Hepatitis B Virus-Upregulated LNC-HUR1 Promotes Cell Proliferation and Tumorigenesis by Blocking p53 Activity

Recent studies have indicated that a number of long noncoding RNAs (lncRNAs) are dysregulated in hepatocellular carcinoma, while their aberrant expressions are associated with tumorigenesis and poor prognosis. To identify hepatitis B virus (HBV)-related lncRNAs, we used RNA deep sequencing to quantify the abundances of lncRNAs in HepG2 cells and HBV transgenic HepG2-4D14 cells. Here, we demonstrate that lnc-HUR1 is significantly upregulated in HepG2-4D14 cells. We found that HBV-encoded hepatitis B x protein can enhance the transcription of lnc-HUR1. Overexpression of lnc-HUR1 promotes cell proliferation, whereas knockdown of lnc-HUR1 inhibits cell growth. We identified that lnc-HUR1 can interact with p53 and inhibit its transcriptional regulation on downstream genes, such as p21 and B cell lymphoma 2-associated X protein. We generated lnc-HUR1 transgenic mice and performed the partial hepatectomy (PHx) to examine liver regeneration. The data showed that the ratio of liver weight to body weight in lnc-HUR1 transgenic mice is higher than that in wild-type (WT) littermates at day 2 and day 3 following hepatectomy. Consistently, the results of bromodeoxyuridine staining on liver sections following hepatectomy indicate that the ratio of bromodeoxyuridine-positive cells in lnc-HUR1 transgenic mice is significantly higher than that in WT mice, suggesting that lnc-HUR1 promotes cell proliferation during liver regeneration. Next, we performed the experiment of diethylnitrosamine-induced tumorigenesis. The data demonstrate that tumor number in lnc-HUR1 transgenic mice is higher compared with control mice, indicating that lnc-HUR1 enhances diethylnitrosamine-induced tumorigenesis. Conclusion: We reveal that HBV-upregulated lnc-HUR1 promotes cell proliferation and tumorigenesis by interacting with p53 to block downstream gene transcription. Our findings suggest that lnc-HUR1 plays an important role in HBV-related hepatocellular carcinoma development and may serve as a therapeutic marker for hepatocellular carcinoma. (Hepatology 2018; 00:000-000).