Interaction of tumor‑associated macrophages with stromal and immune components in solid tumors: Research progress (Review)

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

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.

Prognostic Value of PlGF Upregulation in Prostate Cancer

BACKGROUND

Prostate cancer (PCa) is the second most commonly diagnosed cancer in men worldwide, with metastasis, particularly to bone, being the primary cause of mortality. Currently, prognostic markers like PSA levels and Gleason classification are limited in predicting metastasis, emphasizing the need for novel clinical biomarkers. New molecules predicting tumor progression have been identified over time. Some, such as the immune checkpoint inhibitors (ICIs) PD-1/PD-L1, have become valid markers as theranostic tools essential for prognosis and drug target therapy. However, despite the success of ICIs as an anti-cancer therapy for solid tumors, their efficacy in treating bone metastases has mainly proven ineffective, suggesting intrinsic resistance to this therapy in the bone microenvironment. This study explores the potential of immunological intratumoral biomarkers, focusing on placental growth factor (PlGF), Vascular Endothelial Growth Factor Receptor 1 (VEGFR1), and Programmed Cell Death Protein 1 (PD-1), in predicting bone metastasis formation.

METHODS

we analyzed PCa samples from patients with and without metastasis by immunohistochemical analysis.

RESULTS

Results revealed that PlGF expression is significantly higher in primary tumors of patients that developed metastasis within five years from the histological diagnosis. Additionally, PlGF expression correlates with increased VEGFR1 and PD-1 levels, as well as the presence of intratumoral M2 macrophages.

CONCLUSIONS

These findings suggest that PlGF contributes to an immunosuppressive environment, thus favoring tumor progression and metastatic process. Results here highlight the potential of integrating these molecular markers with existing prognostic tools to enhance the accuracy of metastasis prediction in PCa. By identifying patients at risk for metastasis, clinicians can tailor treatment strategies more effectively, potentially improving survival outcomes and quality of life. This study underscores the importance of further research into the role of intratumoral biomarkers in PCa management.

Evaluation of Tumor-Associated Macrophages and Micro-Vessel Density in Verrucous Carcinoma and Squamous Cell Carcinoma of the Oral Cavity

Background

Tumor-associated macrophages (TAMs) are a crucial cellular component of human tumors, but their exact roles in tumor growth and angiogenesis during cancer progression are still subject to debate. The present study aimed to explore the impact of TAMs on tumor progression and angiogenesis in oral squamous cell carcinoma (OSCC) and oral verrucous carcinoma (OVC).

Materials and Methods

For this cross-sectional study, 60 samples consisting of 40 OSCC and 20 OVC samples were chosen. Immunohistochemical staining was performed on the samples using anti-CD68 and anti-CD31 monoclonal antibodies to evaluate the frequency of TAMs and micro-vessel density (MVD), respectively. The data were analyzed using statistical software SPSS (v. 23) and through the independent samples Student t-test, one-way analysis of variance, and Pearson's correlation coefficient.

Results

The results of our study revealed that the mean number of TAMs and MVD were significantly greater in OSCC samples compared to OVC samples (P = 0.001) (P = 0.004). Also, the average number of TAMs and MVD increased in the high grade of OSCC; however, the correlation between both parameters and histopathological grades of OSCC was significant only for MVD. Our study found no significant correlation between TAMs and MVD (P = 0.005).

Conclusion

Based on the results of our study, both TAMs and MVD were found to be significantly higher in OSCC samples compared to OVC samples. These findings suggest that the progression of oral cancer is associated with an increase in TAMs and vascular density. Additionally, the use of CD68 and CD31 markers may help in differentiating between these two types of tumors.

Engineering macrophages and their derivatives: A new hope for antitumor therapy

Macrophages are central to the immune system and are found in nearly all tissues. Recently, the development of therapies based on macrophages has attracted significant interest. These therapies utilize macrophages' key roles in immunity, their ability to navigate biological barriers, and their tendency to accumulate in tumors. This review explores the advancement of macrophage-based treatments. We discuss the bioengineering of macrophages for improved anti-tumor effects, the use of CAR macrophage therapy for targeting cancer cells, and macrophages as vehicles for therapeutic delivery. Additionally, we examine engineered macrophage products, like extracellular vesicles and membrane-coated nanoparticles, for their potential in precise and less toxic tumor therapy. Challenges in moving these therapies from research to clinical practice are also highlighted. The aim is to succinctly summarize the current status, challenges, and future directions of engineered macrophages in cancer therapy.

Plasma-Derived Extracellular Vesicles and Non-Extracellular Vesicle Components from APCMin/+ Mice Promote Pro-Tumorigenic Activities and Activate Human Colonic Fibroblasts via the NF-κB Signaling Pathway

Colorectal cancer (CRC) is the third most prevalent cancer worldwide. Current studies have demonstrated that tumor-derived extracellular vesicles (EVs) from different cancer cell types modulate the fibroblast microenvironment to contribute to cancer development and progression. Here, we isolated and characterized circulating large EVs (LEVs), small EVs (SEVs) and non-EV entities released in the plasma from wild-type (WT) mice and the APCMin/+ CRC mice model. Our results showed that human colon fibroblasts exposed from APC-EVs, but not from WT-EVs, exhibited the phenotypes of cancer-associated fibroblasts (CAFs) through EV-mediated NF-κB pathway activation. Cytokine array analysis on secreted proteins revealed elevated levels of inflammatory cytokine implicated in cancer growth and metastasis. Finally, non-activated cells co-cultured with supernatant from fibroblasts treated with APC-EVs showed increased mRNA expressions of CAFs markers, the ECM, inflammatory cytokines, as well as the expression of genes controlled by NF-κB. Altogether, our work suggests that EVs and non-EV components from APCMin/+ mice are endowed with pro-tumorigenic activities and promoted inflammation and a CAF-like state by triggering NF-κB signaling in fibroblasts to support CRC growth and progression. These findings provide insight into the interaction between plasma-derived EVs and human cells and can be used to design new CRC diagnosis and prognosis tools.

