Inhibition of the phosphatidylinositol 3-kinase/Akt pathway sensitizes MDA-MB468 human breast cancer cells to cerulenin-induced apoptosis.
Fatty acid synthase is overexpressed in cancer especially in tumors with a poor prognosis. The specific fatty acid synthase inhibitor cerulenin can induce apoptosis in cancer cells. Likewise, phosphatidylinositol 3-kinase (PI3K)/Akt kinase activities are elevated in primary tumors and cancer cell lines. Here, we tested whether inhibition of PI3K/Akt pathway would sensitize cancer cells to cerulenin-induced apoptosis. We show that LY294002, an inhibitor of PI3K, sensitized MDA-MB468 breast cancer cells to cerulenin-induced apoptosis. In MDA-MB468 cells, cerulenin- and LY294002-mediated apoptosis was associated with caspase-3 activation and the release of cytochrome c from mitochondria to cytosol. In addition, we observed additional species of Bak in mitochondria, suggesting a possible Bak activation. Treatment of cells with cerulenin and LY294002 down-regulated the protein levels of X chromosome-linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis 1 (cIAP-1), and Akt, whereas the levels of mitogen-activated protein/extracellular signal-regulated kinase kinase and other antiapoptotic Bcl-2 family proteins (Bcl-2 and Bcl-xl) did not change. Interestingly, the nonspecific caspase inhibitor, z-VAD-FMK, inhibited the down-regulation of Akt, XIAP, and cIAP-1 in cerulenin- and LY294002-treated cells. In conclusion, these studies show that inhibition of PI3K can sensitize cerulenin-induced apoptosis in MBA-MB468 breast cancer cells via activation of caspases, down-regulation of antiapoptotic proteins, such as XIAP, cIAP-1 and Akt, and possibly, activation of Bak in mitochondria.
Liu
Xuesong
X
Department R47S, AP9A, Cancer Research, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064, USA.
Shi
Yan
Y
Giranda
Vincent L
VL
Luo
Yan
Y
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002569:Cerulenin / Q000627:therapeutic use*; D002867:Chromones / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D051058:Oncogene Protein v-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D002867:Chromones; D004791:Enzyme Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D002569:Cerulenin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D045304:Cytochromes c; D051058:Oncogene Protein v-akt; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases