Synergistic effect of radiation and interleukin-6 on hepatitis B virus reactivation in liver through STAT3 signaling pathway.
OBJECTIVE
Hepatitis B virus (HBV) reactivation can occur after radiotherapy (RT) for hepatobiliary malignancies. Our previous in vitro culture study identified interleukin-6 (IL-6) as the main bystander mediator of RT-induced HBV replication. We attempted to examine the molecular mechanism in HBV-transgenic mice.


METHODS
HBV transgenic mice were treated with whole liver RT (4 Gy daily for 5 days) with or without administration of IL-6 (400 ng twice daily for 15 days). The serum level of HBV DNA was measured using real-time polymerase chain reaction, and the IL-6 concentration was measured using enzyme-linked immunosorbent assay. The intensity of immunostaining with antibodies to HBV core protein and phosphorylated signal transducer and activator of transcription (STAT)3 in the mouse liver was qualitatively analyzed. HepG2.2.15 cells (a human hepatoblastoma cell line that persistently produces HBV DNA) were used to investigate the molecular role of IL-6 plus RT in HBV reactivation.


RESULTS
HBV reactivation was induced in vivo with IL-6 plus RT (5.58-fold) compared with RT alone (1.31-fold, p = .005), IL-6 alone (1.31-fold, p = .005), or sham treatment (1.22-fold, p = .004). HBV core protein staining confirmed augmentation of intrahepatic HBV replication. IL-6 plus RT-induced HBV DNA replication in HepG2.2.15 cells was suppressed by the STAT3 inhibitor AG490 and by transfection with dominant-negative STAT3 plasmid. Phosphorylated STAT3 staining was strongest in liver tissue from mice treated with IL-6 plus RT. The mobility shift assay demonstrated that reactivation was mediated through the interaction of phosphorylated STAT3/hepatocyte nuclear factor-3 complex with HBV enhancer 1.


CONCLUSIONS
RT to the liver and longer sustained IL-6 induced HBV reactivation through the STAT3 signal transduction pathway.
Chou
Chia Hung
CH
Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan; Cancer Research Center, National Taiwan University College of Medicine, Taipei, Taiwan; Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
Chen
Pei-Jer
PJ
Jeng
Yung-Ming
YM
Cheng
Ann-Lii
AL
Huang
Li-Rung
LR
Cheng
Jason Chia-Hsien
JC