Anti-VEGF therapy resistance in ovarian cancer is caused by GM-CSF-induced myeloid-derived suppressor cell recruitment

Nanotechnology for boosting ovarian cancer immunotherapy

Ovarian cancer, often referred to as the "silent killer," is notoriously difficult to detect in its early stages, leading to a poor prognosis for many patients. Diagnosis is often delayed until the cancer has advanced, primarily due to its ambiguous and frequently occurring clinical symptoms. Ovarian cancer leads to more deaths than any other cancer of the female reproductive system. The main reasons for the high mortality rates include delayed diagnosis and resistance to treatment. As a result, there is an urgent need for improved diagnostic and treatment options for ovarian cancer. The standard treatments typically involve debulking surgery along with platinum-based chemotherapies. Among patients with advanced-stage cancer who initially respond to current therapies, 50-75% experience a recurrence. Recently, immunotherapy-based approaches to enhance the body's immune response to combat tumor growth have shown promise. Immune checkpoint inhibitors have shown promising results in treating other types of tumors. However, in ovarian cancer, only a few of these inhibitors have been effective because the tumor's environment suppresses the immune system and creates barriers for treatment. This hampers the effectiveness of existing immunotherapies. Nonetheless, advanced immunotherapy techniques and delivery systems based on nanotechnology hold promise for overcoming these challenges.

Beyond Cancer Cells: How the Tumor Microenvironment Drives Cancer Progression

Liver cancer represents a substantial global health challenge, contributing significantly to worldwide morbidity and mortality. It has long been understood that tumors are not composed solely of cancerous cells, but also include a variety of normal cells within their structure. These tumor-associated normal cells encompass vascular endothelial cells, fibroblasts, and various inflammatory cells, including neutrophils, monocytes, macrophages, mast cells, eosinophils, and lymphocytes. Additionally, tumor cells engage in complex interactions with stromal cells and elements of the extracellular matrix (ECM). Initially, the components of what is now known as the tumor microenvironment (TME) were thought to be passive bystanders in the processes of tumor proliferation and local invasion. However, recent research has significantly advanced our understanding of the TME's active role in tumor growth and metastasis. Tumor progression is now known to be driven by an intricate imbalance of positive and negative regulatory signals, primarily influenced by specific growth factors produced by both inflammatory and neoplastic cells. This review article explores the latest developments and future directions in understanding how the TME modulates liver cancer, with the aim of informing the design of novel therapies that target critical components of the TME.

A new perspective on antiangiogenic antibody drug resistance: Biomarkers, mechanisms, and strategies in malignancies

Drug resistance of malignant tumor leads to disease progression be the bottleneck in clinical treatment. Antiangiogenic therapy, which aims to "starve" the tumor by inhibiting angiogenesis, is one of the key strategies in clinical oncology treatments. Recently, dozens of investigational antibody drugs and biosimilars targeting angiogenesis have obtained regulatory approval for the treatment of various malignancies. Moreover, a new generation of bispecific antibodies based on the principle of antiangiogenesis are being advanced for clinical trial to overcome antiangiogenic resistance in tumor treatment or enhance the efficacy of monotherapy. Tumors often develop resistance to antiangiogenesis therapy, presenting as refractory and sometimes even resistant to new therapies, for which there are currently no effective management strategies. Thus, a detailed understanding of the mechanisms mediating resistance to antiangiogenesis antibodies is crucial for improving drug effectiveness and achieving a durable response to antiangiogenic therapy. In this review, we provide a novel perspective on the tumor microenvironment, including antibody structure, tumor stroma, and changes within tumor cells, to analyze the multifactorial reasons underlying resistance to antiangiogenesis antibodies. The review also enumerates biomarkers that indicate resistance and potential strategies for monitoring resistance. Furthermore, based on recent clinical and preclinical studies, we summarize potential strategies and translational clinical trials aimed at overcoming resistance to antiangiogenesis antibodies. This review provides a valuable reference for researchers and clinical practitioners involved in the development of new drugs or therapeutic strategies to overcome antiangiogenesis antibodies resistance.

Ecological and evolutionary dynamics to design and improve ovarian cancer treatment

Ovarian cancer ecosystems are exceedingly complex, consisting of a high heterogeneity of cancer cells. Development of drugs such as poly ADP-ribose polymerase (PARP) inhibitors, targeted therapies and immunotherapies offer more options for sequential or combined treatments. Nevertheless, mortality in metastatic ovarian cancer patients remains high because cancer cells consistently develop resistance to single and combination therapies, urging a need for treatment designs that target the evolvability of cancer cells. The evolutionary dynamics that lead to resistance emerge from the complex tumour microenvironment, the heterogeneous populations, and the individual cancer cell's plasticity. We propose that successful management of ovarian cancer requires consideration of the ecological and evolutionary dynamics of the disease. Here, we review current options and challenges in ovarian cancer treatment and discuss principles of tumour evolution. We conclude by proposing evolutionarily designed strategies for ovarian cancer, with the goal of integrating such principles with longitudinal, quantitative data to improve the treatment design and management of drug resistance. KEY POINTS/HIGHLIGHTS: Tumours are ecosystems in which cancer and non-cancer cells interact and evolve in complex and dynamic ways. Conventional therapies for ovarian cancer inevitably lead to the development of resistance because they fail to consider tumours' heterogeneity and cellular plasticity. Eco-evolutionarily designed therapies should consider cancer cell plasticity and patient-specific characteristics to improve clinical outcome and prevent relapse.

Recent advances in understanding the immune microenvironment in ovarian cancer

The occurrence of ovarian cancer (OC) is a major factor in women's mortality rates. Despite progress in medical treatments, like new drugs targeting homologous recombination deficiency, survival rates for OC patients are still not ideal. The tumor microenvironment (TME) includes cancer cells, fibroblasts linked to cancer (CAFs), immune-inflammatory cells, and the substances these cells secrete, along with non-cellular components in the extracellular matrix (ECM). First, the TME mainly plays a role in inhibiting tumor growth and protecting normal cell survival. As tumors progress, the TME gradually becomes a place to promote tumor cell progression. Immune cells in the TME have attracted much attention as targets for immunotherapy. Immune checkpoint inhibitor (ICI) therapy has the potential to regulate the TME, suppressing factors that facilitate tumor advancement, reactivating immune cells, managing tumor growth, and extending the survival of patients with advanced cancer. This review presents an outline of current studies on the distinct cellular elements within the OC TME, detailing their main functions and possible signaling pathways. Additionally, we examine immunotherapy rechallenge in OC, with a specific emphasis on the biological reasons behind resistance to ICIs.

Nanomedicine Targeting Myeloid-Derived Suppressor Cells Enhances Anti-Tumor Immunity

Cancer immunotherapy, a field within immunology that aims to enhance the host's anti-cancer immune response, frequently encounters challenges associated with suboptimal response rates. The presence of myeloid-derived suppressor cells (MDSCs), crucial constituents of the tumor microenvironment (TME), exacerbates this issue by fostering immunosuppression and impeding T cell differentiation and maturation. Consequently, targeting MDSCs has emerged as crucial for immunotherapy aimed at enhancing anti-tumor responses. The development of nanomedicines specifically designed to target MDSCs aims to improve the effectiveness of immunotherapy by transforming immunosuppressive tumors into ones more responsive to immune intervention. This review provides a detailed overview of MDSCs in the TME and current strategies targeting these cells. Also the benefits of nanoparticle-assisted drug delivery systems, including design flexibility, efficient drug loading, and protection against enzymatic degradation, are highlighted. It summarizes advances in nanomedicine targeting MDSCs, covering enhanced treatment efficacy, safety, and modulation of the TME, laying the groundwork for more potent cancer immunotherapy.

