Rational Design and Synthesis of Highly Stable Haloflavanone DNA Methyltransferase Inhibitors Inducing Tumor Suppressor Gene Re-expression in Cancer Cells

DNA methylation is an epigenetic modification involved in cancer. The clinically approved nucleoside DNA methyltransferase (DNMT) inhibitors 5-azacytidine and 5-aza-2'-deoxycytidine lack selectivity and stability, resulting in high toxicity. Previously, we discovered 3-halo-3-nitroflavanones as non-nucleoside DNMT inhibitors. Here, we designed and synthesized a new series of 2-substituted haloflavanones to increase compound chemical stability. Moreover, replacement of the nitro by an additional halogen enhanced compound potency. Indeed, compound <b>34b</b> (<i>anti</i>-3-bromo-3-chloro-2-methoxyflavanone) exhibited submicromolar DNMT3A inhibitory activity, upregulated the expression of DNMT-targeted genes, and impaired cell proliferation. Importantly, <b>34b</b> triggered a critical cell cycle arrest in the G1/S transition, notably in p53-depleted HCT-116 colorectal cancer cells, which paves the way for novel therapeutic opportunities. <b>34b</b> competes for the same DNMT catalytic pocket as confirmed by saturation transfer difference-nuclear magnetic resonance, but assuming different docking poses as shown by computational studies. Overall, the high stability and activity of <b>34b</b> make it a promising DNMT inhibitor for anticancer research and therapy.