We demonstrated a close link between OGT and CDC27 in MM cells by knockdown of OGT with siOGT, pharmacological inhibition of O-GlcNAcylation with OSMI-1 and pharmacological accumulation of O-GlcNAcylation with Thiamet G. Using mass spectrometry and immunoprecipitation, we identified the O-GlcNAcylated CDC27 protein as a key target protein that may be directly downregulated by OSMI-1 in MM.1S cells. The gene discussed is OGT; the disease is Miyoshi myopathy.