Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. However, there still remains a lack of effective diagnostic and therapeutic targets for this disease. Increasing evidence demonstrates that RNA modifications play an important role in the progression of HCC, but the role of the N7-methylguanosine (m7G) methylation modification in HCC has not been properly evaluated. Thus, the goal of the present study was to investigate the function and mechanism of the m7G methyltransferase WD repeat domain 4 (WDR4) in HCC as well as its clinical relevance and potential value. We first verified the high expression of WDR4 in HCC and observed that upregulated WDR4 expression increased the m7G methylation level in HCC. WDR4 promoted HCC cell proliferation by inducing the G2/M cell cycle transition and inhibiting apoptosis in addition to enhancing metastasis and sorafenib resistance through epithelial-mesenchymal transition (EMT). Furthermore, we observed that c-MYC (MYC) can activate WDR4 transcription and that WDR4 promotes CCNB1 mRNA stability and translation to enhance HCC progression. Mechanistically, we determined that WDR4 enhances CCNB1 translation by promoting the binding of EIF2A to CCNB1 mRNA. Furthermore, CCNB1 was observed to promote PI3K and AKT phosphorylation in HCC and reduce P53 protein expression by promoting P53 ubiquitination. In summary, we elucidated the MYC/WDR4/CCNB1 signalling pathway and its impact on PI3K/AKT and P53. Furthermore, the result showed that the m7G methyltransferase WDR4 is a tumour promoter in the development and progression of HCC and may act as a candidate therapeutic target in HCC treatment.

BackgroundHigh glycolysis efficiency in tumor cells can promote tumor growth. lncRNAs play an important role in the proliferation, metabolism and migration of cancer cells, but their regulation of tumor glycolysis is currently not well researched.MethodsWe analyzed the co-expression of glycolysis-related genes and lncRNAs in The Cancer Genome Atlas (TCGA) database to screen glycolysis-related lncRNAs. Further prognostic analysis and differential expression analysis were performed. We further analyzed the relationship between lncRNAs and tumor immune infiltration. Since WAC antisense RNA 1 (WAC-AS1) had the greatest effect on the prognosis among all screened lncRNAs and had a larger coefficient in the prognostic model, we chose WAC-AS1 for further verification experiments and investigated the function and mechanism of action of WAC-AS1 in hepatocellular carcinoma.ResultsWe screened 502 lncRNAs that have co-expression relationships with glycolytic genes based on co-expression analysis. Among them, 112 lncRNAs were abnormally expressed in liver cancer, and 40 lncRNAs were related to the prognosis of patients. Eight lncRNAs (WAC-AS1, SNHG3, SNHG12, MSC-AS1, MIR210HG, PTOV1-AS1, AC145207.5 and AL031985.3) were used to established a prognostic model. Independent prognostic analysis (P<0.001), survival analysis (P<0.001), receiver operating characteristic (ROC) curve analysis (AUC=0.779) and clinical correlation analysis (P<0.001) all indicated that the prognostic model has good predictive power and that the risk score can be used as an independent prognostic factor (P<0.001). The risk score and lncRNAs in the model were found to be related to a variety of immune cell infiltration and immune functions. WAC-AS1 was found to affect glycolysis and promote tumor proliferation (P<0.01). WAC-AS1 affected the expression of several glycolysis-related genes (cAMP regulated phosphoprotein 19 (ARPP19), CHST12, MED24 and KIF2A) (P<0.01). Under hypoxic conditions, WAC-AS1 regulated ARPP19 by sponging miR-320d to promote glucose uptake and lactate production (P<0.01).ConclusionWe constructed a model based on glycolysis-related lncRNAs to evaluate the prognostic risk of patients. The risk score and lncRNAs in the model were related to immune cell infiltration. WAC-AS1 can regulate ARPP19 to promote glycolysis and proliferation by sponging miR-320d.

Background Hepatocellular carcinoma (HCC) is one of the most prevalent cancers in the world, with a high likelihood of metastasis and a dismal prognosis. The reprogramming of glucose metabolism is critical in the development of HCC. The Warburg effect has recently been confirmed to occur in a variety of cancers, including HCC. However, little is known about the molecular biological mechanisms underlying the Warburg effect in HCC cells. In this study, we sought to better understand how methyltransferase 5, N6‐adenosine (METTL5) controls the development of HCC and the Warburg effect. Methods In the current study, quantitative real‐time polymerase chain reaction and Western blotting were used to detect the expression of METTL5 in HCC tissues and cell lines. Several different cell models and animal models were established to determine the role of METTL5 in glucose metabolism reprogramming and the underlying molecular mechanism of HCC. Glutathione‐S‐transferase pulldown, coimmunoprecipitation, RNA sequencing, non‐targeted metabolomics, polysome profiling, and luciferase reporter assays were performed to investigate the molecular mechanisms of METTL5 in HCC cells. Results We discovered that METTL5 drove glucose metabolic reprogramming to promote the proliferation and metastasis of HCC. Mechanistically, upregulation of METTL5 promoted c‐Myc stability and thus activated its downstream glycolytic genes lactate dehydrogenase A (LDHA), enolase 1 (ENO1), triosephosphate isomerase 1 (TPI1), solute carrier family 2 member 1 (SLC2A1), and pyruvate kinase M2 (PKM2). The c‐Box and ubiquitin binding domain (UBA) regions of ubiquitin specific peptidase 5 (USP5) binded to c‐Myc protein and inhibited K48‐linked polyubiquitination of c‐Myc. Further study revealed that METTL5 controled the USP5 translation process, which in turn regulated the ubiquitination of c‐Myc. Furthermore, we identified cAMP responsive element binding protein 1 (CREB1)/P300 as a critical transcriptional regulator of METTL5 that promoted the transcription of METTL5 in HCC. In patient‐derived tumor xenograft (PDX) models, adenovirus‐mediated knockout of METTL5 had a good antitumor effect and prolonged the survival of PDX‐bearing mice. Conclusions These findings point to a novel mechanism by which CREB1/P300‐METTL5‐USP5‐c‐Myc controls abnormal glucose metabolism and promotes tumor growth, suggesting that METTL5 is a potential therapeutic target and prognostic biomarker for HCC.

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