Limitations and potential of immunotherapy in ovarian cancer

Ovarian cancer (OC) is the third most common gynecological cancer and alone has an emergence rate of approximately 308,069 cases worldwide (2020) with dire survival rates. To put it into perspective, the mortality rate of OC is three times higher than that of breast cancer and it is predicted to only increase significantly by 2040. The primary reasons for such a high rate are that the physical symptoms of OC are detectable only during the advanced phase of the disease when resistance to chemotherapies is high and around 80% of the patients that do indeed respond to chemotherapy initially, show a poor prognosis subsequently. This highlights a pressing need to develop new and effective therapies to tackle advanced OC to improve prognosis and patient survival. A major advance in this direction is the emergence of combination immunotherapeutic methods to boost CD8+ T cell function to tackle OC. In this perspective, we discuss our view of the current state of some of the combination immunotherapies in the treatment of advanced OC, their limitations, and potential approaches toward a safer and more effective response.

Scientific and clinical relevance of non-cellular tumor microenvironment components in ovarian cancer chemotherapy resistance

The tumor microenvironment (TME) components play a crucial role in cancer cells' resistance to chemotherapeutic agents. This phenomenon is exceptionally fundamental in patients with ovarian cancer (OvCa), whose outcome depends mainly on their response to chemotherapy. Until now, most reports have focused on the role of cellular components of the TME, while less attention has been paid to the stroma and other non-cellular elements of the TME, which may play an essential role in the therapy resistance. Inhibiting these components could help define new therapeutic targets and potentially restore chemosensitivity. The aim of the present article is both to summarize the knowledge about non-cellular components of the TME in the development of OvCa chemoresistance and to suggest targeting of non-cellular elements of the TME as a valuable strategy to overcome chemoresistance and to develop new therapeutic strategies in OvCA patients.

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.

Novel specific anti-ESM1 antibodies overcome tumor bevacizumab resistance by suppressing angiogenesis and metastasis

Suppressing tumors through anti-angiogenesis has been established as an effective clinical treatment strategy. Bevacizumab, a monoclonal antibody, is commonly used in various indications. However, two major challenges limit the long-term efficacy of bevacizumab: drug resistance and side effects. Bevacizumab resistance has been extensively studied at the molecular level, but no drug candidates have been developed for clinical use to overcome this resistance. In a previous study conducted by our team, a major finding was that high expression of ESM1 in bevacizumab-resistant tumors is associated with an unfavorable response to treatment. In particular, an increase in ESM1 expression contributes to heightened lung metastasis and microvascular density, which ultimately decreases the tumor's sensitivity to bevacizumab. In contrast, the silencing of ESM1 results in reduced angiogenesis and suppressed tumor growth in tumors resistant to bevacizumab. We put forward the hypothesis that targeting ESM1 could serve as a therapeutic strategy in overcoming bevacizumab resistance. In this study, a variety of anti-ESM1 antibodies with high affinity to human ESM1 were successfully prepared and characterized. Our in vivo study confirmed the establishment of a bevacizumab-resistant human colorectal cancer model and further demonstrated that the addition of anti-ESM1 monoclonal antibodies to bevacizumab treatment significantly improved tumor response while downregulating DLL4 and MMP9. In conclusion, our study suggests that anti-hESM1 monoclonal antibodies have the potential to alleviate or overcome bevacizumab resistance, thereby providing new strategies and drug candidates for clinical research in the treatment of bevacizumab-resistant colorectal cancer.

Estrogens, Estrogen Receptors and Tumor Microenvironment in Ovarian Cancer

Ovarian cancer is one of the most common cancers in women and the most concerning issues in gynecological oncology in recent years. It is postulated that many factors may contribute to the development of ovarian cancer, including hormonal imbalance. Estrogens are a group of hormones that have an important role both in physiological and pathological processes. In ovarian cancer, they may regulate proliferation, invasiveness and epithelial to mesenchymal transition. Estrogen signaling also takes part in the regulation of the biology of the tumor microenvironment. This review summarizes the information connected with estrogen receptors, estrogens and their association with a tumor microenvironment. Moreover, this review also includes information about the changes in estrogen receptor expression upon exposition to various environmental chemicals.

The pathological role of C-X-C chemokine receptor type 4 (CXCR4) in colorectal cancer (CRC) progression; special focus on molecular mechanisms and possible therapeutics

Colorectal cancer (CRC) is comprised of transformed cells and non-malignant cells including cancer-associated fibroblasts (CAF), endothelial vasculature cells, and tumor-infiltrating cells. These nonmalignant cells, as well as soluble factors (e.g., cytokines), and the extracellular matrix (ECM), form the tumor microenvironment (TME). In general, the cancer cells and their surrounding TME can crosstalk by direct cell-to-cell contact and via soluble factors, such as cytokines (e.g., chemokines). TME not only promotes cancer progression through growth-promoting cytokines but also provides resistance to chemotherapy. Understanding the mechanisms of tumor growth and progression and the roles of chemokines in CRC will likely suggest new therapeutic targets. In this line, a plethora of reports has evidenced the critical role of chemokine receptor type 4 (CXCR4)/C-X-C motif chemokine ligand 12 (CXCL12 or SDF-1) axis in CRC pathogenesis. In the current review, we take a glimpse into the role of the CXCR4/CXCL12 axis in CRC growth, metastasis, angiogenesis, drug resistance, and immune escape. Also, a summary of recent reports concerning targeting CXCR4/CXCL12 axis for CRC management and therapy has been delivered.

The recent progress of myeloid-derived suppressor cell and its targeted therapies in cancers

Myeloid-derived suppressor cells (MDSCs) are an immature group of myeloid-derived cells generated from myeloid cell precursors in the bone marrow. MDSCs appear almost exclusively in pathological conditions, such as tumor progression and various inflammatory diseases. The leading function of MDSCs is their immunosuppressive ability, which plays a crucial role in tumor progression and metastasis through their immunosuppressive effects. Since MDSCs have specific molecular features, and only a tiny amount exists in physiological conditions, MDSC-targeted therapy has become a promising research direction for tumor treatment with minimal side effects. In this review, we briefly introduce the classification, generation and maturation process, and features of MDSCs, and detail their functions under various circumstances. The present review specifically demonstrates the environmental specificity of MDSCs, highlighting the differences between MDSCs from cancer and healthy individuals, as well as tumor-infiltrating MDSCs and circulating MDSCs. Then, we further describe recent advances in MDSC-targeted therapies. The existing and potential targeted drugs are divided into three categories, monoclonal antibodies, small-molecular inhibitors, and peptides. Their targeting mechanisms and characteristics have been summarized respectively. We believe that a comprehensive in-depth understanding of MDSC-targeted therapy could provide more possibilities for the treatment of cancer.

Myeloid-Derived Suppressor Cells (MDSCs) in Ovarian Cancer-Looking Back and Forward

Myeloid-derived suppressor cells (MDSCs) play a significant role in the immune system and have been extensively studied in cancer. MDSCs are a heterogeneous population of myeloid cells that accumulate in the tumor microenvironment. Consequently, the high abundance of these cells often leads to immunosuppression, tumor growth, treatment failure, and poor prognosis. Ovarian cancer ranks fifth in cancer deaths among women, accounting for more deaths than any other cancer of the female genital tract. Currently, there is a lack of effective clinical strategies for the treatment of ovarian cancer. Although several studies underline the negative role of human MDSCs in ovarian cancer, this topic is still understudied. The works on MDSCs are summarized here, along with an explanation of why focusing on these cells would be a promising approach for treating ovarian cancer patients.

