The tumor microenvironment (TME), which is composed of stromal cells such as endothelial cells, fibroblasts, and immune cells, provides a supportive niche promoting the growth and invasion of tumors. The TME also raises an immunosuppressive barrier to effective antitumor immune responses and is therefore emerging as a target for cancer immunotherapies. Mast cells (MCs) accumulate in the TME at early stages, and their presence in the TME is associated with poor prognosis in many aggressive human cancers. Some well-established roles of MCs in cancer are promoting angiogenesis and tumor invasion into surrounding tissues. Several mouse models of inducible and spontaneous cancer show that MCs are among the first immune cells to accumulate within and shape the TME. Although MCs and other suppressive myeloid cells are associated with poor prognosis in human cancers, high densities of intratumoral T effector (T(eff)) cells are associated with a favorable prognosis. The latter finding has stimulated interest in developing therapies to increase intratumoral T cell density. However, cellular and molecular mechanisms promoting high densities of intratumoral T(eff) cells within the TME are poorly understood. New evidence suggests that MCs are essential for shaping the immune-suppressive TME and impairing both antitumor T(eff) cell responses and intratumoral T cell accumulation. These roles for MCs warrant further elucidation in order to improve antitumor immunity. Here, we will summarize clinical studies of the prognostic significance of MCs within the TME in human cancers, as well as studies in mouse models of cancer that reveal how MCs are recruited to the TME and how MCs facilitate tumor growth. Also, we will summarize our recent studies indicating that MCs impair generation of protective antitumor T cell responses and accumulation of intratumoral T(eff) cells. We will also highlight some approaches to target MCs in the TME in order to unleash antitumor cytotoxicity.
"He assumed that mast cells directly fulfill nutritional requirements of malignant tissues (130, 141). This is definitely not the case, but the distinct role of mast cells in oncology is still a matter of debate (142). "
[Show abstract][Hide abstract] ABSTRACT: Passive immunotherapy with monoclonal antibodies is an indispensable cornerstone of clinical oncology. Notably, all FDA-approved antibodies comprise the IgG class, although numerous research articles proposed monoclonal antibodies of the IgM, IgG, IgA and IgE classes directed specifically against tumor-associated antigens. In particular, for the IgE isotype class, several recent studies could demonstrate high tumoricidic efficacy. Therefore, this review specifically highlights the latest developments toward IgE-based immunotherapy of cancer. Possible mechanisms and safety aspects of IgE-mediated tumor cell death are discussed with special focus on the attracted immune cells. An outlook is given on how especially comparative oncology could contribute to further developments. Humans and dogs have a highly comparable IgE biology, suggesting that translational AllergoOncology studies in patients with canine cancer could have predictive value for the potential of IgE-based anticancer immunotherapy in human clinical oncology.
[Show abstract][Hide abstract] ABSTRACT: Mast cells have emerged as critical intermediaries in the regulation of peripheral tolerance. Their presence in many precancerous lesions and tumors is associated with a poor prognosis, suggesting mast cells may promote an immunosuppressive tumor microenvironment and impede the development of protective anti-tumor immunity. The studies presented herein investigate how mast cells influence tumor-specific T cell responses. Male MB49 tumor cells, expressing HY antigens, induce anti-tumor IFN-γ(+) T cell responses in female mice. However, normal female mice cannot control progressive MB49 tumor growth. In contrast, mast cell-deficient c-Kit(Wsh) (W(sh)) female mice controlled tumor growth and exhibited enhanced survival. The role of mast cells in curtailing the development of protective immunity was shown by increased mortality in mast cell-reconstituted W(sh) mice with tumors. Confirmation of enhanced immunity in female W(sh) mice was provided by (1) higher frequency of tumor-specific IFN-γ(+) CD8(+) T cells in tumor-draining lymph nodes compared with WT females and (2) significantly increased ratios of intratumoral CD4(+) and CD8(+) T effector cells relative to tumor cells in W(sh) mice compared to WT. These studies are the first to reveal that mast cells impair both regional adaptive immune responses and responses within the tumor microenvironment to diminish protective anti-tumor immunity.
Cancer Immunology and Immunotherapy 06/2012; 61(12). DOI:10.1007/s00262-012-1276-7 · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Paul Ehrlich, a German scientist, discovered what is known as the mast cell in the late 1800's, which has proven to be an important player in the immune system of vertebrates. Mast cells are ubiquitous throughout the tissues of the human body and play numerous roles, both beneficial and destructive. We know they are important in our army of immunity warrior cells, which defend us against viruses, bacteria and parasitic invaders. They are also very well known for the havoc they wreak, causing uncomfortable symptoms due to their release of histamine and other mediators which cause the all too familiar itching, sneezing, urticaria and rhinorrhea of allergic responses. Mast cell activities are diverse and include painful inflammatory reactions in autoimmune conditions such as rheumatoid arthritis. In the gastrointestinal system, mast cells are implicated in diverse actions such as increased gastric acid secretion, polyp formation and uncomfortable conditions such as Irritable Bowel Syndrome. The role of immunology and mast cells in these areas is intriguing but less well understood than their role in allergic responses. Because mast cells have been implicated in both physiologic as well as pathogenic processes, they have been the subjects of avid study. Review of the current literature on mast cell biology reveals that there are many studies of their presence within the tumor microenvironment and evidence, which supports mast cell influence on tumor angiogenesis, tumor invasion, and immune suppression. The studies reviewed in this article concentrate largely on mast cells in human GI malignancies. This review also provides background information regarding mast cells, such as their origination, their location within the body, how they are activated and how they function as mediators.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.