TGFB1 and pancreatic insulinoma: We elected to explore TGFβ superfamily inhibitors because several other labs had found that TGFβ inhibition activates rodent beta cell proliferation (45, 58, 59), and because we observed abnormalities in DYRK1A gene expression as well as abundant mutations in SMAD pathway genes in the proliferating beta cells of insulinomas (60).