USA were most cited (139.46 citations per paper). Since 2015, anti-PD-(L)1 has become the hottest research area.

Conclusions

This bibliometric analysis comprehensively and quantitatively presents the research trends and hotspots based on thousands of publications, and further suggests future research directions. Moreover, the results can benefit researchers to select journals and find potential collaborators. This study can help researchers get a comprehensive impression of the research landscape, historical development, and recent hotspots in lung cancer immunotherapy and provide inspiration for further research.

Novel Identification of Myeloid-Derived Suppressor Cells in Children With Septic Shock

OBJECTIVES

Immunoparalysis in children with septic shock is associated with increased risk of nosocomial infections and death. Myeloid-derived suppressor cells (MDSCs) potently suppress T cell function and may perpetuate immunoparalysis. Our goal was to test the hypothesis that children with septic shock would demonstrate increased proportions of MDSCs and impaired immune function compared with healthy controls.

DESIGN

Prospective observational study.

SETTING

Fifty-four bed PICU in a quaternary-care children's hospital.

PATIENTS

Eighteen children with septic shock and thirty age-matched healthy children.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and stained for cell surface markers to identify MDSCs by flow cytometric analysis, including granulocytic and monocytic subsets. Adaptive and innate immune function was measured by ex vivo stimulation of whole blood with phytohemagglutinin-induced interferon (IFN) γ production and lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α production, respectively. Prolonged organ dysfunction (OD) was defined as greater than 7 days. Children with septic shock had a higher percentage of circulating MDSCs, along with lower LPS-induced TNFα and phytohemagglutinin-induced IFNγ production capacities, compared with healthy controls. A cut-off of 25.2% MDSCs of total PBMCs in initial samples was optimal to discriminate children with septic shock who went on to have prolonged OD, area under the curve equal to 0.86. Children with prolonged OD also had decreased TNFα production capacity over time compared with those who recovered more quickly ( p = 0.02).

CONCLUSIONS

This article is the first to describe increased MDSCs in children with septic shock, along with an association between early increase in MDSCs and adverse OD outcomes in this population. It remains unclear if MDSCs play a causative role in sepsis-induced immune suppression in children. Additional studies are warranted to establish MDSC as a potential therapeutic target.

Selective depletion of polymorphonuclear myeloid derived suppressor cells in tumor beds with near infrared photoimmunotherapy enhances host immune response

The immune system is recognized as an important factor in regulating the development, progression, and metastasis of cancer. Myeloid-derived suppressor cells (MDSCs) are a major immune-suppressive cell type by interfering with T cell activation, promoting effector T cell apoptosis, and inducing regulatory T cell expansion. Consequently, reducing or eliminating MDSCs has become a goal of some systemic immunotherapies. However, by systemically reducing MDSCs, unwanted side effects can occur. Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed treatment that selectively kills targeted cells without damaging adjacent normal cells. The aim of this study is to evaluate the antitumor efficacy of MDSC-directed NIR-PIT utilizing anti-Ly6G antibodies to specifically destroy polymorphonuclear (PMN)-MDSCs in the tumor microenvironment (TME) in syngeneic mouse models. PMN-MDSCs were selectively eliminated within tumors by Ly6G-targeted NIR-PIT. There was significant tumor growth suppression and prolonged survival in three treated tumor models. In the early phase after NIR-PIT, dendritic cell maturation/activation and CD8⁺ T cell activation were enhanced in both intratumoral tissues and tumor-draining lymph nodes, and NK cells demonstrated increased expression of cytotoxic molecules. Host immunity remained activated in the TME for at least one week after NIR-PIT. Abscopal effects in bilateral tumor models were observed. Furthermore, the combination of NIR-PIT targeting cancer cells and PMN-MDSCs yielded synergistic effects and demonstrated highly activated host tumor immunity. In conclusion, we demonstrated that selective local PMN-MDSCs depletion by NIR-PIT could be a promising new cancer immunotherapy.

Myeloid-derived suppressor cells: Cancer, autoimmune diseases, and more

Although cancer immunotherapy using immune checkpoint inhibitors (ICIs) has been recognized as one of the major treatment modalities for malignant diseases, the clinical outcome is not uniform in all cancer patients. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells that possess various strong immunosuppressive activities involving multiple immunocompetent cells that are significantly accumulated in patients who did not respond well to cancer immunotherapies. We reviewed the perspective of MDSCs with emerging evidence in this review. Many studies on MDSCs were performed in malignant diseases. Substantial studies on the participation of MDSCs on non-malignant diseases such as chronic infection and autoimmune diseases, and physiological roles in obesity, aging, pregnancy and neonates have yet to be reported. With the growing understanding of the roles of MDSCs, variable therapeutic strategies and agents targeting MDSCs are being investigated, some of which have been used in clinical trials. More studies are required in order to develop more effective strategies against MDSCs.

