Downregulation of O-GlcNAcylation enhances etoposide-induced p53-mediated apoptosis in HepG2 human liver cancer cells

Etoposide, an anticancer drug that inhibits topoisomerase II, is commonly used in combination chemotherapy. However, the impact of O-GlcNAcylation regulation on etoposides anticancer effects has rarely been investigated. This study evaluated the effect of etoposide on cellular O-GlcNAcylation and whether modulating this process enhances etoposide-induced apoptosis. O-GlcNAc expression was measured after 24 h of etoposide treatment, and the effect of O-GlcNAc transferase (OGT) inhibition by OSMI-1 on etoposides anticancer activity in HepG2 human liver cancer cells was quantitatively analyzed. Additionally, molecular analyses were used to confirm that the observed effects were mediated by p53-induced apoptosis. Etoposide reduced O-GlcNAcylation in a dose-dependent manner without directly interacting with OGT. Cotreatment with 20 M of OSMI-1 lowered the IC50 value for cell viability by approximately 1.64-fold to 60.68 M and increased the EC50 value for cytotoxicity by around 4.07-fold to 43.41 M. Furthermore, this synergistic effect was linked to the activation of the p53/caspase-3/PARP1 pathway. These findings suggest that downregulating O-GlcNAcylation may enhance the efficacy of etoposide-based chemotherapy and help overcome tumor resistance. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/626030v2_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@3cb205org.highwire.dtl.DTLVardef@cb686forg.highwire.dtl.DTLVardef@356662org.highwire.dtl.DTLVardef@1d4dc40_HPS_FORMAT_FIGEXP M_FIG Etoposide, a topoisomerase II inhibitor, reduces O-GlcNAcylation in HepG2 liver cancer cells. Further inhibition of O-GlcNAc transferase by OSMI-1 enhanced etoposide-induced apoptosis, lowering the IC50 for viability and increasing the EC50 for cytotoxicity. This synergy was mediated by the p53, caspase-3/7, PARP1 pathway, suggesting that targeting O-GlcNAcylation may improve etoposide efficacy. C_FIG