Mast cells (MCs) are tissue resident sentinels that orchestrate inflammation in response to helminth infection and allergens. They are also frequently observed in tumors, suggesting their contribution in the transition from persistent inflammation to carcinoma. However, the role of MCs in the contest of colorectal cancer (CRC) microenviroment is still debated. In particular, whether different subsets of MCs infiltrate the tumor in different stages of disease progression and whether and how a bi-directional cross-talk between MCs and tumor cells affects tumor development has not been clarified yet.
To gain insight into these issues we will use both murine models of CRC progression as well as human large intestine biopsies of CRC patients undergoing tumor resection. We will focus on MC phenotype and functions both in term of granule-stored proteases and ability to produce different pro-inflammatory cytokines and pro-angiogenic factors in order to characterize discrete subsets of MCs in tumor microenvironment and their impact on disease progression.
Understanding the role of MCs in tumor development and progression would be of critical importance for the development of new targeted therapies for CRC.
Colorectal cancer (CRC) development and progression are the results of accumulation of genetic alterations as well as the establishment of a pro-tumoral microenvironment.
Due to the complexity of CRC pathogenesis, the identification of novel cellular and molecular players implicated in the loss integrity of the gut epithelial barrier is a pressing unmet need.
Different types of immune cells infiltrate CRC, being mast cells (MCs) one of the earliest recruited, suggesting their contribution to tumor progression. However, the exact role of MCs in tumorigenesis remains controversial: MC-derived mediators can either exert pro-tumorigenic functions, causing progression and spread of the tumor, or anti-tumorigenic functions, limiting tumor growth. Thus, a deeper understanding of distribution and functionality of MC subsets during CRC progression will allow us to unveil novel mechanisms underlying CRC pathogenesis.
Two different subsets of MCs have been identified mainly based on their protease content and their localization. MCs that are predominant in connective tissue and are characterized in mouse by granules containing mainly mast cell proteases (MCPT)-4, -5 and -6 and in human by granules containing both tryptase and chymase and mucosal MCs that are endowed with MCPT-1 and -2 in mice and tryptase in humans. However, due to MC capability to respond to a plethora of different stimuli, MC functions may be modulated depending on the surrounding environment. Little is currently known about the possibility that different MC subsets are endowed of different effector functions in terms of cytokine production.
We propose to employ a multiparametric flow cytometry approach to identify MC subsets endowed with peculiar functional competence and to understand how their functionality is deregulated in the context of colitis-induced and genetic CRC. Compared to classical approaches mainly based on immunohistochemistry, flow cytometry offers the opportunity to have quantitative data reflecting the whole organ and concurrently study MC activation in term of cytokine production.
Dissecting the function of the different MC subsets present at various stages of CRC could provide insights into the understanding of disease pathogenesis and offer the opportunity to discover potential novel biomarkers of prognostic value and/or new targets for therapeutic intervention.