The effects of dendritic cell-based vaccines in the tumor microenvironment: Impact on myeloid-derived suppressor cells

Dendritic cells (DCs) are a heterogenous population of professional antigen presenting cells whose main role is diminished in a variety of malignancies, including cancer, leading to ineffective immune responses. Those mechanisms are inhibited due to the immunosuppressive conditions found in the tumor microenvironment (TME), where myeloid-derived suppressor cells (MDSCs), a heterogeneous population of immature myeloid cells known to play a key role in tumor immunoevasion by inhibiting T-cell responses, are extremely accumulated. In addition, it has been demonstrated that MDSCs not only suppress DC functions, but also their maturation and development within the myeloid linage. Considering that an increased number of DCs as well as the improvement in their functions boost antitumor immunity, DC-based vaccines were developed two decades ago, and promising results have been obtained throughout these years. Therefore, the remodeling of the TME promoted by DC vaccination has also been explored. Here, we aim to review the effectiveness of different DCs-based vaccines in murine models and cancer patients, either alone or synergistically combined with other treatments, being especially focused on their effect on the MDSC population.

Ferroptosis, necroptosis, and pyroptosis in the tumor microenvironment: Perspectives for immunotherapy of SCLC

Small cell lung cancer (SCLC) is an aggressive form of lung cancer characterized by dismal prognosis. Although SCLC may initially respond well to platinum-based chemotherapy, it ultimately relapses and is almost universally resistant to this treatment. Immune checkpoint inhibitors (ICIs) have been approved as the first- and third-line therapeutic regimens for extensive-stage or relapsed SCLC, respectively. Despite this, only a minority of patients with SCLC respond to ICIs partly due to a lack of tumor-infiltrating lymphocytes (TILs). Transforming the immune "cold" tumors into "hot" tumors that are more likely to respond to ICIs is the main challenge for SCLC therapy. Ferroptosis, necroptosis, and pyroptosis represent the newly discovered immunogenic cell death (ICD) forms. Promoting ICD may alter the tumor microenvironment (TME) and the influx of TILs, and combination of their inducers and ICIs plays a synergistical role in enhancing antitumor effects. Nevertheless, the combination of the above two modalities has not been systematically discussed in SCLC therapy. In the present review, we summarize the roles of distinct ICD mechanisms on antitumor immunity and recent advances of ferroptosis-, necroptosis- and pyroptosis-inducing agents, and present perspectives on these cell death mechanisms in immunotherapy of SCLC.

A randomised phase II trial of a trivalent ganglioside vaccine targeting GM2, GD2 and GD3 combined with immunological adjuvant OPT-821 versus OPT-821 alone in metastatic sarcoma patients rendered disease-free by surgery

BACKGROUND

Recurrence after resection of metastatic sarcoma is common. The gangliosides GM2, GD2 and GD3 are strongly expressed across sarcoma subtypes. We hypothesised that generation of anti-ganglioside antibodies would control micrometastases and improve outcomes in sarcoma patients who were disease-free after metastasectomy.

METHODS

We conducted a randomised phase II trial of the immunological adjuvant OPT-821 with a KLH-conjugated ganglioside vaccine targeting GM2, GD2 and GD3, versus OPT-821 alone in patients with metastatic sarcoma following complete metastasectomy. Patients received 10 subcutaneous injections at Weeks 1, 2, 3, 8, 16, 28, 40, 52, 68 and 84 and were followed for evidence of recurrent disease. The primary end-point was relapse-free survival. Secondary end-points included overall survival and serologic response.

RESULTS

A total of 136 patients were randomised, 68 to each arm. The mean age was 51.2, 52.2% were male, 90.4% had relapsed disease, 86.8% had high-grade tumours and 14% had ≥4 metastases resected. Histologies included leiomyosarcoma (33%), spindle cell sarcoma (14%), undifferentiated pleomorphic sarcoma (13%), osteosarcoma (10%), synovial sarcoma (9%), liposarcoma (9%) and others (12%). Most adverse events were Grade ≤2 (83.8% and 70.6% in the vaccine and adjuvant arms, respectively). The most common (≥20% of patients) were injection site reaction (89.7%), fatigue (44.1%) and pyrexia (27.9%) on the vaccine arm, and injection site reaction (69.1%) on the adjuvant only arm. The 1-year relapse-free survival rate (34.5% and 34.8% in the vaccine and OPT-821 monotherapy arm, respectively) did not differ between arms (P = 0.725). One-year overall survival rates were 93.1% and 91.5% in the vaccine and OPT-821 monotherapy arm, respectively (P = 0.578). Serologic responses at week 9 were more frequent on the vaccine arm (96.5% of patients) than in the adjuvant arm (32.8%), and the difference between groups was durable.

