miR-338-3p Is Down-Regulated by Hepatitis B Virus X and Inhibits Cell Proliferation by Targeting the 3′-UTR Region of CyclinD1

Abstract

Hepatitis B virus X protein (HBx) is recognized as an oncogene in hepatocellular carcinoma (HCC). HBx regulates microRNA expression, including down-regulating miR-338-3p in LO2 cells. Here, we investigated miR-338-3p function in HBx-mediated hepatocarcinogenesis. In 23 HBV-infected HCC clinical patient tumor and adjacent non-tumor control tissues, 17 and 19 tumors expressed HBx mRNA and protein, respectively. When considered as a group, HBV-infected HCC tumors had lower miR-338-3p expression than controls; however, miR-338-3p was only significantly down-regulated in HBx-positive tumors, indicating that HBx inversely correlated with miR-338-3p. Functional characterization of miR-338-3p indicated that miR-338-3p mimics inhibited cell proliferation by inducing cell cycle arrest at the G1/S phase as assessed by EdU and cell cycle assays in HBx-expressing LO2 cells. CyclinD1, containing two putative miR-338-3p targets, was confirmed as a direct target using 3′-UTR luciferase reporter assays from cells transfected with mutated binding sites. Mutating the 2397–2403 nt binding site conferred the greatest resistance to miR-338-3p suppression of CyclinD1, indicating that miR-338-3p suppresses CyclinD1 at this site. Overall, this study demonstrates that miR-338-3p inhibits proliferation by regulating CyclinD1, and HBx down-regulates miR-338-3p in HCC. This newly identified miR-338-3p/CyclinD1 interaction provides novel insights into HBx-mediated hepatocarcinogenesis and may facilitate therapeutic development against HCC.

MiR-338-3p regulates neuronal maturation and suppresses glioblastoma proliferation

“…CyclinD1 and associated CDKs may act as a “switch” in the cell cycle, and their activity is inhibited in terminally differentiated neurons but high in the embryonic nervous system [48–51]. Furthermore, CyclinD1 and these CDKs may control angles of neurite formation in hippocampal granule cells [51].…”

miR-338-3p Suppresses Gastric Cancer Progression through a PTEN-AKT Axis by Targeting P-REX2a

“…In addition, miR-338-3p could suppress progression of cancer cells by targeting smoothened in both liver cancer (14) and colorectal carcinoma (15). Recently, hepatitis B virus X protein was found to be associated with the downregulated expression of miR-338-3p, which could inhibit proliferation by regulating cyclin D1 in liver cancer (16,17). However, its role in gastric cancer is unclear until now.…”

Functional polymorphisms in microRNA gene and hepatitis B risk among Asian population: a meta-analysis

“…Not all SNPs located in the regions of microRNA affect miRNA expression, but some play a dominant role in modulating target mRNAs (Potenza et al, 2011;Fu et al, 2012). Hepatitis B is a disease caused by HBV infection, which is a major cause of liver diseases, including chronic hepatitis and liver cirrhosis .…”

“…Interestingly, HBV may in turn alter the microRNA expression pattern by exerting a negative influence on the microRNA processor Drosha . Studies have also shown that miR-338-3p is down regulated by HBV X and inhibits cell proliferation by targeting the 3'-untranslated region of cyclinD1 (Fu et al, 2012).…”