Cancer-Associated Fibroblasts Neutralize the Anti-tumor Effect of CSF1 Receptor Blockade by Inducing PMN-MDSC Infiltration of Tumors

Unraveling the tumor microenvironment of esophageal squamous cell carcinoma through single-cell sequencing: A comprehensive review

Esophageal squamous cell carcinoma (ESCC) is a highly heterogeneous and aggressive malignancy. The progression, invasiveness, and metastatic potential of ESCC are shaped by a multitude of cells within the tumor microenvironment (TME), including tumor cells, immune cells, endothelial cells, as well as fibroblasts and other cell types. Recent advancements in single-cell sequencing technologies have significantly enhanced our comprehension of the diverse landscape of ESCC. Single-cell multi-omics technology, particularly single-cell transcriptome sequencing, have shed light on the expression profiles of individual cells and the molecular characteristics of distinct tumor cell populations. This review summarizes the latest literature on single-cell research in the field of ESCC, aiming to elucidate the heterogeneity of tumor cells, immune cells, and stromal cells at the single-cell level. Furthermore, it explores the impact of cellular interactions within the TME on the progression of ESCC. By compiling a comprehensive overview of single-cell omics research on ESCC, this article aims to enhance our understanding of ESCC diagnosis and treatment by elucidating the intricate interplay within the TME. It explores the cellular composition, spatial arrangement, and functional attributes of the ESCC TME, offering potential therapeutic targets and biomarkers for personalized treatment strategies.

Cytokines in cancer

Cytokines are proteins used by immune cells to communicate with each other and with cells in their environment. The pleiotropic effects of cytokine networks are determined by which cells express cytokines and which cells express cytokine receptors, with downstream outcomes that can differ based on cell type and environmental cues. Certain cytokines, such as interferon (IFN)-γ, have been clearly linked to anti-tumor immunity, while others, such as the innate inflammatory cytokines, promote oncogenesis. Here we provide an overview of the functional roles of cytokines in the tumor microenvironment. Although we have a sophisticated understanding of cytokine networks, therapeutically targeting cytokine pathways in cancer has been challenging. We discuss current progress in cytokine blockade, cytokine-based therapies, and engineered cytokine therapeutics as emerging cancer treatments of interest.

Harnessing the tumor microenvironment: targeted cancer therapies through modulation of epithelial-mesenchymal transition

The tumor microenvironment (TME) is integral to cancer progression, impacting metastasis and treatment response. It consists of diverse cell types, extracellular matrix components, and signaling molecules that interact to promote tumor growth and therapeutic resistance. Elucidating the intricate interactions between cancer cells and the TME is crucial in understanding cancer progression and therapeutic challenges. A critical process induced by TME signaling is the epithelial-mesenchymal transition (EMT), wherein epithelial cells acquire mesenchymal traits, which enhance their motility and invasiveness and promote metastasis and cancer progression. By targeting various components of the TME, novel investigational strategies aim to disrupt the TME's contribution to the EMT, thereby improving treatment efficacy, addressing therapeutic resistance, and offering a nuanced approach to cancer therapy. This review scrutinizes the key players in the TME and the TME's contribution to the EMT, emphasizing avenues to therapeutically disrupt the interactions between the various TME components. Moreover, the article discusses the TME's implications for resistance mechanisms and highlights the current therapeutic strategies toward TME modulation along with potential caveats.

Sustained inhibition of CSF1R signaling augments antitumor immunity through inhibiting tumor-associated macrophages

Tumor-associated macrophages (TAMs) are one of the key immunosuppressive components in the tumor microenvironment (TME) and contribute to tumor development, progression, and resistance to cancer immunotherapy. Several reagents targeting TAMs have been tested in preclinical and clinical studies, but they have had limited success. Here, we show that a unique reagent, FF-10101, exhibited a sustained inhibitory effect against colony-stimulating factor 1 receptor by forming a covalent bond and reduced immunosuppressive TAMs in the TME, which led to strong antitumor immunity. In preclinical animal models, FF-10101 treatment significantly reduced immunosuppressive TAMs and increased antitumor TAMs in the TME. In addition, tumor antigen-specific CD8+ T cells were increased; consequently, tumor growth was significantly inhibited. Moreover, combination treatment with an anti-programmed cell death 1 (anti-PD-1) antibody and FF-10101 exhibited a far stronger antitumor effect than either treatment alone. In human cancer specimens, FF-10101 treatment reduced programmed cell death 1 ligand 1 (PD-L1) expression on TAMs, as observed in animal models. Thus, FF-10101 acts as an immunomodulatory agent that can reduce immunosuppressive TAMs and augment tumor antigen-specific T cell responses, thereby generating an immunostimulatory TME. We propose that FF-10101 is a potential candidate for successful combination cancer immunotherapy with immune checkpoint inhibitors, such as PD-1/PD-L1 blockade.

Targeting CD206+ macrophages disrupts the establishment of a key antitumor immune axis

CD206 is a common marker of a putative immunosuppressive "M2" state in tumor-associated macrophages (TAMs). We made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ TAMs. Early depletion of CD206+ macrophages and monocytes (Mono/Macs) led to the indirect loss of conventional type I dendritic cells (cDC1), CD8 T cells, and NK cells in tumors. CD206+ TAMs robustly expressed CXCL9, contrasting with stress-responsive Spp1-expressing TAMs and immature monocytes, which became prominent with early depletion. CD206+ TAMs differentially attracted activated CD8 T cells, and the NK and CD8 T cells in CD206-depleted tumors were deficient in Cxcr3 and cDC1-supportive Xcl1 and Flt3l expressions. Disrupting this key antitumor axis decreased tumor control by antigen-specific T cells in mice. In human cancers, a CD206Replete, but not a CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, cDC1, and NK signatures and was associated with better survival. These findings negate the unqualified classification of CD206+ "M2-like" macrophages as immunosuppressive.

Targeting tumor-associated macrophages: Novel insights into immunotherapy of skin cancer

BACKGROUND

The incidence of skin cancer is currently increasing, and conventional treatment options inadequately address the demands of disease management. Fortunately, the recent rapid advancement of immunotherapy, particularly immune checkpoint inhibitors (ICIs), has ushered in a new era for numerous cancer patients. However, the efficacy of immunotherapy remains suboptimal due to the impact of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs), a major component of the TME, play crucial roles in tumor invasion, metastasis, angiogenesis, and immune evasion, significantly impacting tumor development. Consequently, TAMs have gained considerable attention in recent years, and their roles have been extensively studied in various tumors. However, the specific roles of TAMs and their regulatory mechanisms in skin cancer remain unclear.

AIM OF REVIEW

This paper aims to elucidate the origin and classification of TAMs, investigate the interactions between TAMs and various immune cells, comprehensively understand the precise mechanisms by which TAMs contribute to the pathogenesis of different types of skin cancer, and finally discuss current strategies for targeting TAMs in the treatment of skin cancer.

KEY SCIENTIFIC CONCEPTS OF OVERVIEW

With a specific emphasis on the interrelationship between TAMs and skin cancer, this paper posits that therapeutic modalities centered on TAMs hold promise in augmenting and harmonizing with prevailing clinical interventions for skin cancer, thereby charting a novel trajectory for advancing the landscape of immunotherapeutic approaches for skin cancer.

