Upregulated MicroRNA-29a by Hepatitis B Virus X Protein Enhances Hepatoma Cell Migration by Targeting PTEN in Cell Culture Model

Abstract

Hepatitis B virus X protein (HBx) plays important roles in the development of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) contribute to cancer development by acting as oncogenes or tumor suppressors. Previously, we reported that HBx was able to promote the migration of hepatoma HepG2 cells. However, the regulation of miRNAs in the development of HBV-related HCC is poorly understood. In the present study, we reported that miR-29a was a novel regulator of migration of hepatoma cells mediated by HBx. Our data showed that the expression of miR-29a was dramatically increased in p21-HBx transgenic mice, HBx-transfected hepatoma HepG2-X (or H7402-X) cells and HepG2.2.15 cells that constitutively replicate HBV. However, our data showed that miR-29a was upregulated in 4 of the 11 clinical HCC samples. We found that the overexpression of miR-29a promoted the migration of HepG2 cells, while a specific miR-29a inhibitor could partially abolish the enhanced migration of HepG2-X cells. Moreover, we identified PTEN was one of the target genes of miR-29a in HepG2 cells. The deletion of the miR-29a-binding site was able to abolish the role of miR-29a in suppression of luciferase activity of the PTEN 3′UTR reporter. Meanwhile, the overexpression of PTEN was able to reverse the promoted migration of HepG2 cells mediated by miR-29a. Moreover, our data showed that the modulation of Akt phosphorylation, a downstream factor of PTEN, was involved in the cell migration enhanced by miR-29a, suggesting that miR-29a is responsible for the cell migration through its target gene PTEN. Thus, we conclude that miR-29a is involved in the regulation of migration of hepatoma cells mediated by HBx through PTEN in cell culture model.

miRNAs affect the development of hepatocellular carcinoma via dysregulation of their biogenesis and expression

“…In addition, miR-21 could target RECK, which negatively regulates MMP-9, and lead to increasing invasion [97]. Moreover, PTEN is one of the target genes of miR-29a and can subsequently lead to Akt phosphorylation, which regulates the migration of hepatoma cells [98]. However, the targeting of PTEN and AKT3 by miR-519d could contribute to hepatocarcinogenesis [99].…”

Tumor Cell Development: A Role for Viruses and Telomerase Activity?

“…This miRNA was observed to be overexpressed in HBx-transfected HCC cells and HepG2 cells that constitutively replicate HBV, as well as in p21-HBx transgenic mice, and such up-regulation favored migration of HepG2 cells. In the same study, miR-29a was shown to target PTEN mRNA, thus reducing PTEN levels and favoring the activation AKT and MMP2 proteins, 110 which are involved in cell proliferation 111 and degradation of extracellular matrix, 112 respectively. Regarding telomerase modulation, there is evidence supporting that PTEN inhibits telomerase activity by reducing TERT mRNA levels, 113 while AKT up-regulates telomerase by phosphorylation of the TERT subunit.…”

The role and clinical implications of microRNAs in hepatocellular carcinoma

“…PTEN and Akt are known to regulate many fundamental cellular functions including cell proliferation/growth, survival, migration, apoptosis, and metabolism [39,40]. Expression of PTEN leads to dephosphorylation of Akt and inhibition of cell growth and migration [41,42]. Overexpression of PTEN by transient transfection with pcDNA3-PTEN plasmid, or knockdown of Akt by siRNA can abolish the enhanced migration of HepG2 cells mediated by miR-29a.…”