Abstract
Hepatocellular carcinoma (HCC) presents significant clinical challenges, necessitating a deeper understanding of its molecular drivers for improved therapeutic strategies. Our study focused on nucleolar protein 9 (NOL9), a 5’-polynucleotide kinase, elucidating its role in HCC pathogenesis and therapeutic response. We found NOL9 to be significantly upregulated in HCC tissues compared to normal counterparts, correlating with larger tumor diameters, advanced pathological grades, and poor patient survival. Furthermore, NOL9 exhibited diagnostic potential, effectively distinguishing HCC samples from normal tissues. High NOL9 expression correlated with poorer prognosis, both in a TCGA-LIHC cohort and our HCC cohort, as well as in patients with poor sorafenib efficacy. Functional assays revealed that NOL9 modulates HCC cell proliferation and apoptosis. Knockdown of NOL9 inhibited cellular proliferation and clonogenic survival while promoting apoptosis, whereas NOL9 overexpression had the opposite effect. In vivo and in vivo studies corroborated these findings, with NOL9 depletion leading to reduced tumor growth. Additionally, NOL9 influenced the HCC cell cycle dynamics, facilitating the G1/S transition and promoting cell proliferation. Mechanistically, NOL9 expression was regulated by DNA methylation and ZNF384. ZNF384 was identified as a key transcriptional regulator of NOL9, enhancing its expression and activating its promoter. DNA methylation analysis revealed an inverse correlation between NOL9 expression and methylation at specific CpG sites, with DNMT1 playing a role in epigenetic regulation. Furthermore, NOL9-mediated cell proliferation was found to be beta-catenin-dependent, with NOL9 activating the wnt/beta-catenin pathway at the transcriptional level, thus promoting HCC cell proliferation. In summary, our study unveils the multifaceted role of NOL9 in HCC pathogenesis, emphasizing its potential as a diagnostic biomarker and therapeutic target. Understanding the intricate molecular mechanisms underlying NOL9 regulation provides insights into HCC biology and opens avenues for the development of targeted therapies to improve patient outcomes.