Hepatocellular carcinoma (HCC) ranks worldwide as one of the most lethal cancers. In spite of the vast existing knowledge about HCC, the pathogenesis of HCC is not completely understood. Discovery of novel genes that contribute to HCC pathogenesis will provide new insights for better understanding and treating HCC. The relatively obscure gene midnolin has been studied for over two decades; however, its biological roles are largely unknown. Our study is the first to demonstrate the functional significance of midnolin in HCC/cancer: Midnolin expression correlates with poor prognosis in HCC patients, and suppression of midnolin severely inhibits tumorigenicity of HCC cells in vitro and in mice and disrupts retinoic acid/lipid metabolism in these cells.

Background & Aims: High metabolic activity is a hallmark of cancers including hepatocellular carcinoma (HCC), a major form of liver cancer. However, the molecular features of HCC with high metabolic activity contributing to the clinical outcomes and their therapeutic implications are poorly understood. We aimed to uncover the metabolic characteristics of HCC that are associated with clinical relevance such as overall survival and response to immunotherapy. Methods: By applying cross-species comparison of genomic data, we integrated gene expression profile data from well-defined mouse models and human HCC tumor tissues to stratify HCC tumors according to their intrinsic metabolic activity. For stratification of HCC tumors, we developed a robust genomic predictor and validated it in 5 HCC cohorts (n=1038). Statistics and informatics approaches were performed to assess clinical significance such as overall survival and response to immunotherapy in metabolic subtypes. Genomic data from patient derived xenograft (PDX) models were integrated to the analysis. Results: Analysis of systematically integrated genomic data revealed three distinct metabolic subtypes of HCC (high, moderate and low metabolic subtypes). The high metabolic subtype is characterized by poor survival, the strongest stem cell features, high genomic instability, high expression of alpha-fetoprotein and KRT19, and activation of EPCAM and SALL4, and poor response to immunotherapy. Importantly, analysis of immune cell population in HCC tumors showed that immune-suppressive regulatory T-cells (Treg) are highly enriched in high metabolic HCC tumors, suggesting that high metabolic activity of HCC cells may trigger activation or infiltration of Treg cells, leading to evasion of HCC cells from anti-cancer immune cells. Interestingly, recent study showed that Treg cells can effectively utilize lactic acid as metabolic fuel for its proliferation. Because high metabolic activity of HCC tumors eventually leads to accumulation of glycolysis by-product lactic acid in tumor microenvironment, we postulate that accumulated lactic acid in tumor microenvironment might account for aggregation of Treg cells in high metabolic HCC tumors, leading to resistance to immunotherapy. In agreement with this, 18F-FDG PET/CT imaging data showed that high metabolic activity of tumors reflected in SUVmax is significantly associated with poorer survival of cancer patients after immunotherapy. Conclusions: We identified clinically and metabolically distinct subtypes of HCC tumors, potential biomarkers associated with these subtypes, and potential mechanism of metabolism-mediated evasion of HCC cells to anti-cancer immunotherapy. Moreover, the metabolic subtypes are well conserved in PDX models, offering a tool for selecting the best preclinical models for future study. Citation Format: Sowon Grace Park, Joann Jung, Yeonwoo Grace Jang, Sung Hwan Lee, Yun-Seong Jeong, Sun Young Yim, Ju-Seog Lee. Clinical significance of glycolytic metabolic activity in liver cancer and its implication to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 296.

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