High density of tryptase-positive mast cells in patients with renal cell carcinoma on hemodialysis: correlation with expression of stem cell factor and protease activated receptor-2

Frenemies in the Microenvironment: Harnessing Mast Cells for Cancer Immunotherapy

Tumor development, progression, and resistance to therapies are influenced by the interactions between tumor cells and the surrounding microenvironment, comprising fibroblasts, immune cells, and extracellular matrix proteins. In this context, mast cells (MCs) have recently emerged as important players. Yet, their role is still controversial, as MCs can exert pro- or anti-tumor functions in different tumor types depending on their location within or around the tumor mass and their interaction with other components of the tumor microenvironment. In this review, we describe the main aspects of MC biology and the different contribution of MCs in promoting or inhibiting cancer growth. We then discuss possible therapeutic strategies aimed at targeting MCs for cancer immunotherapy, which include: (1) targeting c-Kit signaling; (2) stabilizing MC degranulation; (3) triggering activating/inhibiting receptors; (4) modulating MC recruitment; (5) harnessing MC mediators; (6) adoptive transferring of MCs. Such strategies should aim to either restrain or sustain MC activity according to specific contexts. Further investigation would allow us to better dissect the multifaceted roles of MCs in cancer and tailor novel approaches for an "MC-guided" personalized medicine to be used in combination with conventional anti-cancer therapies.

Mast Cell–Tumor Interactions: Molecular Mechanisms of Recruitment, Intratumoral Communication and Potential Therapeutic Targets for Tumor Growth

Mast cells (MCs) are tissue-resident immune cells that are important players in diseases associated with chronic inflammation such as cancer. Since MCs can infiltrate solid tumors and promote or limit tumor growth, a possible polarization of MCs to pro-tumoral or anti-tumoral phenotypes has been proposed and remains as a challenging research field. Here, we review the recent evidence regarding the complex relationship between MCs and tumor cells. In particular, we consider: (1) the multifaceted role of MCs on tumor growth suggested by histological analysis of tumor biopsies and studies performed in MC-deficient animal models; (2) the signaling pathways triggered by tumor-derived chemotactic mediators and bioactive lipids that promote MC migration and modulate their function inside tumors; (3) the possible phenotypic changes on MCs triggered by prevalent conditions in the tumor microenvironment (TME) such as hypoxia; (4) the signaling pathways that specifically lead to the production of angiogenic factors, mainly VEGF; and (5) the possible role of MCs on tumor fibrosis and metastasis. Finally, we discuss the novel literature on the molecular mechanisms potentially related to phenotypic changes that MCs undergo into the TME and some therapeutic strategies targeting MC activation to limit tumor growth.

Clinical, histopathological and immunohistochemical behavior of peri-implant soft tissue

The presence of foreign materials in the tissues, represented in the present study by the insertion of dental implants, creates artificial structures that can sometimes cause adverse consequences, which implies the obligation to perform a complex medical assessment before inserting dental implants. This assessment appreciates the quality of the tissue, depending on which the use of a certain type of biomaterial is indicated and focuses on a certain surgical technique. We assessed the clinical, histopathological (HP) and immunohistochemical (IHC) aspects of peri-implant soft tissue in patients who did not show mobility or imagistic signs of bone resorption, three months after implant insertion, some of them showing no inflammatory clinical signs. Immunohistochemically, on the sections of the peri-implant mucosa, we assessed the presence of mast cells, vascularization and the process of angiogenesis. Mast cells are key cells actively involved in the pathogenesis of peri-implant inflammation, having an immunomodulatory role. Vasodilation and angiogenesis, determined by the release of chemical mediators by degranulation of mast cells under the action of pathogens, induce tissue remodeling, ensuring the healing and formation of a tissue to form a barrier that effectively prevents the development of a bacterial biofilm. Thus, the control of the activity of these cells is important for the management of the local inflammatory process. The correlations between the clinical, HP and IHC behavior of the peri-implant soft tissue bring important information for the clinic, emphasizing the need to identify a therapeutic strategy to modulate mast cell activity, in order to prevent and treat peri-implant disease, to ensure osseointegration and longer survival of the dental implant.

