Objective      To investigate the mechanisms that microRNA221 (miR-221) promotes cancer development in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) as well as HBx protein promotes HepG2 cells aberrant proliferation thr

ough up-regulation of miR-221.       Methods      Recombinant adenovirus with HBx gene (adv-HBx) was used to transfect HepG2 cells. The changes of miR-221 and estrogen receptor α (ERα) mRNA were validated by real-time fluorescence quantitative PCR

and the protein levels of ERα were quantified by Western blotting. Cell cycle was detected by flow cytometry. miR-221 mimic and miR-221 inhibitor were used to transfect HepG2 cells respectively. The changes of miR-221 and ERα mRNA in HBx-HepG2 cells were determined by real-time fluorescence quantitative PCR

and ERα protein levels were quantified by Western blotting.       Results      RT-PCR results confirmed that HBx was highly expressed in HepG2 cells after adv-HBx transfection. In 48 h after transfection

HBx protein enhanced the expression of miR-221 (495.84±61.16 vs 239.25±21.15

P

＜0.05)

decreased ERα at protein level (0.24±0.01 vs 0.61±0.02

P

＜0.05)

and promoted aberrant proliferation of HepG2 cells [(31.73±3.53)% vs (56.08±1.56)%

P

=0.01

]

. Cell transfection and Western blotting results indilated that miR-221 decreased the expression of ERα protein (

P

0.05) while miR-221 inhibitor increased it (

P

0.05)

which suggested that ERα might be an important target of miR-221.       Conclusion      HBx may decrease the protective effects of ERα against HCC by up-regulation of miR-221

and then promote aberrant proliferation of hepatocarcinoma cells. miR-221 may be a potential target for hepatocarcinoma therapy.