Abundance Of Mast Cells Research Articles

MRGPRX2-mediated mast cell activation by substance P from overloaded human tenocytes induces inflammatory and degenerative responses in tendons

Mast cells are immune cells minimally present in normal tendon tissue. The increased abundance of mast cells in tendinopathy biopsies and at the sites of tendon injury suggests an unexplored role of this cell population in overuse tendon injuries. Mast cells are particularly present in tendon biopsies from patients with more chronic symptom duration and a history of intensive mechanical loading. This study, therefore, examined the cross talk between mast cells and human tendon cells in either static or mechanically active conditions in order to explore the potential mechanistic roles of mast cells in overuse tendon injuries. A coculture of isolated human tenocytes and mast cells (HMC-1) combined with Flexcell Tension System for cyclic stretching of tenocytes was used. Additionally, human tenocytes were exposed to agonists and antagonists of substance P (SP) receptors. Mast cell degranulation was assessed by measuring β-hexosaminidase activity. Transwell and cell adhesion assays were used to evaluate mast cell migration and binding to tendon extracellular matrix components (collagen and fibronectin), respectively. Gene expressions were analyzed using real time qRT-PCR. Our results indicate that mechanical stimulation of human tenocytes leads to release of SP which, in turn, activates mast cells through the Mas-related G-protein-coupled receptor X2 (MRGPRX2). The degranulation and migration of mast cells in response to MRGPRX2 activation subsequently cause human tenocytes to increase their expression of inflammatory factors, matrix proteins and matrix metalloproteinase enzymes. These observations may be important in understanding the mechanisms by which tendons become tendinopathic in response to repetitive mechanical stimulation.

An ovine model for investigation of the microenvironment of the male mammary gland.

The specific biology of the male breast remains relatively unexplored in spite of the increasing global prevalence of male breast cancer. Delineation of the microenvironment of the male breast is restricted by the low availability of human samples and a lack of characterisation of appropriate animal models. Unlike the mouse, the male ovine gland persists postnatally. We suggest that the male ovine mammary gland constitutes a promising adjunctive model for the male breast. In this study, we evaluate the male ovine mammary gland microenvironment, comparing intact and neutered males. Assessment of the glandular histo-anatomy highlights the resemblance of the male gland to that of neonatal female sheep and confirms the presence of rudimentary terminal duct lobular units. Irrespective of neutered status, cell proliferation in epithelial and stromal compartments is similarly low in males, and cell proliferation in epithelial cells and in the intralobular stroma is significantly lower than in pubertal female sheep. Between 42% and 72% of the luminal mammary epithelial cells in the male gland express the androgen receptor and expression is significantly reduced by neutering. Luminal epithelial cells within the intact and neutered male gland also express oestrogen receptor alpha, but minimal progesterone receptor expression is observed. The distribution of leukocytes within the ducts and stroma is similar to the mammary gland of female sheep and females of other species. Both macrophages and T lymphocytes are intercalated in the epithelial bilayer and are more abundant in the intralobular stroma than the interlobular stroma, suggesting that they may have a protective immunological function within the vestigial glandular tissue of the male sheep. Mast cells are also observed within the stroma. These cells cluster near the glandular tissue and are frequently located adjacent to blood vessels. The abundance of mast cells is significantly higher in intact males compared to neutered males, suggesting that hormone signalling may impact mast cell recruitment. In this study, we demonstrate the utility of the male ovine mammary gland as a model for furthering our knowledge of postnatal male mammary biology.

Identification of novel immune cell signature in gastroesophageal reflux disease: altered mucosal mast cells and dendritic cell profile.

