Human lung carcinoma A549 cells, human breast cancer MDA-MB-231 cells, and colorectal carcinoma HCT116 cells all stably expressing Flag-XIAP WT were established and their endogenous OGT protein and total cellular O-GlcNAc modification levels were investigated to explore the role of XIAP and OGT in cancer cells (Fig. 5a). Here, OGT is linked to breast carcinoma.