Frenemies in the Microenvironment: Harnessing Mast Cells for Cancer Immunotherapy

Mast cell activation induced by tamoxifen citrate via MRGPRX2 plays a potential adverse role in breast cancer treatment

Breast cancer is the most common malignant tumor endangering women's life and health. Tamoxifen citrate (TAM) is the first-line drug of adjuvant endocrine therapy for estrogen receptor-positive (ER+) breast cancer patients. Some sporadic cases have described rare adverse reactions of TAM with potentially life-threatening dermatological manifestations, which were associated with skin allergy. Mas related G protein-coupled receptor X2 (MRGPRX2) on human mast cells is the key target for skin allergy. We aimed to investigate the mechanism of TAM-induced allergic reactions and their potential effects on TAM treatment for breast cancer. In our study, TAM can specifically bind with MRGPRX2, which was mainly driven by hydrophobic force. TAM formed hydrogen bonds with TRP243, TRP248, and GLU164 residues in MRGPRX2. TAM induced calcium mobilization and degranulation of mast cells via MRGPRX2. Besides, TAM induced passive cutaneous anaphylaxis and active systemic anaphylaxis in C57BL/6 mice. The release of β-hexosaminidase, histamine, tumor necrosis factor-α, monocyte chemoattractant protein 1, and interleukin-8 were increased by TAM in vitro and in vivo. Furthermore, we found that MCF-7 and T-47D breast cancer cells can recruit mast cells to adjacent cancerous tissues. Besides, mast cell activation induced by TAM via MRGPRX2 significantly promoted the proliferation and migration of MCF-7 and T-47D cells, which can be effectively reversed by mast cell membrane stabilizer clarithromycin and MRGPRX2 silencing. This study proposed an anti-allergic therapeutic strategy for breast cancer treatment with TAM, while also the potential of MRGPRX2 as an adjunctive target.

Prognostic value and clinical significance of IL-33 expression in patients with uterine corpus endometrial carcinoma

Uterine corpus endometrial carcinoma (UCEC) is one of the most common malignant tumours of the female genital tract. In the occurrence, progression and prognosis of UCEC, chronic inflammation plays an important role, making it pivotal to identify inflammatory response-related endometrial diseases. The cytokine interleukin-33 (IL-33) plays significant roles in immune responses, and has been associated with inappropriate allergic reactions, autoimmune diseases, and cancer pathology. In the past decade, studies have begun to uncover the pivotal roles of IL-33 in shaping tumour microenvironment (TME), where it may promote or inhibit tumorigenesis and development depending on the specific tumour types. However, the association between IL-33 expression and UCEC remains unclear. Here we investigated the expression profiles of IL-33 in pan-cancer based on TCGA database. Then, differential gene expression analysis and correlation analysis of IL-33 was investigated in UCEC. In addition, functional enrichment analysis and Kaplan-Meier survival analysis were performed to predict the potential function of IL-33 and its role in the prognosis of UCEC patients. Also, a nomogram model was constructed to predict the prognosis of UCEC. The expression of the inflammatory factor NF-κB p65 and the IL-33, along with its receptor ST2, was analyzed in UCEC tumour tissues and normal tissues of clinical specimens through immunohistochemical staining. Meanwhile, we used toluidine blue staining and methanol Congo red staining to observe the infiltration of mast cells and eosinophils in the endometrial tissue. The results of Kaplan-Meier plotter data indicated that patients with lower IL-33 expression had poorer progression-free interval than those with higher expression. Based on the results of multifactor Cox regression, a nomogram was generated to predict UCEC occurrence risk and prognosis. Clinical specimen characteristics also confirmed a negative correlation between IL-33 expression and UCEC staging and grading. This comprehensive analysis of IL-33, based on bioinformatics and immunohistochemistry, revealed that IL-33 has the function of inhibiting UCEC occurrence and progression and can be served as a beneficial prognostic marker in the clinic.