Heartburn pathogenesis in GERD remains incompletely understood. We aimed to identify differences in the immune cell signature and sensory mucosal markers between reflux phenotypes and healthy asymptomatic subjects. Thirty-seven patients with heartburn symptoms were phenotyped endoscopically and with objective reflux studies into erosive reflux disease (ERD) (N=10), nonerosive reflux disease (NERD) (N=9), functional heartburn (FH) (N=9), and Barrett's esophagus (BO) (N=9). Bulk mRNA-sequencing(RNA-seq) was conducted on RNA extracted from endoscopic biopsies, and immune cell deconvolution analysis was performed using CIBERSORT. RNA-seq findings were validated by immunofluorescent staining for CD1a, nerve growth factor (NGF), and mast cell tryptase in corresponding patient biopsies. Transcriptomic analysis detected higher mast cell abundance in BO, ERD, and NERD compared to healthy controls (p<0.05), with decreased dendritic cell infiltration in BO, ERD, and NERD patients compared to healthy controls and FH patients. CD1a-positive dendritic cell infiltration was significantly higher in the healthy esophageal mucosa at protein level compared to BO (p=0.0005), ERD (p=0.0004), and FH patients (p=0.0096). Moreover, NGF co-expression on mast cells in GERD patients was significantly higher than in healthy controls (p=0.0094). The mucosa in patients with GERD had a significant increase in NGF expression on mast cells, suggesting an upregulation of signalling for neuronal sprouting in GERD. Moreover, decreased dendritic cell abundance in GERD esophageal mucosa may play a role in reduced oral tolerance and development of subsequent immune responses which may participate in esophageal sensitivity.

Identify and validate circadian regulators as potential prognostic markers and immune infiltrates in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneity pathological malignant cancer with leading causes of morbidity and mortality. EGFR inhibitors, immune checkpoint inhibitors have become novel treatments. However, the mechanism still remained uncertain. Several studies have confirmed that the circadian rhythms induce multiple malignancies developing. We utilized multi-omics analysis to demonstrate the crosstalk between circadian clock genes and tumor microenvironment in HNSCC. Firstly, we performed the LASSO Cox regression analysis based on the 16 important clock genes. A 7-gene risk model was successfully established in TCGA and validated in GEO datasets. Next, CIBERSORT and ESTIMATE methods were performed to display the immune landscape of high risk and low risk groups, and the results showed that high abundance of mast cells activated, dendritic cells activated and neutrophils were positively correlated with poor OS. To further identify hub genes, Kaplan Meier plot was applied in all TCGA and GEO datasets and two hub genes (PER2, and PER3) were identified, especially PER3, which was found strongly associated with immune score, PDCD1, CD4 + and CD8 + T cells in HNSCCC. Moreover, to explore the innate mechanism of circadian-induced pathway, we constructed a circadian-related ceRNA regulatory network containing 34 lncRNAs, 3 miRNAs and 4 core circadian genes. In-vitro experiments also verified that Per2 or Per3 could suppressed the proliferation, migration and invasion of HNSC. This study unraveled the association between PER3 and prognosis in patients with HNSC and the innate mechanism remains to be elucidated.

Abstract B036: Immune cell profiling of human prostate tumors identifies a protective and pathological role for intratumoral mast cells in the development of biochemical recurrence and metastasis

