Exploring the Role of ENO1 in Regulating Cell Proliferation and Cell Cycle in Hepatocellular Carcinoma: Insights from Proteomic Analysis

Abstract Background and Aims: Hepatocellular carcinoma (HCC), a prevalent solid organ malignancy, is intricately linked to the glycolytic enzyme Alpha-enolase (ENO1). ENO1's overexpression is associated with malignant tumor progression and poor clinical outcomes, yet its role in HCC cell proliferation and differentiation warrants further investigation. This study focuses on identifying ENO1-interacting proteins in HCC, exploring their involvement in cell proliferation and the cell cycle. Materials and Methods: We employed RNA interference to downregulate ENO1 in HepG2 cells, evaluating effects on cell proliferation, cycle progression, and key signaling pathways using MTT assays, flow cytometry, and Western blotting. Identifying ENO1-interacting proteins involved combining RNAi and co-immunoprecipitation with isobaric tags (iTRAQ). We confirmed five proteins central to proliferation and cell cycle regulation through immunofluorescence microscopy and additional co-immunoprecipitation. Pathway analysis and follow-up experiments were conducted for further elucidation. Results: ENO1 silencing significantly inhibited HepG2 cell proliferation and extended G2/M and S phases. We identified 40 ENO1-interacting proteins with notable expression changes, including PCNA, HSP90, PCBP1, PSME1, and PEBP1. Significant downregulation was observed in PCNA, various cyclins, and phosphorylated ERK1/2, MAPK, and AKT, alongside an upregulation of P21. However, levels of CDK1, CDK2, ERK1/2, MAPK, and AKT remained unchanged. Conclusions: This study highlights the glycolytic pathway's crucial role in HCC development. The identified ENO1-interacting proteins like PCNA, HSP90, PCBP1, PSME1, and PEBP1 are key in tumor development, differentiation, invasion, and metastasis. The interaction between ENO1 and PCNA, influencing cell cycle regulators and phosphorylation processes, offers new insights into HCC molecular dynamics and potential therapeutic avenues.