Single-cell multiomics reveals simvastatin inhibits pan-cancer epithelial-mesenchymal transition via the MEK/ERK pathway in XBP1+ mast cells

Distant metastasis is the leading cause of cancer-related mortality, and achieving survival benefits through advancements in systemic therapy remains challenging. Mast cells play a dual role in shaping the tumor microenvironment (TME) and influencing distant metastasis, underscoring the significant research value of targeting mast cells for systemic therapy in advanced cancer. We investigated variations in mast cell infiltration levels in primary and metastatic malignancies using immunocyte infiltration analysis. Mast cell subsets were identified from pan-cancer distant metastasis single-cell sequencing data through dimensionality reduction clustering and cell type annotation, combined with cell trajectory and communication network analyses. A prognostic model was established using WGCNA and 12 machine learning algorithms to identify potential mast cell targets. Drug sensitivity and Mendelian randomization analyses were conducted to select potential drugs targeting mast cells, and their effects on epithelial-mesenchymal transition (EMT) were validated through in vitro experiments, including wound healing, transwell, and western blot assays. Results revealed that activated mast cells show increased infiltration in metastatic tumors, correlating with poor survival duration. XBP1+ mast cells were identified as key components of the inhibitory TME, potentially involved in EMT activation. Simvastatin was identified as a potential drug, reversing EMT induced by XBP1+ mast cells in pan-cancer. Aberrant activation of MEK/ERK signaling in XBP1+ mast cells can stimulate cancer cell EMT by modulating degranulation, while Simvastatin can inhibit EMT by suppressing degranulation.

Expression, regulation, and function of PD-L1 on non-tumor cells in the tumor microenvironment

Antiprogrammed death ligand 1 (PD-L1) therapy is a leading immunotherapy, but only some patients with solid cancers benefit. Overwhelming evidence has revealed that PD-L1 is expressed on various immune cells in the tumor microenvironment (TME), including macrophages, dendritic cells, and regulatory T cells, modulating tumor immunity and influencing tumor progression. PD-L1 can also be located on tumor cell membranes as well as in exosomes and cytoplasm. Accordingly, the dynamic expression and various forms of PD-L1 might explain the therapy's limited efficacy and resistance. Herein a systematic summary of the expression of PD-L1 on different immune cells and their regulatory mechanisms is provided to offer a solid foundation for future studies.

Intracellular Osteopontin Promotes the Release of TNFα by Mast Cells to Restrain Neuroendocrine Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer that emerges as tumors become resistant to hormone therapies or, rarely, arises de novo in treatment-naïve patients. The urgent need for effective therapies against NEPC is hampered by the limited knowledge of the biology governing this lethal disease. Based on our prior observations in the transgenic adenocarcinoma of the mouse prostate (TRAMP) spontaneous prostate cancer model, in which the genetic depletion of either mast cells (MC) or the matricellular protein osteopontin (OPN) increases NEPC frequency, we tested the hypothesis that MCs can restrain NEPC through OPN production, using in vitro co-cultures between murine or human tumor cell lines and MCs, and in vivo experiments. We unveiled a role for the intracellular isoform of OPN, so far neglected compared with the secreted isoform. Mechanistically, we unraveled that the intracellular isoform of OPN promotes TNFα production in MCs via the TLR2/TLR4-MyD88 axis, specifically triggered by the encounter with NEPC cells. We found that MC-derived TNFα, in turn, hampered the growth of NEPC. We then identified the protein syndecan-1 (SDC1) as the NEPC-specific TLR2/TLR4 ligand that triggered this pathway. Interrogating published single-cell RNA-sequencing data, we validated this mechanism in a different mouse model. Translational relevance of the results was provided by in silico analyses of available human NEPC datasets and by immunofluorescence on patient-derived adenocarcinoma and NEPC lesions. Overall, our results show that MCs actively inhibit NEPC, paving the way for innovative MC-based therapies for this fatal tumor. We also highlight SDC1 as a potential biomarker for incipient NEPC.