Abstract Background: Immunobiological factors may, in part, contribute to racial disparities in prostate cancer (PCa), the second leading cause of cancer-related death for US men. African American (AA) men face a greater risk of developing PCa and having a poorer outcome of this disease, compared to Caucasian American (CA) men. The goal of this study is to identify immune-specific differences influencing PCa health disparity as well as PCa progression. Methods: Ex vivo tumor biopsies were obtained following radical prostatectomy (RP) from 51 treatment-naïve patients (26 AA, 25 CA) under approved IRB protocols. Total RNA from fresh frozen tissue was isolated and amplified by PCR using NanoString multiplexed target enrichment protocols. We evaluated differences in resulting transcripts by self-reported race, pathology, and other clinical and pathologic features. Relative abundances of immune cell subsets were determined using computational methods, including previously published deconvolution algorithms, to estimate cellular content. Results: We identified differentially expressed genes between AA and CA tumors that are characterized by genes regulating Natural Killer (NK) cell function and Wnt signaling cancer pathways. Among the entire cohort, high expression of two of these differentially expressed genes, DVL2 and MAP3K5, were associated with worse biochemical recurrence (BCR)-free and metastasis-free survival. No difference in immune cell abundance was observed by self-reported race. Strikingly, among the entire cohort, low abundance of intratumoral mast cells was also associated with worse PCa pathology and poorer BCR-free and metastasis-free survival. Conclusions: Using a race-matched military cohort, we found that AA and CA tumors differ in the expression levels of Wnt and NK signaling-related pathways, yet cellular estimations of immune abundance did not significantly differ. Remarkably, the level of mast cell abundance within tumors at time of RP may be protective and prolong BCR-free and metastasis-free survival of patients. These types of in-depth immune profiling assessments have the potential to guide precision medicine and treatment decisions in the clinic. Disclaimer: The contents of this publication are the sole responsibility of the author(s) and do not necessarily reflect the views, opinions or policies of Uniformed Services University of the Health Sciences (USUHS), The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., the Department of Defense (DoD), the Departments of the Army, Navy, or Air Force. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Government. Citation Format: Cara Schafer, Jiji Jiang, Sally Elsamanoudi, Darryl Nousome, Denise Young, Yingjie Song, Isabell Sesterhenn, Gregory Chesnut, Shyh-Han Tan. Immune cell profiling of human prostate tumors identifies a protective and pathological role for intratumoral mast cells in the development of biochemical recurrence and metastasis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B036.

Elevated Mast Cell Abundance Is Associated with Enrichment of CCR2+ Cytotoxic T Cells and Favorable Prognosis in Lung Adenocarcinoma.

Comprehensive characterization of mast cells in lung adenocarcinoma elucidates their heterogeneity and identifies interplay between mast cells and CCR2+ T cells that is associated with a favorable prognosis.

Examining Transcriptomic Differences Underlying Mycosis Fungoides in Skin of Color and White Patients

Abstract Mycosis Fungoides (MF), the most common type of cutaneous T-cell lymphoma, typically presents with an erythematous or dyspigmented rash that can progress to tumors and ulcerations on the skin. MF is more common in skin of color (SOC) patients, where it presents earlier and at a higher T-stage. This has led to poorer prognosis in SOC patients, with the poorest prognosis in African Americans. The pathogenesis regarding this racial disparity remains poorly understood. We compared MF skin samples from SOC and White patients to determine differentially expressed genes and elucidate transcriptomic differences. An immune panel of 343 genes were hybridized to 8 MF SOC and 8 MF White skin samples. The resulting gene signatures were analyzed to determine significant differentially expressed genes. Analysis revealed that SOC has significant downregulation of critical immune response genes involved in the recruitment of immune cells to sites of inflammation, including CCR1, CCR2, and CCR3. Genes involved in ‘chemokine signaling,’ ‘differentiation and maintenance of myeloid cells,’ and ‘cell migration and adhesion,’ were downregulated in SOC MF biopsies as compared to White skin MF biopsies. Furthermore, SOC MF biopsies have a greater abundance of mast cells, whereas White skin MF biopsies have a greater abundance of neutrophils. These transcriptomic differences suggest that MF may have a unique pathogenesis in SOC that involves significant downregulation of the host’s immune response. This potentially provides insight into the presentation of MF at a more advanced stage and aggressive course in SOC as compared to White skin. This insight may facilitate the development of immunotherapies targeted to SOC to address this racial disparity. SD - recipient of the Dermatology Foundation DRSA; JMR - recipient of the Skin of Color Society Reseach Grant; ASB - recipient of the American Skin Association Milstein Research Scholar Award for Melanoma/Non-Melanoma Skin Cancer

Abstract 5940: Enhanced mast cell abundance is associated with the enrichment of CCR2+ cytotoxic T cells and favorable prognosis in lung adenocarcinoma