Modulation of tumor immune microenvironment by TAS-115, a multi-receptor tyrosine kinase inhibitor, promotes antitumor immunity and contributes anti-PD-1 antibody therapy

TAS-115 is an oral multi-receptor tyrosine kinase inhibitor that strongly inhibits kinases implicated in antitumor immunity, such as colony stimulating factor 1 receptor and vascular endothelial growth factor receptor. Because these kinases are associated with the modulation of immune pathways, we investigated the immunomodulatory activity of TAS-115. An in vitro cytokine assay revealed that TAS-115 upregulated interferon γ (IFNγ) and interleukin-2 secretion by T cells, suggesting that TAS-115 activated T cells. Gene expression analysis suggested that TAS-115 promoted M1 macrophage differentiation. In in vivo experiments, although TAS-115 exerted a moderate antitumor effect in the MC38 mouse colorectal cancer model under immunodeficient conditions, this effect was enhanced under immunocompetent conditions. Furthermore, combination of TAS-115 and anti-PD-1 antibody exhibited greater antitumor activity than either treatment alone. Flow cytometry analysis showed the increase in IFNγ- and granzyme B (Gzmb)-secreting tumor-infiltrating T cells by TAS-115 treatment. The combination treatment further increased the percentage of Gzmb+CD8+ T cells and decreased the percentage of macrophages compared with either treatment alone. These results highlight the potential therapeutic effect of TAS-115 in combination with PD-1 blockade, mediated via activation of antitumor immunity by TAS-115.

Immunosuppressive cells in oncolytic virotherapy for glioma: challenges and solutions

Glioblastoma is a highly aggressive form of brain cancer characterized by the abundance of myeloid lineage cells in the tumor microenvironment. Tumor-associated macrophages and microglia (TAM) and myeloid-derived suppressor cells (MDSCs), play a pivotal role in promoting immune suppression and tumor progression. Oncolytic viruses (OVs) are self-amplifying cytotoxic agents that can stimulate local anti-tumor immune responses and have the potential to suppress immunosuppressive myeloid cells and recruit tumor-infiltrating T lymphocytes (TILs) to the tumor site, leading to an adaptive immune response against tumors. However, the impact of OV therapy on the tumor-resident myeloid population and the subsequent immune responses are not yet fully understood. This review provides an overview of how TAM and MDSC respond to different types of OVs, and combination therapeutics that target the myeloid population to promote anti-tumor immune responses in the glioma microenvironment.

In silico enhancer mining reveals SNS-032 and EHMT2 inhibitors as therapeutic candidates in high-grade serous ovarian cancer

BACKGROUND

Epigenomic dysregulation has been linked to solid tumour malignancies, including ovarian cancers. Profiling of re-programmed enhancer locations associated with disease has the potential to improve stratification and thus therapeutic choices. Ovarian cancers are subdivided into histological subtypes that have significant molecular and clinical differences, with high-grade serous carcinoma representing the most common and aggressive subtype.

METHODS

We interrogated the enhancer landscape(s) of normal ovary and subtype-specific ovarian cancer states using publicly available data. With an initial focus on H3K27ac histone mark, we developed a computational pipeline to predict drug compound activity based on epigenomic stratification. Lastly, we substantiated our predictions in vitro using patient-derived clinical samples and cell lines.

RESULTS

Using our in silico approach, we highlighted recurrent and privative enhancer landscapes and identified the differential enrichment of a total of 164 transcription factors involved in 201 protein complexes across the subtypes. We pinpointed SNS-032 and EHMT2 inhibitors BIX-01294 and UNC0646 as therapeutic candidates in high-grade serous carcinoma, as well as probed the efficacy of specific inhibitors in vitro.

CONCLUSION

Here, we report the first attempt to exploit ovarian cancer epigenomic landscapes for drug discovery. This computational pipeline holds enormous potential for translating epigenomic profiling into therapeutic leads.

Society for Immunotherapy of Cancer (SITC) consensus definitions for resistance to combinations of immune checkpoint inhibitors with targeted therapies

Immunotherapy offers deep and durable disease control to some patients, but many tumors do not respond to treatment with single-agent immune checkpoint inhibitors (ICIs). One strategy to enhance responses to immunotherapy is via combinations with signal transduction inhibitors, such as antiangiogenic therapies, which not only directly target cancer cells but also could potentially favorably modulate the tumor immune microenvironment. Combination strategies with ICIs have demonstrated enhanced antitumor activity compared with tumor-targeted or antiangiogenic therapy alone in randomized trials in a variety of solid tumor settings, leading to regulatory approval from the US Food and Drug Administration and agencies in other countries for the treatment of endometrial cancer, kidney cancer, melanoma, and hepatocellular carcinoma. Despite improved survival and response rates for some patients when antiangiogenic or targeted therapies are administered with ICIs, many patients continue to progress after combination treatment and urgently need new strategies to address this manifestation of resistance to immunotherapy. Previously, the Society for Immunotherapy of Cancer (SITC) published consensus definitions for resistance to single-agent anti-PD-(L)1. To provide guidance for clinical trial design and to support analyses of emerging molecular and immune profiling data surrounding mechanisms of resistance to ICI-based combinations, SITC convened a follow-up workshop in 2021 to develop consensus definitions for resistance to multiagent ICI combinations. This manuscript reports the consensus clinical definitions for combinations of anti-PD-(L)1 ICIs and targeted therapies. Definitions for resistance to ICIs in combination with chemotherapy and with other ICIs will be published in companion volumes to this paper.

Hypoxic microenvironment in cancer: molecular mechanisms and therapeutic interventions

Having a hypoxic microenvironment is a common and salient feature of most solid tumors. Hypoxia has a profound effect on the biological behavior and malignant phenotype of cancer cells, mediates the effects of cancer chemotherapy, radiotherapy, and immunotherapy through complex mechanisms, and is closely associated with poor prognosis in various cancer patients. Accumulating studies have demonstrated that through normalization of the tumor vasculature, nanoparticle carriers and biocarriers can effectively increase the oxygen concentration in the tumor microenvironment, improve drug delivery and the efficacy of radiotherapy. They also increase infiltration of innate and adaptive anti-tumor immune cells to enhance the efficacy of immunotherapy. Furthermore, drugs targeting key genes associated with hypoxia, including hypoxia tracers, hypoxia-activated prodrugs, and drugs targeting hypoxia-inducible factors and downstream targets, can be used for visualization and quantitative analysis of tumor hypoxia and antitumor activity. However, the relationship between hypoxia and cancer is an area of research that requires further exploration. Here, we investigated the potential factors in the development of hypoxia in cancer, changes in signaling pathways that occur in cancer cells to adapt to hypoxic environments, the mechanisms of hypoxia-induced cancer immune tolerance, chemotherapeutic tolerance, and enhanced radiation tolerance, as well as the insights and applications of hypoxia in cancer therapy.

Dynamic host immunity and PD-L1/PD-1 blockade efficacy: developments after "IFN-γ from lymphocytes induces PD-L1 expression and promotes progression of ovarian cancer"

In the article titled "IFN-γ from lymphocytes induces PD-L1 expression and promotes progression of ovarian cancer" in 2015, we showed that PD-L1 expression is induced by IFN-γ from lymphocytes in the tumour microenvironment. This article proposed that PD-L1 expression in cancer cells is not stable but varies among cases, or even within a case, which is influenced by the stromal infiltration of cytotoxic lymphocytes. Immune-checkpoint inhibitors, especially anti-PD-1/PD-L1 therapies, are now widely used to treat various types of cancer. Predictive biomarkers for the efficacy of immune-checkpoint inhibitors include PD-L1 expression, MSI/mismatch repair deficiency and high tumour mutation burden. However, clinical trials have proven that their use in ovarian cancer is still challenging. Reliable biomarkers and new treatment strategies may be sought by elucidating the complex immune microenvironment of ovarian cancer. Although the interaction between cytotoxic lymphocytes and PD-1/PD-L1 on tumour cells is at the centre of therapeutic targets, other immune checkpoints and various immunosuppressive cells also play important roles in ovarian cancer. Targeting these role players in combination with PD-1/PD-L1 blockade may be a promising therapeutic strategy.

