Discovery of Incednine as a Potent Modulator of the Anti-apoptotic Function of Bcl-xL from Microbial Origin

• Published in: Journal of the American Chemical Society 2008-02, Vol.130 (6), p.1822-1823
• Main Authors: Futamura, Yushi, Sawa, Ryuichi, Umezawa, Yoji, Igarashi, Masayuki, Nakamura, Hikaru, Hasegawa, Kimiko, Yamasaki, Mikio, Tashiro, Etsu, Takahashi, Yoshikazu, Akamatsu, Yuzuru, Imoto, Masaya
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents - pharmacology; Apoptosis - drug effects; bcl-X Protein - antagonists & inhibitors; bcl-X Protein - genetics; Cell Line, Tumor; Disaccharides - chemistry; Disaccharides - isolation & purification; Disaccharides - pharmacology; Doxorubicin - pharmacology; Drug Screening Assays, Antitumor; Humans; Lactams - chemistry; Lactams - isolation & purification; Lactams - pharmacology; Magnetic Resonance Spectroscopy - methods; Magnetic Resonance Spectroscopy - standards; Molecular Conformation; Reference Standards; Streptomyces - drug effects
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja710124p

Anti-apoptotic oncoproteins Bcl-2 and Bcl-xL are overexpressed in many cancers and play a crucial role in cancer initiation, progression, and resistance to chemotherapy. Therefore, the discovery of a functional inhibitor for these proteins and improved understanding of the molecular mechanisms of these proteins will be an aid to novel anti-tumor therapies. Here, using chemical−genetic cell-based screening, we have discovered a chemically and biologically unique substance, incednine, as a novel functional modulator of Bcl-2/Bcl-xL from the fermentation broth of Streptomyces sp. ML693-90F3. This compound was isolated as a HCl salt by solvent extraction and using centrifugal liquid−liquid partition chromatography. Its structure was elucidated by spectroscopic analysis, X-ray crystallographic analysis, and computational studies. Incednine has a molecular formula, C42H63N3O8, and consists of a novel skeletal structure, enol-ether amide in a 24-membered macrolactam core, with two aminosugars. Bcl-xL-overexpressing Ms-1 cells displayed resistance to several anti-tumor agents; however, anti-tumor agent-induced cell death was observed only when cells were treated with incednine. Overexpression of Bcl-xL inhibited cell death in Bax-overexpressing HEK293T cells by forming a complex with Bax, whereas Bcl-xL failed to inhibit cell death in the presence of incednine without affecting the heterodimerization of Bcl-xL and Bax. These findings suggest that incednine serves as a potent modulator of the anti-apoptotic Bcl-2/Bcl-xL distinct from the other known Bcl-2 inhibitors and could provide a chemical probe to study the underlying mechanisms of Bcl-2/Bcl-xL.