RESUMEN
Constitutive Hedgehog (Hh) signaling underlies several human tumors, including basal cell carcinoma (BCC) and basaloid follicular hamartoma in skin. Intriguingly, superficial BCCs arise as de novo epithelial buds resembling embryonic hair germs, collections of epidermal cells whose development is regulated by canonical Wnt/beta-catenin signaling. Similar to embryonic hair germs, human BCC buds showed increased levels of cytoplasmic and nuclear beta-catenin and expressed early hair follicle lineage markers. We also detected canonical Wnt/ beta-catenin signaling in epithelial buds and hamartomas from mice expressing an oncogene, M2SMO, leading to constitutive Hh signaling in skin. Conditional overexpression of the Wnt pathway antagonist Dkk1 in M2SMO-expressing mice potently inhibited epithelial bud and hamartoma development without affecting Hh signaling. Our findings uncover a hitherto unknown requirement for ligand-driven, canonical Wnt/ beta-catenin signaling for Hh pathway-driven tumorigenesis, identify a new pharmacological target for these neoplasms and establish the molecular basis for the well-known similarity between early superficial BCCs and embryonic hair germs.
Asunto(s)
Carcinoma Basocelular/genética , Proteínas Hedgehog/genética , Neoplasias Cutáneas/genética , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Animales , Linaje de la Célula , Células Epiteliales/metabolismo , Folículo Piloso/embriología , Hamartoma/genética , Humanos , Ratones , Proteínas Oncogénicas/genética , Transducción de SeñalRESUMEN
Pancreatic ductal adenocarcinoma (PDA) constitutes a lethal disease that affects >30,000 people annually in the United States. Deregulation of Hedgehog signaling has been implicated in the pathogenesis of PDA. To gain insights into the role of the pathway during the distinct stages of pancreatic carcinogenesis, we established a mouse model in which Hedgehog signaling is activated specifically in the pancreatic epithelium. Transgenic mice survived to adulthood and developed undifferentiated carcinoma, indicating that epithelium-specific Hedgehog signaling is sufficient to drive pancreatic neoplasia but does not recapitulate human pancreatic carcinogenesis. In contrast, simultaneous activation of Ras and Hedgehog signaling caused extensive formation of pancreatic intraepithelial neoplasias, the earliest stages of human PDA tumorigenesis, and accelerated lethality. These results indicate the cooperation of Hedgehog and Ras signaling during the earliest stages of PDA formation. They also mark Hedgehog pathway components as relevant therapeutic targets for both early and advanced stages of pancreatic ductal neoplasia.