Nitric Oxide-Donating Acetylsalicylic Acid Induces Apoptosis in Chronic Lymphocytic Leukemia Cells and Shows Strong Antitumor Efficacy In vivo

Purpose: Nitric oxide-donating acetylsalicylic acid (NO-ASA) has been shown to possess an antineoplastic effect in Wnt-/beta-catenin-active cancers. As chronic lymphocytic leukemia (CLL) cells exhibit aberrantly active Wnt signaling, we investigated the effect of the para-isomer of NO-ASA on CLL cell survival in vitro and in a CLL-like xenograft mouse model. Experimental Design: Apoptosis in primary CLL cells was determined by flow cytometric annexin V-FITC (fluorescein isothiocyanate)/PI (propidium iodide) staining and immunoblotting of caspases, poly(ADP-ribose) polymerase (PARP), and antiapoptotic proteins. Interference of NO-ASA with Wnt/beta-catenin signaling was analyzed through immunoblots of different pathway members. Influence of caspase activation was investigated by pretreatment with a pan-caspase inhibitor. CLL-like JVM3 cells were subcutaneously inoculated into irradiated nude mice that were treated with 100 mg of para-NO-ASA/kg of body weight p.o. (by mouth) for 21 days. Results: para-NO-ASA induced apoptosis in CLL cells with an LC50 (lethal concentration) of 8.72 + 0.04 mu mol/L, whereas healthy blood cells were not affected. Furthermore, the compound induced caspase 9, caspase 3, and PARP cleavage. In addition, cleavage of beta-catenin and downregulation of beta-catenin/lymphoid enhancer factor (Lef)-1 targets was observed. para-NO-ASA demonstrated strong antitumor efficacy in the xenograft mouse model with a tumor inhibtion rate of 83.4%. During therapy, no gross toxicity could be observed. Conclusions: para-NO-ASA selectively induces apoptosis in primary CLL cells and efficiently reduces tumor growth in a CLL-like xenograftmodel. As NO-ASA is orally available and is generally well tolerated, para-NO-ASA might be a promising new compound for CLL therapy. Clin Cancer Res; 17(2); 286-93. (C)2010 AACR.