Clinical implications on HBV preS/S mutations and the effects of preS2 deletion on mitochondria, liver fibrosis, and cancer development.

BACKGROUND & AIMS PreS mutants of HBV have been reported to be associated with hepatocellular carcinoma (HCC). We conducted a longitudinal study of the role of HBV preS mutations on development of HCC, particularly in chronic hepatitis B (CHB) patients having low HBV DNA or ALT levels, and investigated effects of secretion-defective preS2 deletion mutant (preS2ΔMT) on hepatocyte damage in vitro and liver fibrosis in vivo. APPROACH AND RESULTS Association of preS mutations with HCC in 343 CHB patients was evaluated by retrospective case-control follow-up study. Effects of preS2ΔMT on HBsAg retention, ER stress, calcium accumulation, mitochondrial dysfunction, and liver fibrosis were examined. Multivariate analysis revealed significant association of preS mutations with HCC (HR: 3.210, 95% CI: 1.072-9.613; p=0.037) including cases with low HBV DNA or ALT levels (HR: 2.790, 95% CI: 1.133-6.873; p=0.026). Antiviral therapy reduced HCC risk, including cases with preS mutations. preS2ΔMT expression promoted HBsAg retention in ER and unfolded protein response (UPR). TEM examination, MitoTracker staining, real-time ATP assay, and calcium staining of preS2ΔMT-expressing cells revealed aberrant ER and mitochondrial ultrastructure, reduction of mitochondrial membrane potential and ATP production, and calcium overload. Serum HBV secretion levels were ~100-fold lower in preS2ΔMT-infected hu-FRG mice than in WT HBV-infected mice. preS2ΔMT-infected mice displayed upregulation of UPR and caspase-3, and enhanced liver fibrosis. CONCLUSIONS PreS mutations were significantly associated with HCC development in CHB patients, including those low HBV DNA or ALT levels. Antiviral therapy reduced HCC occurrence in CHB patients, including those with preS mutations. Intracellular accumulation of mutated HBsAg induced or promoted ER stress, calcium overload, mitochondrial dysfunction, impaired energy metabolism, liver fibrosis, and HCC.