Apoptosis and inactivation of the PI3-kinase pathway by tetrocarcin A in breast cancers

• Published in: Biochemical and biophysical research communications 2007-04, Vol.356 (1), p.260-265
• Main Authors: Nakajima, Hiroo, Sakaguchi, Koichi, Fujiwara, Ikuya, Mizuta, Mitsuhiko, Tsuruga, Mie, Magae, Junji, Mizuta, Naruhiko
• Format: Article
• Language: English
• Subjects: 3-Phosphoinositide-Dependent Protein Kinases; Akt; Aminoglycosides - pharmacology; ANTIBIOTICS; Antibiotics, Antineoplastic - pharmacology; APOPTOSIS; Apoptosis - drug effects; Bcl-2; bcl-2-Associated X Protein - metabolism; Bcl-X L; bcl-X Protein - metabolism; BIOSYNTHESIS; Blotting, Western; BORON CHLORIDES; Breast cancer; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Breast Neoplasms - physiopathology; CARCINOMAS; Caspase; Caspase 3 - metabolism; Caspase 9 - metabolism; Cell Line, Tumor; CELL PROLIFERATION; Cell Survival - drug effects; Dephosphorylation; Dose-Response Relationship, Drug; Enzyme Activation - drug effects; GENE REGULATION; GLUCOSE; Humans; INACTIVATION; MAMMARY GLANDS; PDK1; Phosphatidylinositol 3-Kinases - metabolism; PHOSPHORYLATION; Phosphorylation - drug effects; PI3-kinase; Protein-Serine-Threonine Kinases - metabolism; PROTEINS; Proto-Oncogene Proteins c-akt - metabolism; PTEN; PTEN Phosphohydrolase - metabolism; RADIOLOGY AND NUCLEAR MEDICINE; Signal Transduction - drug effects; Survival factor; Tetrocarcin A; UPTAKE
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2007.02.136

A survival kinase, Akt, is a downstream factor in the phosphatidylinositide-3′-kinase-dependent pathway, which mediates many biological responses including glucose uptake, protein synthesis and the regulation of proliferation and apoptosis, which is assumed to contribute to acquisition of malignant properties of human cancers. Here we find that an anti-tumor antibiotic, tetrocarcin A, directly induces apoptosis of human breast cancer cells. The apoptosis is accompanied by the activation of a proteolytic cascade of caspases including caspase-3 and -9, and concomitantly decreases phosphorylation of Akt, PDK1, and PTEN, a tumor suppressor that regulates the activity of Akt through the dephosphorylation of polyphosphoinositides. Tetrocarcin A affected neither expression of Akt, PDK1, or PTEN, nor did it affect the expression of Bcl family members including Bcl-2, Bcl-X L, and Bax. These results suggest that tetrocarcin A could be a potent chemotherapeutic agent for human breast cancer targeting the phosphatidylinositide-3′-kinase/Akt signaling pathway.