Abstract Mast cells constitute indispensably immunoregulatory sentinel cells in tumor microenvironment, however, their functions are poorly characterized in lung adenocarcinoma (LUAD). Here, we performed flow cytometry and single-cell RNA sequencing to comprehensively characterize LUAD infiltrating MCs. MCs exhibited remarkably functional heterogeneity and were enriched in ground-glass opacity featured LUAD (gLUAD). The MCs in gLUAD exhibited proinflammatory and chemotactic properties while the MCs in radiologically solid LUAD (sLUAD) were associated with tumor angiogenesis. MCs were an important source of CCL2 that correlated with the recruitment of CCR2+ cytotoxic T lymphocytes (CTLs), which represent a specific subcluster of pre-exhausted T cells with tissue-resident memory phenotype and enhanced cytotoxicity. Increased infiltration of MCs-CCR2+ CTLs and their colocalization showed a strong association with favorable prognosis after surgery but were not associated with improved survival after chemotherapy. Collectively, these findings reveal a key role of MCs in LUAD and their potential crosstalk with CTLs, suggesting that targeting MCs may be a novel immunotherapeutic strategy for LUAD. Citation Format: Fan Fan, Xiaoming Zhang, Haiquan Chen. Enhanced mast cell abundance is associated with the enrichment of CCR2+ cytotoxic T cells and favorable prognosis in lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5940.

Development of a Reactive Stroma Gene Signature (RSGS) Score to Characterize the Longitudinal Cellular and Molecular Alterations in the Tissue Microenvironment of Locally Advanced Cervical Cancer in Response to Radiotherapy at Single-Cell Resolution

<h3>Purpose/Objective(s)</h3> Understanding how the tumor-associated tissue microenvironment impacts and reflects the response and effectiveness of chemoradiotherapy in cervical and vaginal cancer will open avenues for future clinical interventions and appropriate selection of radiation dose delivered via brachytherapy. <h3>Materials/Methods</h3> Biopsies of tumor and adjacent normal tissue from 7 cervical and vaginal cancer patients were collected longitudinally at baseline and after 45 Gy of ionizing radiation (IR) and analyzed by single-cell RNA sequencing to better understand the tumor, immune, and stromal determinants of response and resistance. Five of the 7 patients had biopsies available at 3 months and were included in this analysis. The single-cell transcriptomes of 4 cervical cancer patients (adenocarcinomas N=3, squamous cell carcinoma N=1) and one patient diagnosed with vaginal cancer (squamous cell carcinoma) were characterized. <h3>Results</h3> Of 5 patients evaluated at 3 months following high-dose-rate brachytherapy, 3 had a complete response, one had persistent disease and one had distant relapse in the peritoneum. Collectively, over 70,000 cells were analyzed in this study. We compared the single-cell transcriptomes of 2 poor responders versus 3 patients with a complete clinical response. The tumor tissue of poor responders had a molecular and cellular signature indicative of a reactive stroma (VCAM1+ fibroblasts, CXCR4+ endothelial cells, and elevated expression of select collagens), with infiltration of immunosuppressive lymphoid and myeloid cells. We developed a reactive stroma gene signature (RSGS) score, which was enriched in cells from irradiated tumor biopsies collected from subjects with poor outcomes. In contrast, the RSGS score was consistently low in normal biopsies at both baseline and post-IR across all subjects, with one exception. The subject with distant relapse showed RSGS score enrichment in the normal post-IR biopsy. When evaluating the cell proportions of immune cell populations, we observed that the abundance of mast cells was consistently lower (< 0.05%) in normal biopsies at both baseline and post-IR. Likewise, the proportion of mast cells in post-IR biopsies was also low in subjects with complete responses. However, in subjects with poor outcomes, the mast cell abundance increased at least three-fold compared to matched baseline tumor biopsies. <h3>Conclusion</h3> Importantly, the findings stemming from this study suggest that treatment-refractory disease upregulated tumor-promoting stromal and immune responses after initiating radiotherapy that was not observed in the tumor microenvironments of complete clinical responders; thus nominating molecular factors that can potentially be therapeutically exploited to improve the efficacy of radiation-based therapies in patients diagnosed with cervical and vaginal cancer. Future studies with larger cohorts enabled by more scalable in situ approaches will be necessary to assess the generalizability of these findings.

