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
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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.
Xinliang Mao, e-mail: [email protected]
Tingjun Hou, e-mail: [email protected]
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.
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.
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