Shifting cold to hot tumors by nanoparticle-loaded drugs and products

Cold tumors lack antitumor immunity and are resistant to therapy, representing a major challenge in cancer medicine. Because of the immunosuppressive spirit of the tumor microenvironment (TME), this form of tumor has a low response to immunotherapy, radiotherapy, and also chemotherapy. Cold tumors have low infiltration of immune cells and a high expression of co-inhibitory molecules, such as immune checkpoints and immunosuppressive molecules. Therefore, targeting TME and remodeling immunity in cold tumors can improve the chance of tumor repression after therapy. However, tumor stroma prevents the infiltration of inflammatory cells and hinders the penetration of diverse molecules and drugs. Nanoparticles are an intriguing tool for the delivery of immune modulatory agents and shifting cold to hot tumors. In this review article, we discuss the mechanisms underlying the ability of nanoparticles loaded with different drugs and products to modulate TME and enhance immune cell infiltration. We also focus on newest progresses in the design and development of nanoparticle-based strategies for changing cold to hot tumors. These include the use of nanoparticles for targeted delivery of immunomodulatory agents, such as cytokines, small molecules, and checkpoint inhibitors, and for co-delivery of chemotherapy drugs and immunomodulatory agents. Furthermore, we discuss the potential of nanoparticles for enhancing the efficacy of cancer vaccines and cell therapy for overcoming resistance to treatment.

Unraveling the role of cancer-associated fibroblasts in colorectal cancer

Within the intricate milieu of colorectal cancer (CRC) tissues, cancer-associated fibroblasts (CAFs) act as pivotal orchestrators, wielding considerable influence over tumor progression. This review endeavors to dissect the multifaceted functions of CAFs within the realm of CRC, thereby highlighting their indispensability in fostering CRC malignant microenvironment and indicating the development of CAFs-targeted therapeutic interventions. Through a comprehensive synthesis of current knowledge, this review delineates insights into CAFs-mediated modulation of cancer cell proliferation, invasiveness, immune evasion, and neovascularization, elucidating the intricate web of interactions that sustain the pro-tumor metabolism and secretion of multiple factors. Additionally, recognizing the high level of heterogeneity within CAFs is crucial, as they encompass a range of subtypes, including myofibroblastic CAFs, inflammatory CAFs, antigen-presenting CAFs, and vessel-associated CAFs. Innovatively, the symbiotic relationship between CAFs and the intestinal microbiota is explored, shedding light on a novel dimension of CRC pathogenesis. Despite remarkable progress, the orchestrated dynamic functions of CAFs remain incompletely deciphered, underscoring the need for continued research endeavors for therapeutic advancements in CRC management.

Myeloid effector cells in cancer

The role of myeloid cells in tumor immunity is multifaceted. While dendritic cells support T cell-mediated tumor control, the highly heterogenous populations of macrophages, neutrophils, and immature myeloid cells were generally considered immunosuppressive. This view has led to effective therapies reinvigorating tumor-reactive T cells; however, targeting the immunosuppressive effects of macrophages and neutrophils to boost the cancer immunity cycle was clinically less successful. Recent studies interrogating the role of immune cells in the context of successful immunotherapy affirm the key role of T cells, but simultaneously challenge the idea that the cytotoxic function of T cells is the main contributor to therapy-driven tumor regression. Rather, therapy-activated intra-tumoral T cells recruit and activate or reprogram several myeloid effector cell types, the presence of which is necessary for tumor rejection. Here, we reappreciate the key role of myeloid effector cells in tumor rejection as this may help to shape future successful immunotherapies.

Effects of different hypoxia exposure on myeloid-derived suppressor cells in mice

For many people living at high altitudes for long or short periods of time, hypoxia is a challenge affecting many aspects of the body, including the immune system. Recently, myeloid-derived suppressor cells (MDSCs) have emerged as an immune cell population that plays an important role in several pathological conditions. However, to the best of our knowledge, there are no data regarding the behavior of MDSCs under hypoxic conditions. Therefore, the aim of this study is to investigate the monocytic type (M)- and polymorphonuclear type (PMN)-MDSC ratios in different hypoxic conditions to reveal the relationship between MDSCs and high-altitude hypoxia, as well as to determine whether MDSCs are involved in the regulation of the immune balance under hypoxic conditions as immunosuppressive factors. For the first time, we showed that MDSC abundance varies under different lengths of hypoxic exposure. We found that acute normobaric hypoxia led to an initial increase in the number of M-MDSCs, which decreased within 30 d. Both M- and PMN-MDSC ratios initially decreased under hypobaric hypoxia conditions within 30 d, but after 6 months in the real high altitude environment, M-MDSC ratio increased significantly. In summary, our data suggest that different hypoxic conditions influence MDSCs in mice, thereby contributing to a better understanding of the process of hypoxia adaptation and the occurrence and development of high-altitude disease.

CMTM7 shapes the chronic inflammatory and immunosuppressive tumor microenvironment in hepatocellular carcinoma as an M2 macrophage biomarker

Transmembrane domain-containing 7 (CMTM7) is a protein located at the plasma membrane. It plays a role in regulating the development and immune microenvironment of tumor cells. However, the impact of CMTM7 on hepatocellular carcinoma (HCC) is not well understood. To better understand the role of CMTM7 in HCC, the correlations of CMTM7 with clinical characteristics, patient prognosis, chronic inflammation, and immune cell infiltration were analyzed using tissue microarray slides, sequencing datasets and various analysis tools (Web). The bulk sequencing analysis indicated that elevated expression of CMTM7 appears to promote chronic inflammation, immunosuppression, M2 macrophage infiltration, a diminished response to cancer immunotherapy, and an unfavorable clinical prognosis in patients with hepatocellular carcinoma (HCC). Further investigation through single-cell RNA sequencing and multiple fluorescence staining demonstrated that CMTM7 serves as a molecular marker for M2 macrophages and is associated with T cell exhaustion as well as highly plastic stem-like characteristics. We propose that CMTM7 may represent a novel immune checkpoint for HCC patients experiencing suboptimal therapeutic outcomes. Utilizing the Connectivity Map and AutoDock Vina, we predicted two potential compounds targeting CMTM7-fasudil and arachidonyltrifluoromethane-as promising therapeutic candidates. Collectively, these findings suggest that CMTM7-positive macrophages play significant roles in establishing an immunosuppressive tumor microenvironment while promoting highly plastic and stem-like traits in HCC cells, ultimately contributing to poor prognostic outcomes.

The complex role of regulatory cells in breast cancer: implication for immunopathogenesis and immunotherapy

Breast cancers (BCs) are frequently linked to an immunosuppressive microenvironment that facilitates tumor evasion of anti-cancer immunity. The cells that suppress the immune system such as regulatory B cells (Bregs), regulatory T cells (Tregs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), play a crucial role in immune resistance. Also, tumor progression and immune evasion of cancers are facilitated by cytokines and factors released by tumor cells or immunosuppressive cells. Targeting these regulatory cells therapeutically, whether through elimination, inactivation, or reprogramming, has resulted in hopeful anti-tumor reactions. Yet, the substantial diversity and adaptability of these cells, both in terms of appearance and function, as well as their variation over time and depending on where they are in the body, have posed significant challenges for using them as reliable biomarkers and creating focused therapies that could target their creation, growth, and various tumor-promoting roles. The immunotherapy approaches in BC and their effectiveness in treating certain subtypes are still in their initial phases. In this review, we thoroughly outlined the characteristics, roles, and possible treatment options for these immune-suppressing cells in the tumor environment.

Multi-omics analysis deciphers intercellular communication regulating oxidative stress to promote oral squamous cell carcinoma progression

Oral squamous cell carcinoma (OSCC) is a common malignant tumor in the head and neck, associated with high recurrence and poor prognosis. We performed an integrated analysis of single-cell RNA and spatial transcriptomic data from cancerous and normal tissues to create a comprehensive atlas of epithelial cells and cancer-associated fibroblasts (CAFs). Our findings show that AKR1C3+ epithelial cells, located at the tumor's stromal front, exhibit significant copy number variation and poor prognostic indicators, suggesting a role in tumor invasion. We also identified a distinct group of early-stage CAFs (named OSCC_Normal, characterized by ADH1B+, MFAP4+, and PLA2G2A+) that interact with AKR1C3+ cells, where OSCC_Normal may inhibit the FOXO1 redox switch in these epithelial cells via the IGF1/IGF1R pathway, causing oxidative stress overload. Conversely, AKR1C3+ cells use ITGA6/ITGB4 receptor to counteract the effects of OSCC_Normal, promoting cancer invasion. This study unveils complex interactions within the OSCC tumor microenvironment.

