THE CHARACTERIZATION OF HSA-MIR148A IN HEPATOCARCINOGENESIS

Abstract

Chronic Hepatitis B Virus (HBV) infection is a global health problem because of its connection to acute and chronic liver diseases as well as hepatocellular carcinoma (HCC). There is increasing evidence showing that HBV contributes to HCC due to persistently high levels of trans-activating protein---hepatitis B encoded x antigen (HBxAg). Studies have shown that the HBxAg affects and alters the activity of many different transcription factors and plays an essential role in several cytoplasmic signaling transduction pathways, such as Wnt signaling pathways. One of the upregulated genes, designated URG11, was found transactivated by HBxAg. URG11 could stimulate the ß-catenin promoter and hepatocellular growth and survival which suggest that URG11 may be a regulatory element in the ß-catenin signaling pathways. microRNA148a (miR148a) was identified from two miRNA microarrays as one of the up-regulated miRNAs in cells stably expressing HBxAg or over-expressing URG11. Moreover, the expression of miR148a was also elevated in HBV-mediated HCC patient tissue samples. To study the function of miR148a, HepG2 (hepatoblastoma) and Hep3B (hepatoma) cells stably expressing HBxAg or over-expressing URG11 were transduced by recombinant lentiviruses encoding anti-miR148a. anti-miR148a suppressed cell proliferation, cell cycle progression, cell migration, anchorage independent growth in soft agar and subcutaneous tumor formation in SCID mice. Further, introduction of anti-miR148a increased PTEN protein and mRNA expression, suggesting that PTEN was suppressed by miR148a. In addition, anti-miR148a blocked the stimulation of Akt signaling, resulting in decreased expression of ß-catenin. Thus, miR148a may play a central role in HBxAg/URG11 mediated HCC, and may be an early diagnostic marker and/or therapeutic target associated with this tumor type.