Loperamide, an antidiarrheal agent, is frequently used to treat patients with leukemia with symptoms of diarrhea during treatment. However, the effect of loperamide on leukemia cells is unknown. The MTT assay was used to explore the cytotoxic effect of loperamide on leukemia cells. Morphological analysis and flow cytometry were performed to determine the level of apoptosis in leukemia cells following loperamide treatment. Western blotting was conducted to test the activation of the apoptotic pathway. The comet assay was used to determine the DNA damage induced by loperamide. Loperamide potently inhibited the proliferation of leukemia cell lines and primary leukemia cells from 9 patients with acute myeloid leukemia (AML) and 6 patients with acute lymphocytic leukemia (ALL) in a dose-dependent manner. Loperamide increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase, decreased the expression of myeloid cell lekeumia-1 and induced the apoptosis of leukemia cells. In addition, treatment with 20 µM loperamide increased the expression level of the protein rH2ax and promoted the formation of long DNA comet tails, thus triggering DNA damage in leukemia cells. Finally, DNA damage was confirmed by the activation of the ataxia telangiectasia mutated serine/threonine kinase (ATM)-checkpoint kinase 2 (Chk2) signaling pathway. The phosphorylation level of ATM (Ser1981) and Chk2 (Thr68) was activated and upregulated following DNA damage triggered by loperamide. Loperamide was demonstrated to perform an inhibitory role in the growth of leukemia cell lines and primary leukemia cells. Of note, apoptosis and DNA damage were induced following loperamide treatment in leukemia cell lines and primary leukemia cells.
Keywords: DNA damage; apoptosis; leukemia; loperamide; mechanism.