Myeloid‑derived suppressor cells: Key immunosuppressive regulators and therapeutic targets in colorectal cancer (Review)

Globally, colorectal cancer (CRC) is the third most common type of cancer. CRC has no apparent symptoms in the early stages of disease, and most patients receive a confirmed diagnosis in the middle or late disease stages. The incidence of CRC continues to increase, and the affected population tends to be younger. Therefore, determining how to achieve an early CRC diagnosis and treatment has become a top priority for prolonging patient survival. Myeloid‑derived suppressor cells (MDSCs) are a group of bone marrow‑derived immuno‑negative regulatory cells that are divided into two subpopulations, polymorphonuclear‑MDSCs and monocytic‑MDSCs, based on their phenotypic similarities to neutrophils and monocytes, respectively. These cells can inhibit the immune response and promote cancer cell metastasis in the tumour microenvironment (TME). A large aggregation of MDSCs in the TME is often a marker of cancer and a poor prognosis in inflammatory diseases of the intestine (such as colonic adenoma and ulcerative colitis). In the present review, the phenotypic classification of MDSCs in the CRC microenvironment are first discussed. Then, the amplification, role and metastatic mechanism of MDSCs in the CRC TME are described, focusing on genes, gene modifications, proteins and the intestinal microenvironment. Finally, the progress in CRC‑targeted therapies that aim to modulate the quantity, function and structure of MDSCs are summarized in the hope of identifying potential screening markers for CRC and improving CRC prognosis and therapeutic options.

Prognostic role of chemokine-related genes in acute myeloid leukemia

Background

Chemotactic cytokines play a crucial role in the development of acute myeloid leukemia (AML). Thus, investigating the mechanisms of chemotactic cytokine-related genes (CCRGs) in AML is of paramount importance.

Methods

Using the TCGA-AML, GSE114868, and GSE12417 datasets, differential expression analysis identified differentially expressed CCRGs (DE-CCRGs). These genes were screened by overlapping differentially expressed genes (DEGs) between AML and control groups with CCRGs. Subsequently, functional enrichment analysis and the construction of a protein-protein interaction (PPI) network were conducted to explore the functions of the DE-CCRGs. Univariate Cox regression, least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analyses identified relevant prognostic genes and developed a prognostic model. Survival analysis of the prognostic gene was performed, followed by functional similarity analysis, immune analysis, enrichment analysis, and drug prediction analysis.

Results

Differential expression analysis revealed 6,743 DEGs, of which 29 DE-CCRGs were selected for this study. Functional enrichment analysis indicated that DE-CCRGs were primarily involved in chemotactic cytokine-related functions and pathways. Six prognostic genes (CXCR3, CXCR2, CXCR6, CCL20, CCL4, and CCR2) were identified and incorporated into the risk model. The model's performance was validated using the GSE12417 dataset. Survival analysis showed significant differences in AML overall survival (OS) between prognostic gene high and low expression groups, indicating that prognostic gene might be significantly associated with patient survival. Additionally, nine different immune cells were identified between the two risk groups. Correlation analysis revealed that CCR2 had the most significant positive correlation with monocytes and the most significant negative correlation with resting mast cells. The tumor immune dysfunction and exclusion score was lower in the high-risk group.

Conclusion

CXCR3, CXCR2, CXCR6, CCL20, CCL4, and CCR2 were identified as prognostic genes correlated to AML and the tumor immune microenvironment. These findings offerred novel insights into the prevention and treatment of AML.

Impaired Proliferation of CD8+ T Cells Stimulated with Monocyte-Derived Dendritic Cells Previously Matured with Thapsigargin-Stimulated LAD2 Human Mast Cells

CD8+ T cells are essential for adaptive immunity against infection and tumors. Their ability to proliferate after stimulation is crucial to their functionality. Dendritic cells (DCs) are professional antigen-presenting cells that induce their proliferation. Here, we show that thapsigargin-induced LAD2 mast cell (MC) line-released products can impair the ability of monocyte-derived DCs to induce CD8+ T-cell proliferation and the generation of Th1 cytokine-producing T cells. We found that culture medium conditioned with LAD2 MCs previously stimulated with thapsigargin (thapsLAD2) induces maturation of DCs as determined by the maturation markers CD80, CD83, CD86, and HLA-DR. However, thapsLAD2-matured DCs produced no detectable TNFα or IL-12 during the maturation. In addition, although their surface expression of PD-L1 was comparable with the immature or TLR7/8-agonist (R848)-matured DCs, their TIM-3 expression was significantly higher than in immature DCs and even much higher than in R848-matured DCs. In addition, contrary to R848-matured DCs, the thapsLAD2-matured DCs only tended to induce enhanced proliferation of CD4+ T cells than immature DCs. For CD8+ T cells, this tendency was not even detected because thapsLAD2-matured and immature DCs comparably induced their proliferation, which contrasted with the significantly enhanced proliferation induced by R848-matured DCs. Furthermore, these differences were comparably recapitulated in the ability of the tested DCs to induce IFNγ- and IFNγ/TNFα-producing T cells. These findings show a novel mechanism of MC-mediated regulation of adaptive immune responses.

