Abstract 3493: ON 01910. Na, a clinical trial stage multi-kinase inhibitor, induces apoptosis in chronic lymphocytic leukemia (CLL) cells through inhibition of PI3K/AKT and activation of the JNK pathway resulting in NOXA and BIM upregulation

Abstract

Abstract Chronic Lymphocytic leukemia (CLL), the most common leukemia in Western countries, is a clinically heterogeneous disease characterized by the accumulation of mature B lymphocytes, where disease progression is driven by survival and proliferation signals provided by the tumor microenvironment. ON 01910. Na (Onconova Therapeutics) belongs to the family of styryl benzyl sulfones, a novel family of non-ATP competitive kinase inhibitors. ON 01910. Na is under clinical development in hematologic and solid tumors. Here we show that ON 01910. Na induced apoptosis in CLL samples (n=28) in vitro, without showing significant toxicity against T-cells or normal B-cells. Twenty four CLL samples were highly sensitive to ON 01910. Na (mean IC50=0.89 μM) a concentration readily achieved in phase I clinical trials, three showed moderate sensitivity (mean IC50=4.26 μM) and one was resistant (IC50 >8 μM). There were no significant differences in ON01910. Na cytotoxicity against CLL cells expressing mutated (mean IC50=1.33 μM) or unmutated (mean IC50 =1.22μM) IgVH sequences. ON 01910. Na was similarly effective against tumor cells carrying 17p or 11q deletions. ON 01910. Na activated Bax and Bak, leading to mitochondrial depolarization. To delineate the upstream pathways underlying ON 01910. Na induced apoptosis, we performed Gene Expression Profiling (GEP) in CLL cells treated in vitro for 4 and 10 hours with ON 01910. Na. Gene Set Enrichment Analysis (GSEA) identified gene sets indicating BCR and PI3K inhibition (FDR<0.2). In keeping with PI3K inhibition, we found that ON 19010. Na inhibited phosphorylation of Akt and Foxo3a, and FOXO3 target genes, including Bim, were upregulated. In addition, GSEA identified induction of AP-1 gene sets (FDR<0.01) suggesting the generation of reactive oxygen species (ROS) by ON 01910. Na. Consistently, we found a rapid increase in ROS in cells treated with ON 01910. Na and ROS scavengers protected cells from its cytotoxic effect. ROS upregulated the proapoptotic BH3-only protein Noxa, and knockdown of Noxa by shRNA decreased the sensitivity to the drug by 60%. Our results identify ON 01910. Na as a promising agent in the treatment of CLL with an interesting dual mechanism of action: inhibition of the PI3K/AKT survival pathway with Foxo mediated upregulation of BIM and the induction of oxidative stress resulting in Noxa upregulation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3493.