Abstract 3166: The role of CD4 T cells in murine model of NASH-promoted HCC

Abstract

Abstract Aim: Non-alcoholic steatohepatitis (NASH), a common condition in obese patients, is an important risk factor for hepatocellular carcinoma (HCC). However, only little information exists about the immunological mechanisms of how NASH promotes HCC. This study was designed to better understand the role of adaptive immunity during the process of NASH-promoted hepatocarcinogenesis. Experimental procedure: Methionine choline deficient (MCD) diet is widely used to induce NASH. In this study we fed Lap-tTA-myc mice, which develop HCC, with MCD diet. Choline-deficient and amino acid-defined (CDAA) diet and high fat (HF) diet was also used to induce NASH in B6 mice. GK1.5 antibody was used to deplete CD4 T cells. Gas chromatography-mass spectrometry was performed to identify free fatty acids. Difference immune cell subsets were identified by flow cytometry. Cell death was measured by 7AAD/Annexin V staining. Results: MCD diet accelerated tumor development in MYC-on mice. A robust selective decrease of hepatic CD4 but not CD8 T cells was observed in NASH mice, which was exacerbated by MYC transgene expression. The selective decrease of hepatic CD4 T cells was also observed in B6 mice treated with CDAA or HF diet suggesting it's a general phenomena in NASH. As expected higher level of cell death was detected in hepatic CD4 T cells after NASH. Phenotypic analysis demonstrated that these CD4 T cells had a CD44highCD62Llow effector memory phenotype and produced more IFNγ. Selective CD4 T cell depletion further accelerated HCC development suggesting an important role of these cells for tumor development. Next, we studied the cause of CD4 T cell death. In co-culture experiments we demonstrated that lipid-laden hepatocytes from mice on MCD diet induced selective CD4 but not CD8 T cells death through a contact-independent mechanism. FFAs were found from hepatocyte culture medium to be responsible for T cell cytotoxicity, and linoleic acid recapitulates the selective toxicity to CD4 T cells. Blocking ROS abolished linoleic acid-induced CD4 T cell death. In vivo study showed that N-acetyl cysteine reversed the NASH-induced hepatic CD4 T cell decrease and delayed NASH-promoted tumor development. Conclusion: Our results suggest the critical role of CD4 T cells in the disease progression of NASH to HCC, and provide a new link between lipid metabolism dysfunction with impaired anti-tumor surveillance. Citation Format: Chi Ma, Dean Felsher, Tim Greten. The role of CD4 T cells in murine model of NASH-promoted HCC. [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 3166. doi:10.1158/1538-7445.AM2015-3166