Abstract 4566: Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions

Hepatocellular carcinoma (HCC) is usually associated with chronic liver injury, typically cirrhosis, although it could be developed in apparenty intact livers. To explore the tumorigenetic mechanisms underlying these different conditions, we compared mRNA expression profiles in mouse liver tumors induced by repeated injections of CCl4 (cirrhotic protocol) and a single diethylnitrosamine (DEN) injection at 2-week-old (non-cirrhotic protocol) using a cDNA microarray. In the CCl4 model, numerous small tumors appeared in cirrhotic liver parenchyma, while in the DEN model, multiple large tumors developed in a non-cirrhotic background. We identified tumor-specific genes that were differentially expressed in either CCl4 or DEN model, as well as expressed in both models. The levels and patterns of mRNA expression of these genes were verified by RT-qPCR analyses. The mRNA expression of Igf2, H19, Krt20, and Cbr3 were predominantly increased in CCl4 tumors; that of Gpc3, Tff3, Akr1c18, Afp, and Abcd2 were predominantly increased in DEN tumors; that of Ly6d, Cpe, Slpi, and Scd2 was increased at similar levels in CCl4 and DEN tumors. The mRNA expresion of Igf2bp3, which is known to be functionally correlated with Igf2, was also increased only in CCl4 tumors. A positive correlation was found between the expression of Igf2 mRNA and H19 mRNA. The mRNA expresion of these liver tumor-specific genes was not significantly correlated with the proliferative activity of tumor cells, as estimated by Ki-67 immunohistochemistry, either in CCl4 or DEN tumors. Interestingly, all of these genes, with only exception being Cbr3, were highly expressed in the mouse livers during the fetal/neonatal periods. We also examined mRNA expression of these genes in liver tumors induced by chronic thioacetamide (TAA) treatment, another cirrhotic liver tumor protocol, and found that TAA-induced tumors shared a similar pattern of expression profile as that of CCl4 tumors. We further investigated mRNA expression of the genes in mouse liver tumors induced by the Sleeping Beauty transposon-mediated somatic integration of active Akt (myrAkt) and mutant Hras (HrasV12) genes. Hydrodynamic tail vein injection of the oncogenes rapidly induced multiple liver tumors within 2 months without developing chronic liver injury or cirrhosis. These tumors overexpressed most of the above genes, except for Igf2, Igfbp3, H19, and Tff3. Our results show that mouse liver tumors reactivate numerous fetal/neonatal genes, some of which are specific to the cirrhotic (e.g., Igf2) and non-cirrhotic (e.g., Gpc3, Tff3, Akr1c18) modes of pathogenesis. Furthermore, the IGF2 axis, H19, and Tff3 might be specifically involved in the processes during the development of liver tumors, not simply reflecting neoplastic transformation of hepatocytes. Citation Format: Xi Chen, Masahiro Yamamoto, Kiyonaga Fujii, Yasuharu Nagahama, Bing Xin, Takako Ooshio, Yoko Okada, Yuji Nishikawa. Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4566. doi:10.1158/1538-7445.AM2015-4566