DNMT1 and breast cancer: We demonstrated here that the transcription of DNA methyltransferases DNMT1, DNMT3A, DNMT3B and COQ3 genes as well as the histone methyltransferase DOT1, SUV39H1 and SUV39H2 were downregulated in GBK-treated MCF-7 cells (Supplementary Figure 3B), indicating that GBK could inhibit breast cancer progression by reducing the DNA methylation level in the promoters of tumor suppressor genes or the global genome.