Reciprocal Interactions Between the Gut Microbiome and Mammary Tissue Mast Cells Promote Metastatic Dissemination of HR+ Breast Tumors.

Establishing commensal dysbiosis, defined as an inflammatory gut microbiome with low biodiversity, before breast tumor initiation, enhances early dissemination of hormone receptor-positive (HR+) mammary tumor cells. Here, we sought to determine whether cellular changes occurring in normal mammary tissues, before tumor initiation and in response to dysbiosis, enhanced dissemination of HR+ tumors. Commensal dysbiosis increased both the frequency and profibrogenicity of mast cells in normal, non-tumor-bearing mammary tissues, a phenotypic change that persisted after tumor implantation. Pharmacological and adoptive transfer approaches demonstrated that profibrogenic mammary tissue mast cells from dysbiotic animals were sufficient to enhance dissemination of HR+ tumor cells. Using archival HR+ patient samples, we determined that enhanced collagen levels in tumor-adjacent mammary tissue positively correlated with mast cell abundance and HR+ breast cancer recurrence. Together, these data demonstrate that mast cells programmed by commensal dysbiosis activate mammary tissue fibroblasts and orchestrate early dissemination of HR+ breast tumors.

Identification of Mast Cell-Based Molecular Subtypes and a Predictive Signature in Clear Cell Renal Cell Carcinoma.

Background: Kidney renal clear cell carcinoma (KIRC) is a common malignant tumor of the urinary system. Surgery is the preferred treatment option; however, the rate of distant metastasis is high. Mast cells in the tumor microenvironment promote or inhibit tumorigenesis depending on the cancer type; however, their role in KIRC is not well-established. Here, we used a bioinformatics approach to evaluate the roles of mast cells in KIRC. Methods: To quantify mast cell abundance based on gene sets, a single-sample gene set enrichment analysis (ssGSEA) was utilized to analyze three datasets. Weighted correlation network analysis (WGCNA) was used to identify the genes most closely related to mast cells. To identify new molecular subtypes, the nonnegative matrix factorization algorithm was used. GSEA and least absolute shrinkage and selection operator (LASSO) Cox regression were used to identify genes with high prognostic value. A multivariate Cox regression analysis was performed to establish a prognostic model based on mast cell-related genes. Promoter methylation levels of mast cell-related genes and relationships between gene expression and survival were evaluated using the UALCAN and GEPIA databases. Results: A prolonged survival in KIRC was associated with a high mast cell abundance. KIRC was divided into two molecular subtypes (cluster 1 and cluster 2) based on mast cell-related genes. Genes in Cluster 1 were enriched for various functions related to cancer development, such as the TGFβ signaling pathway, renal cell carcinoma, and mTOR signaling pathway. Based on drug sensitivity predictions, sensitivity to doxorubicin was higher for cluster 2 than for cluster 1. By a multivariate Cox analysis, we established a clinical prognostic model based on eight mast cell-related genes. Conclusion: We identified eight mast cell-related genes and constructed a clinical prognostic model. These results improve our understanding of the roles of mast cells in KIRC and may contribute to personalized medicine.

