Correlation of serum tryptase levels with total number of nevi, Breslow thickness, ulceration, and mitotic index in melanoma patients: evaluation of a promising prognostic marker

Protease Profile of Tumor-Associated Mast Cells in Melanoma

Mast cells (MCs) produce a variety of mediators, including proteases—tryptase, chymase, and carboxypeptidases—which are important for the immune response. However, a detailed assessment of the mechanisms of biogenesis and excretion of proteases in melanoma has yet to be carried out. In this study, we present data on phenotype and secretory pathways of proteases in MCs in the course of melanoma. The development of melanoma was found to be accompanied by the appearance in the tumor-associated MC population of several pools with a predominant content of one or two specific proteases with a low content or complete absence of others. Elucidation of the molecular and morphological features of the expression of MC proteases in melanoma allows us a fresh perspective of the pathogenesis of the disease, and can be used to clarify MCs classification, the disease prognosis, and evaluate the effectiveness of ongoing antitumor therapy.

Tryptase Regulates the Epigenetic Modification of Core Histones in Mast Cell Leukemia Cells

Mast cells are immune cells that store large amounts of mast cell-restricted proteases in their secretory granules, including tryptase, chymase and carboxypeptidase A3. In mouse mast cells, it has been shown that tryptase, in addition to its canonical location in secretory granules, can be found in the nuclear compartment where it can impact on core histones. Here we asked whether tryptase can execute core histone processing in human mast cell leukemia cells, and whether tryptase thereby can affect the epigenetic modification of core histones. Our findings reveal that triggering of cell death in HMC-1 mast cell leukemia cells is associated with extensive cleavage of core histone 3 (H3) and more restricted cleavage of H2B. Tryptase inhibition caused a complete blockade of such processing. Our data also show that HMC-1 cell death was associated with a major reduction of several epigenetic histone marks, including H3 lysine-4-mono-methylation (H3K4me1), H3K9me2, H3 serine-10-phosphorylation (H3S10p) and H2B lysine-16-acetylation (H2BK16ac), and that tryptase inhibition reverses the effect of cell death on these epigenetic marks. Further, we show that tryptase is present in the nucleus of both viable and dying mast cell leukemia cells. In line with a role for tryptase in regulating nuclear events, tryptase inhibition caused increased proliferation of the mast cell leukemia cells. Altogether, the present study emphasizes a novel principle for how epigenetic modification of core histones is regulated, and provides novel insight into the biological function of human mast cell tryptase.

The emerging role of mast cells in skin cancers: involved cellular and molecular mechanisms

Skin cancers are the most common cancers worldwide. They can be divided into nonmelanoma skin cancers (NMSC) including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and less common lymphomas and merkel cell carcinoma, and melanomas. Melanomas comprise less than 5% of skin cancer rate but are responsible for more than 90% of skin cancer death. Mast cells (MCs) are multifunctional cells that play an important role in inflammatory and allergic reactions. They attract other key players of the immune system by releasing cytokines. Healthy human skin comprises MCs under physiological status, and the number can increase under certain conditions including skin malignancies postulating their possible role in pathogenesis of and immunity against skin cancers. MCs respond to cytokines released by tumor stromal cells, release mediators (including histamine and tryptase), and induce the neovascularization, degradation of extracellular matrix (ECM), and induce mitogenesis. However, MCs may use molecular mechanisms to exert immunosuppressive activity including releasing complement C3, lower expression of CD40L, and overexpression of enzymes with vitamin D3 metabolizing activity including CYP27A1 and CYP27B1. This review summarizes the current knowledge on the role of MCs in pathogenesis and immunity against skin cancers.

Protective role of mouse mast cell tryptase Mcpt6 in melanoma

Tryptase-positive mast cells populate melanomas, but it is not known whether tryptase impacts on melanoma progression. Here we addressed this and show that melanoma growth is significantly higher in tryptase-deficient (Mcpt6^-/- ) versus wild-type mice. Histochemical analysis showed that mast cells were frequent in the tumor stroma of both wild-type and Mcpt6^-/- mice, and also revealed their presence within the tumor parenchyma. Confocal microscopy analysis revealed that tryptase was taken up by the tumor cells. Further, tryptase-positive granules were released from mast cells and were widely distributed within the tumor tissue, suggesting that tryptase could impact on the tumor microenvironment. Indeed, gene expression analysis showed that the absence of Mcpt6 caused decreased expression of numerous genes, including Cxcl9, Tgtp2, and Gbp10, while the expression of 5p-miR3098 was enhanced. The levels of CXCL9 were lower in serum from Mcpt6^-/- versus wild-type mice. In further support of a functional impact of tryptase on melanoma, recombinant tryptase (Mcpt6) was taken up by cultured melanoma cells and caused reduced proliferation. Altogether, our results indicate a protective role of mast cell tryptase in melanoma growth.

Eruptive Melanocytic Nevi: A Review

Eruptive melanocytic nevi (EMN) is a phenomenon characterized by the sudden onset of nevi. Our objective was to compile all published reports of EMN to identify possible precipitating factors and to evaluate the clinical appearance and course. We conducted a systematic bibliographic search and selected 93 articles, representing 179 patients with EMN. The suspected causes were skin and other diseases (50%); immunosuppressive agents, chemotherapy or melanotan (41%); and miscellaneous, including idiopathic (9%). The clinical manifestations could largely be divided into two categories: EMN associated with skin diseases were frequently few in number (fewer than ten nevi), large, and localized to the site of previous skin disease, whereas those due to other causes presented most often with multiple small widespread nevi. In general, EMN seem to persist unchanged after their appearance, but development over several years or fading has also been reported. Overall, 16% of the cases had at least one histologically confirmed dysplastic nevus. Five cases of associated melanoma were reported. We conclude that the clinical appearance of EMN may differ according to the suggested triggering factor. Based on the clinical distinction, we propose a new subclassification of EMN: (1) widespread eruptive nevi (WEN), with numerous small nevi, triggered by, for example, drugs and internal diseases, and (2) Köbner-like eruptive nevi, often with big and few nevi, associated with skin diseases and most often localized at the site of previous skin disease/trauma. The nature of the data precluded assessment of risk of malignant transformation.