Myeloid-Derived Suppressor Cells in Cancer and COVID-19 as Associated with Oxidative Stress

Myeloid-derived suppressor cells MDSCs are a heterogeneous population of cells that expand beyond their physiological regulation during pathologies such as cancer, inflammation, bacterial, and viral infections. Their key feature is their remarkable ability to suppress T cell and natural killer NK cell responses. Certain risk factors for severe COVID-19 disease, such as obesity and diabetes, are associated with oxidative stress. The resulting inflammation and oxidative stress can negatively impact the host. Similarly, cancer cells exhibit a sustained increase in intrinsic ROS generation that maintains the oncogenic phenotype and drives tumor progression. By disrupting endoplasmic reticulum calcium channels, intracellular ROS accumulation can disrupt protein folding and ultimately lead to proteostasis failure. In cancer and COVID-19, MDSCs consist of the same two subtypes (PMN-MSDC and M-MDSC). While the main role of polymorphonuclear MDSCs is to dampen the response of T cells and NK killer cells, they also produce reactive oxygen species ROS and reactive nitrogen species RNS. We here review the origin of MDSCs, their expansion mechanisms, and their suppressive functions in the context of cancer and COVID-19 associated with the presence of superoxide anion •O2- and reactive oxygen species ROS.

Intraperitoneal Monocytes plus IFNs as a Novel Cellular Immunotherapy for Ovarian Cancer: Mechanistic Characterization and Results from a Phase I Clinical Trial

PURPOSE

Ovarian cancer is the most lethal gynecologic cancer and intrinsically resistant to checkpoint immunotherapies. We sought to augment innate immunity, building on previous work with IFNs and monocytes.

PATIENTS AND METHODS

Preclinical experiments were designed to define the mechanisms of cancer cell death mediated by the combination of IFNs α and γ with monocytes. We translated these preclinical findings into a phase I trial of autologous IFN-activated monocytes administered intraperitoneally to platinum-resistant or -refractory ovarian cancer patients.

RESULTS

IFN-treated monocytes induced caspase 8-dependent apoptosis by the proapoptotic TRAIL and mediated by the death receptors 4 and 5 (DR4 and DR5, respectively) on cancer cells. Therapy was well tolerated with evidence of clinical activity, as 2 of 9 evaluable patients had a partial response by RECIST criteria, and 1 additional patient had a CA-125 response. Upregulation of monocyte-produced TRAIL and cytokines was confirmed in peripheral blood. Long-term responders had alterations in innate and adaptive immune compartments.

CONCLUSIONS

Given the mechanism of cancer cell death, and the acceptable tolerability of the clinical regimen, this platform presents a possibility for future combination therapies to augment anticancer immunity. See related commentary by Chow and Dorigo, p. 299.

Stress hormones are associated with inflammatory cytokines and attenuation of T-cell function in the ascites from patients with high grade serous ovarian cancer

Mounting evidence suggests that chronic stress and subsequent distress can promote ovarian cancer progression. These altered psychological states have been linked to sustained release of stress hormones, activation of the β-adrenergic receptors in ovarian cancer cells, and induction of pro-tumoral signaling pathways. In addition, data suggest that chronic stress promotes an inflammatory landscape highlighted by increased infiltration of tumor-associated macrophages into the ovarian tumor microenvironment (TME). In ovarian cancer, ascites is a unique TME comprised of tumor, and immune cells, which secrete pro-tumoral cytokines and chemokines that modulate tumor-associated immunity. However, our knowledge about how stress hormones impact the ascites TME remains limited. We hypothesized that the ascites harbors measurable levels of stress hormones, and accumulation of these in the ascites generates a pro-tumorigenic, inflammatory, and immunosuppressive TME. We evaluated ascites samples from 49 patients with high grade serous ovarian cancer (HGSOC) and quantified cortisol and stress hormones metabolites, metanephrine (MN), and normetanephrine (NMN) in all samples. We also measured 38 individual cytokines in the ascites, including several pro-inflammatory cytokines, such as IL-6, which were positively correlated to MN or NMN levels of those samples. Conversely, we found cortisol levels were negatively correlated to several pro-inflammatory cytokines. As T-cells are integral to the TME and our analyses identified cytokines in the ascites known to modulate T-cell function, we characterized ascites-derived T-cells and assessed the impact of stress hormones on the T-cell phenotype. Our data show an altered CD4+/CD8+ T-cell ratio and a heterogeneous expression of exhaustion markers in T-cells from the ascites, while ascites-derived CD8+ T-cells exposed to epinephrine had decreased co-expression CD38 and Granzyme B. To extend these findings to animal models, we subjected ovarian cancer-bearing mice to daily restraint stress, which resulted in increased tumor growth in two models. Congruent with our human analyses, we detected corticosterone, MN, and NMN in the ascites from tumor-bearing mice, and these stress hormones correlated with several inflammatory cytokines. Moreover, daily restraint stress leads to increased CD4+PD-1+/CD8+PD-1+ T-cell ratio in the ovarian tumor microenvironment. Overall, these data highlight a role of stress hormones in the ascites TME as a driver of tumor-associated inflammation, T-cell suppression, and disease progression.

Endothelial-Specific Molecule 1 Inhibition Lessens Productive Angiogenesis and Tumor Metastasis to Overcome Bevacizumab Resistance

The development of drug resistance in malignant tumors leads to disease progression, creating a bottleneck in treatment. Bevacizumab is widely used clinically, and acts by inhibiting angiogenesis to "starve" tumors. Continuous treatment can readily induce rebound proliferation of tumor blood vessels, leading to drug resistance. Previously, we found that the fragment crystallizable (Fc) region of bevacizumab cooperates with the Toll-like receptor-4 (TLR4) ligand to induce M2b polarization in macrophages and secrete tumor necrosis factor-α (TNFα), which promotes immunosuppression, tumor metastasis, and angiogenesis. However, the downstream mechanism underlying TNFα-mediated bevacizumab resistance requires further investigation. Our RNA-Seq analysis results revealed that the expression of endothelial cell specific molecule-1 (ESM1) increased significantly in drug-resistant tumors and promoted metastasis and angiogenesis in vitro and in vivo. Furthermore, TNFα induced the upregulation of ESM1, which promotes metastasis and angiogenesis and regulates matrix metalloprotease-9 (MMP9), vascular endothelial growth factor (VEGF), and delta-like ligand-4 molecules (DLL4). Accordingly, the curative effect of bevacizumab improved by neutralizing ESM1 with high-affinity anti-ESM1 monoclonal antibody 1-2B7 in bevacizumab-resistant mice. This study provides important insights regarding the molecular mechanism by which TNFα-induced ESM1 expression promotes angiogenesis, which is significant for elucidating the mechanism of bevacizumab drug resistance and possibly identifying appropriate biosimilar molecules.

Potent GCN2 Inhibitor Capable of Reversing MDSC-Driven T Cell Suppression Demonstrates In Vivo Efficacy as a Single Agent and in Combination with Anti-Angiogenesis Therapy

General control nonderepressible 2 (GCN2) protein kinase is a cellular stress sensor within the tumor microenvironment (TME), whose signaling cascade has been proposed to contribute to immune escape in tumors. Herein, we report the discovery of cell-potent GCN2 inhibitors with excellent selectivity against its closely related Integrated Stress Response (ISR) family members heme-regulated inhibitor kinase (HRI), protein kinase R (PKR), and (PKR)-like endoplasmic reticulum kinase (PERK), as well as good kinome-wide selectivity and favorable PK. In mice, compound 39 engages GCN2 at levels ≥80% with an oral dose of 15 mg/kg BID. We also demonstrate the ability of compound 39 to alleviate MDSC-related T cell suppression and restore T cell proliferation, similar to the effect seen in MDSCs from GCN2 knockout mice. In the LL2 syngeneic mouse model, compound 39 demonstrates significant tumor growth inhibition (TGI) as a single agent. Furthermore, TGI mediated by anti-VEGFR was enhanced by treatment with compound 39 demonstrating the complementarity of these two mechanisms.

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.

