MALAT1 promotes malignancy of HBV-related hepatocellular carcinoma by regulating IGF2BP3-mediated nuclear-cytoplasmic shuttling

Hepatitis B virus (HBV) X protein (HBx) plays a critical role in the progression of HBV-related hepatocellular carcinoma (HCC). Long non-coding RNAs (lncRNAs) regulate various biological processes and contribute to HCC development, with their therapeutic potential in disease progression recently gaining significant attention. However, the involvement of lncRNAs in HBx-related hepatocarcinogenesis and the underlying regulatory mechanisms remain unclear. In this study, we conducted a comprehensive analysis of multi-database sequencing data to identify metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) as an HBx-associated lncRNA and observed its upregulation in HBV-related HCC tissues and cells upon HBx expression. Additionally, high MALAT1 expression was correlated with poor prognosis and advanced HCC progression. MALAT1 overexpression significantly promoted the proliferation, migration, and invasion of HCC cells. Mechanistic investigations revealed that MALAT1 was transported to the cytoplasm and enhanced RNA stability in a N6-methyladenosine (m6A)-dependent manner through direct interaction with and recruitment of insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3). Targeting MALAT1 in vivo with antisense oligonucleotides (ASO)-MALAT1 treatment effectively suppressed the progression of xenograft tumors and orthotopic liver tumors in HBx-related HCC. Moreover, hydrodynamic-based gene delivery (HGD) was utilized to introduce anti-HBx transposon plasmids into murine hepatocytes, thereby suppressing MALAT1-m6A-mediated HBV-related hepatocarcinogenesis in HBx transgenic (HBx-Tg) mice. Overall, our findings shed novel light on the regulatory role of IGF2BP3-mediated MALAT1 nuclear-cytoplasmic shuttling and RNA stabilization via m6A modification during HCC progression. These results suggest that m6A-based MALAT1 expression serves as a novel diagnostic and prognostic biomarker for targeted epigenetic intervention in HBV-related HCC.