Is it time for a new classification of mast cells? What do we know about mast cell heterogeneity?

Mast cells (MCs) are derived from committed precursors that leave the hematopoietic tissue, migrate in the blood, and colonize peripheral tissues where they terminally differentiate under microenvironment stimuli. They are distributed in almost all vascularized tissues where they act both as immune effectors and housekeeping cells, contributing to tissue homeostasis. Historically, MCs were classified into 2 subtypes, according to tryptic enzymes expression. However, MCs display a striking heterogeneity that reflects a complex interplay between different microenvironmental signals delivered by various tissues, and a differentiation program that decides their identity. Moreover, tissue-specific MCs show a trained memory, which contributes to shape their function in a specific microenvironment. In this review, we summarize the current state of our understanding of MC heterogeneity that reflects their different tissue experiences. We describe the discovery of unique cell molecules that can be used to distinguish specific MC subsets in vivo, and discuss how the improved ability to recognize these subsets provided new insights into the biology of MCs. These recent advances will be helpful for the understanding of the specific role of individual MC subsets in the control of tissue homeostasis, and in the regulation of pathological conditions such as infection, autoimmunity, and cancer.

Pathological significance and prognostic roles of densities of CD57+ cells, CD68+ cells, and mast cells, and their ratios in clear cell renal cell carcinoma

The immune system is closely associated with malignant behavior in renal cell carcinoma (RCC). Therefore, understanding the pathological roles of immune cells in tumor stroma is essential to discuss the pathological characteristics of RCC. In this study, the clinical significance of densities of CD57+ cells, CD68+ cells, and mast cells, and their ratios were investigated in patients with clear cell RCC. The densities of CD57+, CD68+, and mast cells were evaluated by immunohistochemical techniques in 179 patients. Proliferation index, apoptotic index, and microvessel density were evaluated by using anti-Ki-67, anti-cleaved caspase-3, and anti-CD31 antibodies, respectively. The density of CD57+ cell was negatively correlated with grade, pT stage, and metastasis, although densities of CD68+ cell and mast cell were positively correlated. Ratios of CD68+ cell/CD57+ cell and mast cell/CD57+ cell were significantly correlated with grade, pT stage, and metastasis. Survival analyses showed that the CD68+ cell/CD57+ cell ratio was a significant predictor for cause-specific survival by multivariate analyses (hazard ratio = 1.41, 95% confidence interval = 1.03-1.93, P = .031) and was significantly correlated with proliferation index, apoptotic index, and microvessel density (r = .47, P <. 001; r = -.31, P < .001; and r = .40, P < .001, respectively). In conclusion, CD57+ cells, CD68+ cells, and mast cells played important roles in malignancy in clear cell RCC. The CD68+ cell/CD57+ cell ratio was strongly correlated with pathological features and prognosis in these patients because this ratio reflected the status of cancer cell proliferation, apoptosis, and angiogenesis.

The relationship between breast cancer molecular subtypes and mast cell populations in tumor microenvironment

Mast cells (MCs) are a part of the innate immune system. The MC functions toward cancer are partially based on the release of chymase and tryptase. However, the MC effect on breast cancer is controversial. The aim of our study was to investigate the presence of MCs in breast cancer tumors of different molecular subtypes and their relationships with other pathological prognostic factors. Tryptase- and chymase-positive mast cell densities were evaluated by immunohistochemistry in 108 primary invasive breast cancer tissue samples. Positive cells were counted within the tumor bed and at the invasive margin. For all analyzed MC subpopulations, we observed statistically significant differences between individual molecular subtypes of breast cancer. The significantly higher numbers of intratumoral chymase- and tryptase-positive mast cells were observed in luminal A and luminal B tumors compared to triple-negative and HER2+ non-luminal lesions. A denser MC infiltration was associated with lower tumor grade, higher ER and PR expression, lower proliferation rate as well as the lack of HER2 overexpression. The results obtained in our study indicate a possible association of chymase- and tryptase-positive MCs with more favorable cancer immunophenotype and with beneficial prognostic indicators in breast cancer.

