Targeting MutT homolog 1 (MTH1) for breast cancer suppression by a novel MTH1 inhibitor MA-24 with tumor-selective toxicity

Abstract

Background: Breast cancer is a commonly diagnosed cancer worldwide. Human MutT homolog 1 (MTH1) is found to be elevated in breast tumors and cancer cells are addicted to MTH1 for sur-vival. Pharmacological inhibition of MTH1 may be potentially beneficial in the treatment of breast cancer.
 Methods: MA-24 was screened by malachite green colorimetric assay from MTH1 inhibitors and the kinetic characteristics of MA-24 was assessed. Binding features of MA-24 with MTH1 was as-certained through molecular docking, and cytotoxic activity of MA-24 was validated in vitro and in vivo. Target engagement assays, comet assay and western blot confirmed that the intracellular target and mechanism of MA-24. 
 Results: MA-24 with potent antitumor bioactivity both in vitro and in vivo. MA-24 competitively inhibited the MTH1 and further induce DNA strand breaks, leading to increased apoptosis of cancer cells depending on upregulation of cleaved-caspase 3 – cleaved-PARP axis. Especially, MA-24 exhibited a powerful efficacy and safety in vivo (tumor growth inhibition rate: 61.8%).
 Conclusions: MA-24 possesses a broad spectrum of breast cancer cytotoxicity and offered valuable insights for overcoming the challenges of chemotherapy-related toxicity, which holds great po-tential for further development MA-24 as an anti-cancer drug.