A virtual screen identified C96 as a novel inhibitor of phosphatidylinositol 3-kinase that displays potent preclinical activity against multiple myeloma in vitro and in vivo

$('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); Juan Tang 1 , 2 , * , Jingyu Zhu 1 , 2 , * , Yang Yu 3 , Zubin Zhang 1 , 2 , Guodong Chen 1 , 2 , Xiumin Zhou 4 , Chunhua Qiao 3 , Tingjun Hou 1 , 5 , Xinliang Mao 1 , 2 , 6 1 Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou, China 2 Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, The First Affiliated Hospital, Soochow University, Suzhou, China 3 Department of Medicinal Chemistry, College of Pharmaceutical Sciences, Soochow University, Suzhou, China 4 Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China 5 College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China 6 Collaborative Innovation Center of Hematology, Suzhou, China * These authors contributed equally to this work. Correspondence to: Xinliang Mao, e-mail: xinliangmao@suda.edu.cn Tingjun Hou, e-mail: tingjunhou@zju.edu.cn Key words: C96; apoptosis; PI3K/AKT signal pathway; multiple myeloma; virtual screen Received: December 05, 2013      Accepted: May 18, 2014      Published: May 21, 2014 Abbreviations: 4E-BP1 , eIF4E-binding protein 1; DMSO , dimethyl sulfoxide; FITC , fluorescein isothiocyanate; GAPDH , glyceraldehyde 3-phosphate dehydrogenase; IGF-1 , insulin-like growth factor-1; IGF-1R , insulin-like growth factor-1 receptor; IMDM , Iscove's modified Dulbecco's medium; MM , multiple myeloma; mTOR , mammalian target of Rapamycin; MTT , 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-sodium bromide; PARP , poly(ADP-ribose) polymerase; PDB , protein data bank; PI , propidium iodide; PI3K , phosphatidylinositol 3-kinase; PTEN , phosphatase and tensin homolog; SDS , sodium dodecyl sulfate; TBS , Tris-buffered saline. ABSTRACT The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is emerging as a promising therapeutic target for multiple myeloma (MM). In the present study, we performed a virtual screen against 800,000 of small molecule compounds by targeting PI3Kγ. C96, one of such compounds, inhibited PI3K activated by insulin-like growth factor-1 (IGF-1), but did not suppress IGF-1R activation. The cell-free assay revealed that C96 preferred to inhibit PI3Kα and δ, but was not active against AKT1, 2, 3 or mTOR. C96 inhibited PI3K activation in a time- and concentration-dependent manner. Consistent with its inhibition on PI3K/AKT, C96 downregulated the activation of mTOR, p70S6K, 4E-BP1, but did not suppress other kinases such as ERK and c-Src. Inhibition of the PI3K/AKT signaling pathway by C96 led to MM cell apoptosis which was demonstrated by Annexin V staining and activation of the pro-apoptotic signals. Furthermore, C96 displayed potent anti-myeloma activity in a MM xenograft model in nude mice. Oral administration of 100 mg/kg bodyweight almost fully suppressed tumor growth within 16 days, but without gross toxicity. Importantly, AKT activation was suppressed in tumor tissues from C96-treated mice, which was consistent with delayed tumor growth. Thus, we identified a novel PI3K inhibitor with a great potential for MM therapy.