CONCLUSIONS

A sustained serologic response to vaccination was induced with the vaccine, but no difference in recurrence-free or overall survival was observed between treatment arms.

CLINICALTRIALS

gov identifier: NCT01141491.

Myeloid derived suppressor cells in tumor microenvironment: Interaction with innate lymphoid cells

Human myeloid-derived suppressor cells (MDSC) represent a stage of immature myeloid cells and two main subsets can be identified: monocytic and polymorphonuclear. MDSC contribute to the establishment of an immunosuppressive tumor microenvironment (TME). The presence and the activity of MDSC in patients with different tumors correlate with poor prognosis. As previously reported, MDSC promote tumor growth and use different mechanisms to suppress the immune cell-mediated anti-tumor activity. Immunosuppression mechanisms used by MDSC are broad and depend on their differentiation stage and on the pathological context. It is known that some effector cells of the immune system can play an important role in the control of tumor progression and metastatic spread. In particular, innate lymphoid cells (ILC) contribute to control tumor growth representing a potential, versatile and, immunotherapeutic tool. Despite promising results obtained by using new cellular immunotherapeutic approaches, a relevant proportion of patients do not benefit from these therapies. Novel strategies have been investigated to overcome the detrimental effect exerted by the immunosuppressive component of TME (i.e. MDSC). In this review, we summarized the characteristics and the interactions occurring between MDSC and ILC in different tumors discussing how a deeper knowledge on MDSC biology could represent an important target for tumor immunotherapy capable of decreasing immunosuppression and enhancing anti-tumor activity exerted by immune cells.

Pharmacological modulation of myeloid-derived suppressor cells to dampen inflammation

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population with potent suppressive and regulative properties. MDSCs’ strong immunosuppressive potential creates new possibilities to treat chronic inflammation and autoimmune diseases or induce tolerance towards transplantation. Here, we summarize and critically discuss different pharmacological approaches which modulate the generation, activation, and recruitment of MDSCs in vitro and in vivo, and their potential role in future immunosuppressive therapy.

Ablation of NLRP3 inflammasome rewires MDSC function and promotes tumor regression

Myeloid-derived suppressor cells (MDSCs) are myeloid precursors that exert potent immunosuppressive properties in cancer. Despite the extensive knowledge on mechanisms implicated in mobilization, recruitment, and function of MDSCs, their therapeutic targeting remains an unmet need in cancer immunotherapy, suggesting that unappreciated mechanisms of MDSC-mediated suppression exist. Herein, we demonstrate an important role of NLRP3 inflammasome in the functional properties of MDSCs in tumor-bearing hosts. Specifically, Nlrp3-deficient mice exhibited reduced tumor growth compared to wild-type animals and induction of robust anti-tumor immunity, accompanied by re-wiring of the MDSC compartment. Interestingly, both monocytic (M-MDSCs) and granulocytic (G-MDSCs) subsets from Nlrp3^-/- mice displayed impaired suppressive activity and demonstrated significant transcriptomic alterations supporting the loss-of-function and associated with metabolic re-programming. Finally, therapeutic targeting of NLRP3 inhibited tumor development and re-programmed the MDSC compartment. These findings propose that targeting NLRP3 in MDSCs could overcome tumor-induced tolerance and may provide new checkpoints of cancer immunotherapy.

The immunomodulatory role of all-trans retinoic acid in tumor microenvironment

Retinoids are essential nutrients for human beings. Among them, all-trans retinoic acid (ATRA), considered one of the most active metabolites, plays important roles in multiple biological processes. ATRA regulates the transcription of target genes by interacting with nuclear receptors bonded to retinoic acid response elements (RAREs). Besides its differentiation-inducing effect in the treatment of acute promyelocytic leukemia and some solid tumor types, its immunoregulatory role in tumor microenvironment (TME) has attracted considerable attention. ATRA not only substantially abrogates the immunosuppressive effect of tumor-infiltrating myeloid-derived suppressor cells but also activates the anti-tumor effect of CD8 + T cells. Notably, the combination of ATRA with other therapeutic approaches, including immune checkpoint inhibitors (ICIs), tumor vaccines, and chemotherapy, has been extensively investigated in a variety of tumor models and clinical trials. In this review, we summarize the current understanding of the role of ATRA in cancer immunology and immunotherapy, dissect the underlying mechanisms of ATRA-mediated activation or differentiation of different types of immune cells, and explore the potential clinical significance of ATRA-based cancer therapy.

