The role of macrophages in the tumor microenvironment and tumor metabolism

Robust anti-tumor immunity through the integration of targeted lipid nanoparticle-based mRNA nanovaccines with PD-1/PD-L1 blockade

Tumor mRNA vaccines present a personalized approach in cancer immunotherapy, encoding distinct tumor antigens to evoke robust immune responses and offering the potential against emerging tumor variants. Despite this, the clinical advancement of tumor mRNA vaccines has been hampered by their limited delivery capacity and inefficient activation of antigen-presenting cells (APCs). Herein, we employed microfluidics technology to engineer mannose-modified lipid-based nanovaccines for specifically targeting APCs. The encapsulation process efficiently entrapped the cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) agonist along with mRNA encoding antigens. The targeted nanovaccines (TNVs) exhibited a narrow particle size distribution, ensuring consistent and efficient delivery. These TNVs significantly enhanced gene expression of mRNA, facilitating antigen presentation and immune activation. When compared to non-targeted nanovaccines, TNVs outperformed in terms of antigen presentation and immune activation. Furthermore, the combination of anti-PD-L1 antibodies with TNVs elicited a synergistic anti-tumor effect. This was attributed to the anti-PD-L1 antibodies' ability to overcome the immune suppression of tumor cells. Our findings suggest that the combination treatment elicited the most robust anti-tumor immune activation and immune memory effect. These results indicate that integrating tumor mRNA vaccines with immune checkpoint inhibitors or other immunostimulatory agents may be crucial for enhancing the immune response.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

The role of tumor-associated macrophages in tumor immune evasion

BACKGROUND

Tumor growth is closely linked to the activities of various cells in the tumor microenvironment (TME), particularly immune cells. During tumor progression, circulating monocytes and macrophages are recruited, altering the TME and accelerating growth. These macrophages adjust their functions in response to signals from tumor and stromal cells. Tumor-associated macrophages (TAMs), similar to M2 macrophages, are key regulators in the TME.

METHODS

We review the origins, characteristics, and functions of TAMs within the TME. This analysis includes the mechanisms through which TAMs facilitate immune evasion and promote tumor metastasis. Additionally, we explore potential therapeutic strategies that target TAMs.

RESULTS

TAMs are instrumental in mediating tumor immune evasion and malignant behaviors. They release cytokines that inhibit effector immune cells and attract additional immunosuppressive cells to the TME. TAMs primarily target effector T cells, inducing exhaustion directly, influencing activity indirectly through cellular interactions, or suppressing through immune checkpoints. Additionally, TAMs are directly involved in tumor proliferation, angiogenesis, invasion, and metastasis. Developing innovative tumor-targeted therapies and immunotherapeutic strategies is currently a promising focus in oncology. Given the pivotal role of TAMs in immune evasion, several therapeutic approaches have been devised to target them. These include leveraging epigenetics, metabolic reprogramming, and cellular engineering to repolarize TAMs, inhibiting their recruitment and activity, and using TAMs as drug delivery vehicles. Although some of these strategies remain distant from clinical application, we believe that future therapies targeting TAMs will offer significant benefits to cancer patients.

Targeting the adenosine signaling pathway in macrophages for cancer immunotherapy

One of the ways in which macrophages support tumorigenic growth is by producing adenosine, which acts to dampen antitumor immune responses and is generated by both tumor and immune cells in the tumor microenvironment (TME). Two cell surface expressed molecules, CD73 and CD39, boost catalytic adenosine triphosphate, leading to further increased adenosine synthesis, under hypoxic circumstances in the TME. There are four receptors (A1, A2A, A2B, and A3) expressed on macrophages that allow adenosine to perform its immunomodulatory effect. Researchers have shown that adenosine signaling is a key factor in tumor progression and an attractive therapeutic target for treating cancer. Several antagonistic adenosine-targeting biological therapies that decrease the suppressive action of tumor-associated macrophages have been produced and explored to transform this result from basic research into a therapeutic advantage. Here, we'll review the newest findings from studies of pharmacological compounds that target adenosine receptors, and their potential therapeutic value based on blocking the suppressive action of macrophages in tumors.

Exosome-mediated communication between gastric cancer cells and macrophages: implications for tumor microenvironment

Gastric cancer (GC) is a malignant neoplasm originating from the epithelial cells of the gastric mucosa. The pathogenesis of GC is intricately linked to the tumor microenvironment within which the cancer cells reside. Tumor-associated macrophages (TAMs) primarily differentiate from peripheral blood monocytes and can be broadly categorized into M1 and M2 subtypes. M2-type TAMs have been shown to promote tumor growth, tissue remodeling, and angiogenesis. Furthermore, they can actively suppress acquired immunity, leading to a poorer prognosis and reduced tolerance to chemotherapy. Exosomes, which contain a myriad of biologically active molecules including lipids, proteins, mRNA, and noncoding RNAs, have emerged as key mediators of communication between tumor cells and TAMs. The exchange of these molecules via exosomes can markedly influence the tumor microenvironment and consequently impact tumor progression. Recent studies have elucidated a correlation between TAMs and various clinicopathological parameters of GC, such as tumor size, differentiation, infiltration depth, lymph node metastasis, and TNM staging, highlighting the pivotal role of TAMs in GC development and metastasis. In this review, we aim to comprehensively examine the bidirectional communication between GC cells and TAMs, the implications of alterations in the tumor microenvironment on immune escape, invasion, and metastasis in GC, targeted therapeutic approaches for GC, and the efficacy of potential GC drug resistance strategies.

