NF-κB may be a potential therapeutic target for acute myelogenous leukemia (AML) because NF-κB activation is found in primitive human AML blast cells. In this report, we initially discovered that the potent antineoplastic effect of niclosamide, a Food and Drug Administration-approved antihelminthic agent, was through inhibition of the NF-κB pathway in AML cells. Niclosamide inhibited the transcription and DNA binding of NF-κB. It blocked tumor necrosis factor-induced IκBα phosphorylation, translocation of p65, and expression of NF-κB-regulated genes. Niclosamide inhibited the steps TAK1→IκB kinase (IKK) and IKK→IκBα. Niclosamide also increased the levels of reactive oxygen species (ROS) in AML cells. Quenching ROS by the glutathione precursor N-acetylcysteine attenuated niclosamide-induced apoptosis. Our results together suggest that niclosamide inhibited the NF-κB pathway and increased ROS levels to induce apoptosis in AML cells. On translational study of the efficacy of niclosamide against AML, niclosamide killed progenitor/stem cells from AML patients but spared those from normal bone marrow. Niclosamide was synergistic with the frontline chemotherapeutic agents cytarabine, etoposide, and daunorubicin. It potently inhibited the growth of AML cells in vitro and in nude mice. Our results support further investigation of niclosamide in clinical trials of AML patients. Cancer Res; 70(6); 2516-27. ©2010 AACR.

Purpose: The "gate-keeper" mutations T674I platelet-derived growth factor receptor a (PDGFRa) in hypereosinophilic syndrome (HES) and T315I Bcr-Abl in chronic myeloid leukemia (CML) are resistant to imatinib and the second-generation small-molecule tyrosine kinase inhibitors (TKI). However, to combat acquired resistance to imatinib, an alternative approach is to decrease the expression of the addicted gene to efficiently kill resistant malignant hematologic cells. The purpose of this study was to evaluate the strategy of shutting down the transcription and expression of FIP1-like-1 (FIP1L1)-PDGFRa and Bcr-Abl with SNS-032, an inhibitor of cyclin-dependent kinase 7 (CDK7) and CDK9 in phase I clinical trials.Experimental Design: The effects of SNS-032 on PDGFRa and Bcr-Abl signaling pathways, apoptosis, and cell cycling were analyzed in TKI-resistant cells of HES and CML. The in vivo antitumor activity of SNS-032 was assessed with xenografted BaF3-T674I FIP1L1-PDGFRa and KBM5-T315I Bcr-Abl cells in nude mouse models.Results: SNS-032 inhibited the phosphorylation on Ser5 and Ser2 of RNA polymerase II. SNS-032 decreased both the mRNA and protein levels of FIP1L1-PDGFRa and Bcr-Abl and inhibited the proliferation of malignant cells expressing FIP1L1-PDGFRa or Bcr-Abl. It also decreased the phosphorylation of downstream molecules. It induced apoptosis by triggering both the mitochondrial pathway and the death receptor pathway.Conclusions: This CDK7/9 inhibitor potently inhibits FIP1L1-PDGFRa-positive HES cells and Bcr-Ablpositive CML cells regardless of their sensitivity to imatinib. SNS-032 may have potential in treating hematologic malignancy by abrogating oncogene addiction.

No abstract

No abstract

No abstract