Synthesis and Biological Evaluation of Benzimidazole Derivatives As the G9a Histone Methyltransferase Inhibitors That Induce Autophagy and Apoptosis of Breast Cancer Cells

G9a (also known as KMT1C or EHMT2) is initially identified as a H3K9 methyltransferase that specifically mono- and dimethylates 'Lys-9' of histone H3 (H3K9me1 and H3K9me2, respectively) in euchromatin. It is overexpressed in various human cancers and employed as a promising target in cancer therapy. We discovered a benzoxazole scaffold through virtual high-throughput screening, and designed, synthesized 24 derivatives and investigated for inhibition of G9a. After several rounds of kinase and anti-proliferative activity screening, we discovered a potent G9a antagonist (GA001) with an IC value of 1.32μM that could induce autophagy via AMPK in MCF7 cells. In addition, we found high concentration of GA001 could induce apoptosis via p21-Bim signal cascades in MCF7 cells. Our results highlight a new approach for the development of a novel drug targeting G9a with a potential to induce autophagy and apoptosis for future breast cancer therapy.