Antibiotic-induced disturbances of the gut microbiota result in accelerated breast tumor growth

SummaryThe gut microbiota’s function in regulating health has seen it linked to disease progression in several cancers. However, there is limited research detailing its influence in breast cancer (BrCa). This study found that antibiotic-induced perturbation of the gut microbiota significantly increases tumor progression in multiple BrCa mouse models. Metagenomics highlights the common loss of several bacterial species following antibiotic administration. One such bacteria, Faecalibaculum rodentium, rescued this increased tumor growth. Single-cell transcriptomics identified an increased number of cells with a stromal signature in tumors, and subsequent histology revealed an increased abundance of mast cells in the tumor stromal regions. We show that administration of a mast cell stabilizer, cromolyn, rescues increased tumor growth in antibiotic treated animals but has no influence on tumors from control cohorts. These findings highlight that BrCa-microbiota interactions are different from other cancers studied to date and suggest new research avenues for therapy development.

Mast Cells in Human Cutaneous Neurofibromas: Density, Subtypes, and Association with Clinical Features in Neurofibromatosis 1

Background: Cutaneous neurofibromas (cNFs) are hallmarks of neurofibromatosis 1 (NF1) and cause the main disease burden in adults with NF1. Mast cells are a known component of cNFs. However, no comprehensive characterization of mast cells in cNFs is available, and their contributions to cNF growth and symptoms such as itch are not known. Methods: We collected 60 cNFs from ten individuals with NF1, studied their mast cell proteinase content, and compared the mast cell numbers to selected clinical features of the tumors and patients. The tumors were immunolabeled for the mast cell markers CD117, tryptase, and chymase, and the percentage of immunopositive cells was determined using computer-assisted methods. Results: The median proportions of positive cells were 5.5% (range 0.1–14.4) for CD117, 4.0% (1.2–7.0) for tryptase, and 5.0% (1.1–15.9) for chymase. The median densities of cells immunopositive for CD117, tryptase, and chymase were 280, 243, and 250 cells/mm2, respectively. Small tumors, growing tumors, and tumors from patients below the median age of 33 years displayed a high proportion of mast cells. Cells expressing both tryptase and chymase were the predominant mast cell type in cNFs, followed by cells expressing chymase only. Conclusion: The results highlight the abundance of mast cells in cNFs and that their number and subtypes clearly differ from those previously reported in unaffected skin.

Reciprocal interactions between the gut microbiome and mammary tissue microenvironment promote distant regulation of breast tumor metastasis

Abstract Establishing commensal dysbiosis, defined as an inflammatory gut microbiome with low biodiversity, prior to breast tumor initiation enhances early dissemination of hormone-receptor positive (HR+) mammary tumor cells into the circulation, distal lymph nodes, and lungs. Here, we sought to define mammary tissue mediators of dysbiosis-induced tumor dissemination. Commensal dysbiosis increased mast cell numbers in the pre-malignant mammary tissue, with numbers remaining elevated in the presence of a tumor. During early tumor progression, increased mast cell numbers correlated with increased numbers of activated fibroblasts and collagen I protein levels in mammary tissues. Fibroblast activation and tissue remodeling are associated with enhanced breast tumor metastasis. Although mast cell degranulation is known to trigger fibrosis in other disease models, it is unknown whether mammary tissue mast cells influence dissemination of tumor cells. To investigate the role of mast cells during tumor dissemination, mice were treated with mast cell stabilizers ketotifen or cromolyn. Notably, inhibition of mast cell degranulation significantly reduced fibroblast activation and dissemination of tumor cells into the blood of dysbiotic animals. Collagen levels in mammary tissues from women diagnosed with HR+ breast cancer also correlated with mast cell abundance, suggesting mast cell-mediated fibroblast activation is relevant to human disease. Together, these data demonstrate that mast cells recruited into the pre-malignant mammary tissue in response to commensal dysbiosis orchestrate early dissemination of HR+ breast tumors through activation of tissue fibroblasts.

A role for mast cells in geographic atrophy.