Myeloid derived suppressor cells and innate immune system interaction in tumor microenvironment

The tumor microenvironment is a complex domain that not only contains tumor cells but also a plethora of other host immune cells. By nature, the tumor microenvironment is a highly immunosuppressive milieu providing growing conditions for tumor cells. A major immune cell population that contributes most in the development of this immunosuppressive microenvironment is the MDSC, a heterogenous population of immature cells. Although found in small numbers only in the bone marrow of healthy individuals, they readily migrate to the lymph nodes and tumor site during cancer pathogenesis. MDSC mediated disruption of antitumor T cell activity is a major cause of the immunosuppression at the tumor site, but recent findings have shown that MDSC mediated dysfunction of other major immune cells might also play an important role. In this article we will review how crosstalk with MDSC alters the activity of both conventional and unconventional immune cells that inhibits the antitumor immunity and promotes cancer progression.

[Clinical Progress in the Immunotherapy of Small Cell Lung Cancer]

Small cell lung cancer is a kind of malignant tumor with strong invasiveness and poor prognosis, and the classic therapeutic modality of the disease remains multidisciplinary and comprehensive treatment. Treatment options for small cell lung cancer have been stalled for a long time, and new opportunities have emerged in recent years due to the development and initial experience of immunotherapeutic drugs. Clinical trials of some selected immune checkpoint inhibitors have confirmed the efficacy and safety in small cell lung cancer. Based on the results of phase III clinical trials (Impower133 and CASPIAN), Atezolizumab or Durvalumab in combination with chemotherapy has been approved by the U.S. Food and Drug Administration for the first-line treatment of extensive-stage small cell lung cancer. Clinical trials involving immune checkpoint inhibitors are being actively carried out and provide different perspectives for the management of small cell lung cancer. This article aimed to review the clinical progress in immunotherapy of small cell lung cancer.
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BCMA-targeted therapies for multiple myeloma: strategies to maximise efficacy and minimize adverse events

INTRODUCTION

Immunotherapies targeting B cell maturation antigen (BCMA) in multiple myeloma are transitioning through trials and entering the clinic, and will likely become a core pillar in myeloma therapeutics. These agents demonstrate unprecedented activity in multiply relapsed patients, but - notwithstanding the short follow-up times - their survival curves do not appear to demonstrate a plateau, and the treatments inevitably bring with them a range of toxicities that might be associated with tolerability issues.

AREAS COVERED

We will briefly lay out the current therapeutic landscape in multiple myeloma, before introducing BCMA and explaining its significance. We will address in turn the three key classes of anti-BCMA immunotherapies: antibody-drug conjugates, bispecific antibodies and chimeric antigen receptor T cells. We describe the mechanisms of action of these classes and review the evidence supporting their efficacy and toxicities. We then bring all three therapies into one discussion that explores how to mitigate toxicities and overcome myeloma's ability to resist these potent treatments.

EXPERT OPINION

Finally, we take the discussion back to the clinic, and consider how we might deploy anti-BCMA therapies most effectively for our patients. We consider the sequencing of treatment, and what further evidence is needed to more fully inform our therapy decisions.

Tissue-Resident Innate Immune Cell-Based Therapy: A Cornerstone of Immunotherapy Strategies for Cancer Treatment

Cancer immunotherapy has led to impressive advances in cancer treatment. Unfortunately, in a high percentage of patients is difficult to consistently restore immune responses to eradicate established tumors. It is well accepted that adaptive immune cells, such as B lymphocytes, CD4⁺ helper T lymphocytes, and CD8⁺ cytotoxic T-lymphocytes (CTLs), are the most effective cells able to eliminate tumors. However, it has been recently reported that innate immune cells, including natural killer cells (NK), dendritic cells (DC), macrophages, myeloid-derived suppressor cells (MDSCs), and innate lymphoid cells (ILCs), represent important contributors to modulating the tumor microenvironment and shaping the adaptive tumor response. In fact, their role as a bridge to adaptive immunity, make them an attractive therapeutic target for cancer treatment. Here, we provide a comprehensive overview of the pleiotropic role of tissue-resident innate immune cells in different tumor contexts. In addition, we discuss how current and future therapeutic approaches targeting innate immune cells sustain the adaptive immune system in order to improve the efficacy of current tumor immunotherapies.

