Clinical Implications of HBV PreS/S Mutations and the Effects of PreS2 Deletion on Mitochondria, Liver Fibrosis, and Cancer Development

Abstract

BaCKgRoUND aND aIMS: PreS mutants of HBV have been reported to be associated with HCC. We conducted a longitudinal study of the role of HBV preS mutations in the development of HCC, particularly in patients with chronic hepatitis B (CHB) having low HBV DNA or alanine aminotransferase (ALT) levels, and investigated the 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 patients with CHB was evaluated by a retrospective case-control follow-up study. Effects of preS2ΔMT on HBsAg retention, endoplasmic reticulum (ER) stress, calcium accumulation, mitochondrial dysfunction, and liver fibrosis were examined. Multivariate analysis revealed a 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 the ER and unfolded protein response (UPR). Transmission electron microscopic 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 ~100fold lower in preS2ΔMT-infected humanized Fah-/-/ Rag2-/-/ Il2rg-/-triple knockout mice than in wild-type HBV-infected mice. PreS2ΔMT-infected mice displayed up-regulation of UPR and caspase-3 and enhanced liver fibrosis.

Global prevalence and phylogeny of hepatitis B virus (HBV) drug and vaccine resistance mutations

“… 66 , 67 S‐gene mutations have been associated with HCC development, potentially because stop codons contribute to an accumulation of surface protein within hepatocytes. 68 …”

“…66,67 S-gene mutations have been associated with HCC development, potentially because stop codons contribute to an accumulation of surface protein within hepatocytes. 68 While evidence is lacking for a mechanistic relationship between the presence of common RAMs such as M204I/V+L180M and HCC, an association has been reported. 9 It is possible that alterations in viral replicative capacity can underpin changes in pathogenicity, 8,9 but more work is required to determine the extent to which RAMs and VEMs may have functional significance in disease outcomes beyond that of drug or vaccine escape.…”

“…For example, RAMs in HBV reverse transcriptase, A181T/V, M204I and M204V, cause corresponding changes in the overlapping region of HBsAg (W172 stop, W196S/L/Stop and I195M, respectively) 66,67. S-gene mutations have been associated with HCC development, potentially because stop codons contribute to an accumulation of surface protein within hepatocytes 68.…”

Hepatitis B virus–induced hepatocarcinogenesis: A virological and oncological perspective

“…The same study investigated the effects of the most common preS2 deletion in such patients (a short segment with 11 amino acids deleted in the preS2 region before proline). Huh7 cells expressing this preS2 mutated region had intracellular retention of HBsAg, which resulted in impairment of mitochondrial function, which in turn contributed to hepatocyte apoptosis, increased liver fibrosis and finally boosted the risk of HCC 53 . Beside the aspects related to HBV infection, the risk of HCC can be affected by metabolic factors and comorbidities.…”

Chemical-induced degradation of PreS2 mutant surface antigen reverses HBV-mediated hepatocarcinogenesis

“…Studies have shown that type II GGH carrying PreS2-LHBS has a significant association with HCC, cirrhosis, and the decreased survival rate [12,13]. In addition, compared to wild-type LHBS, PreS2-LHBS shows higher ER retention that induces a substantial ER stress, leading to calcium accumulation, mitochondrial dysfunction, and genomic instability [14,15]. Notably, the PreS2 deletion region corresponded to the epitope of CD8 T cell, suggesting the immune-escape attribute of this mutant [11].…”