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

Naturally evolved immune-escape PreS2 mutant is an oncogenic caveat of liver cirrhosis and hepatocellular carcinoma (HCC) during chronic hepatitis B virus (HBV) infection. Notably, PreS2 mutants is prevalent in above 50% of patients with HCC. Intrahepatic expression of PreS2 mutant large surface antigen (PreS2-LHBS) induces endoplasmic reticulum stress, mitochondria dysfunction, cytokinesis failure and subsequent chromosome hyperploidy. In this study, we ask if long-term inhibition of PreS2-LHBS may act to reverse HBV-mediated hepatocarcinogenesis. We set up a stability reporter platform and identified ABT199 as an inhibitor of PreS2-LHBS from a library of 1068 FDA-approved drugs. Treatment of ABT199 induced PreS2-LHBS degradation without affecting the general cell viability, as shown in hepatoma and immortalized hepatocyte cell lines. We found that ABT199 induced the recruitment of PreS2-LHBS to ring-shaped structures in close proximity to lysosomal marker Lamp1 and multivesicular body marker Rab7. Simultaneously, inhibitions of lysosomal degradation or microautophagy restored the expression of PreS2-LHBS. Specifically, a 24-hr treatment of ABT199 reduced DNA damages and cytokinesis failure induced by PreS2-LHBS. Persistent treatment of ABT199 for 3 weeks reversed chromosome hyperploidy in PreS2-LHBS cells and suppressed anchorage-independent growth of HBV-positive hepatoma cell line. Together, we showed that ABT199 provoked selective degradation of PreS2-LHBS through the induction of microautophagy, and a long-term treatment of ABT199 reversed oncogenic mechanisms induced by HBV. Our results indicate that long-term degradation of PreS2-LHBS may serve as a novel therapeutic strategy to constrain HBV-mediated hepatocarcinogenesis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=66 SRC="FIGDIR/small/477454v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1720c85org.highwire.dtl.DTLVardef@943121org.highwire.dtl.DTLVardef@1257a22org.highwire.dtl.DTLVardef@1756348_HPS_FORMAT_FIGEXP M_FIG C_FIG Author summaryHBV PreS2 mutant large surface antigen (PreS2-LHBS) is an oncoprotein that induces liver cirrhosis and liver cancer. This study identified ABT199 as a potential inhibitor of PreS2-LHBS. We found that ABT199 could trigger the degradation of PreS2-LHBS through the induction of microautophagy. Moreover, a long-term treatment of ABT199 significantly reversed LHBS-induced oncogenic events including DNA damage, mitotic failure, chromosome hyperploidy, and anchorage-independent growth. This study not only identifies a specific inhibitor of PreS2-LHBS but also highlights a plausible strategy to constrain HBV-mediated hepatocarcinogenesis through targeting the degradation of PreS2-LHBS.