EZH2 promotes hepatocellular carcinoma progression through modulating miR-22/galectin-9 axis

Area of Science:

• Hepatocellular Carcinoma (HCC) Research
• Epigenetics and Gene Regulation
• Immunology and Cancer Microenvironment

Background:

• Interferon-γ (IFN-γ) influences the tumor microenvironment in hepatocellular carcinoma (HCC) via Kupffer cell galectin-9.
• The role and regulation of IFN-γ-induced galectin-9 in HCC cells remain unclear.

Purpose of the Study:

• To investigate IFN-γ's effect on galectin-9 expression in HCC cells.
• To elucidate the regulatory mechanisms of galectin-9 in HCC development.
• To determine the biological role of galectin-9 and miR-22 in HCC progression.

Main Methods:

• Quantitative PCR and Western blotting to assess galectin-9 and EZH2 levels.
• Bioinformatics and luciferase assays to confirm miR-22 binding to galectin-9.
• Methylation-specific PCR, bisulfite sequencing PCR, and ChIP assays to analyze miR-22 promoter methylation and EZH2 occupancy.
• Cell proliferation, migration, invasion, and apoptosis assays to evaluate the functional effects of galectin-9 and miR-22.

Main Results:

• IFN-γ upregulates galectin-9 and EZH2 in HCC cell lines.
• Galectin-9 is a target of miR-22, and EZH2 epigenetically represses miR-22 expression via H3K27 trimethylation at its promoter.
• Overexpression of miR-22 suppressed HCC cell growth, invasion, and metastasis; galectin-9 also demonstrated antitumor effects, enhancing miR-22's activity.

Conclusions:

• EZH2 promotes galectin-9 expression by epigenetically silencing miR-22.
• Galectin-9 functions as a tumor suppressor in HCC, contrary to its known immunosuppressive role.
• This study reveals a novel epigenetic regulatory pathway involving EZH2, miR-22, and galectin-9 in HCC progression.