MAMMALIAN TARGET OF RAPAMYCIN REGULATES VASCULAR ENDOTHELIAL GROWTH FACTOR-DEPENDENT LIVER CYSTS GROWTH IN POLYCYSTIN-2 DEFECTIVE MICE

摘要

Polycystic Liver Disease may complicate ADPKD, a disease caused by mutations in polycystins, proteins that regulate signaling, morphogenesis and differentiation in epithelial cells. The cystic biliary epithelium (LCE) secretes VEGF, which promotes liver cyst growth via autocrine and paracrine mechanisms. Expression of IGF-1, IGF1-R, phospho-mTOR and the PKA-dependent phosphorylation of ERK1/2 are also upregulated in LCE. We have hypothesized that mTOR represents a common pathway for the regulation of HIF1α-dependent VEGF secretion by IGF-1 and ERK1/2.MethodsConditional polycystin-2-defective (Pkd2KO) mice were used for in vivo studies and to isolate cystic cholangiocytes (LCEC). Expression of phospho-mTOR, VEGF, cleaved-caspase-3 (CC3), PCNA, IGF-1, IGF-1R, pERK, p-P70S6K, HIF1α and VEGF in LCE, LCEC and WT-cholangiocytes was studied by immunohistochemistry, Western blot, or ELISA. Cystic area was measured by computer-assisted morphometry of panCK-stained sections. Cell proliferation in vitro was studied by MTS and BrdU assays.