TAK1 Promotes an Immunosuppressive Tumor Microenvironment through Cancer-Associated Fibroblast Phenotypic Conversion in Pancreatic Ductal Adenocarcinoma

PURPOSE

We aim to clarify the precise function of TGFβ1-activated kinase 1 (TAK1) in cancer-associated fibroblasts (CAF) within human pancreatic ductal adenocarcinoma (PDAC) by investigating its role in cytokine-mediated signaling pathways.

EXPERIMENTAL DESIGN

The expression of TAK1 in pancreatic cancer was confirmed by The Cancer Genome Atlas data and human pancreatic cancer specimens. CAFs from freshly resected PDAC specimens were cultured and used in a three-dimensional model for direct and indirect coculture with PDAC tumors to investigate TAK1 function. Additionally, organoids from [LSL-KrasG12D/+, LSL-Trp53R172H/+, Pdx1-Cre (KPC)] mice were mixed with CAFs and injected subcutaneously into C57BL/6 mice to explore in vivo functional interactions of TAK1.

RESULTS

The Cancer Genome Atlas data revealed significant upregulation of TAK1 in PDAC, associating with a positive correlation with the T-cell exhaustion signature. Knockdown of TAK1 in CAFs decreased the inflammatory CAF signature and increased the myofibroblastic CAF signature both in vitro and in vivo. The absence of TAK1 hindered CAF proliferation, blocked several inflammatory factors via multiple pathways associated with immunosuppression, and hindered epithelial-mesenchymal transition and outgrowth in vitro in spheroid cocultures with PDAC cells. Additionally, TAK1 inhibitor restrained tumor growth, increased CD4+ and CD8+ T-cell abundance, and reduced immunosuppressive cells present in vivo.

CONCLUSIONS

Blocking the TAK1+ CAF phenotype leads to the conversion of protumorigenic CAFs to antitumorigenic CAFs. This highlights TAK1 as a potential therapeutic target, particularly in CAFs, and represents a novel avenue for combined immunotherapy in PDAC.

Insights into CSF-1R Expression in the Tumor Microenvironment

The colony-stimulating factor 1 receptor (CSF-1R) plays a pivotal role in orchestrating cellular interactions within the tumor microenvironment (TME). Although the CSF-1R has been extensively studied in myeloid cells, the expression of this receptor and its emerging role in other cell types in the TME need to be further analyzed. This review explores the multifaceted functions of the CSF-1R across various TME cellular populations, including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs), cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs). The activation of the CSF-1R by its ligands, colony-stimulating factor 1 (CSF-1) and Interleukin-34 (IL-34), regulates TAM polarization towards an immunosuppressive M2 phenotype, promoting tumor progression and immune evasion. Similarly, CSF-1R signaling influences MDSCs to exert immunosuppressive functions, hindering anti-tumor immunity. In DCs, the CSF-1R alters antigen-presenting capabilities, compromising immune surveillance against cancer cells. CSF-1R expression in CAFs and ECs regulates immune modulation, angiogenesis, and immune cell trafficking within the TME, fostering a pro-tumorigenic milieu. Notably, the CSF-1R in CSCs contributes to tumor aggressiveness and therapeutic resistance through interactions with TAMs and the modulation of stemness features. Understanding the diverse roles of the CSF-1R in the TME underscores its potential as a therapeutic target for cancer treatment, aiming at disrupting pro-tumorigenic cellular crosstalk and enhancing anti-tumor immune responses.

Targeting the MET gene: unveiling therapeutic opportunities in immunotherapy within the tumor immune microenvironment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) represents the most prevalent histological subtype of lung cancer. Within this disease, the MET gene emerges as a critical therapeutic target, exhibiting various forms of dysregulation. Although MET tyrosine kinase inhibitors, HGF/c-MET targeting antibodies, and antibody-drug conjugates constitute the primary treatment modalities for patients with MET-altered NSCLC, numerous questions remain regarding their optimal application. The advent of immunotherapy holds promise for enhancing therapeutic outcomes in patients with MET-altered NSCLC. MET mutations can reshape the tumor immune microenvironment of NSCLC by reducing tumor immunogenicity, inducing exhaustion in immune-activated cells, and promoting immune evasion, which are crucial for modulating treatment responses. Furthermore, we emphasize the promising synergy of immunotherapy with emerging treatments and the challenges and opportunities in refining these approaches to improve patient outcomes.

Consensus, debate, and prospective on pancreatic cancer treatments

Pancreatic cancer remains one of the most aggressive solid tumors. As a systemic disease, despite the improvement of multi-modality treatment strategies, the prognosis of pancreatic cancer was not improved dramatically. For resectable or borderline resectable patients, the surgical strategy centered on improving R0 resection rate is consensus; however, the role of neoadjuvant therapy in resectable patients and the optimal neoadjuvant therapy of chemotherapy with or without radiotherapy in borderline resectable patients were debated. Postoperative adjuvant chemotherapy of gemcitabine/capecitabine or mFOLFIRINOX is recommended regardless of the margin status. Chemotherapy as the first-line treatment strategy for advanced or metastatic patients included FOLFIRINOX, gemcitabine/nab-paclitaxel, or NALIRIFOX regimens whereas 5-FU plus liposomal irinotecan was the only standard of care second-line therapy. Immunotherapy is an innovative therapy although anti-PD-1 antibody is currently the only agent approved by for MSI-H, dMMR, or TMB-high solid tumors, which represent a very small subset of pancreatic cancers. Combination strategies to increase the immunogenicity and to overcome the immunosuppressive tumor microenvironment may sensitize pancreatic cancer to immunotherapy. Targeted therapies represented by PARP and KRAS inhibitors are also under investigation, showing benefits in improving progression-free survival and objective response rate. This review discusses the current treatment modalities and highlights innovative therapies for pancreatic cancer.

Macrophages: Key Players in the Battle against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a challenging subtype of breast cancer characterized by the absence of estrogen and progesterone receptors and HER2 expression, leading to limited treatment options and a poorer prognosis. TNBC is particularly prevalent in premenopausal African-descent women and is associated with aggressive tumor behavior and higher metastatic potential. Tumor-associated macrophages (TAMs) are abundantly present within the TNBC microenvironment and play pivotal roles in promoting tumor growth, progression, and metastasis through various mechanisms, including immune suppression and enhancement of angiogenesis. This review provides an in-depth overview of TNBC, focusing on its epidemiology, its molecular characteristics, and the critical influence of TAMs. It discusses the pathological and molecular aspects that define TNBC's aggressive nature and reviews current and emerging therapeutic strategies aimed at targeting these dynamics. Special attention is given to the role of TAMs, exploring their potential as therapeutic targets due to their significant impact on tumor behavior and patient outcomes. This review aims to highlight the complexities of the TNBC landscape and to present the innovative approaches that are currently being pursued to improve therapeutic efficacy and patient survival.

CAF-induced physical constraints controlling T cell state and localization in solid tumours

Solid tumours comprise cancer cells that engage in continuous interactions with non-malignant cells and with acellular components, forming the tumour microenvironment (TME). The TME has crucial and diverse roles in tumour progression and metastasis, and substantial efforts have been dedicated into understanding the functions of different cell types within the TME. These efforts highlighted the importance of non-cell-autonomous signalling in cancer, mediating interactions between the cancer cells, the immune microenvironment and the non-immune stroma. Much of this non-cell-autonomous signalling is mediated through acellular components of the TME, known as the extracellular matrix (ECM), and controlled by the cells that secrete and remodel the ECM - the cancer-associated fibroblasts (CAFs). In this Review, we delve into the complex crosstalk among cancer cells, CAFs and immune cells, highlighting the effects of CAF-induced ECM remodelling on T cell functions and offering insights into the potential of targeting ECM components to improve cancer therapies.

Tumor-associated macrophages: A sentinel of innate immune system in tumor microenvironment gone haywire

The tumor microenvironment (TME) is a critical determinant in the initiation, progression, and treatment outcomes of various cancers. Comprising of cancer-associated fibroblasts (CAF), immune cells, blood vessels, and signaling molecules, the TME is often likened to the soil supporting the seed (tumor). Among its constituents, tumor-associated macrophages (TAMs) play a pivotal role, exhibiting a dual nature as both promoters and inhibitors of tumor growth. This review explores the intricate relationship between TAMs and the TME, emphasizing their diverse functions, from phagocytosis and tissue repair to modulating immune responses. The plasticity of TAMs is highlighted, showcasing their ability to adopt either protumorigenic or anti-tumorigenic phenotypes based on environmental cues. In the context of cancer, TAMs' pro-tumorigenic activities include promoting angiogenesis, inhibiting immune responses, and fostering metastasis. The manuscript delves into therapeutic strategies targeting TAMs, emphasizing the challenges faced in depleting or inhibiting TAMs due to their multifaceted roles. The focus shifts towards reprogramming TAMs to an anti-tumorigenic M1-like phenotype, exploring interventions such as interferons, immune checkpoint inhibitors, and small molecule modulators. Noteworthy advancements include the use of CSF1R inhibitors, CD40 agonists, and CD47 blockade, demonstrating promising results in preclinical and clinical settings. A significant section is dedicated to Chimeric Antigen Receptor (CAR) technology in macrophages (CAR-M cells). While CAR-T cells have shown success in hematological malignancies, their efficacy in solid tumors has been limited. CAR-M cells, engineered to infiltrate solid tumors, are presented as a potential breakthrough, with a focus on their development, challenges, and promising outcomes. The manuscript concludes with the exploration of third-generation CAR-M technology, offering insight into in-vivo reprogramming and nonviral vector approaches. In conclusion, understanding the complex and dynamic role of TAMs in cancer is crucial for developing effective therapeutic strategies. While early-stage TAM-targeted therapies show promise, further extensive research and larger clinical trials are warranted to optimize their targeting and improve overall cancer treatment outcomes.

Emerging Trends in Gastrointestinal Cancer Targeted Therapies: Harnessing Tumor Microenvironment, Immune Factors, and Metabolomics Insights

Gastrointestinal (GI) cancers are the leading cause of new cancer cases and cancer-related deaths worldwide. The treatment strategies for patients with GI tumors have focused on oncogenic molecular profiles associated with tumor cells. Recent evidence has demonstrated that the tumor cell functions are modulated by its microenvironment, compromising fibroblasts, extracellular matrices, microbiome, immune cells, and the enteric nervous system. Along with the tumor microenvironment components, alterations in key metabolic pathways have emerged as a hallmark of tumor cells. From these perspectives, this review will highlight the functions of different cellular components of the GI tumor microenvironment and their implications for treatment. Furthermore, we discuss the major metabolic reprogramming in GI tumor cells and how understanding metabolic rewiring could lead to new therapeutic strategies. Finally, we briefly summarize the targeted agents currently being studied in GI cancers. Understanding the complex interplay between tumor cell-intrinsic and -extrinsic factors during tumor progression is critical for developing new therapeutic strategies.

Metabolic reprogramming of hypoxic tumor-associated macrophages through CSF-1R targeting favors treatment efficiency in colorectal cancers

BACKGROUND

Tumor-associated macrophages participate in the complex network of support that favors tumor growth. Among the various strategies that have been developed to target these cells, the blockade of the colony-stimulating factor 1 receptor (CSF-1R) receptor is one of the most promising ones. Here, we characterize the resulting state of human macrophages exposed to a CSF-1R kinase inhibitor.

METHODS

Using RNA sequencing and metabolomics approach, we characterize the reprogramming of human monocyte-derived macrophages under CSF-1R targeting.

RESULTS

We find that CSF-1R receptor inhibition in human macrophages is able to impair cholesterol synthesis, fatty acid metabolism and hypoxia-driven expression of dihydropyrimidine dehydrogenase, an enzyme responsible for the 5-fluorouracil macrophage-mediated chemoresistance. We show that this inhibition of the CSF-1R receptor leads to a downregulation of the expression of sterol regulatory element-binding protein 2, a transcription factor that controls cholesterol and fatty acid synthesis. We also show that the inhibition of extracellular signal-regulated kinase 1/2 phosphorylation resulting from targeting the CSF-1R receptor destabilizes the expression of hypoxic induced factor 2 alpha in hypoxia resulting in the downregulation of dihydropyrimidine dehydrogenase expression restoring the sensitivity to 5-fluorouracil in colorectal cancer.

CONCLUSIONS

These results reveal the unexpected metabolic rewiring resulting from the CSF-1R receptor targeting of human macrophages and its potential to reverse macrophage-mediated chemoresistance in colorectal tumors.

Tumor-associated macrophages within the immunological milieu: An emerging focal point for therapeutic intervention

Tumor-associated macrophages play an important role in the tumor immune microenvironment, and regulating the function of tumor-associated macrophages has important therapeutic potential in tumor therapy. Mature macrophages could migrate to the tumor microenvironment, influencing multiple factors such as tumor cell proliferation, invasion, metastasis, extracellular matrix remodeling, immune suppression, and drug resistance. As a major component of the tumor microenvironment, tumor-associated macrophages crosstalk with other immune cells. Currently, tumor-associated macrophages have garnered considerable attention in tumor therapy, broadening the spectrum of drug selection to some extent, thereby aiding in mitigating the prevailing clinical drug resistance dilemma. This article summarizes the recent advances in tumor-associated macrophages concerning immunology, drug targeting mechanisms for tumor-associated macrophages treatment, new developments, and existing challenges, offering insights for future therapeutic approaches. In addition, this paper summarized the impact of tumor-associated macrophages on current clinical therapies, discussed the advantages and disadvantages of targeted tumor-associated macrophages therapy compared with existing tumor therapies, and predicted and discussed the future role of targeted tumor-associated macrophages therapy and the issues that need to be focused on.

The Role of Tumor Microenvironment in Pancreatic Cancer Immunotherapy: Current Status and Future Perspectives

Pancreatic cancer comprises different subtypes, where most cases include ductal adenocarcinoma (PDAC). It is one of the deadliest tumor types, with a poor prognosis. In the majority of patients, the disease has already spread by the time of diagnosis, making full recovery unlikely and increasing mortality risk. Despite developments in its detection and management, including chemotherapy, radiotherapy, and targeted therapies as well as advances in immunotherapy, only in about 13% of PDAC patients does the overall survival exceed 5 years. This may be attributed, at least in part, to the highly desmoplastic tumor microenvironment (TME) that acts as a barrier limiting perfusion, drug delivery, and immune cell infiltration and contributes to the establishment of immunologically 'cold' conditions. Therefore, there is an urgent need to unravel the complexity of the TME that promotes PDAC progression and decipher the mechanisms of pancreatic tumors' resistance to immunotherapy. In this review, we provide an overview of the major cellular and non-cellular components of PDAC TME, as well as their biological interplays. We also discuss the current state of PDAC therapeutic treatments and focus on ongoing and future immunotherapy efforts and multimodal treatments aiming at remodeling the TME to improve therapeutic efficacy.

Cancer associated fibroblasts and metabolic reprogramming: unraveling the intricate crosstalk in tumor evolution

Metabolic reprogramming provides tumors with an energy source and biofuel to support their survival in the malignant microenvironment. Extensive research into the intrinsic oncogenic mechanisms of the tumor microenvironment (TME) has established that cancer-associated fibroblast (CAFs) and metabolic reprogramming regulates tumor progression through numerous biological activities, including tumor immunosuppression, chronic inflammation, and ecological niche remodeling. Specifically, immunosuppressive TME formation is promoted and mediators released via CAFs and multiple immune cells that collectively support chronic inflammation, thereby inducing pre-metastatic ecological niche formation, and ultimately driving a vicious cycle of tumor proliferation and metastasis. This review comprehensively explores the process of CAFs and metabolic regulation of the dynamic evolution of tumor-adapted TME, with particular focus on the mechanisms by which CAFs promote the formation of an immunosuppressive microenvironment and support metastasis. Existing findings confirm that multiple components of the TME act cooperatively to accelerate the progression of tumor events. The potential applications and challenges of targeted therapies based on CAFs in the clinical setting are further discussed in the context of advancing research related to CAFs.

Clinical landscape of macrophage-reprogramming cancer immunotherapies

Tumour-associated macrophages (TAMs) sustain a tumour-supporting and immunosuppressive milieu and therefore aggravate cancer prognosis. To modify TAM behaviour and unlock their anti-tumoural potential, novel TAM-reprogramming immunotherapies are being developed at an accelerating rate. At the same time, scientific discoveries have highlighted more sophisticated TAM phenotypes with complex biological functions and contradictory prognostic associations. To understand the evolving clinical landscape, we reviewed current and past clinically evaluated TAM-reprogramming cancer therapeutics and summarised almost 200 TAM-reprogramming agents investigated in more than 700 clinical trials. Observable overall trends include a high frequency of overlapping strategies against the same therapeutic targets, development of more complex strategies to improve previously ineffective approaches and reliance on combinatory strategies for efficacy. However, strong anti-tumour efficacy is uncommon, which encourages re-directing efforts on identifying biomarkers for eligible patient populations and comparing similar treatments earlier. Future endeavours will benefit from considering the shortcomings of past treatment strategies and accommodating the emerging complexity of TAM biology.

Macrophage-based cancer immunotherapy: Challenges and opportunities

Macrophages play crucial roles in the tumor microenvironment (TME), exerting diverse functions ranging from promoting tumor growth and metastasis to orchestrating anti-tumor immune responses. Their plasticity allows them to adopt distinct activation states, often called M1-like (pro-inflammatory) and M2-like (anti-inflammatory or pro-tumoral), significantly influencing tumor progression and response to therapy. Harnessing the potential of macrophages in cancer immunotherapy has emerged as a promising strategy, with increasing interest in targeting these cells directly or modulating their functions within the TME. This review explores the intricate interplay between macrophages, the TME, and immunotherapeutic approaches. We discuss the dynamic phenotypic and functional heterogeneity of tumor-associated macrophages (TAMs), their impact on disease progression, and the mechanisms underlying their response to immunotherapy. Furthermore, we highlight recent advancements in macrophage-based immunotherapeutic strategies, including macrophage-targeting agents, adoptive cell transfer, and engineering approaches. Understanding the complex crosstalk between macrophages and the TME is essential for developing effective immunotherapeutic interventions that exploit the immunomodulatory functions of macrophages to enhance anti-tumor immunity and improve clinical outcomes for cancer patients.

LIFR regulates cholesterol-driven bidirectional hepatocyte-neutrophil cross-talk to promote liver regeneration

Liver regeneration is under metabolic and immune regulation. Despite increasing recognition of the involvement of neutrophils in regeneration, it is unclear how the liver signals to the bone marrow to release neutrophils after injury and how reparative neutrophils signal to hepatocytes to reenter the cell cycle. Here we report that loss of the liver tumour suppressor Lifr in mouse hepatocytes impairs, whereas overexpression of leukaemia inhibitory factor receptor (LIFR) promotes liver repair and regeneration after partial hepatectomy or toxic injury. In response to physical or chemical damage to the liver, LIFR from hepatocytes promotes the secretion of cholesterol and CXCL1 in a STAT3-dependent manner, leading to the efflux of bone marrow neutrophils to the circulation and damaged liver. Cholesterol, via its receptor ERRα, stimulates neutrophils to secrete hepatocyte growth factor to accelerate hepatocyte proliferation. Altogether, our findings reveal a LIFR-STAT3-CXCL1-CXCR2 axis and a LIFR-STAT3-cholesterol-ERRα-hepatocyte growth factor axis that form bidirectional hepatocyte-neutrophil cross-talk to repair and regenerate the liver.

Recent Progress on Nanomedicine-Mediated Repolarization of Tumor-Associated Macrophages for Cancer Immunotherapy

Tumor-associated macrophages (TAMs) constitute the largest number of immune cells in the tumor microenvironment (TME). They play an essential role in promoting tumor progression and metastasis, which makes them a potential therapeutic target for cancer treatment. TAMs are usually divided into two categories: pro-tumoral M2-like TAMs and antitumoral M1 phenotypes at either extreme. The reprogramming of M2-like TAMs toward a tumoricidal M1 phenotype is of particular interest for the restoration of antitumor immunity in cancer immunotherapy. Notably, nanomedicines have shown great potential for cancer therapy due to their unique structures and properties. This review will briefly describe the biological features and roles of TAMs in tumor, and then discuss recent advances in nanomedicine-mediated repolarization of TAMs for cancer immunotherapy. Finally, perspectives on nanomedicine-mediated repolarization of TAMs for effective cancer immunotherapy are also presented.

A detailed insight into macrophages' role in shaping lung carcinogenesis

Despite significant advancements in cancer treatment in recent decades, the high mortality rate associated with lung cancer remains a significant concern. The development and proper execution of new targeted therapies needs more deep knowledge regarding the lung cancer associated tumour microenvironment. One of the key component of that tumour microenvironment is the lung resident macrophages. Although in normal physiological condition the lung resident macrophages are believed to maintain lung homeostasis, but they may also initiate a vicious inflammatory response in abnormal conditions which is linked to lung cancer development. Depending on the activation pathway, the lung resident macrophages are either of M1 or M2 sub-type. The M1 and M2 sub-types differ significantly in various prospectuses, from phenotypic markers to metabolic pathways. In addition to this generalized classification, the recent advancement of the multiomics technology is able to identify some other sub-types of lung resident macrophages. Researchers have also observed that these different sub-types can manipulate the pathogenesis of lung carcinogenesis in a context dependent manner and can either promote or inhibit the development of lung carcinogenesis upon receiving proper activation. As proper knowledge about the role played by the lung resident macrophages' in shaping the lung carcinogenesis is limited, so the main purpose of this review is to bring all the available information under the same roof. We also elaborated the different mechanisms involved in maintenance of the plasticity of M1/M2 sub-type, as this plasticity can be a good target for lung cancer treatment.

