If stromal cells respond distinctly to SHH and IHH ligands, then IHH may play a more prominent role in angiogenesis in LAD than SHH due to the lower potency of IHH (Fig. 4a) analogous to the diminished pathway response of Gas1−/−;Boc−/− fibroblasts in pancreatic cancer [70]. This evidence concerns the gene BOC and familial pancreatic carcinoma.