OGT and neoplasm: Thus, O-GlcNAcylation is extremely responsive to increases in glucose uptake.31, 77 Onodera et al.38 showed that O-GlcNAcylation of some proteins was observed only in malignant cells, and glucose deprivation or inhibition of HBP or OGT significantly reduced tumor-specific O-GlcNAcylation in 3D cultures.