Identification of nonsense mutations in hepatitis B virus S gene in patients with hepatocellular carcinoma developed after lamivudine therapy.
BACKGROUND
Lamivudine is widely used in patients with chronic hepatitis B virus (HBV) infection. In cirrhotic patients, long-term lamivudine therapy significantly reduced the risk of hepatocellular carcinoma (HCC). However, in a small but substantial portion of patients, HCC still developed despite lamivudine therapy. Prolonged usage of lamivudine led to mutations in the polymerase gene, where concurrent nonsense mutations in the HBV S gene occasionally occurred. The significance of such mutations in hepatocarcinogenesis remains elusive. Here, we aimed to understand the oncogenicity of HBV pre-S/S nonsense mutations identified in patients with HCC that developed after lamivudine therapy.


METHODS
Of 141 consecutive hepatitis B surface antigen-positive HCC patients, 8 developed HCC after receiving lamivudine therapy. The HBV pre-S/S sequences in their serum and tissue samples were analysed. A sex- and age-matched group of HCC patients who never received lamivudine therapy were included as controls. Site-directed mutagenesis experiments were performed to generate identified pre-S/S nonsense mutations in expression vectors for tumourigenicity analysis.


RESULTS
Seven of eight patients in the lamivudine-treated group harboured nonsense mutations in the S gene compared with none in the control group (P<0.001). Site-directed mutagenesis and transient transfection experiments revealed that these mutants could transactivate oncogene promoters. NIH3T3 cells stably expressing sL21*, sW156* and sW172* pre-S/S mutants had increased tumourigenicity in nude mice.


CONCLUSIONS
HCCs developed in lamivudine-treated patients who frequently carried nonsense mutations in the S gene. Such pre-S/S mutants are potentially oncogenic and might counteract the effect of lamivudine in preventing hepatocarcinogenesis.
Liver Research Unit, Chang Gung Medical Center, Taipei, Taiwan.
Ming-Wei
MW
Lai
Shiu-Feng
SF
Huang
Chao-Wei
CW
Hsu
Mei-Hui
MH
Chang
Yun-Fan
YF
Liaw
Chau-Ting
CT
Yeh
D000328:Adult; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000209:etiology*; D018389:Codon, Nonsense / Q000187:drug effects*; D005260:Female; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics; D019694:Hepatitis B, Chronic / Q000150:complications / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use*; D008113:Liver Neoplasms / Q000209:etiology; D008297:Male; D051379:Mice; D008875:Middle Aged; D041681:NIH 3T3 Cells; D009368:Neoplasm Transplantation; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use; D014759:Viral Envelope Proteins / Q000235:genetics*
D018389:Codon, Nonsense; D018894:Reverse Transcriptase Inhibitors; C118669:S envelope protein, hepatitis B virus; D014759:Viral Envelope Proteins; D019259:Lamivudine