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An Oncogenic Hepatocyte-Induced Orthotopic Mouse Model of Hepatocellular Cancer Arising in the Setting of Hepatic Inflammation and Fibrosis
Published on: September 12, 2019
SMG1 in hepatocellular carcinoma: A context-dependent tumor suppressor and a targetable node for NMD-directed
1Hepatobiliary Unit, Division of Gastroenterology, Department of Internal Medicine, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
Abstract:
Hepatocellular carcinoma (HCC) is a leading cause of cancer death, yet immune checkpoint inhibitors (ICIs) benefit only a minority of patients-a limitation attributed to low tumor mutational burden (TMB) and an immunologically cold microenvironment. SMG1, a serine/threonine kinase of the phosphatidylinositol 3-kinase-related kinase (PIKK) superfamily, sits at the intersection of RNA surveillance, the DNA damage response, and oncogenic signaling. As the master kinase of nonsense-mediated mRNA decay (NMD), SMG1 phosphorylates UPF1 to degrade transcripts bearing premature termination codons; independently, it restrains tumor growth by phosphorylating p53 (Ser15) and promoting Cdc25A turnover. SMG1 was originally identified as a tumor-suppressive modulator of sorafenib resistance in HCC (Nam, S.W. et al., 2014), and subsequent work shows SMG1 is reduced in HCC, predicts adverse outcome, and is recurrently silenced by reversible promoter hypermethylation. Paradoxically, the same kinase conceals mutation-derived neoantigens, and its selective inhibition (e.g., KVS0001) raises HLA class I neoantigen presentation toward high-TMB levels and improves checkpoint-inhibitor efficacy in preclinical and liver-specific models. This critical review integrates SMG1 structural biology, clinicopathology, signaling, sorafenib resistance, and NMD-directed immunotherapy, grading established versus inferential mechanisms, and nominates SMG1 and NMD as dual, context-dependent targets for HCC precision oncology.
Insights
SMG1 kinase, crucial in cancer, can be targeted to improve immunotherapy for hepatocellular carcinoma (HCC). Inhibiting SMG1 may enhance immune response and treatment efficacy in HCC patients.
Area of Science:
- Oncology
- Molecular Biology
- Immunology
Background:
- Hepatocellular carcinoma (HCC) is a major cause of cancer mortality.
- Immune checkpoint inhibitors (ICIs) show limited efficacy in HCC due to low tumor mutational burden and an immunosuppressive tumor microenvironment.
- SMG1, a kinase involved in RNA surveillance and DNA damage response, plays a dual role in HCC.
Purpose of the Study:
- To review the multifaceted roles of SMG1 in hepatocellular carcinoma.
- To explore SMG1's involvement in sorafenib resistance and its impact on the tumor microenvironment.
- To evaluate SMG1 and nonsense-mediated mRNA decay (NMD) as potential therapeutic targets for HCC immunotherapy.
Main Methods:
- Integration of structural biology, clinicopathology, signaling pathways, and NMD-directed immunotherapy data.
- Analysis of SMG1's role in regulating tumor growth, DNA damage response, and RNA surveillance.
- Review of preclinical and liver-specific models investigating SMG1 inhibition.
Main Results:
- SMG1 restrains tumor growth but paradoxically conceals neoantigens in HCC.
- SMG1 is reduced in HCC, predicting poor outcomes and is silenced by promoter hypermethylation.
- Selective SMG1 inhibition enhances HLA class I neoantigen presentation and improves ICI efficacy in preclinical models.
Conclusions:
- SMG1 and NMD are context-dependent targets for precision oncology in HCC.
- Targeting SMG1 offers a novel strategy to overcome resistance to ICIs in hepatocellular carcinoma.
- Further research into SMG1-directed immunotherapy could improve HCC treatment outcomes.
