Hsp 90 inhibitor induces KG1 a cell differentiation and apoptosis via Akt / NF-κ B signaling

Heat-shock protein 90 (Hsp 90) acts as a molecular chaperone that maintains protein stability and regulates cell proliferation, survival, differentiation and apoptosis. The present study investigated the effect of Hsp90 inhibition on human acute myeloid leukemia (AML) cells using the novel small-molecule inhibitor SNX-2112. We found that SNX-2112 more potently inhibited KG-1a cell growth than the classical Hsp90 inhibitor 17-(2-dimethylaminoethyl)amino-17-demethoxygeldanamycin as determined by CCK-8 assay. Flow cytometry was used to examine the cell cycle, differentiation, and apoptosis, and western blotting and qRT-PCR were used to analyze the underlying mechanism. The results revealed that low concentrations of SNX-2112 arrested the cells in the G2/M phase and induced their differentiation and apoptosis, possibly by suppressing Akt and inhibitor of κB kinase, a component of the nuclear factor (NF)-κB signaling pathway. We also found that SNX-2112 increased the expression of the differentiation transcription factors PU.1 and CCAAT-enhancer-binding protein-α. Thus, SNX-2112 induced KG-1a cell differentiation, cell cycle arrest and apoptosis via modulation of Akt and NF-κB signaling, suggesting that it is a promising therapeutic agent for the treatment of AML. Introduction Acute myeloid leukemia (AML) is a clinically and biologically heterogeneous clonal hematologic disorder that is common and lethal in adults (1). Even with improvements in diagnosis and supportive care, the 5-year survival rate for adults with AML is only 30%. There have been no breakthroughs in AML treatment in the last 40 years, although in the past decade, an increasing number of potential drug targets have been identified (2). Heat shock protein 90 (Hsp 90) is a chaperone protein required for the folding and stabilization of proteins involved in intracellular signaling such as Akt and the nuclear factor (NF)-κB signaling pathway component inhibitor of κB kinase (IKK) α, which regulate cell survival, proliferation and differentiation (3,4). Hsp90 is overexpressed in many types of cancer relative to normal tissues and is therefore considered a potential anticancer drug target (3,5). There are sixteen different Hsp90 inhibitors that have entered clinical testing including first generation Hsp90 inhibitors (geldanamycin and its derivatives) and second generation Hsp90 inhibitors (NVP-AUY922 and SNX-5422). However, there is no FDA approved Hsp90 inhibitor nor standardized assay to ascertain Hsp90 inhibition. The most clinically significant off-target toxicity with the geldanamycin derivatives was hepatotoxicity resulting from the presence of a benzoquinone moiety. In addition to hepatotoxicity, ocular and cardiac toxicities also limited further clinical development of these drugs (6-8). Therefore, development of an Hsp90 inhibitor with better pharmacological properties and a safety profile is important. Most Hsp90 inhibitors exhibit great anti-acute myeloid leukemia effects. The second-generation Hsp90 inhibitor NVP-AUY922-AG was demonstrated to be cytotoxic in myeloid cell lines and primary AML cells (9), and other Hsp90 inhibitors were tested in phase I clinical trials and have been well tolerated in patients with advanced AML (10). SNX-2112 is a novel inhibitor that competitively binds to the N-terminal ATP-binding site of Hsp90 and has shown anticancer activity in vitro and in vivo (3,11). A hallmark of AML is that leukemic blast cells are arrested at an early stage of differentiation. It has therefore been suggested that therapies promoting differentiation may be Hsp90 inhibitor induces KG-1a cell differentiation and apoptosis via Akt/NF-κB signaling JIN-HONG QIN1,2, KUN WANG1, XIN-LU FU3, PENG-JUN ZHOU1, ZHONG LIU1,2, DAN-DAN XU1, YI-FEI WANG1,2, DE-PO YANG4, QIU-LING XIE1,2 and QIU-YING LIU1,2,4 1Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, and 2Guangdong Provincial Key Laboratory of Bioengineering Medicine, Jinan University, Guangzhou, Guangdong 510632; 3Laboratory Animal Center and 4School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, Guangdong 510275, P.R. China Received December 3, 2016; Accepted May 23, 2017 DOI: 10.3892/or.2017. 5797 Correspondence to: Qiu-Ying Liu, Guangzhou Jinan Biomedicine Research and Development Center, Jinan University, 601 West HuangPu Road, Guangzhou, Guangdong 510632, P.R. China E-mail: qiuying_liu@126.com Professor Qiu-Ling Xie, Guangdong Provincial Key Laboratory of Bioengineering Medicine, Jinan University, 601 West HuangPu Road, Guangzhou, Guangdong 510632, P.R. China E-mail: txql@jnu.edu. cn Abbreviations: AML, acute myeloid leukemia; GM, geldanamycin; 17-AAG, 17-(2-dimethylaminoethyl)amino-17-demethoxygeldanamycin; ATRA, all-trans-retinoic acid; CMP, common myeloid progenitor; GMP, granulocyte-monocyte progenitor; Bar, bardoxolone methyl