Hepatocellular carcinoma is highly chemoresistant, and
ATP-binding cassette subfamily G member 2 (ABCG2) is thought to play a critical role in this drug resistance. The present study aims to develop effective therapeutic strategies to decrease ABCG2 expression level and to surmount drug resistance in
hepatocellular carcinoma chemotherapy. First, we verified a positive correlation between the
ABCG2 protein level and the drug resistance of
hepatocellular carcinoma cell lines. ABCG2 was preferentially expressed in highly chemoresistant
hepatocellular carcinoma cancer stem cells (CSC) enriched with CD133. In addition, ABCG2 was N-linked glycosylated in
hepatocellular carcinoma cells, and this modification was involved in sustaining its protein stability. The N-linked glycosylation (NLG) inhibitor
tunicamycin dramatically reduced ABCG2 expression, altered its subcellular localization, and reversed its drug efflux effect in multiple
hepatocellular carcinoma cell lines. Furthermore,
tunicamycin reduced the expression levels of several CSC markers and suppressed the tumorigenicity of CD133(+) CSCs.
Tunicamycin combined with
cisplatin (CDDP) inhibited
proliferating cell nuclear antigen (
PCNA) expression and increased the cleavage of PARP; this effect was partially rescued by the overexpression of ABCG2 or Akt-myr. The combination
therapy more effectively suppressed
tumor growth in xenograft mice than did single-agent
therapy with either drug. Finally, the CDDP treatment combined with
UDP-GlcNAc-
dolichol-
phosphate N-acetylglucosamine-1
phosphate transferase (DPAGT1) knockdown recapitulated the effect observed when CDDP was used in combination with
tunicamycin. In summary, our results suggest that
tunicamycin may reverse the drug resistance and improve the efficacy of combination treatments for
hepatocellular carcinomas by targeting the DPAGT1/Akt/ABCG2 pathway.