PD-1/PD-L1, MDSC Pathways, and Checkpoint Inhibitor Therapy in Ph(-) Myeloproliferative Neoplasm: A Review

There has been significant progress in immune checkpoint inhibitor (CPI) therapy in many solid tumor types. However, only a single failed study has been published in treating Ph(-) myeloproliferative neoplasm (MPN). To make progress in CPI studies on this disease, herein, we review and summarize the mechanisms of activation of the PD-L1 promoter, which are as follows: (a) the extrinsic mechanism, which is activated by interferon gamma (IFN γ) by tumor infiltration lymphocytes (TIL) and NK cells; (b) the intrinsic mechanism of EGFR or PTEN loss resulting in the activation of the MAPK and AKT pathways and then stat 1 and 3 activation; and (c) 9p24 amplicon amplification, resulting in PD-L1 and Jak2 activation. We also review the literature and postulate that many of the failures of CPI therapy in MPN are likely due to excessive MDSC activities. We list all of the anti-MDSC agents, especially those with ruxolitinib, IMID compounds, and BTK inhibitors, which may be combined with CPI therapy in the future as part of clinical trials applying CPI therapy to Ph(-) MPN.

Sustained Drug Release From Liposomes for the Remodeling of Systemic Immune Homeostasis and the Tumor Microenvironment

Myeloid Derived Suppressor Cells (MDSCs) play important roles in constituting the immune suppressive environment promoting cancer development and progression. They are consisted of a heterogeneous population of immature myeloid cells including polymorphonuclear MDSC (PMN-MDSC) and monocytes MDSC (M-MDSC) that are found in both the systemic circulation and in the tumor microenvironment (TME). While previous studies had shown that all-trans retinoic acid (ATRA) could induce MDSC differentiation and maturation, the very poor solubility and fast metabolism of the drug limited its applications as an immune-modulator for cancer immunotherapy. We aimed in this study to develop a drug encapsulated liposome formulation L-ATRA with sustained release properties and examined the immuno-modulation effects. We showed that the actively loaded L-ATRA achieved stable encapsulation and enabled controlled drug release and accumulation in the tumor tissues. In vivo administration of L-ATRA promoted the remodeling of the systemic immune homeostasis as well as the tumor microenvironment. They were found to promote MDSCs maturation into DCs and facilitate immune responses against cancer cells. When used as a single agent treatment, L-ATRA deterred tumor growth, but only in immune-competent mice. In mice with impaired immune functions, L-ATRA at the same dose was not effective. When combined with checkpoint inhibitory agents, L-ATRA resulted in greater anti-cancer activities. Thus, L-ATRA may present a new IO strategy targeting the MDSCs that needs be further explored for improving the immunotherapy efficacy in cancer.

Advanced Biomaterials for Cell-Specific Modulation and Restore of Cancer Immunotherapy

The past decade has witnessed the explosive development of cancer immunotherapies. Nevertheless, low immunogenicity, limited specificity, poor delivery efficiency, and off-target side effects remain to be the major limitations for broad implementation of cancer immunotherapies to patient bedside. Encouragingly, advanced biomaterials offering cell-specific modulation of immunological cues bring new solutions for improving the therapeutic efficacy while relieving side effect risks. In this review, focus is given on how functional biomaterials can enable cell-specific modulation of cancer immunotherapy within the cancer-immune cycle, with particular emphasis on antigen-presenting cells (APCs), T cells, and tumor microenvironment (TME)-resident cells. By reviewing the current progress in biomaterial-based cancer immunotherapy, here the aim is to provide a better understanding of biomaterials' role in targeting modulation of antitumor immunity step-by-step and guidelines for rationally developing targeting biomaterials for more personalized cancer immunotherapy. Moreover, the current challenge and future perspective regarding the potential application and clinical translation will also be discussed.

