[NPLOC4 promotes proliferation, invasion, and migration of hepatocellular carcinoma cells via enhancing Wnt/β-catenin-mediated mitophagy].

OBJECTIVES: Dysregulation of mitophagy contributes to the initiation and progression of hepatocellular carcinoma (HCC). Nuclear protein localization 4 homolog (NPLOC4) is an essential protein involved in various cellular processes and has been implicated in multiple cancers. Recent studies have suggested that NPLOC4 participates in the regulation of mitophagy; however, its role in HCC remains unclear. This study aims to investigate the role of NPLOC4 in mitophagy and its underlying regulatory mechanisms in HCC.

METHODS: RNA sequencing data from the GSE277232 and GSE251942 datasets obtained from the Gene Expression Omnibus (GEO) database were analyzed together with mitophagy-related genes collected from the GeneCards database to identify differentially expressed mitophagy-related genes in HCC. NPLOC4 expression was further analyzed and validated by Western blotting. Small interfering RNA (siRNA)-mediated knockdown of NPLOC4 was performed in HCC cells for functional loss-of-function assays. Mitophagy levels were evaluated by analyzing the expression of mitophagy-related proteins, transmission electron microscopy, and immunofluorescence staining.

RESULTS: Bioinformatics analysis identified NPLOC4 as a key differentially expressed mitophagy-related gene. NPLOC4 was significantly upregulated in HCC tissues and was associated with poor clinical prognosis (all P<0.05). Knockdown of NPLOC4 inhibited HCC cell proliferation, migration, and invasion, while promoting apoptosis (all P<0.05). In addition, NPLOC4 knockdown suppressed mitophagy and the Wnt/β-catenin signaling pathway in HCC cells (all P<0.05). Treatment with the Wnt agonist BML-284 abolished the inhibitory effect of NPLOC4 knockdown on mitophagy (P<0.05), indicating that NPLOC4 regulates mitophagy through activation of the Wnt/β-catenin pathway. Furthermore, treatment with the mitophagy inducer carbonyl cyanide m-chlorophenyl hydrazone (CCCP) reversed the inhibitory effects of NPLOC4 knockdown on HCC cell proliferation, migration, and invasion (all P<0.05), suggesting that NPLOC4 silencing suppresses HCC progression by regulating mitophagy.

CONCLUSIONS: NPLOC4 is highly expressed in HCC. Downregulation of NPLOC4 inhibits activation of the Wnt/β-catenin signaling pathway, thereby inhibiting mitophagy and ultimately inhibiting HCC cell proliferation, migration, and invasion. These findings suggest that NPLOC4 may serve as a potential biomarker and therapeutic target for HCC.