Mast cells (MCs) are the initial responders of innate immunity and their degranulation contribute to various etiologies. While the abundance of MCs in the choroid implies their fundamental importance in the eye, little is known about the significance of MCs and their degranulation in choroid. The cause of geographic atrophy (GA), a progressive dry form of age-related macular degeneration is elusive and there is currently no therapy for this blinding disorder. Here we demonstrate in both human GA and a rat model for GA, that MC degranulation and MC-derived tryptase are central to disease progression. Retinal pigment epithelium degeneration followed by retinal and choroidal thinning, characteristic phenotypes of GA, were driven by continuous choroidal MC stimulation and activation in a slow release fashion in the rat. Genetic manipulation of MCs, pharmacological intervention targeting MC degranulation with ketotifen fumarate or inhibition of MC-derived tryptase with APC 366 prevented all of GA-like phenotypes following MC degranulation in the rat model. Our results demonstrate the fundamental role of choroidal MC involvement in GA disease etiology, and will provide new opportunities for understanding GA pathology and identifying novel therapies targeting MCs.

Mast cell-based molecular subtypes and signature associated with clinical outcome in early-stage lung adenocarcinoma.

Mast cells are a major component of the immune microenvironment in tumour tissues and modulate tumour progression by releasing pro‐tumorigenic and antitumorigenic molecules. Regarding the impact of mast cells on the outcomes of patients with lung adenocarcinoma (LUAD) patient, several published studies have shown contradictory results. Here, we aimed at elucidating the role of mast cells in early‐stage LUAD. We found that high mast cell abundance was correlated with prolonged survival in early‐stage LUAD patients. The mast cell‐related gene signature and gene mutation data sets were used to stratify early‐stage LUAD patients into two molecular subtypes (subtype 1 and subtype 2). The neural network‐based framework constructed with the mast cell‐related signature showed high accuracy in predicting response to immunotherapy. Importantly, the prognostic mast cell‐related signature predicted the survival probability and the potential relationship between TP53 mutation, c‐MYC activation and mast cell activities. The meta‐analysis confirmed the prognostic value of the mast cell‐related gene signature. In summary, this study might improve our understanding of the role of mast cells in early‐stage LUAD and aid in the development of immunotherapy and personalized treatments for early‐stage LUAD patients.

Identification of tumor-infiltrating immune cells and prognostic validation of tumor-infiltrating mast cells in adrenocortical carcinoma: results from bioinformatics and real-world data

ABSTRACT Objective The purpose of this study was to explore the composition of tumor-infiltrating immune cells (TIIC) and prognostic significance of tumor-infiltrating mast cells (TIMC) in adrenocortical carcinoma (ACC). Methods The gene expression profiles of ACC were downloaded from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GSE90713, GSE12368). The abundance of TIICs in ACC samples was calculated by CIBERSORT algorithm and immunohistochemistry was used to identify mast cells of 39 tumor samples from Fudan University Shanghai Cancer Center (FUSCC). Differentially expressed genes (DEGs) were analyzed by LIMMA package using R software. Survival analysis was analyzed by Kaplan-Meier method and Cox regression models. Results The abundance of mast cells (p = .008) was positively correlated with ACC patients’ outcome in TCGA cohort and was also positively correlated with both overall survival (p < .05) and progression-free survival (p < .05) in FUSCC cohort. Different TIMC infiltrations showed significant changes in signaling pathways including DNA replication, nuclear chromosome segregation, and meiotic cell cycle process of ACC. In addition, elevated expression of eight hub genes (KIF18A, CDCA8, SKA1, CEP55, BUB1, CDK1, SGOL1, SGOL2) related to the abundance of TIMC in ACC was significantly correlated with the poor prognosis of the patients. Conclusion In conclusion, higher TIMC infiltration was positively correlated with ACC patients’ outcome in both TCGA and FUSCC cohort. Lower TIMC infiltration and elevated expression of hub genes (KIF18A, CDCA8, SKA1, CEP55, BUB1, CDK1, SGOL1, SGOL2) are markedly correlated with aggressive progression and poor prognosis, which might shed lights on novel targets for treatment strategies.