Clinical perspectives on the age-related increase of immunosuppressive activity

The aging process is associated with a remodeling of the immune system involving chronic low-grade inflammation and a gradual decline in the function of the immune system. These processes are also called inflammaging and immunosenescence. The age-related immune remodeling is associated with many clinical changes, e.g., risk for cancers and chronic infections increases, whereas the efficiency of vaccination and immunotherapy declines with aging. On the other hand, there is convincing evidence that chronic inflammatory states promote the premature aging process. The inflammation associated with aging or chronic inflammatory conditions stimulates a counteracting immunosuppression which protects tissues from excessive inflammatory injuries but promotes immunosenescence. Immunosuppression is a driving force in tumors and chronic infections and it also induces the tolerance to vaccination and immunotherapies. Immunosuppressive cells, e.g., myeloid-derived suppressor cells (MDSC), regulatory T cells (Treg), and type M2 macrophages, have a crucial role in tumorigenesis and chronic infections as well as in the tolerance to vaccination and immunotherapies. Interestingly, there is substantial evidence that inflammaging is also associated with an increased immunosuppressive activity, e.g., upregulation of immunosuppressive cells and anti-inflammatory cytokines. Given that both the aging and chronic inflammatory states involve the activation of immunosuppression and immunosenescence, this might explain why aging is a risk factor for tumorigenesis and chronic inflammatory states and conversely, chronic inflammatory insults promote the premature aging process in humans.

Retinoic Acid Induces an IFN-Driven Inflammatory Tumour Microenvironment, Sensitizing to Immune Checkpoint Therapy

With immune checkpoint therapy (ICT) having reshaped the treatment of many cancers, the next frontier is to identify and develop novel combination therapies to improve efficacy. Previously, we and others identified beneficial immunological effects of the vitamin A derivative tretinoin on anti-tumour immunity. Although it is known that tretinoin preferentially depletes myeloid derived suppressor cells in blood, little is known about the effects of tretinoin on the tumour microenvironment, hampering the rational design of clinical trials using tretinoin in combination with ICT. Here, we aimed to identify how tretinoin changed the tumour microenvironment in mouse tumour models, using flow cytometry and RNAseq, and we sought to use that information to establish optimal dosing and scheduling of tretinoin in combination with several ICT antibodies in multiple cancer models. We found that tretinoin rapidly induced an interferon dominated inflammatory tumour microenvironment, characterised by increased CD8+ T cell infiltration. This phenotype completely overlapped with the phenotype that was induced by ICT itself, and we confirmed that the combination further amplified this inflammatory milieu. The addition of tretinoin significantly improved the efficacy of anti-CTLA4/anti-PD-L1 combination therapy, and staggered scheduling was more efficacious than concomitant scheduling, in a dose-dependent manner. The positive effects of tretinoin could be extended to ICT antibodies targeting OX40, GITR and CTLA4 monotherapy in multiple cancer models. These data show that tretinoin induces an interferon driven, CD8+ T cell tumour microenvironment that is responsive to ICT.

Evolution and Targeting of Myeloid Suppressor Cells in Cancer: A Translational Perspective

Simple Summary

Immunotherapy is achieving impressive results in the treatment of several cancers. While the main strategies aim to re-invigorate the specific lymphocyte anti-tumor response, many studies underline that altered myeloid cell frequency and functions can dramatically interfere with the responsiveness to cancer therapies. Therefore, many novel strategies targeting TAMs and MDSCs in combination with classical treatments are under continuous evolution at both pre-clinical and clinical levels, showing encouraging results. Herein, we depict a comprehensive overview of myeloid cell generation and function in a cancer setting, and the most relevant strategies for their targeting that are currently in clinical use or under pre-clinical development.

Abstract

In recent years, the immune system has emerged as a critical regulator of tumor development, progression and dissemination. Advanced therapeutic approaches targeting immune cells are currently under clinical use and improvement for the treatment of patients affected by advanced malignancies. Among these, anti-PD1/PD-L1 and anti-CTLA4 immune checkpoint inhibitors (ICIs) are the most effective immunotherapeutic drugs at present. In spite of these advances, great variability in responses to therapy exists among patients, probably due to the heterogeneity of both cancer cells and immune responses, which manifest in diverse forms in the tumor microenvironment (TME). The variability of the immune profile within TME and its prognostic significance largely depend on the frequency of the infiltrating myeloid cells, which often represent the predominant population, characterized by high phenotypic heterogeneity. The generation of heterogeneous myeloid populations endowed with tumor-promoting activities is typically promoted by growing tumors, indicating the sequential levels of myeloid reprogramming as possible antitumor targets. This work reviews the current knowledge on the events governing protumoral myelopoiesis, analyzing the mechanisms that drive the expansion of major myeloid subsets, as well as their functional properties, and highlighting recent translational strategies for clinical developments.