LncRNA HOTAIR play important roles in the epigenetic regulation of carcinogenesis and progression in liver cancer. Previous studies suggest that the overexpression of HOTAIR predicts poor prognosis. In this study, through transcriptome sequencing data and in vitro experiments, we found that HOTAIR were more highly expressed and there is significantly positive relationship between HOTAIR and NUAK1 in liver cancer tissues and cell lines. miR-145-5p was downregulated and showed negative correlation with HOTAIR and NUAK1. Transfect Sh-HOTAIR, LZRS-HOTAIR, miR-145 mimic, miR-145 inhibitor to change the expression of HOTAIR and miR-145-5p. The addition of HTH-01-015 inhibits the expression of NUAK1. HOTAIR knockdown, miR-145-5p upregulation and NUAK1 inhibition all repressed migration, invasion and metastasis and reversed the epithelial-to-mesenchymal transition in SNU-387 and HepG2 cells. We also showed that HOTAIR recruiting and binding PRC2 (EZH2) epigenetically represses miR-145-5p, which controls the target NUAK1, thus contributing to liver cancer cell-EMT process and accelerating tumor metastasis. Moreover, it is demonstrated that HOTAIR crosstalk with miR-145-5p/NUAK1 during epigenetic regulation. Our findings indicate that HOTAIR/miR-145-5p/NUAK1 axis acts as an EMT regulator and may be candidate prognostic biomarker and targets for new therapies in liver cancer.

The Hox transcript antisense intergenic RNA (HOTAIR) has been identified as a tumor gene, and its expression in HCC is significantly increased. HOTAIR is associated with the proliferation, invasion, metastasis and poor prognosis of HCC. In addition, HOTAIR can also regulate the expression and function of microRNA by recruiting the polycomb repressive complex 2 (PRC2) and competitive adsorption, thus promoting the occurrence and development of HCC. In this review, we discussed the two mechanisms of HOTAIR regulating miRNA through direct binding miRNA and indirect regulation, and emphasized the role of HOTAIR in HCC through miRNA, explained the regulatory pathway of HOTAIR-miRNA-mRNA and introduced the role of this pathway in HCC proliferation, drug resistance, invasion and metastasis.

Introduction. Increasing evidence shows that Hox transcript antisense RNA (HOTAIR) plays a vital role in liver cancer initiation and progression by affecting the proliferation, invasion, migration and apoptosis of liver cancer cells. However, the underlying mechanism of how HOTAIR exerts its functions in liver cancer cells remains unclear. Previous studies have shown that HOTAIR affects the invasion and migration of liver cancer cells by regulating the expression of E-cadherin. Snail2, a transcription factor involved in epithelial-mesenchymal transition, directly binds to the E-boxes of the E-cadherin promoter to repress its transcription. The aim of the study was to examine the correlation between HOTAIR and Snail2 in the HOTAIR/Snail2/E-cadherin signal pathway and explore the role of HOTAIR in the proliferation, invasion, migration and apoptosis of liver cancer cells. Materials and methods. 50 matched normal liver tissues and 373 liver cancer tissues were analysed and evaluated. HepG2 and SNU-387 cells were cultured and transfected with plasmids knocking down HOTAIR to disrupt HOTAIR expression. Cell scratch and transwell assays were performed to examine the migration and invasion of HepG2 and SNU-387 cells; in addition, the expression of MMP2 and MMP9 was detected by immunoblotting analysis, RT-qPCR analysis, immunofluorescence analysis, and bioinformatics analysis, which elucidated the regulatory relationship between HOTAIR and Snail2. We used flow cytometry and JC-1 probe analysis assays to clarify the function of HOTAIR in liver cancer cell apoptosis. Results. The HOTAIR mRNA was upregulated in liver cancer tissues, which was related to worse overall survival. HOTAIR induced the expression of matrix metalloproteinase-9 (MMP9) and metalloproteinase-2 (MMP2), leading to degradation of extracellular matrix. HOTAIR knockdown significantly reduced the doubling time and inhibited cell migration and invasion of liver cancer cells. Furthermore, HOTAIR depletion induced mitochondrial-related apoptosis in HepG2 and SNU-387 cell lines. Conclusions. In this study, we proposed a novel mechanism in which HOTAIR promotes invasion and migration of liver cancer cells by regulating the nuclear localization of Snail2. Keywords: hepatocellular carcinoma Snail2 proliferation invasion migration apoptosis mitochondria

DNA methylation is a fundamental epigenetic regulator in hepatocellular carcinoma (HCC). However, a key paradox remains: how do ubiquitously expressed enzymes like DNMTs and TETs achieve locus-specific regulation without intrinsic sequence specificity? This review aims to elucidate the “lncRNA–DNA methylation axis,” examining how long non-coding RNAs (lncRNAs) confer specificity and plasticity to methylation machinery. We synthesized current literature focusing on the structural mechanisms (e.g., R-loops, DNA:RNA triplexes) by which lncRNAs interact with DNMTs and TETs. We further analyzed the bidirectional regulation between lncRNAs and methylation enzymes and their impact on HCC phenotypes. lncRNAs function as modular scaffolds and guides, directing methylation machinery to specific genomic loci. Rather than binary switches, they act as an “epigenetic rheostat,” fine-tuning methylation intensity to balance stability with plasticity. Crucially, a reciprocal feedback loop exists: aberrant DNA methylation suppresses tumor-suppressive lncRNAs, which in turn unleashes DNMT activity, locking cells into a malignant state. This axis drives proliferation, metastasis, metabolic reprogramming, and therapeutic resistance. The lncRNA–DNA methylation axis is a central determinant of epigenetic heterogeneity in HCC. Moving beyond descriptive cataloging to a mechanistic understanding of this network offers new perspectives for developing targeted epigenetic therapies and biomarkers.