IL-33-mediated mast cell activation promotes gastric cancer through macrophage mobilization

The contribution of mast cells in the microenvironment of solid malignancies remains controversial. Here we functionally assess the impact of tumor-adjacent, submucosal mast cell accumulation in murine and human intestinal-type gastric cancer. We find that genetic ablation or therapeutic inactivation of mast cells suppresses accumulation of tumor-associated macrophages, reduces tumor cell proliferation and angiogenesis, and diminishes tumor burden. Mast cells are activated by interleukin (IL)-33, an alarmin produced by the tumor epithelium in response to the inflammatory cytokine IL-11, which is required for the growth of gastric cancers in mice. Accordingly, ablation of the cognate IL-33 receptor St2 limits tumor growth, and reduces mast cell-dependent production and release of the macrophage-attracting factors Csf2, Ccl3, and Il6. Conversely, genetic or therapeutic macrophage depletion reduces tumor burden without affecting mast cell abundance. Therefore, tumor-derived IL-33 sustains a mast cell and macrophage-dependent signaling cascade that is amenable for the treatment of gastric cancer.

Increased mast cell abundance in adipose tissue of metabolic syndrome: relevance to the proinflammatory state and increased adipose tissue fibrosis.

Metabolic Syndrome (MetS) affects 35% of American adults > 40 yr and portends an increased risk for both atherosclerotic cardiovascular disease (ASCVD) and diabetes. The role of mast cells in the proinflammatory state of MetS is not well elucidated. We propose that mast cells in subcutaneous adipose tissue (SAT) of MetS patients without diabetes or clinical ASCVD contribute to insulin resistance and inflammation. Matched controls ( n = 15) and MetS ( n = 19) subjects were recruited from Sacramento, CA, and selected based on Adult Treatment Panel III criteria. SAT biopsy was performed on all subjects and processed for immunohistochemistry. The SAT sections were stained using Astra Blue stain and tryptase stain for mast cells. Fasting blood was obtained for chemistries and biomarkers. Abundance of mast cells (Astra Blue stain) in SAT of MetS subjects compared with controls was increased 2.5-fold ( P < 0.0001). Mast cells correlated positively and significantly with waist circumference, glucose, triglycerides, homeostatic model of assessment-insulin resistance (HOMA-IR), AT insulin resistance, leptin, interleukin (IL)-1β, IL-6, chemerin, p38 MAPK activity, and nuclear factor κB activity in circulating monocytes. Mast cells also correlated significantly with markers of fibrosis and angiogenesis. Tryptase staining of mast cells in AT revealed a significant increase ( P = 0.008) with similar correlations. We make the novel observation that there are increased mast cells in SAT of MetS, and these mast cells correlate with insulin resistance (hepatic and adipose tissue), inflammation, and AT fibrosis. Hence, these immune cells appear to occupy a pivotal role in the pathogenesis of MetS.

Mast Cell Mediators Inhibit Osteoblastic Differentiation and Extracellular Matrix Mineralization.

Mast cells are multifunctional immune cells that participate in many important processes such as defense against pathogens, allergic reactions, and tissue repair. These cells perform their functions through the release of a wide variety of mediators. This release occurs mainly through cross-linking IgE (immunoglobulin E) bound to high affinity IgE receptors by multivalent antigens. The abundance of mast cells in connective tissue, surrounding blood vessels, and their involvement in the early stages of bone repair support the possibility of physiological and pathological interactions between mast cells and osteoblasts. However, the participation of mast cell mediators in osteogenesis is not fully understood. Therefore, the objective of this work was to investigate the role of mast cell mediators in the acquisition of the osteogenic phenotype in vitro. The results show that pooled mast cell mediators can affect proliferation, morphology, and cytoskeleton of osteoblastic cells, and impair the activity and expression of alkaline phosphatase as well as the expression of bone sialoprotein. Also, mast cell mediators inhibit the expression of mRNA for those proteins and inhibit the formation and maturation of calcium nodules and consequently inhibit mineralization. Therefore, mast cell mediators can modulate osteogenesis and are potential therapeutic targets for treatments of bone disorders.