Oncogenic potential of IDH1R132C mutant in cholangiocarcinoma development in mice

AIM: To investigate whether IDH1R132 C mutant in combination with loss of p53 and activated Notch signaling promotes intrahepatic cholangiocarcinoma(ICC) development.METHODS: We applied hydrodynamic injection and sleeping beauty mediated somatic integration to induce loss of p53(via sh P53), activation of Notch [via intracellular domain of Notch1(NICD)] and/or overexpression of IDH1R132 C mutant together with the sleeping beauty transposase into the mouse liver. Specifically, we co-expressed sh P53 and NICD(sh P53/NICD, n = 4), sh P53 and IDH1R132C(sh P53/IDH1R132 C, n = 3), NICD and IDH1R132C(NICD/IDH1R132 C, n = 4), as well as NICD, sh P53 and IDH1R132C(NICD/sh P53/IDH1R132 C, n = 9) in mice. Mice were monitored for liver tumor development and euthanized at various time points. Liver histology was analyzed by hematoxylin and eosin staining. Molecular features of NICD/sh P53/IDH1R132 C ICC tumor cells were characterized by Myc tag, Flag tag, Ki-67, p-Erk and p-AKT immunohistochemical staining. Desmoplastic reaction in tumor tissues was studied by Picro-Sirius red staining.RESULTS: We found that co-expression of sh P53/NICD, sh P53/IDH1R132 C or NICD/IDH1R132 C did not lead to liver tumor formation. In striking contrast, coexpression of NICD/sh P53/IDH1R132 C resulted in ICC development in mice(P 0.01). The tumors could be identified as early as 12 wk post hydrodynamic injection. Tumors rapidly progressed, and by 18 wk post hydrodynamic injection, multiple cystic lesions could be identified on the liver surface. NICD/sh P53/IDH1R132 C liver tumors shared multiple histological features of human ICCs, including hyperplasia of irregular glands. Importantly, all tumor cells were positive for the biliary epithelial cell marker cytokeratin 19. Extensive collagen fibers could be visualized in tumor tissues using Sirus red staining, duplicating the desmoplastic reaction observed in human ICC. Tumors were highly proliferative and expressed ectopically injected genes. Together these studies supported that NICD/sh P53/IDH1R132 C liver tumors were indeed ICCs. Finally, no p-AKT or p-ERK positive staining was observed, suggesting that NICD/sh P53/IDH1R132 C driven ICC development was independent of AKT/m TOR and Ras/MAPK signaling cascades. CONCLUSION: We have generated a simple, nongermline murine ICC model with activated Notch, loss of p53 and IDH1R132 C mutant. The study supported the oncogenic potential of IDH1R132 C.