OAcGD2 is the O-acetyl derivative of GD2 ganglioside. Tumors that express GD2 often concomitantly express OAcGD2. Biological functions of OAcGD2 remain unclear, but O-acetylation is frequently associated with cancer aggressiveness. O-acetylation of GD3 protected glioma cells from apoptosis, enhanced their survival, and conferred chemoresistance of leukemia cells. In addition, O-acetylation plays an important role in modulating the plasticity of chromatin structure in CSCs by changing the electrical property of acetylated sites of histone and covering up the ubiquitination sites to stabilize many non-histone proteins. The presence of OAcGD2 in breast cancer cell lines has been reported, but its role in breast cancer and CSCs remains unknown.