Infiltrating mast cells promote renal cell carcinoma angiogenesis by modulating PI3K→︀AKT→︀GSK3β→︀AM signaling

The recruitment of vascular endothelial cells from the tumor microenvironment (TME) to promote angiogenesis plays key roles in the progression of renal cell carcinoma (RCC). The potential impact of immune cells in the TME on RCC angiogenesis, however, remains unclear. Here, we found that recruitment of mast cells resulted in increased RCC angiogenesis in both in vitro cell lines and in vivo mouse models. Mechanistic analyses revealed that RCC recruited mast cells by modulating PI3K→AKT→GSK3β→AM signaling. A clinical survey of human RCC samples also showed that higher expression of the PI3K→AKT→GSK3β→AM signaling pathway correlated with increased angiogenesis. Interruption of PI3K→AKT→GSK3β→AM signaling via specific inhibitors led to decreased recruitment of mast cells, and targeting this infiltrating mast cell-related signaling via an AKT-specific inhibitor suppressed RCC angiogenesis in xenograft mouse models. Together, these results identified a novel role of infiltrating mast cells in RCC angiogenesis and metastasis and suggest a new strategy for treating RCC by targeting this newly identified signaling pathway.

Stromal expression of Fer suppresses tumor progression in renal cell carcinoma and is a predictor of survival

Fps/Fes related (Fer) is a non-receptor tyrosine kinase that is expressed in fibroblasts, immune cells and endothelial cells. Fer serves an important pathological role in cell survival, angiogenesis and the immune system. However, the pathological role of Fer expression in the stromal cells surrounding renal cell carcinoma (RCC) has not been previously investigated. In the present study, immunohistochemical analysis of Fer was performed using the formalin-fixed tissue samples of 152 patients with RCC. The proliferative and apoptotic indices were used to represent the percentage of proliferation marker protein Ki-67- and cleaved caspase-3-positive cells, respectively. The microvessel density was defined as the number of cluster of differentiation (CD) 31-positively stained vessels/mm². In addition, CD57⁺ and CD68⁺ cells were counted using semi-quantification of natural killer (NK) cells and macrophages. Fer expression in stromal cells was negatively associated with Fuhrman grade, pathological tumor stage and metastasis (P<0.001). Fer expression in stromal cells was negatively associated with CD68⁺ macrophage density, whereas it was positively associated with CD57⁺ NK cell density. Kaplan-Meier estimators indicated that decreased stromal Fer expression was a predictive marker of decreased cause-specific survival rate (P<0.001). Furthermore, low expression of Fer was identified as being an independent marker of decreased cause-specific survival using multivariate analysis (hazard ratio, 7.4; 95% confidence interval, 1.7-33.0; P<0.001). The results of the present study suggested that low Fer expression in stromal cells is associated with increased malignant aggressiveness and decreased survival in patients with RCC. CD57⁺ NK cell and CD68⁺ macrophage regulation in cancer-stromal tissue is considered to affect RCC pathology.

High infiltration of mast cells positive to tryptase predicts worse outcome following resection of colorectal liver metastases

BACKGROUND

Accumulation of tumor-infiltrating mast cells (MCs) predicts poor survival in several cancers after resection. However, its effect on the prognosis of patients with colorectal liver metastases (CRLM) is not known.

METHODS

Our retrospective study included 135 patients who underwent potentially curative resection for CRLM between 2001 and 2010. Expression of tryptase, MAC387, CD83, and CD31, which are markers for MCs, macrophages, mature dendritic cells, and vascular endothelial cells, respectively, was determined via immunohistochemistry of resected tumor specimens. The relationship between immune cell infiltration and long-term outcome was investigated.

