Description
Canonical Hedgehog (Hh) signaling regulates the expression of genes that are critical to the patterning and development of a variety of organ systems. In adult, both ligand-dependent and ligand-independent Hh pathway activation are known to promote tumorigenesis. Recent studies have shown that in tumors promoted by Hh ligand, activation occurs within the stromal microenvironment (Yauch et al., 2009). In situ hybridization of the pathway target gene, Ptch1, shows that signaling is located at stromal perivascular fibroblast-like cells in xenograft tumor sections derived from Hh-expressing colorectal cancer cell lines.