Metformin improved a heterologous prime-boost of dual-targeting cancer vaccines to inhibit tumor growth in a melanoma mouse model

Therapeutic cancer vaccines, which induce anti-tumor immunity by targeting specific antigens, constitute a promising approach to cancer therapy. Our previous work proposed an optimized heterologous immunization strategy using cancer gene vaccines co-targeting MUC1 and survivin. Administration of a DNA vaccine three times within a week followed by a single recombinant MVA (rMVA) boost was able to efficiently induce anti-tumor immunity and inhibit tumor growth in tumor-bearing mouse models However, the complex immunosuppressive tumor microenvironment always limits infiltration by vaccine-induced T cells. Modifying the immunosuppressive microenvironment of tumors would be a breakthrough in enhancing the therapeutic effects of a cancer vaccine. Recent studies have reported that metformin, a type 2 diabetes drug, may ameliorate the tumor microenvironment, thereby enhancing anti-tumor immunity. Here, we tested whether the combinational therapeutic strategy of cancer vaccines administered with a heterologous prime-boost strategy with metformin enhanced anti-tumor effects in a melanoma mouse model. The results showed that metformin promoted the transition of M2-tumor-associated macrophages (M2-TAM) to M1-TAM, induced more tumor-infiltrating proliferative CD4 and CD8 T cells, and decreased exhausted T cells. This combinational treatment induced anti-tumor immunity from cancer vaccines, ameliorating the tumor microenvironment, showing improved tumor inhibition, and prolonging survival in tumor-bearing mice compared with either a cancer vaccine or metformin alone.

Targeting the Depletion of M2 Macrophages: Implication in Cancer Immunotherapy

We have witnessed the emergence of immunotherapy against various cancers that resulted in significant clinical responses and particularly in cancers that were resistant to chemotherapy. These milestones have ignited the development of novel strategies to boost the anti-tumor immune response for immune-suppressed tumors in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most abundant cells in the TME, and their frequency correlates with poor prognosis. Hence, several approaches have been developed to target TAMs in effort to restore the anti-tumor immune response and inhibit tumor growth and metastasis. One approach discussed herein is targeting TAMs via their depletion. Several methods have been reported for TAMs depletion including micro-RNAs, transcription factors (e.g., PPARγ, KLF4, STAT3, STAT6, NF-κB), chemokines and chemokine receptors, antibodies-mediated blocking the CSF-1/CSF-1R pathway, nanotechnology, and various combination treatments. In addition, various clinical trials are currently examining the targeting of TAMs. Many of these methods also have side effects that need to be monitored and reduced. Future perspectives and directions are discussed.

Adhesion G Protein-Coupled Receptor G2 Promotes Hepatocellular Carcinoma Progression and Serves as a Neutrophil-Related Prognostic Biomarker

Adhesion G protein-coupled receptor G2 (ADGRG2) is an orphan adhesion G protein-coupled receptor (GPCR), which performs a tumor-promoting role in certain cancers; however, it has not been systematically investigated in hepatocellular carcinoma (HCC). In the current study, we utilized multiple databases to analyze the expression and diagnostic and prognostic value of ADGRG2 in HCC and its correlation with immune infiltration and inflammatory factors. The function and upstream regulatory miRNA of ADGRG2 were validated through qPCR, Western blot, CCK8, wound healing, and dual luciferase assays. It turned out that ADGRG2 was significantly higher in HCC and had a poor survival rate, especially in AFP ≤ 400 ng/mL subgroups. Functional enrichment analysis suggested that ADGRG2 may be involved in cancer pathways and immune-related pathways. In vitro, siRNA-mediated ADGRG2 silencing could inhibit the proliferation and migration of Huh7 and HepG2 cells. There was a highly significant positive correlation between ADGRG2 and neutrophils. Moreover, NET-related genes were filtered and confirmed, such as ENO1 and S100A9. Meanwhile, the high expression of ADGRG2 was also accompanied by the highest number of inflammatory cytokines, chemokines, and chemokine receptors and good immunotherapy efficacy. Finally, AGDGR2 may be sensitive to two drugs (PIK-93 and NPK76-II-72-1) and can be targeted by miR-326. In conclusion, ADGRG2 may serve as a novel biomarker and drug target for HCC diagnosis, immunotherapy, and prognosis and was related to neutrophils and the inflammatory process of liver cancer development.

Targeting immune checkpoints on tumor-associated macrophages in tumor immunotherapy

Unprecedented breakthroughs have been made in cancer immunotherapy in recent years. Particularly immune checkpoint inhibitors have fostered hope for patients with cancer. However, immunotherapy still exhibits certain limitations, such as a low response rate, limited efficacy in certain populations, and adverse events in certain tumors. Therefore, exploring strategies that can improve clinical response rates in patients is crucial. Tumor-associated macrophages (TAMs) are the predominant immune cells that infiltrate the tumor microenvironment and express a variety of immune checkpoints that impact immune functions. Mounting evidence indicates that immune checkpoints in TAMs are closely associated with the prognosis of patients with tumors receiving immunotherapy. This review centers on the regulatory mechanisms governing immune checkpoint expression in macrophages and strategies aimed at improving immune checkpoint therapies. Our review provides insights into potential therapeutic targets to improve the efficacy of immune checkpoint blockade and key clues to developing novel tumor immunotherapies.