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.

Immune cell networking in solid tumors: focus on macrophages and neutrophils

The tumor microenvironment is composed of tumor cells, stromal cells and leukocytes, including innate and adaptive immune cells, and represents an ecological niche that regulates tumor development and progression. In general, inflammatory cells are considered to contribute to tumor progression through various mechanisms, including the formation of an immunosuppressive microenvironment. Macrophages and neutrophils are important components of the tumor microenvironment and can act as a double-edged sword, promoting or inhibiting the development of the tumor. Targeting of the immune system is emerging as an important therapeutic strategy for cancer patients. However, the efficacy of the various immunotherapies available is still limited. Given the crucial importance of the crosstalk between macrophages and neutrophils and other immune cells in the formation of the anti-tumor immune response, targeting these interactions may represent a promising therapeutic approach against cancer. Here we will review the current knowledge of the role played by macrophages and neutrophils in cancer, focusing on their interaction with other immune cells.

A novel immune-nutritional score predicts response to neoadjuvant immunochemotherapy after minimally invasive esophagectomy for esophageal squamous cell carcinoma

Background

The role of neoadjuvant immunochemotherapy (NICT) has gradually attracted attention in recent years. To date, sensitive and reliable blood indicators to forecast the therapeutic response are still lacking. This study aimed to conduct a novel predictive score based on a variety of peripheral hematological immune-nutritional indicators to predict the therapeutic response in esophageal squamous cell carcinoma (ESCC) receiving NICT.

Methods

There were 206 ESCC patients receiving NICT retrospectively recruited. With pathological complete response (pCR) as the dependent variable, independent risk variables of various peripheral blood immune-nutritional indexes were screened by logistic regression analyses to establish an integrative score.

Results

By logical regression analyses, lymphocyte to monocyte ratio (LMR) and body mass index (BMI) were independent risk factors among all immune-nutritional indices. Then, an integrative score named BMI-LMR score (BLS) was established. Compared with BMI or LMR, BLS was related to complications, especially for respiratory complication (P=0.012) and vocal cord paralysis (P=0.021). Among all patients, 61 patients (29.6%) achieved pCR after NICT. BLS was significantly related to pCR [odds ratio (OR)=0.269, P<0.001)]. Patients in high BLS cohort demonstrated higher 3-year overall survival (OS) (89.9% vs. 67.9%, P=0.001) and disease-free survival (DFS) (81.2% vs. 62.1%, P=0.001). BLS served as an independent factor of DFS [hazard ratio (HR) =2.044, P =0.020) and OS (HR =2.960, P =0.019).

Conclusion

The BLS, based on immune-nutritional indicators of BMI and LMR, employed as a straightforward, accurate, and useful indicator of pCR and prognostic prediction in ESCC patients undergoing NICT.

The role of vascular endothelial cells in tumor metastasis

Vascular endothelial cells (VECs) are an integral component of the inner lining of blood vessels, and their functions are essential for the proper functioning of the vascular system. The tight junctions formed by VECs act as a significant barrier to the intravasation and extravasation of tumor cells (TCs). In addition to that, the proliferation, activation, and migration of VECs play a vital role in the growth of new blood vessels, a process known as tumor angiogenesis, which is closely related to the malignant progression of tumors. However, during tumor progression, VECs undergo endothelial-to-mesenchymal transition (EndMT), which further promotes tumor progression. Furthermore, VECs act as the first line of defense against effector immune cells and help prevent immune cells from infiltrating into tumor tissues. VECs also secrete various cytokines that can contribute to regulating the stemness of tumor stem cells. Thus, it has been increasingly recognized that dysfunction of VECs is one of the key driving forces behind tumor metastasis, and therapeutic strategies targeting VECs have the potential to be an effective means of antitumor therapy. This review aims to present a comprehensive overview of the role and mechanisms of VECs in regulating tumor progression and metastasis, providing insights into the possibilities for the development of novel antitumor therapies that target VECs.

Targeting the Tumor-Tumor Microenvironment Crosstalk

INTRODUCTION

Cancer development and progression is a complex process influenced by co-evolution of the cancer cells and their microenvironment. However, traditional anti-cancer therapy is mostly targeted toward cancer cells. To improve the efficacy of cancer drugs, the complex interactions between the tumor (T) and the tumor microenvironment (TME) should be considered while developing therapeutics.

AREAS COVERED

The present review article will discuss the components of T-TME as well as the potential to co-target these two distinct elements. We document that these approaches have resulted in success in preventing tumor progression and metastasis, albeit in animal models in some cases. Lastly, it is important to consider the tissue context and tumor type as these could significantly modify the role of these molecules/pathways and hence the overall likelihood of response. Furthermore, we discuss the potential strategies to target the components of tumor microenvironment in anti-cancer therapy. PubMed and ClinicalTrials.gov was searched through May 2023.

EXPERT OPINION

The tumor-tumor microenvironment cross talk and heterogeneity are major mechanisms conferring resistance to standard of care. Better understanding of the tissue specific T-TME interactions and dual targeting has the promise of improving cancer control and clinical outcomes.