Cancer-associated fibroblasts promote proliferation, angiogenesis, metastasis and immunosuppression in gastric cancer

Despite advances in surgery, radiotherapy and immunotherapy, the mortality rate for gastric cancer remains one of the highest in the world. A large body of evidence has demonstrated that cancer-associated fibroblasts (CAFs), as core members of the stroma, can secrete cytokines, proteins and exosomes to create a tumour microenvironment that is conducive to cancer cell survival. CAFs can also interact with cancer cells to form a complex signalling network, enabling cancer cells to more easily metastasise to other organs and tissues in the body and develop metastatic foci. In this review, we provide an overview of the CAFs concept and activators. We focus on elucidating their effects on immune cells, intratumoural vasculature, extracellular matrix, as well as cancer cell activity, metastatic power and metabolism, and on enhancing the metastatic ability of cancer cells through activation of JAK/STAT, NF/κB and CXCL12/CXCR4. Various therapeutic agents targeting CAFs are also under development and are expected to improve the prognosis of gastric cancer in combination with existing treatment options.

Influencing factors and solution strategies of chimeric antigen receptor T-cell therapy (CAR-T) cell immunotherapy

Chimeric antigen receptor T-cesll therapy (CAR-T) has achieved groundbreaking advancements in clinical application, ushering in a new era for innovative cancer treatment. However, the challenges associated with implementing this novel targeted cell therapy are increasingly significant. Particularly in the clinical management of solid tumors, obstacles such as the immunosuppressive effects of the tumor microenvironment, limited local tumor infiltration capability of CAR-T cells, heterogeneity of tumor targeting antigens, uncertainties surrounding CAR-T quality, control, and clinical adverse reactions have contributed to increased drug resistance and decreased compliance in tumor therapy. These factors have significantly impeded the widespread adoption and utilization of this therapeutic approach. In this paper, we comprehensively analyze recent preclinical and clinical reports on CAR-T therapy while summarizing crucial factors influencing its efficacy. Furthermore, we aim to identify existing solution strategies and explore their current research status. Through this review article, our objective is to broaden perspectives for further exploration into CAR-T therapy strategies and their clinical applications.

An update to experimental and clinical aspects of tumor-associated macrophages in cancer development: hopes and pitfalls

Tumor-associated macrophages (TAMs) represent one of the most abundant tumor-infiltrating stromal cells, and their normal function in tumor microenvironment (TME) is to suppress tumor cells by producing cytokines which trigger both direct cell cytotoxicity and antibody-mediated immune response. However, upon prolonged exposure to TME, the classical function of these so-called M1-type TAMs can be converted to another type, "M2-type," which are recruited by tumor cells so that they promote tumor growth and metastasis. This is the reason why the accumulation of TAMs in TME is correlated with poor prognosis in cancer patients. Both M1- and M2-types have high degree of plasticity, and M2-type cells can be reprogrammed to M1-type for therapeutic purposes. This characteristic introduces TAMs as promising target for developing novel cancer treatments. In addition, inhibition of M2-type cells and blocking their recruitment in TME, as well as their depletion by inducing apoptosis, are other approaches for effective immunotherapy of cancer. In this review, we summarize the potential of TAMs to be targeted for cancer immunotherapy and provide an up-to-date about novel strategies for targeting TAMs.

TSG-6+ cancer-associated fibroblasts modulate myeloid cell responses and impair anti-tumor response to immune checkpoint therapy in pancreatic cancer

Resistance to immune checkpoint therapy (ICT) presents a growing clinical challenge. The tumor microenvironment (TME) and its components, namely tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), play a pivotal role in ICT resistance; however, the underlying mechanisms remain under investigation. In this study, we identify expression of TNF-Stimulated Factor 6 (TSG-6) in ICT-resistant pancreatic tumors, compared to ICT-sensitive melanoma tumors, both in mouse and human. TSG-6 is expressed by CAFs within the TME, where suppressive macrophages expressing Arg1, Mafb, and Mrc1, along with TSG-6 ligand Cd44, predominate. Furthermore, TSG-6 expressing CAFs co-localize with the CD44 expressing macrophages in the TME. TSG-6 inhibition in combination with ICT improves therapy response and survival in pancreatic tumor-bearing mice by reducing macrophages expressing immunosuppressive phenotypes and increasing CD8 T cells. Overall, our findings propose TSG-6 as a therapeutic target to enhance ICT response in non-responsive tumors.

Gastric cancer fibroblasts affect the effect of immunotherapy and patient prognosis by inducing micro-vascular production

Introduction

Immunotherapy is critical for treating many cancers, and its therapeutic success is linked to the tumor microenvironment. Although anti-angiogenic drugs are used to treat gastric cancer (GC), their efficacy remains limited. Cancer-associated fibroblast (CAF)-targeted therapies complement immunotherapy; however, the lack of CAF-specific markers poses a challenge. Therefore, we developed a CAF angiogenesis prognostic score (CAPS) system to evaluate prognosis and immunotherapy response in patients with GC, aiming to improve patient stratification and treatment efficacy.

Methods

We assessed patient-derived GC CAFs for promoting angiogenesis using EdU, cell cycle, apoptosis, wound healing, and angiogenesis analysis.

Results

We then identified CAF-angiogenesis-associated differentially-expressed genes, leading to the development of CAPS, which included THBS1, SPARC, EDNRA, and VCAN. We used RT-qPCR to conduct gene-level validation, and eight GEO datasets and the HPA database to validate the CAPS system at the gene and protein levels. Six independent GEO datasets were utilized for validation. Overall survival time was shorter in the high- than the low-CAPS group. Immune microenvironment and immunotherapy response analysis showed that the high-CAPS group had a greater tendency toward immune escape and reduced immunotherapy efficacy than the low-CAPS group.

Discussion

CAPS is closely associated with GC prognosis and immunotherapy outcomes. It is therefore an independent predictor of GC prognosis and immunotherapy efficacy.

Therapeutic implications of signaling pathways and tumor microenvironment interactions in esophageal cancer

Esophageal cancer (EC) is significantly influenced by the tumor microenvironment (TME) and altered signaling pathways. Downregulating these pathways in EC is essential for suppressing tumor development, preventing metastasis, and enhancing therapeutic outcomes. This approach can increase tumor sensitivity to treatments, enhance patient outcomes, and inhibit cancer cell proliferation and spread. The TME, comprising cellular and non-cellular elements surrounding the tumor, significantly influences EC's development, course, and treatment responsiveness. Understanding the complex relationships within the TME is crucial for developing successful EC treatments. Immunotherapy is a vital TME treatment for EC. However, the heterogeneity within the TME limits the application of anticancer drugs outside clinical settings. Therefore, identifying reliable microenvironmental biomarkers that can detect therapeutic responses before initiating therapy is crucial. Combining approaches focusing on EC signaling pathways with TME can enhance treatment outcomes. This integrated strategy aims to interfere with essential signaling pathways promoting cancer spread while disrupting factors encouraging tumor development. Unraveling aberrant signaling pathways and TME components can lead to more focused and efficient treatment approaches, identifying specific cellular targets for treatments. Targeting the TME and signaling pathways may reduce metastasis risk by interfering with mechanisms facilitating cancer cell invasion and dissemination. In conclusion, this integrative strategy has significant potential for improving patient outcomes and advancing EC research and therapy. This review discusses the altered signaling pathways and TME in EC, focusing on potential future therapeutics.

Breast Cancer Treatment Strategies Targeting the Tumor Microenvironment: How to Convert "Cold" Tumors to "Hot" Tumors

Breast cancer characterized as "cold tumors" exhibit low levels of immune cell infiltration, which limits the efficacy of conventional immunotherapy. Recent studies have focused on strategies using nanotechnology combined with tumor microenvironment modulation to transform "cold tumors" into "hot tumors". This approach involves the use of functionalized nanoparticles that target and modify the tumor microenvironment to promote the infiltration and activation of antitumor immune cells. By delivering immune activators or blocking immunosuppressive signals, these nanoparticles activate otherwise dormant immune responses, enhancing tumor immunogenicity and the therapeutic response. These strategies not only promise to increase the response rate of breast cancer patients to existing immunotherapies but also may pave new therapeutic avenues, providing a new direction for the immunotherapy of breast cancer.

