Hedgehog signaling in the tumor microenvironment

Summary

The tumor microenvironment includes the normal cells, molecules, and blood vessels that surround and feed a tumor cell.¹ Within the tumor microenvironment, there are stromal cells, such as fibroblasts, endothelial cells, and infiltrating immune cells, that support the tumor.² Recent reports suggest a model in which Hedgehog ligands secreted by epithelial tumor cells activate Hedgehog signaling in surrounding stromal cells, which results in the expression and secretion of factors into the tumor microenvironment that support tumor growth.³ This type of paracrine (cell-to-cell) Hedgehog signaling may play a role in the development of colorectal, ovarian, and pancreatic cancer.^3-6 In certain B-cell malignancies, reverse paracrine Hedgehog signaling has been postulated.^7,8