New insights into antiangiogenic therapy resistance in cancer: Mechanisms and therapeutic aspects

Angiogenesis is a hallmark of cancer and is required for tumor growth and progression. Antiangiogenic therapy has been revolutionarily developing and was approved for the treatment of various types of cancer for nearly two decades, among which bevacizumab and sorafenib continue to be the two most frequently used antiangiogenic drugs. Although antiangiogenic therapy has brought substantial survival benefits to many cancer patients, resistance to antiangiogenic drugs frequently occurs during clinical treatment, leading to poor outcomes and treatment failure. Cumulative evidence has demonstrated that the intricate interplay among tumor cells, bone marrow-derived cells, and local stromal cells critically allows for tumor escape from antiangiogenic therapy. Currently, drug resistance has become the main challenge that hinders the therapeutic efficacies of antiangiogenic therapy. In this review, we describe and summarize the cellular and molecular mechanisms conferring tumor drug resistance to antiangiogenic therapy, which was predominantly associated with redundancy in angiogenic signaling molecules (e.g., VEGFs, GM-CSF, G-CSF, and IL17), alterations in biological processes of tumor cells (e.g., tumor invasiveness and metastasis, stemness, autophagy, metabolic reprogramming, vessel co-option, and vasculogenic mimicry), increased recruitment of bone marrow-derived cells (e.g., myeloid-derived suppressive cells, tumor-associated macrophages, and tumor-associated neutrophils), and changes in the biological functions and features of local stromal cells (e.g., pericytes, cancer-associated fibroblasts, and endothelial cells). We also review potential biomarkers to predict the response to antiangiogenic therapy in cancer patients, which mainly consist of imaging biomarkers, cellular and extracellular proteins, a certain type of bone marrow-derived cells, local stromal cell content (e.g., pericyte coverage) as well as serum or plasma biomarkers (e.g., non-coding RNAs). Finally, we highlight the recent advances in combination strategies with the aim of enhancing the response to antiangiogenic therapy in cancer patients and mouse models. This review introduces a comprehensive understanding of the mechanisms and biomarkers associated with the evasion of antiangiogenic therapy in cancer, providing an outlook for developing more effective approaches to promote the therapeutic efficacy of antiangiogenic therapy.

Immunosuppressive tumor microenvironment in Uterine Serous Carcinoma via CCL7 signal with myeloid-derived suppressor cells

Serous carcinoma of the uterus (USC) is a pathological subtype of high-grade endometrial cancers, with no effective treatment for advanced cases. Since such refractory tumors frequently harbor anti-tumor immune tolerance, many immunotherapies have been investigated for various malignant tumors using immuno-competent animal models mimicking their local immunities. In this study, we established an orthotopic mouse model of high-grade endometrial cancer and evaluated the local tumor immunity to explore the efficacy of immunotherapies against USC. A multivariate analysis of 62 human USC cases revealed that the tumor infiltrating cell status, few CD8+ cells and abundant myeloid-derived suppressor cells (MDSCs), was an independent prognostic factor (p<0.005). A murine endometrial cancer cell (mECC) was obtained from C57BL/6 mice via endometrium-specific deletion of Pten and Tp53, and another high-grade cell (HPmECC) was established by further overexpressing Myc in mECCs. HPmECCs exhibited higher capacities of migration and anchorage-independent proliferation than mECCs (p<0.01, p<0.0001), and when both types of cells were inoculated into the uterus of C57BL/6 mice, the prognosis of mice bearing HPmECC-derived tumors was significantly poorer (p<0.001). Histopathological analysis of HPmECC orthotopic tumors showed serous carcinoma-like features with prominent tumor infiltration of MDSCs (p<0.05), and anti Gr-1 antibody treatment significantly prolonged the prognosis of HPmECC-derived tumor-bearing mice (p<0.05). High CCL7 expression was observed in human USC and HPmECC, and MDSCs migration was promoted in a CCL7 concentration-dependent manner. These results indicate that anti-tumor immunity is suppressed in USC due to increased number of tumor-infiltrating MDSCs via CCL signal.

Targeting oncogene and non-oncogene addiction to inflame the tumour microenvironment

Immune checkpoint inhibitors (ICIs) have revolutionized the clinical management of multiple tumours. However, only a few patients respond to ICIs, which has generated considerable interest in the identification of resistance mechanisms. One such mechanism reflects the ability of various oncogenic pathways, as well as stress response pathways required for the survival of transformed cells (a situation commonly referred to as 'non-oncogene addiction'), to support tumour progression not only by providing malignant cells with survival and/or proliferation advantages, but also by establishing immunologically 'cold' tumour microenvironments (TMEs). Thus, both oncogene and non-oncogene addiction stand out as promising targets to robustly inflame the TME and potentially enable superior responses to ICIs.

Polyamine Immunometabolism: Central Regulators of Inflammation, Cancer and Autoimmunity

Polyamines are ubiquitous, amine-rich molecules with diverse processes in biology. Recent work has highlighted that polyamines exert profound roles on the mammalian immune system, particularly inflammation and cancer. The mechanisms by which they control immunity are still being described. In the context of inflammation and autoimmunity, polyamine levels inversely correlate to autoimmune phenotypes, with lower polyamine levels associated with higher inflammatory responses. Conversely, in the context of cancer, polyamines and polyamine biosynthetic genes positively correlate with the severity of malignancy. Blockade of polyamine metabolism in cancer results in reduced tumor growth, and the effects appear to be mediated by an increase in T-cell infiltration and a pro-inflammatory phenotype of macrophages. These studies suggest that polyamine depletion leads to inflammation and that polyamine enrichment potentiates myeloid cell immune suppression. Indeed, combinatorial treatment with polyamine blockade and immunotherapy has shown efficacy in pre-clinical models of cancer. Considering the efficacy of immunotherapies is linked to autoimmune sequelae in humans, termed immune-adverse related events (iAREs), this suggests that polyamine levels may govern the inflammatory response to immunotherapies. This review proposes that polyamine metabolism acts to balance autoimmune inflammation and anti-tumor immunity and that polyamine levels can be used to monitor immune responses and responsiveness to immunotherapy.

Immunological control of ovarian carcinoma by chemotherapy and targeted anticancer agents

At odds with other solid tumors, epithelial ovarian cancer (EOC) is poorly sensitive to immune checkpoint inhibitors (ICIs), largely reflecting active immunosuppression despite CD8⁺ T cell infiltration at baseline. Accumulating evidence indicates that both conventional chemotherapeutics and targeted anticancer agents commonly used in the clinical management of EOC not only mediate a cytostatic and cytotoxic activity against malignant cells, but also drive therapeutically relevant immunostimulatory or immunosuppressive effects. Here, we discuss such an immunomodulatory activity, with a specific focus on molecular and cellular pathways that can be harnessed to develop superior combinatorial regimens for clinical EOC care.

Long non-coding RNA PAARH promotes hepatocellular carcinoma progression and angiogenesis via upregulating HOTTIP and activating HIF-1α/VEGF signaling

Hepatocellular carcinoma (HCC) is one of the leading lethal malignancies and a hypervascular tumor. Although some long non-coding RNAs (lncRNAs) have been revealed to be involved in HCC. The contributions of lncRNAs to HCC progression and angiogenesis are still largely unknown. In this study, we identified a HCC-related lncRNA, CMB9-22P13.1, which was highly expressed and correlated with advanced stage, vascular invasion, and poor survival in HCC. We named this lncRNA Progression and Angiogenesis Associated RNA in HCC (PAARH). Gain- and loss-of function assays revealed that PAARH facilitated HCC cellular growth, migration, and invasion, repressed HCC cellular apoptosis, and promoted HCC tumor growth and angiogenesis in vivo. PAARH functioned as a competing endogenous RNA to upregulate HOTTIP via sponging miR-6760-5p, miR-6512-3p, miR-1298-5p, miR-6720-5p, miR-4516, and miR-6782-5p. The expression of PAARH was significantly positively associated with HOTTIP in HCC tissues. Functional rescue assays verified that HOTTIP was a critical mediator of the roles of PAARH in modulating HCC cellular growth, apoptosis, migration, and invasion. Furthermore, PAARH was found to physically bind hypoxia inducible factor-1 subunit alpha (HIF-1α), facilitate the recruitment of HIF-1α to VEGF promoter, and activate VEGF expression under hypoxia, which was responsible for the roles of PAARH in promoting angiogenesis. The expression of PAARH was positively associated with VEGF expression and microvessel density in HCC tissues. In conclusion, these findings demonstrated that PAARH promoted HCC progression and angiogenesis via upregulating HOTTIP and activating HIF-1α/VEGF signaling. PAARH represents a potential prognostic biomarker and therapeutic target for HCC.