Myelomodulatory treatments augment the therapeutic benefit of oncolytic viroimmunotherapy in murine models of malignant peripheral nerve sheath tumors

Introduction

Malignant peripheral nerve sheath tumors (MPNST) pose a significant therapeutic challenge due to high recurrence rates after surgical resection and a largely ineffective response to traditional chemotherapy. An alternative treatment strategy is oncolytic viroimmunotherapy, which can elicit a durable and systemic antitumor immune response and is Food and Drug Administration (FDA)-approved for the treatment of melanoma. Unfortunately, only a subset of patients responds completely, underscoring the need to address barriers hindering viroimmunotherapy effectiveness.

Methods

Here we investigated the therapeutic utility of targeting key components of the MPNST immunosuppressive microenvironment to enhance viroimmunotherapy's antitumor efficacy in three murine models, one of which showed more immunogenic characteristics than the others.

Results

Myelomodulatory therapy with pexidartinib, a small molecule inhibitor of CSF1R tyrosine kinase, and the oncolytic herpes simplex virus T-VEC exhibited the most significant increase in median survival time in the highly immunogenic model. Additionally, targeting myeloid cells with the myelomodulatory therapy trabectedin, a small molecule activator of caspase-8 dependent apoptosis, augmented the survival benefit of T-VEC in a less immunogenic MPNST model. However, tumor regressions or shrinkages were not observed. Depletion experiments confirmed that the enhanced survival benefit relied on a T cell response. Furthermore, flow cytometry analysis following combination viroimmunotherapy revealed decreased M2 macrophages and myeloid-derived suppressor cells and increased tumor-specific gp70+ CD8 T cells within the tumor microenvironment.

Discussion

In summary, our findings provide compelling evidence for the potential to leverage viroimmunotherapy with myeloid cell targeting against MPNST and warrant further investigation.

Melanoma-associated fibroblasts in tumor-promotion flammation and antitumor immunity: novel mechanisms and potential immunotherapeutic strategies

Melanoma, renowned for its aggressive behavior and resistance to conventional treatments, stands as a formidable challenge in the oncology landscape. The dynamic and complex interplay between cancer cells and the tumor microenvironment has gained significant attention, revealing Melanoma-Associated Fibroblasts (MAFs) as central players in disease progression. The heterogeneity of MAFs endows them with a dual role in melanoma. This exhaustive review seeks to not only shed light on the multifaceted roles of MAFs in orchestrating tumor-promoting inflammation but also to explore their involvement in antitumor immunity. By unraveling novel mechanisms underlying MAF functions, this review aims to provide a comprehensive understanding of their impact on melanoma development. Additionally, it delves into the potential of leveraging MAFs for innovative immunotherapeutic strategies, offering new avenues for enhancing treatment outcomes in the challenging realm of melanoma therapeutics.

Critical role of CD206+ macrophages in promoting a cDC1-NK-CD8 T cell anti-tumor immune axis

Tumor-associated macrophages (TAMs) are frequently categorized as being 'M1' or 'M2' polarized, even as substantial data challenges this binary modeling of macrophage cell state. One molecule consistently referenced as a delineator of a putative immunosuppressive 'M2' state is the surface protein CD206. We thus made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ 'M2-like' TAMs and assess their correspondence with pro-tumoral immunity. Early, but not late depletion of CD206+ macrophages and monocytes (here, 'Mono/Macs') led to an indirect loss of a key anti-tumor network of NK cells, conventional type I dendritic cells (cDC1) and CD8 T cells. Among myeloid cells, we found that the CD206+ TAMs are the primary producers of CXCL9, and able to differentially attract activated CD8 T cells. In contrast, a population of stress-responsive TAMs ("Hypoxic" or Spp1+) and immature monocytes, which lack CD206 expression and become prominent following early depletion, expressed markedly diminished levels of CXCL9. Those NK and CD8 T cells which enter CD206-depleted tumors express vastly reduced levels of the corresponding receptor Cxcr3, the cDC1-attracting chemokine Xcl1 and cDC1 growth factor Flt3l transcripts. Consistent with the loss of this critical network, early CD206+ TAM depletion decreased tumor control by antigen specific CD8 T cells in mice. Likewise, in humans, the CD206Replete, but not the CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, NK cell and stimulatory cDC1 gene signatures and transcriptomic signatures skewed towards CD206Replete Mono/Macs associated with better survival. Together, these findings negate the unqualified classification of CD206+ 'M2-like' macrophages as immunosuppressive by illuminating contexts for their role in organizing a critical tumor-reactive archetype of immunity.

Endothelial cell Notch signaling programs cancer-associated fibroblasts to promote tumor immune evasion

Stromal cells within the tumor tissue promote immune evasion as a critical strategy for cancer development and progression, but the underlying mechanisms remain poorly understood. In this study, we explore the role of endothelial cells (ECs) in the regulation of the immunosuppressive tumor microenvironment. Using mouse pancreatic ductal adenocarcinoma (PDAC) models, we found that canonical Notch signaling in endothelial cells suppresses the recruitment of antitumor T cells and promotes tumor progression by inhibiting the pro-inflammatory functions of cancer-associated fibroblasts (CAFs). Abrogation of endothelial Notch signaling modulates EC-derived angiocrine factors to enhance the pro-inflammatory activities of CAFs, which drive CXCL9/10-CXCR3-mediated T cell recruitment to inhibit tumor growth. Additionally, abrogation of endothelial Notch unleashed interferon gamma responses in the tumor microenvironment, upregulated PDL1 expression on tumor cells, and sensitized PDAC to PD1-based immunotherapy. Collectively, these data uncover a pivotal role of endothelial cells in shaping the immunosuppressive microenvironment, and suggest the potential of targeting EC-CAF interaction as a novel therapeutic modality to boost antitumor immunity.

Macrophages as Targets in Hepatocellular Carcinoma Therapy

Hepatocellular carcinoma (HCC) is a malignant tumor with a complex and diverse immunosuppressive microenvironment. Tumor-associated macrophages (TAM) are an essential component of the tumor immune microenvironment. TAMs typically exist in two primary states: anti-tumor M1 macrophages and protumor M2 macrophages. Remarkably, TAMs possess high plasticity, enabling them to switch between different subtypes or alter their biological functions in response to the tumor microenvironment. Based on research into the biological role of TAMs in the occurrence and development of malignant tumors, including HCC, TAMs are emerging as promising targets for novel tumor treatment strategies. In this review, we provide a detailed introduction to the origin and subtypes of TAMs, elucidate their interactions with other cells in the complex tumor microenvironment of HCC, and describe the biological roles, characteristics, and mechanisms of TAMs in the progression of HCC. Furthermore, we furnish an overview of the latest therapeutic strategies targeting TAMs.

Potential therapeutic targets in myeloid cell therapy for overcoming chemoresistance and immune suppression in gastrointestinal tumors

In the tumor microenvironment (TME), myeloid cells play a pivotal role. Myeloid-derived immunosuppressive cells, including tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), are central components in shaping the immunosuppressive milieu of the tumor. Within the TME, a majority of TAMs assume an M2 phenotype, characterized by their pro-tumoral activity. These cells promote tumor cell growth, angiogenesis, invasion, and migration. In contrast, M1 macrophages, under appropriate activation conditions, exhibit cytotoxic capabilities against cancer cells. However, an excessive M1 response may lead to pro-tumoral inflammation. As a result, myeloid cells have emerged as crucial targets in cancer therapy. This review concentrates on gastrointestinal tumors, detailing methods for targeting macrophages to enhance tumor radiotherapy and immunotherapy sensitivity. We specifically delve into monocytes and tumor-associated macrophages' various functions, establishing an immunosuppressive microenvironment, promoting tumorigenic inflammation, and fostering neovascularization and stromal remodeling. Additionally, we examine combination therapeutic strategies.

