Therapeutic Effect of Quinacrine, an Antiprotozoan Drug, by Selective Suppression of p-CHK1/2 in p53-Negative Malignant Cancers.

Quinacrine (QNC), antiprotozoan drug commonly used against Malaria and Giardiasis, has been recently tried for rheumatics and prion diseases via drug repositioning. In addition, several reports suggest antitumor effects of QNC through suppression of NF-κB and activation of p53. This study demonstrates the anticancer effect of QNC via a novel pathway through the elimination of checkpoint kinase 1/2 (Chk1/2) under p53-inactivated conditions. Inhibition of p53 by PFT-α or siRNA promotes QNC-induced apoptosis in normal fibroblast and p53-intact cancer cells. Considering that Chk1/2 kinases exert an essential role in the control of cell cycle, inhibition of Chk1/2 by QNC may induce cell death via uncontrolled cell cycle progression. Indeed, QNC reduces Chk1/2 expression under p53-impaired cancer cells and induces cell death in the G2-M phase. QNC increases the binding between p-Chk1/2 and β-TrCP and promotes proteasome-dependent degradation. Moreover, QNC treatment displayed antitumor effects in a Villin-Cre;p53+/LSL-R172H intestinal cancer mouse model system as well as HCT116 p53-/- xenografts.Implications: QNC has been used for the past over 70 years without obvious side effects, as such it is a plausible drug candidate for relapsed cancers, small-cell lung cancer, breast cancer as well as various p53-inactivated human malignancies. Mol Cancer Res; 16(6); 935-46. ©2018 AACR. ©2018 American Association for Cancer Research.