(Im)maturity in Tumor Ecosystem

Tumors have special features that make them distinct from their normal counterparts. Immature cells in a tumor mass and their critical contributions to the tumorigenesis will open new windows toward cancer therapy. Incomplete cellular development brings versatile and unique functionality in the cellular tumor ecosystem, such as what is seen for highly potential embryonic cells. There is evidence that maturation of certain types of cells in this ecosystem can recover the sensitivity of the tumor. Therefore, understanding more about the mechanisms that contributed to this immaturity will render new therapeutic approaches in cancer therapy. Targeting such mechanisms can be exploited as a supplementary to the current immunotherapeutic treatment schedules, such as immune checkpoint inhibitor (ICI) therapy. The key focus of this review is to discuss the impact of (im)maturity in cellular tumor ecosystems on cancer progression, focusing mainly on immaturity in the immune cell compartment of the tumor, as well as on the stemness of tumor cells.

FcγRIIB potentiates differentiation of myeloid-derived suppressor cells to mediate tumor immunoescape

Background: FcγRIIB, the sole inhibitory receptor of the Fc gamma receptor family, plays pivotal roles in innate and adaptive immune responses. However, the expression and function of FcγRIIB in myeloid-derived suppressor cells (MDSCs) remains unknown. This study aimed to investigate whether and how FcγRIIB regulates the immunosuppressive activity of MDSCs during cancer development. Methods: The MC38 and B16-F10 tumor-bearing mouse models were established to investigate the role of FcγRIIB during tumor progression. FcγRIIB-deficient mice, adoptive cell transfer, mRNA-sequencing and flow cytometry analysis were used to assess the role of FcγRIIB on immunosuppressive activity and differentiation of MDSCs. Results: Here we show that FcγRIIB was upregulated in tumor-infiltrated MDSCs. FcγRIIB-deficient mice showed decreased accumulation of MDSCs in the tumor microenvironment (TME) compared with wild-type mice. FcγRIIB was required for the differentiation and immunosuppressive activity of MDSCs. Mechanistically, tumor cell-derived granulocyte-macrophage colony stimulating factor (GM-CSF) increased the expression of FcγRIIB on hematopoietic progenitor cells (HPCs) by activating specificity protein 1 (Sp1), subsequently FcγRIIB promoted the generation of MDSCs from HPCs via Stat3 signaling. Furthermore, blockade of Sp1 dampened MDSC differentiation and infiltration in the TME and enhanced the anti-tumor therapeutic efficacy of gemcitabine. Conclusion: These results uncover an unrecognized regulatory role of the FcγRIIB in abnormal differentiation of MDSCs during cancer development and suggest a potential therapeutic target for anti-tumor therapy.

The Role of Myeloid-Derived Suppressor Cells in the Treatment of Pancreatic Cancer

Pancreatic cancer has the highest mortality rate of all major cancers, with a 5-year survival rate of about 10%. Early warning signs and symptoms of pancreatic cancer are vague or nonexistent, and most patients are diagnosed in Stage IV, when surgery is not an option for about 80%-85% of patients. For patients with inoperable pancreatic cancer, current conventional treatment modalities such as chemotherapy and radiotherapy (RT) have suboptimal efficacy. Tumor progression is closely associated with the tumor microenvironment, which includes peripheral blood vessels, bone marrow-derived inflammatory cells, fibroblasts, immune cells, signaling molecules, and extracellular matrix. Tumor cells affect the microenvironment by releasing extracellular signaling molecules, inducing peripheral immune tolerance, and promoting tumor angiogenesis. In turn, the immune cells of the tumor affect the survival and proliferation of cancer cells. Myeloid-derived suppressor cells are key cellular components in the tumor microenvironment and exert immunosuppressive functions by producing cytokines, recognizing other immune cells, and promoting tumor growth and metastasis. Myeloid-derived suppressor cells are the main regulator of the tumor immune response and a key target for tumor treatments. Since the combination of RT and immunotherapy is the main strategy for the treatment of pancreatic cancer, it is very important to understand the immune mechanisms which lead to MDSCs generation and the failure of current therapies in order to develop new target-based therapies. This review summarizes the research advances on the role of Myeloid-derived suppressor cells in the progression of pancreatic cancer and its treatment application in recent years.

"γδT Cell-IL17A-Neutrophil" Axis Drives Immunosuppression and Confers Breast Cancer Resistance to High-Dose Anti-VEGFR2 Therapy

Angiogenesis is an essential physiological process and hallmark of cancer. Currently, antiangiogenic therapy, mostly targeting the vascular endothelial growth factor (VEGF)/VEGFR2 signaling axis, is commonly used in the clinic for solid tumors. However, antiangiogenic therapies for breast cancer patients have produced limited survival benefits since cancer cells rapidly resistant to anti-VEGFR2 therapy. We applied the low-dose and high-dose VEGFR2 mAb or VEGFR2-tyrosine kinase inhibitor (TKI) agents in multiple breast cancer mouse models and found that low-dose VEGFR2 mAb or VEGFR2-TKI achieved good effects in controlling cancer progression, while high-dose treatment was not effective. To further investigate the mechanism involved in regulating the drug resistance, we found that high-dose anti-VEGFR2 treatment elicited IL17A expression in γδ T cells via VEGFR1-PI3K-AKT pathway activation and then promoted N2-like neutrophil polarization, thus inducing CD8⁺ T cell exhaustion to shape an immunosuppressive microenvironment. Combining anti-VEGFR2 therapy with immunotherapy such as IL17A, PD-1 or Ly-6G mAb therapy, which targeting the immunomodulatory axis of "γδT17 cells-N2 neutrophils" in vivo, showed promising therapeutic effects in breast cancer treatment. This study illustrates the potential mechanism of antiangiogenic therapy resistance in breast cancer and provides synergy treatment for cancer.

Ovarian cancer modulates the immunosuppressive function of CD11b+Gr1+ myeloid cells via glutamine metabolism

OBJECTIVE

Immature CD11b + Gr1+ myeloid cells that acquire immunosuppressive capability, also known as myeloid-derived suppressor cells (MDSCs), are a heterogeneous population of cells that regulate immune responses. Our study's objective was to elucidate the role of ovarian cancer microenvironment in regulating the immunosuppressive function of CD11b+Gr1+ myeloid cells.

METHODS

All studies were performed using the intraperitoneal ID8 syngeneic epithelial ovarian cancer mouse model. Myeloid cell depletion and immunotherapy were carried out using anti-Gr1 mAb, gemcitabine treatments, and/or anti-PD1 mAb. The treatment effect was assessed by a survival curve, in situ luciferase-guided imaging, and histopathologic evaluation. Adoptive transfer assays were carried out between congenic CD45.2 and CD45.1 mice. Immune surface and intracellular markers were assessed by flow cytometry. ELISA, western blot, and RT-PCR techniques were employed to assess the protein and RNA expression of various markers. Bone marrow-derived myeloid cells were used for ex-vivo studies.

RESULTS

The depletion of Gr1+ immunosuppressive myeloid cells alone and in combination with anti-PD1 immunotherapy inhibited ovarian cancer growth. In addition to the adoptive transfer studies, these findings validate the role of immunosuppressive CD11b+Gr1+ myeloid cells in promoting ovarian cancer. Mechanistic investigations showed that ID8 tumor cells and their microenvironments produced recruitment and regulatory factors for immunosuppressive CD11b+Gr1+ myeloid cells. CD11b+Gr1+ myeloid cells primed by ID8 tumors showed increased immunosuppressive marker expression and acquired an energetic metabolic phenotype promoted primarily by increased oxidative phosphorylation fueled by glutamine. Inhibiting the glutamine metabolic pathway reduced the increased oxidative phosphorylation and decreased immunosuppressive markers' expression and function. Dihydrolipoamide succinyl transferase (DLST), a subunit of α-KGDC in the TCA cycle, was found to be the most significantly elevated gene in tumor-primed myeloid cells. The inhibition of DLST reduced oxidative phosphorylation, immunosuppressive marker expression and function in myeloid cells.