IVT-mRNA reprogramming of myeloid cells for cancer immunotherapy

In the past decade, in vitro transcribed messenger RNAs (IVT-mRNAs) have emerged as promising therapeutic molecules. The clinical success of COVID-19 mRNA vaccines developed by Pfizer-BioNTech and Moderna, have demonstrated that IVT-mRNAs can be safely and successfully used in a clinical setting, and efforts are underway to develop IVT-mRNAs for therapeutic applications. Current applications of mRNA-based therapy have been focused on (1) mRNA vaccines for infectious diseases and cancer treatment; (2) protein replacement therapy; (3) gene editing therapy; and (4) cell-reprogramming therapies. Due to the recent clinical progress of cell-based immunotherapies, the last direction-the use of IVT-mRNAs as a therapeutic approach to program immune cells for the treatment of cancer has received extensive attention from the cancer immunotherapy field. Myeloid cells are important components of our immune system, and they play critical roles in mediating disease progression and regulating immunity against diseases. In this chapter, we discussed the progress of using IVT-mRNAs as a therapeutic approach to program myeloid cells against cancer and other immune-related diseases. Towards this direction, we first reviewed the pharmacology of IVT-mRNAs and the biology of myeloid cells as well as myeloid cell-targeting therapeutics. We then presented a few cases of current IVT-mRNA-based approaches to target and reprogram myeloid cells for disease treatment and discussed the advantages and limitations of these approaches. Finally, we presented our considerations in designing mRNA-based approaches to target myeloid cells for disease treatment.

Glucose-driven histone lactylation promotes the immunosuppressive activity of monocyte-derived macrophages in glioblastoma

Immunosuppressive macrophages restrict anti-cancer immunity in glioblastoma (GBM). Here, we studied the contribution of microglia (MGs) and monocyte-derived macrophages (MDMs) to immunosuppression and mechanisms underlying their regulatory function. MDMs outnumbered MGs at late tumor stages and suppressed T cell activity. Molecular and functional analysis identified a population of glycolytic MDM expressing GLUT1 with potent immunosuppressive activity. GBM-derived factors promoted high glycolysis, lactate, and interleukin-10 (IL-10) production in MDMs. Inhibition of glycolysis or lactate production in MDMs impaired IL-10 expression and T cell suppression. Mechanistically, intracellular lactate-driven histone lactylation promoted IL-10 expression, which was required to suppress T cell activity. GLUT1 expression on MDMs was induced downstream of tumor-derived factors that activated the PERK-ATF4 axis. PERK deletion in MDM abrogated histone lactylation, led to the accumulation of intratumoral T cells and tumor growth delay, and, in combination with immunotherapy, blocked GBM progression. Thus, PERK-driven glucose metabolism promotes MDM immunosuppressive activity via histone lactylation.

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Effects of folate deficiency and sex on carcinogenesis in a mouse model of oral cancer

OBJECTIVES

To investigate the effects of dietary folate and sex on histopathology of oral squamous cell carcinoma in mice.

MATERIALS AND METHODS

Mice (C57Bl/6, 30/sex) were fed either a deficient folate or sufficient folate diet. Vehicle or 4-nitroquinoline1-oxide (50 μg/mL) in vehicle were administered in drinking water for 20 weeks, followed by 6 weeks of regular drinking water. Oral lesions were observed weekly. Tongues were studied for histopathologic changes. Immunohistochemical techniques were used to measure cell proliferation (Ki67+), and to quantify expression of folate receptor, reduced folate carrier, and proton-coupled folate transporter. T cells, macrophages, and neutrophils were counted and normalized to area.

RESULTS

All 4NQO-treated mice developed oral tumors. Dietary folate level did not affect tumor burden. More tumors were observed on the ventral aspect of the tongue than in other locations within the oral cavity. 4-nitroquinoline-1-oxide-treated mice displayed 27%-46% significantly lower expression of all three folate transport proteins; diet and sex had no effect on folate transporter expression. T-cell and neutrophil infiltration in tongues were 9.1-fold and 18.1-fold increased in the 4-nitroquinoline-1-oxide-treated mouse tongues than in controls.

CONCLUSION

Treatment with 4NQO was the primary factor in determining cancer development, decreased folate transport expression, and lymphoid cell infiltration.

Characteristics and significance of programmed cell death-related gene expression signature in skin cutaneous melanoma

BACKGROUND

Programmed cell death (PCD) pathways play crucial roles in the pathogenesis of skin cutaneous melanoma (SKCM). Understanding their prognostic significance and clinical implications is imperative for the development of personalized treatment strategies.

METHODS

A total of 1466 PCD-related genes were analyzed using data from The Cancer Genome Atlas (TCGA)-SKCM cohort (n = 353). Prognostic cell death index (CDI) was established and validated through survival analysis and predictive modeling. Functional enrichment, protein-protein interaction (PPI), consensus clustering, and tumor microenvironment assessment and drug sensitivity analysis were performed to elucidate the biological and clinical relevance of CDI.

RESULTS

CDI effectively stratified SKCM patients into high and low-risk groups, demonstrating significant differences in survival outcomes. It exhibited predictive value for survival at 1, 3, and 5 years. The concordance index (C-index) was 0.794 in the training set, and 0.792 and 0.821 in the internal and external validation sets, respectively. The corresponding area under curve (AUC) was all above 0.75 in these data sets. Functional enrichment analysis revealed significant associations with immune response and inflammatory processes. PPI analysis identified key molecular modules associated with apoptosis and chemokine signaling. Consensus clustering unveiled three discernible subtypes demonstrating notable disparities in survival outcomes based on CDI expression profiles. Assessment of the tumor microenvironment highlighted correlations with immune cell infiltration such as M1 macrophages and T cells. Drug sensitivity analysis indicated tight correlations between CDI levels and response to immunotherapy.

CONCLUSION

Our comprehensive analysis establishes the prognostic significance of PCD-related genes in SKCM. CDI emerges as a promising prognostic biomarker, offering insights into tumor biology and potential implications for personalized treatment strategies. Further validation and clinical integration of CDI are warranted to improve SKCM management and patient outcomes.

Targeting the "tumor microenvironment": RNA-binding proteins in the spotlight in colorectal cancer therapy

Colorectal cancer (CRC) is the third most common cancer and has the second highest mortality rate among cancers. The development of CRC involves both genetic and epigenetic abnormalities, and recent research has focused on exploring the ex-transcriptome, particularly post-transcriptional modifications. RNA-binding proteins (RBPs) are emerging epigenetic regulators that play crucial roles in post-transcriptional events. Dysregulation of RBPs can result in aberrant expression of downstream target genes, thereby affecting the progression of colorectal tumors and the prognosis of patients. Recent studies have shown that RBPs can influence CRC pathogenesis and progression by regulating various components of the tumor microenvironment (TME). Although previous research on RBPs has primarily focused on their direct regulation of colorectal tumor development, their involvement in the remodeling of the TME has not been systematically reported. This review aims to highlight the significant role of RBPs in the intricate interactions within the CRC tumor microenvironment, including tumor immune microenvironment, inflammatory microenvironment, extracellular matrix, tumor vasculature, and CRC cancer stem cells. We also highlight several compounds under investigation for RBP-TME-based treatment of CRC, including small molecule inhibitors such as antisense oligonucleotides (ASOs), siRNAs, agonists, gene manipulation, and tumor vaccines. The insights gained from this review may lead to the development of RBP-based targeted novel therapeutic strategies aimed at modulating the TME, potentially inhibiting the progression and metastasis of CRC.

Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.