Effect of Polycomb Repressive Complex 2 on the Proliferation, Migration, Invasion, and Apoptosis of Gastric Cancer Cells by Targeting H3K27 Activation

Background: Gastric cancer is a globally prevalent malignancy characterized by dysregulated cellular processes including epigenetic modifications. However, the Polycomb Repressive Complex 2 (PRC2), a pivotal epigenetic regulator, modulates gene expression through trimethylation of histone H3 at lysine 27 (H3K27me3), thereby orchestrating cellular identity and function. Therefore, this study aimed to elucidate the impact of PRC2 and H3K27me3 on critical cellular behaviors, such as proliferation, migration, invasion, and apoptosis, which holds the potential to unveil novel insights into gastric cancer progression. Methods: Human gastric cancer cells NCI-N87 were seeded in a 6-well plate and were divided into the normal, siRNA-negative control (siRNA-NC), siRNA-Enhancer of zeste homolog 2 (siRNA-EZH2), and siRNA-SUZ12 polycomb repressive complex 2 subunit (siRNA-SUZ12) groups. The cells were transfected to knock down the expression of PRC2 core subunits, siRNA-Enhancer of zeste homolog 2 (EZH2) and SUZ12 polycomb repressive complex 2 subunit (SUZ12). Moreover, Western Blot analysis and Quantitative real-time reverse-transcription PCR (qRT-PCR) were carried out to determine the expression levels of the EZH2 and SUZ12 in gastric cancer cells. Furthermore, the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was employed to examine cell proliferation, the Transwell assay was employed to determine cell migration and invasion, and flow cytometry was used to evaluate cell apoptosis rate. Additionally, the confocal laser scanning technique was utilized to assess H3K27 methylation in gastric cancer cells. Finally, the interaction between PRC2 and H3K27 was evaluated using co-immunoprecipitation (Co-IP). Results: Compared to the siRNA-NC group, there was a significant decrease in the levels of EZH2 protein and mRNA in the cells of the siRNA-EZH2 group and SUZ12 protein and mRNA in the siRNA-SUZ12 group ( p < 0.05). Furthermore, both the siRNA-EZH2 and siRNA-SUZ12 groups showed significantly reduced cell survival rates, and decreased count of migrating and invading cells, while exhibited significantly increased apoptosis rate compared to the siRNA-NC group. Moreover, the expression level of H3K27me3 significantly elevated in these cells ( p < 0.05). Additionally, Co-IP results revealed a significant interaction of EZH2 and SUZ12 with H3K27me3. Conclusion: This study delved into the impact of the PRC2 on gastric cancer cell behavior, focusing on the targeted regulation of histone H3K27me3. The findings suggest that PRC2 might modulate cellular proliferation, migration, invasion, and apoptosis within gastric cancer cells. Nevertheless, rigorous experimental validation is essential to establish causal relationship and gain deeper mechanistic insights into PRC2s role in gastric cancer.