Occult infection with hepatitis B virus PreS variants synergistically promotes hepatocellular carcinoma development in a high-fat diet context by generating abnormal ceramides.

BACKGROUND

Some occult hepatitis B virus (HBV) infections are resulted from PreS mutations that reduce secretion of envelope protein (HBsAg). We investigated the ceramide amounts and species in hepatocytes infected with PreS variants that were isolated from HBsAg-seronegative patients with hepatocellular carcinoma (HCC) and the ceramide effects on autochthonous HCC development in murine models.

METHODS

HBV PreS/S regions from 35 HBsAg-seronegative HCC patients were sequenced. Hepatocyte cell lines and male C57BL/6J mouse livers were transfected with two PreS variant representatives. The ceramides with variated lengths of fatty acyl chains were quantified. Tumour development was examined in the HBV-transfected mice fed different diet types.

RESULTS

In HBsAg-seronegative HCC patients, nonneoplastic liver tissues harboured HBsAg and replication-competent HBV. The most frequently detected PreS/S variants carried mutations of altered amino acid properties in HBsAg compared with an isolate from one HBsAg-seronegative HCC patient. Hepatocyte infection with PreS variants caused HBsAg retention within the endoplasmic reticulum and generated more amounts of ceramides with C16:0 ceramide elevated the highest. Saturated fatty acids aggravated the PreS variant-infected hepatocytes to generate abnormal amounts and species of ceramides, which with HBV proteins synergistically activated NLRP3 inflammasome in liver inflammatory macrophages. Liver tumours were only detected in HBV-transfected mice fed high-fat diet, with higher tumour loads in the PreS variant-transfected, associated with abnormal ceramide generation.

CONCLUSIONS

HBV PreS mutations which altered amino acid properties of envelope proteins inhibited HBsAg secretion. Hepatocyte infection with PreS variants generated abnormal ceramides which with HBV proteins coactivated NLRP3 inflammasome in liver macrophages to promote autochthonous HCC development.