Mast cell maturation accompanies neovascularization during skin tumor progression

Abstract

In spite of evidence indicating an association between mast cells, tumor progression andangiogenesis, the role of these cells in neo‐vascularization and tumor progression remains obscure. This study aims to understand the involvement of mast cells in these processes. Tumors were induced by topical application of DMBA and TPA on BALB/c mice. Tumors were processed for routine histology, flow cytometry or biochemical analysis. Tumor progression was divided into phases I, II and III. At phase I tumors exhibited a large number of mast cells, which increased in phase II, but did not increase further. The expression of secretory granule components (mMCP‐4, mMCP‐5, mMCP‐6, mMCP‐7, carboxipeptidase A and histamine) and their activity was also altered during tumor progression. The activity of tryptase and chymase increased primarily in phases II and III, when there is no increase in the number of mast cells associated the tumor. An increase in new blood vessels, particularly in phase I, was observed. Whereas, in phases II and III there was no significant increase in new blood vessels, there was an enlargement of existing blood vessels. The pattern of expression of granule specific components even when there is no increase the number of the mast cells, suggests that mast cells found in tumors are in process of maturation mainly at phases II and III and this maturation correlates with neovascularization during skin tumor progression.