Abstract 2802: High fat diet increases development of hepatocellular carcinoma in glycine N-methyltransferase deficient mice

Abstract

Abstract Introduction: Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. HCC typically arises in patients with chronic liver disease or cirrhosis, yet it is increasingly associated with non-alcoholic fatty liver disease (NAFLD), specifically nonalcoholic steatohepatitis (NASH) in the absence of cirrhosis. NAFLD is associated with obesity, metabolic syndrome, and/or patients with type II diabetes. Our previous studies have shown that high fat diet induced hepatic steatosis increases proliferation of hepatocytes and the growth of malignant tumors in a murine model. Glycine N-MethylTransferase (GNMT) expression is lost in over 95% of HCC, and mice deficient in GNMT develop spontaneous HCC by 6 months of age. We hypothesized that GNMT deficient mice would have an increased susceptibility for the development and growth of HCC when a fed high fat diet. Methods: Wildtype and GNMT deficient mice were placed on lean diet (LD, 13% calories from fat) or high fat diet (HFD, 42% calories from fat) at eight weeks of age. An initial cohort of mice were sacrificed after 3 months on diet (6 months of age) to assess for early tumor burden. A second cohort of mice was analyzed by magnetic resonance imaging (MRI) after 6 months on diet (9 months of age) and then sacrificed to assess for late stage disease. All mice were assessed for body weight, liver weight, pancreatic weight, and proliferative index (Ki67). Results: GNMT deficient mice failed to gain weight when placed on HFD, which remained at levels equivalent to wildtype LD mice. At three months of age, wildtype mice on HFD had significantly enlarged livers due to hepatic steatosis. HFD fed GNMT deficient mouse livers were nearly 50% the size of wildtype livers and contained only minimal fatty deposits. Further, livers from HFD and LD fed GNMT mice were equivalent after 3 months, yet they were larger than wildtype mice fed LD. After six months on diet, MRI analysis showed significantly larger livers in HFD fed GNMT mice compared to LD fed GNMT mice due to extensive tumor burden. All wildtype mice lacked any tumors after six months regardless of diet. Histological analysis revealed a heightened cellular proliferation via Ki67 staining in GNMT deficient livers compared to wildtype livers. In comparison, GNMT silencing also occurs in pancreatic cancer, yet none of the GNMT deficient mice developed pancreatic tumors. However, small focal areas of pancreatitis were detected regardless of diet. Additionally, pancreatic weight was significantly decreased in HFD fed GNMT deficient mice compared the LD GNMT deficient mice. Conclusions: While high fat diet did not induce obesity in GNMT deficient mice, it significantly increased cellular proliferation and primary tumor growth in the liver. Understanding dietary factors that impact the microenvironment of the liver and contribute to HCC development and progression is vital to finding new therapeutics for this malignancy. Citation Format: Michael N. VanSaun, Alisha Mendonsa, Fanuel Messaggio, Nagaraj Nagathihalli, Lee Gorden. High fat diet increases development of hepatocellular carcinoma in glycine N-methyltransferase deficient mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2802. doi:10.1158/1538-7445.AM2017-2802