Hepatitis B virus-encoded X protein (HBx) plays a pivotal role in hepatocellular carcinoma (HCC) progression and treatment resistance. Interestingly, our previous study unexpectedly showed that full-length HBx sensitized HCC cells to lapatinib by up-regulating erb-b2 receptor tyrosine kinase 3 (ERBB3). We further aimed to map the exact motif within the HBx sequence responsible for lapatinib sensitization.
MATERIALS AND METHODS:
The exact motif responsible for the lapatinib sensitization was assessed by construction of various fragments of HBx. Cell viability was examined by the MTT assay and crystal violet staining.
Our investigation found that lapatinib sensitivity and up-regulation of ERBB3 promoter activity were observed only in HCC cells expressing C-terminal residues of HBx. Furthermore, C-terminal HBx peptide induced ERBB3 protein expression and sensitivity to lapatinib.
These results not only indicate that the C-terminus of HBx is required for lapatinib sensitivity, but also provide clues to developing a predictive biomarker for response of HCC to lapatinib in the future.