CONCLUSION

Our study shows that the ovarian cancer microenvironment can regulate the metabolism and function of immunosuppressive CD11b + Gr1+ myeloid cells and modulate its immune microenvironment. Targeting glutamine metabolism via DLST in immunosuppressive myeloid cells decreased their activity, leading to a reduction in the immunosuppressive tumor microenvironment. Thus, targeting glutamine metabolism has the potential to enhance the success of immunotherapy in ovarian cancer.

Antidiabetic DPP-4 Inhibitors Reprogram Tumor Microenvironment That Facilitates Murine Breast Cancer Metastasis Through Interaction With Cancer Cells via a ROS-NF-кB-NLRP3 Axis

Improvement of understanding of the safety profile and biological significance of antidiabetic agents in breast cancer (BC) progression may shed new light on minimizing the unexpected side effect of antidiabetic reagents in diabetic patients with BC. Our recent finding showed that Saxagliptin (Sax) and Sitagliptin (Sit), two common antidiabetic dipeptidyl peptidase-4 inhibitors (DPP-4i) compounds, promoted murine BC 4T1 metastasis via a ROS–NRF2–HO-1 axis in nonobese diabetic–severe combined immunodeficiency (NOD-SCID) mice. However, the potential role of DPP-4i in BC progression under immune-competent status remains largely unknown. Herein, we extended our investigation and revealed that Sax and Sit also accelerated murine BC 4T1 metastasis in orthotopic, syngeneic, and immune-competent BALB/c mice. Mechanically, we found that DPP-4i not only activated ROS–NRF2–HO-1 axis but also triggered reactive oxygen species (ROS)-dependent nuclear factor kappa B (NF-κB) activation and its downstream metastasis-associated gene levels in vitro and in vivo, while NF-кB inhibition significantly abrogated DPP-4i-driven BC metastasis in vitro. Meanwhile, inhibition of NRF2–HO-1 activation attenuated DPP-4i-driven NF-кB activation, while NRF2 activator ALA enhanced NF-кB activation, indicating an essential role of ROS–NRF2–HO-1 axis in DPP-4i-driven NF-кB activation. Furthermore, we also found that DPP-4i increased tumor-infiltrating CD45, MPO, F4/80, CD4, and Foxp3-positive cells and myeloid-derived suppressor cells (MDSCs), and decreased CD8-positive lymphocytes in metastatic sites, but did not significantly alter cell viability, apoptosis, differentiation, and suppressive activation of 4T1-induced splenic MDSCs. Moreover, we revealed that DPP-4i triggered ROS-NF-κB-dependent NLRP3 inflammasome activation in BC cells, leading to increase in inflammation cytokines such as interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), vascular endothelial growth factor (VEGF), intercellular cell adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), IL-1β and IL-33, and MDSCs inductors granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF, and M-CSF, which play a crucial role in the remodeling of tumor immune-suppressive microenvironment. Thus, our findings suggest that antidiabetic DPP-4i reprograms tumor microenvironment that facilitates murine BC metastasis by interaction with BC cells via a ROS–NRF2–HO-1–NF-κB–NLRP3 axis. This finding not only provides a mechanistic insight into the oncogenic ROS–NRF2–HO-1 in DPP-4i-driven BC progression but also offers novel insights relevant for the improvement of tumor microenvironment to alleviate DPP-4i-induced BC metastasis.

Myeloid-derived suppressor cells as immunosuppressive regulators and therapeutic targets in cancer

Myeloid-derived suppressor cells (MDSCs) are a heterogenic population of immature myeloid cells with immunosuppressive effects, which undergo massive expansion during tumor progression. These cells not only support immune escape directly but also promote tumor invasion via various non-immunological activities. Besides, this group of cells are proved to impair the efficiency of current antitumor strategies such as chemotherapy, radiotherapy, and immunotherapy. Therefore, MDSCs are considered as potential therapeutic targets for cancer therapy. Treatment strategies targeting MDSCs have shown promising outcomes in both preclinical studies and clinical trials when administrated alone, or in combination with other anticancer therapies. In this review, we shed new light on recent advances in the biological characteristics and immunosuppressive functions of MDSCs. We also hope to propose an overview of current MDSCs-targeting therapies so as to provide new ideas for cancer treatment.

Metabolic reprogramming of myeloid-derived suppressor cells: An innovative approach confronting challenges

Immune cells such as T cells, macrophages, dendritic cells, and other immunoregulatory cells undergo metabolic reprogramming in cancer and inflammation-derived microenvironment to meet specific physiologic and functional demands. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that are characterized by immunosuppressive activity, which plays a key role in host immune homeostasis. In this review, we have discussed the core metabolic pathways, including glycolysis, lipid and fatty acid biosynthesis, and amino acid metabolism in the MDSCs under various pathologic situations. Metabolic reprogramming is a determinant of the phenotype and functions of MDSCs, and is therefore a novel therapeutic possibility in various diseases.

Recent advancements of antiangiogenic combination therapies in ovarian cancer

Ovarian cancer is a deadly malignancy with a growing therapeutic armamentarium, though achieving sustained benefit in the clinic remains largely elusive. Through biomarker and genetic analysis, several pathways of resistance and sensitivity to commonly used therapeutics have been identified, expanding the potential of identifying unique drug combinations and indicating new directions for improving clinical outcomes. Here, we review the mechanisms of angiogenic response and antiangiogenic therapy in ovarian cancer, as well as the interactions it exhibits with the immune and DNA damage response pathways. We discuss results from clinical trials examining the combinations of antiangiogenics, PARP inhibitors, and immune checkpoint inhibitors are also discussed, as well as several ongoing trials.

Tumor-related stress regulates functional plasticity of MDSCs

Myeloid-derived suppressor cells (MDSCs) impair protective anti-tumor immunity and remain major obstacles that stymie the effectiveness of promising cancer therapies. Diverse tumor-derived stressors galvanize the differentiation, intra-tumoral expansion, and immunomodulatory function of MDSCs. These tumor-associated 'axes of stress' underwrite the immunosuppressive programming of MDSCs in cancer and contribute to the phenotypic/functional heterogeneity that characterize tumor-MDSCs. This review discusses various tumor-associated axes of stress that direct MDSC development, accumulation, and immunosuppressive function, as well as current strategies aimed at overcoming the detrimental impact of MDSCs in cancer. To better understand the constellation of signals directing MDSC biology, we herein summarize the pivotal roles, signaling mediators, and effects of reactive oxygen/nitrogen species-related stress, chronic inflammatory stress, hypoxia-linked stress, endoplasmic reticulum stress, metabolic stress, and therapy-associated stress on MDSCs. Although therapeutic targeting of these processes remains mostly pre-clinical, intercepting signaling through the axes of stress could overcome MDSC-related immune suppression in tumor-bearing hosts.

Human endoglin-CD3 bispecific T cell engager antibody induces anti-tumor effect in vivo

Rationale: Endoglin, also known as CD105, is a homo-dimeric membrane glycoprotein required for angiogenesis and serves as a marker for cancer vasculature. In this study, we constructed a bispecific T-cell engager (BiTE) antibody that targets human endoglin and CD3 (hEND-CD3/BiTE). We examined BiTE binding to endoglin-expressing cells and its effects on the cytolytic activity of T cells and cancer development.

