[Preliminary study on the biological role of suppressor of Zeste 12 in hepatocellular carcinoma].

Objective: To investigate the expression and function of Zeste 12 homolog (SUZ12) in hepatocellular carcinoma (HCC), and to preliminarily explore its biological role and underlying molecular mechanisms in HCC. Methods: This cell-based experimental study was conducted at the Basic Laboratory of the General Hospital of Southern Theater Command of the PLA from June 2024 to June 2025. The mRNA and protein expression levels of SUZ12 in HCC tissues and their correlations with clinicopathological features were analyzed using The Cancer Genome Atlas (TCGA). The prognostic impact of SUZ12 on HCC patients was evaluated using the K-M plotter database. SUZ12 overexpression and knockdown models were established in human hepatocellular carcinoma cells (HepG2). Transfection efficiency was verified by quantitative real-time polymerase chain reaction (qPCR) and Western blot. The effects of SUZ12 on HCC cell proliferation, invasion, and migration were assessed via Cell Counting Kit-8 assay (CCK-8), colony formation assay, and Transwell assay. The interaction between SUZ12 and enhancer of Zeste homolog 2 (EZH2) was validated by Co-Immunoprecipitation (Co-IP). Western blot was further used to preliminarily examine the effects of SUZ12 on the protein expression levels of H3K27me3 and CDKN1A. Statistical analyses were performed using two independent-sample t-tests. Results: In HCC tissues, SUZ12 mRNA levels were significantly higher than those in normal liver tissues (TPM=7.644 vs. 4.643, t=-6.648, P<0.001), and SUZ12 protein expression levels were also significantly elevated (Z-score=0.004 vs.-1.621, t=-9.815, P<0.001). The mRNA expression level of SUZ12 showed an increasing trend with higher clinical stage (normal: 4.643; stage Ⅰ: 7.071; stage Ⅱ: 7.085; stage Ⅲ: 8.677 TPM,H=36.700, P<0.001) and pathological grade (normal: 4.643; grade 1: 5.589; grade 2: 7.032; grade 3: 8.586 TPM, H=38.200, P<0.001). In the CCK-8 assay, the cell viability value in the SUZ12 overexpression group was higher than that in the control group; the relative absorbance at 450 nm on day 1(0.370±0.020 vs. 0.379±0.010, t=0.376, P=0.725), day 2 (0.477±0.016 vs. 0.370±0.069, t=-4.391, P=0.005), day 3 (0.900±0.022 vs. 0.816±0.024, t=-6.577, P=0.001), day 4 (1.601±0.017 vs. 1.390±0.026, t=-2.477, P=0.048). The cell viability value in the SUZ12 knockdown group was lower than that in the control group; the relative absorbance at 450 nm on day 1 (0.277±0.005 vs. 0.287±0.001, t=1.737, P=0.133), day 2 (0.344±0.002 vs. 0.377±0.006, t=4.677, P=0.010), day 3 (0.643±0.006 vs. 0.720±0.006, t=4.142, P=0.012), day 4 (1.065±0.015 vs. 1.210±0.031, t=8.941, P<0.001). In the colony formation assay, the number of colonies formed in the SUZ12 overexpression group was significantly higher than that in the control group [(775.000±51.884) colonies vs. (429.333±16.756 )colonies, t=-6.340, P=0.003]; the number of colonies decreased in the knockdown group [(150.666±4.055) colonies vs. (272.666±7.172) colonies, t=13.917, P<0.001]. In the Transwell assay, the invasion ability [(329.000±33.291) cells vs. (229.333±12.732) cells, t=-4.564, P=0.010] and migration ability [(325.333±7.310) cells vs. (217.333±1.732) cells, t=-14.120, P<0.001)] were significantly enhanced in the SUZ12 overexpression group compared to the control group; the invasion ability [(269.000±19.467) cells vs. (374.000±22.500) cells, t=3.529, P=0.024] and migration ability [(163.333±8.412) cells vs. (272.333±19.220) cells, t=6.194, P=0.020] were significantly weakened in the SUZ12 knockdown group compared to the control group. Western blot results suggested that high expression of SUZ12 downregulated the protein expression level of CDKN1A. Conclusion: SUZ12 high expression is associated with malignant biological behaviors of HCC cells. The SUZ12/EZH2/CDKN1A axis may represent a potential therapeutic target for patients with advanced HCC.