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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
LKB1 dictates sensitivity to immunotherapy through Skp2-mediated ubiquitination of immune checkpoint proteins in HCC
Masoud Khodarahmi1, Danial Amiri Manjili1, Foroozan Yarahmadi1
1School of Medicine,Tehran University of Medical Sciences,Tehran, Iran.
Objectives:
Hepatocellular carcinoma (HCC) is a highly aggressive malignancy with limited treatment options, particularly in advanced stages. Immune checkpoint inhibitors (ICIs) targeting PD-1, PD-L1, and CTLA-4 have shown promise in cancer immunotherapy, but response rates in HCC remain variable.
Materials And Methods:
Hep3B and HepG2 HCC cells were cultured and genetically manipulated to overexpress or deplete LKB1. Western blotting, real-time PCR, and immunofluorescence were used to assess PD-L1 expression at the protein and mRNA levels. The role of Skp2 in PD-L1 regulation was evaluated through shRNA-mediated knockdown and overexpression. Additionally, kinase-dead LKB1 mutants were expressed to determine the importance of LKB1 kinase activity in PD-L1 stability. ImageJ software and Python-based computational tools were employed for quantitative analysis of immunofluorescence and Western blot data.
Results:
LKB1 overexpression up-regulated PD-L1 protein levels in HCC cells, while its depletion reduced PD-L1 expression, indicating a post-translational regulatory mechanism. Although Skp2 expression remained unchanged upon LKB1 modulation, Skp2 overexpression in LKB1-deficient cells increased PD-L1 levels, suggesting a context-dependent role for Skp2 in PD-L1 stability. Furthermore, wild-type LKB1, but not the kinase-dead mutant, restored PD-L1 expression, highlighting the essential role of LKB1 kinase activity in PD-L1 regulation.
Conclusion:
This study identifies LKB1 as a critical regulator of PD-L1 stability in HCC, with implications for tumor immune evasion and immunotherapy response. While Skp2 appears to influence PD-L1 stability in specific contexts, LKB1's kinase activity is essential for PD-L1 regulation.
Insights
Liver kinase B1 (LKB1) regulates programmed death-ligand 1 (PD-L1) stability in hepatocellular carcinoma (HCC). LKB1 kinase activity is crucial for PD-L1 regulation, impacting tumor immune evasion and immunotherapy response.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Hepatocellular carcinoma (HCC) is an aggressive cancer with limited treatment options.
- Immune checkpoint inhibitors (ICIs) show promise but have variable response rates in HCC.
Purpose of the Study:
- To investigate the role of Liver kinase B1 (LKB1) in regulating programmed death-ligand 1 (PD-L1) expression in HCC.
- To determine the mechanism by which LKB1 influences PD-L1 stability and its implications for immunotherapy.
Main Methods:
- Genetic manipulation of LKB1 and Skp2 in Hep3B and HepG2 HCC cells.
- Western blotting, real-time PCR, and immunofluorescence to assess PD-L1 expression.
- Analysis of LKB1 kinase activity using kinase-dead mutants and computational tools.
Main Results:
- LKB1 overexpression increased PD-L1 protein levels, while depletion reduced them, indicating post-translational regulation.
- Skp2 showed a context-dependent role in PD-L1 stability.
- LKB1's kinase activity, not just its presence, was essential for PD-L1 regulation.
Conclusions:
- LKB1 is a critical regulator of PD-L1 stability in HCC.
- LKB1 kinase activity is essential for PD-L1 regulation, influencing tumor immune evasion.
- Findings have implications for improving HCC immunotherapy response.
