MPS1 TTK inhibitor is an inhibitor of monopolar spindle 1 (MPS1 TTK; IC50 = 5.8 nM), a kinase involved in mitotic spindle checkpoint signaling that is overexpressed in certain cancerous tumors. It inhibits MPS1 phosphorylation of kinetochore scaffold 1 (KNL1) and increases the rate of mitosis and the number of cells entering anaphase within 15 minutes, indicating MPS1 checkpoint inhibition, when used at a concentration of 100 nM. MPS1 TTK inhibitor (50 and 100 nM) increases the number of missegregated chromosomes, with an increased number of errors at 100 nM compared with 50 nM. It also inhibits colony formation of DLD1, HCT116, and U2OS cells (IC50s = 24.6, 20.1, and 20.6 nM, respectively).
DW532 is one of simplified analogues of hematoxylin that has shown broad-spectrum inhibition on tyrosine kinases and in vitro anti-cancer activities. DW532 inhibited EGFR and VEGFR2 in vitro kinase activity (the IC50 values were 4.9 and 5.5 μmol L, respectively), and suppressed their downstream signaling. DW532 dose-dependently inhibited tubulin polymerization via direct binding to tubulin, thus disrupting the mitotic spindle assembly and leading to abnormal cell division. In a panel of human cancer cells, DW532 (1 and 10 μmol L) induced G2 M phase arrest and cell apoptosis, which subsequently resulted in cytotoxicity. Knockdown of BubR1 or Mps1, the two core proteins of the spindle assembly checkpoint dramatically decreased DW532-induced cell cycle arrest in MDA-MB-468 cells. Moreover, treatment with DW532 potently and dose-dependently suppressed angiogenesis in vitro and in vivo. ( Acta Pharmacol Sin. 2014 Jul;35(7):916-28.)