Identification of HOXC Gene Family as Prognostic and Immune-Related Biomarkers in Breast Cancer Through mRNA Transcriptional Profile and Experimental Validation

Breast cancer (BC) is the most common malignancy in women worldwide, and more effective biomarkers are urgently needed for the prevention and treatment of BC. Our study aimed to investigate the role of the HOXC gene family (HOXCs) and its relationship with the immune response in BC. The differential expression of HOXCs and its clinical prognostic significance in BC were explored using bioinformatics analysis, and the cBioPortal database was used to evaluate the genetic mutation profile of the HOXCs in BC. The results indicated that the expression levels of HOXC4, 10, 11, 12, and 13 were significantly increased in BC tissues compared with the normal tissues, and expressions of these genes were closely associated with BC stage, among them, high expression levels of HOXC10 and HOXC13 predicted poor outcome in BC patients. In addition, to elucidate the essential role of HOXCs in the tumor microenvironment and immunotherapeutic response of BC, the impact of HOXCs on the regulation of immune infiltration in BC was comprehensively assessed. The result showed that HOXC10 and HOXC13 expressions were significantly positively linked with the infiltration levels of CD8+T cell and M1 macrophage, while they were negatively related to Mast and Natural killer cells, suggesting the important influence of HOXCs on regulating tumor immunity in BC patients. Lastly, the RT-qPCR assay was employed to validate HOXCs expression in samples of BC patients. In conclusion, HOXCs may be a promising prognostic indicator and could regulate the immune infiltration in BC patients, thus being a promising targeted immunotherapy for BC.

The regulatory role and mechanism of mast cells in tumor microenvironment

Mast cells (MCs) have emerged as pivotal contributors to both the defensive immune response and immunomodulation. They also exhibit regulatory functions in modulating pathological processes across various allergic diseases. The impact of MC presence within tumor tissues has garnered considerable attention, yielding conflicting findings. While some studies propose that MCs within tumor tissues promote tumor initiation and progression, others advocate an opposing perspective. Notably, evidence emphasizes the dual role of MCs in cancer, both as promoters and suppressors, is crucial for optimizing cancer treatment strategies. These conflicting viewpoints have generated substantial controversy, underscoring the need for a comprehensive understanding of MC's role in tumor immune responses.

Role of mast cells activation in the tumor immune microenvironment and immunotherapy of cancers

The mast cell is an important cellular component that plays a crucial role in the crosstalk between innate and adaptive immune responses within the tumor microenvironment (TME). Recently, numerous studies have indicated that mast cells related to tumors play a dual role in regulating cancers, with conflicting results seemingly determined by the degranulation medium. As such, mast cells are an ignored but very promising potential target for cancer immunotherapy based on their immunomodulatory function. In this review, we present a comprehensive overview of the roles and mechanisms of mast cells in diverse cancer types. Firstly, we evaluated the infiltration density and location of mast cells on tumor progression. Secondly, mast cells are activated by the TME and subsequently release a range of inflammatory mediators, cytokines, chemokines, and lipid products that modulate their pro-or anti-tumor functions. Thirdly, activated mast cells engage in intercellular communication with other immune or stromal cells to modulate the immune status or promote tumor development. Finally, we deliberated on the clinical significance of targeting mast cells as a therapeutic approach to restrict tumor initiation and progression. Overall, our review aims to provide insights for future research on the role of mast cells in tumors and their potential as therapeutic targets for cancer treatment.