Methods: The in vitro effects of hEND-CD3/BiTE, including binding to target cells, T-cell activation, proliferation, and cytotoxicity, were examined in endoglin-expressing 293T cells, human umbilical vascular endothelial cells, tumor-derived endothelial cells, and CD3⁺ T cells. An in vivo xenograft tumor model was established using A549 human lung cancer cells. The therapeutic efficacy of hEND-CD3/BiTE was assessed by monitoring tumor growth, angiogenesis, and mouse survival.

Results: hEND-CD3/BiTE specifically bound to endoglin-expressing cells and CD3⁺ T cells in vitro and stimulated T-cell activation, proliferation, and Th1 cytokine secretion, and promoted T-cell-mediated cytolysis of endoglin-expressing cells. The hEND-CD3/BiTE in vivo caused minimal toxicity to major organs, reduced tumor neoangiogenesis, inhibited tumor growth, and significantly improved mouse survival.

Conclusions: Our study demonstrated the therapeutic potential of hEND-CD3/BiTE and provided a novel approach to clinical cancer treatment.

Tumor Immune Microenvironment during Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) has been shown to play a critical role in tumor development from initiation to metastasis. EMT could be regarded as a continuum, with intermediate hybrid epithelial and mesenchymal phenotypes having high plasticity. Classical EMT is characterized by the phenotype change of epithelial cells to cells with mesenchymal properties, but EMT is also associated with multiple other molecular processes, including tumor immune evasion. Some previous studies have shown that EMT is associated with the cell number of immunosuppressive cells, such as myeloid-derived suppressor cells, and the expression of immune checkpoints, such as programmed cell death-ligand 1, in several cancer types. At the molecular level, EMT transcriptional factors, including Snail, Zeb1, and Twist1, produce or attract immunosuppressive cells or promote the expression of immunosuppressive checkpoint molecules via chemokine production, leading to a tumor immunosuppressive microenvironment. In turn, immunosuppressive factors induce EMT in tumor cells. This feedback loop between EMT and immunosuppression promotes tumor progression. For therapy directly targeting EMT has been challenging, the elucidation of the interactive regulation of EMT and immunosuppression is desirable for developing new therapeutic approaches in cancer. The combination of immune checkpoint inhibitors and immunotherapy targeting immunosuppressive cells could be a promising therapy for EMT.

Assessing Preclinical Research Models for Immunotherapy for Gynecologic Malignancies

Gynecologic malignancies are increasing in incidence, with a plateau in clinical outcomes necessitating novel treatment options. Immunotherapy and modulation of the tumor microenvironment are rapidly developing fields of interest in gynecologic oncology translational research; examples include the PD-1 (programmed cell death 1) and CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) axes and the Wnt pathway. However, clinical successes with these agents have been modest and lag behind immunotherapy successes in other malignancies. A thorough contextualization of preclinical models utilized in gynecologic oncology immunotherapy research is necessary in order to effectively and efficiently develop translational medicine. These include murine models, in vitro assays, and three-dimensional human-tissue-based systems. Here, we provide a comprehensive review of preclinical models for immunotherapy in gynecologic malignancies, including benefits and limitations of each, in order to inform study design and translational research models. Improved model design and implementation will optimize preclinical research efficiency and increase the translational value to positive findings, facilitating novel treatments that improve patient outcomes.

Comments on the ambiguity of selected surface markers, signaling pathways and omics profiles hampering the identification of myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSC) are important immune-regulatory cells but their identification remains difficult. Here, we provide a critical view on selected surface markers, transcriptional and translational pathways commonly used to identify MDSC by specific, their developmental origin and new possibilities by transcriptional or proteomic profiling. Discrimination of MDSC from their non-suppressive counterparts is a prerequisite for the development of successful therapies. Understanding the switch mechanisms that direct granulocytic and monocytic development into a pro-inflammatory or anti-inflammatory direction will be crucial for therapeutic strategies. Manipulation of these myeloid checkpoints are exploited by tumors and pathogens, such as M. tuberculosis (Mtb), HIV or SARS-CoV-2, that induce MDSC for immune evasion. Thus, specific markers for MDSC identification may reveal also novel molecular candidates for therapeutic intervention at the level of MDSC.

Novel Combinatorial Approaches to Tackle the Immunosuppressive Microenvironment of Prostate Cancer

Prostate cancer (PCa) is the second-most common cancer in men worldwide and treatment options for patients with advanced or aggressive prostate cancer or recurrent disease continue to be of limited success and are rarely curative. Despite immune checkpoint blockade (ICB) efficacy in some melanoma, lung, kidney and breast cancers, immunotherapy efforts have been remarkably unsuccessful in PCa. One hypothesis behind this lack of efficacy is the generation of a distinctly immunosuppressive prostate tumor microenvironment (TME) by regulatory T cells, MDSCs, and type 2 macrophages which have been implicated in a variety of pathological conditions including solid cancers. In PCa, Tregs and MDSCs are attracted to TME by low-grade chronic inflammatory signals, while tissue-resident type 2 macrophages are induced by cytokines such as IL4, IL10, IL13, transforming growth factor beta (TGFβ) or prostaglandin E2 (PGE2) produced by Th2 cells. These then drive tumor progression, therapy resistance and the generation of castration resistance, ultimately conferring a poor prognosis. The biology of MDSC and Treg is highly complex and the development, proliferation, maturation or function can each be pharmacologically mediated to counteract the immunosuppressive effects of these cells. Herein, we present a critical review of Treg, MDSC and M2 involvement in PCa progression but also investigate a newly recognized type of immune suppression induced by the chronic stimulation of the sympathetic adrenergic signaling pathway and propose targeted strategies to be used in a combinatorial modality with immunotherapy interventions such as ICB, Sipuleucel-T or antitumor vaccines for an enhanced anti-PCa tumor immune response. We conclude that a strategic sequence of therapeutic interventions in combination with additional holistic measures will be necessary to achieve maximum benefit for PCa patients.

Myeloid-Derived Suppressor Cells: Facilitators of Cancer and Obesity-Induced Cancer

Immature myeloid cells at varied stages of differentiation, known as myeloid-derived suppressor cells (MDSC), are present in virtually all cancer patients. MDSC are profoundly immune-suppressive cells that impair adaptive and innate antitumor immunity and promote tumor progression through nonimmune mechanisms. Their widespread presence combined with their multitude of protumor activities makes MDSC a major obstacle to cancer immunotherapies. MDSC are derived from progenitor cells in the bone marrow and traffic through the blood to infiltrate solid tumors. Their accumulation and suppressive potency are driven by multiple tumor- and host-secreted proinflammatory factors and adrenergic signals that act via diverse but sometimes overlapping transcriptional pathways. MDSC also accumulate in response to the chronic inflammation and lipid deposition characteristic of obesity and contribute to the more rapid progression of cancers in obese individuals. This article summarizes the key aspects of tumor-induced MDSC with a focus on recent progress in the MDSC field.

Potential Novel Ovarian Cancer Treatment Targeting Myeloid-Derived Suppressor Cells

Diagnosis by biopsy is difficult in the ovary since it is located deep in the abdomen. As a result, ovarian cancer is mostly found insidiously during exploratory laparotomy. Consequently, the early diagnosis of ovarian cancer is often difficult. The likelihood of peritoneal dissemination increases with the progress of ovarian cancer. With further progression, ovarian cancer metastasizes to the momentum, retroperitoneal lymph nodes, large intestine, small intestine, diaphragm, spleen, and other organs. Ovarian cancer has been considered a tumor that has a favorable response to chemotherapy, but more effective treatments are still being explored. Tumors use their own immune escape mechanism to evade host immunity. The immune checkpoint (IC) mechanism, one of the immune escape mechanisms, is established by programmed cell death-1 (PD-1)/PD-ligand-1 (PD-L1) communication. It has been shown that inhibiting PD-1/PD-L1 communication in various malignancies produces antitumor effects. However, the antitumor effect of ICI monotherapy on ovarian cancer is limited in actual clinical practice. In this review, we describe a novel cancer immunotherapeutic agent that targets myeloid-derived suppressor cells (MDSCs).