RESULTS

The median follow-up time was 48.4 months for all patients and 57.5 months for survivors. Overall survival (OS) rates at 1, 3, and 5 years were 91.0, 62.4, and 37.4 %, respectively. Five-year disease-free survival (DFS) and OS rates were 21.6 and 38.1 %, respectively, in patients with high MC infiltration, and 42.6 and 55.6 %, respectively, in patients with low MC infiltration (p < 0.01 for both DFS and OS). Infiltration of other types of immune cells did not correlate with survival. Multivariate analyses indicated that hypoalbuminemia and high peritumoral MC infiltration were significant predictors of unfavorable OS.

CONCLUSION

High peritumoral MC infiltration predicts poor prognosis in patients who underwent hepatectomy for CRLM. The number of MCs in metastatic lesions is important for predicting the prognosis of CRLM patients and as an indication of therapy.

Tumour progression and cancer-induced pain: a role for protease-activated receptor-2?

The role of proteases in modifying the microenvironment of tumour cells has long been recognised. With the discovery of the protease-activated receptor family of G protein-coupled receptors a mechanism for cells to sense and respond directly to proteases in their microenvironment was revealed. Many early studies described the roles of protease-activated receptors in the cellular events that occur during blood coagulation and inflammation. More recently, studies have begun to focus on the roles of protease-activated receptors in the establishment, progression and metastasis of a variety of tumours. This review will focus on the expression of protease-activated receptor-2 and its activators by normal and neoplastic tissues, and describe current evidence that activation of protease-activated receptor-2 is an important event at multiple stages of tumour progression and in pain associated with cancer.

SCF/C-KIT signaling modulates tryptase expression in acute myeloid leukemia cells

Tryptase is a serine protease with a variety of biological functions. Recently, elevated serum tryptase has been detected in certain patients with acute myeloid leukemia (AML). However, the underlying mechanism for the regulation of tryptase expression remains elusive. In this study, we aimed to investigate the role of stem cell factor (SCF)/C-KIT signaling in regulating the expression of tryptase in AML cells. We found a significant positive correlation between tryptase and C-KIT expression levels in AML patients. Furthermore, real-time PCR, Western blot and ELISA analysis showed that SCF upregulated tryptase mRNA and protein expression in U937 cells, and that this effect was abolished by pretreatment with PD98059 and SB230580. In addition, levels of phosphorylated ERK1/2 and p38MAPK correlated with tryptase levels. Taken together, these data suggest that the expression of tryptase is regulated by SCF/C-KIT signaling via the ERK1/2 and p38MAPK pathways.

Evaluation of peri-implant mucosa: clinical, histopathological and immunological aspects

OBJECTIVE

The aim was to compare the inflammatory response in peri-implant mucosa between patients with peri-implantitis (PP-group) and patients with healthy peri-implant tissues (HP-group).

MATERIALS AND METHODS

Two fragments of peri-implant mucosa of 18 patients were collected and serial sections were performed for histological and immunohistochemical analysis.

RESULTS

When compared with HP-group, PP-group showed higher immunostained cell density for TGF-β, IL-17 and CD31, beyond greater density of red cells, leukocytes, mast cells chymase (MCC) and mast cell tryptase (MCT). HP-group patients showed higher IL-13 expression and increased amount of collagen fibres when compared with PP-group. In PP-group there was significant positive correlation between MCT density and density of blood vessels immunostained, and between MCC density and density of blood vessels immunostained. There was significant negative correlation between the IL-17 density and collagen percentage.

CONCLUSIONS

This study demonstrated that in patients with peri-implantitis there was higher of TGF-β and IL-17, indicating that these cytokines are directly involved in the inflammatory process. Thus, understanding the influence of cytokines in the peri-implantitis installation, new therapies could be developed in order to inhibit the synthesis of IL-17 and induce synthesis of IL-13 in peri-implant tissue, contributing to increase the longevity of the implant.