Fatty acid synthase inhibition triggers apoptosis during S phase in human cancer cells.
C75, an inhibitor of fatty acid synthase (FAS), induces apoptosis in cultured human cancer cells. Its proposed mechanism of action linked high levels of malonyl-CoA after FAS inhibition to potential downstream effects including inhibition of carnitine palmitoyltransferase-1 (CPT-1) with resultant inhibition of fatty acid oxidation. Recent data has shown that C75 directly stimulates CPT-1 increasing fatty acid oxidation in MCF-7 human breast cancer cells despite inhibitory concentrations of malonyl-CoA. In light of these findings, we have studied fatty acid metabolism in MCF7 human breast cancer cells to elucidate the mechanism of action of C75. We now report that: (a) in the setting of increased fatty acid oxidation, C75 inhibits fatty acid synthesis; (b) C273, a reduced form of C75, is unable to inhibit fatty acid synthesis and is nontoxic to MCF7 cells; (c) C75 and 5-(tetradecyloxy)-2-furoic acid (TOFA), an inhibitor of acetyl-CoA carboxylase, both cause a significant reduction of fatty acid incorporation into phosphatidylcholine, the major membrane phospholipid, within 2 h; (d) pulse chase studies with [(14)C]acetate labeling of membrane lipids show that both C75 and TOFA accelerate the decay of (14)C-labeled lipid from membranes within 2 h; (e) C75 also promotes a 2-3-fold increase in oxidation of membrane lipids within 2 h; and (f) because interference with phospholipid synthesis during S phase is known to trigger apoptosis in cycling cells, we performed double-labeled terminal deoxynucleotidyltransferase-mediated nick end labeling and BrdUrd analysis with both TOFA and C75. C75 triggered apoptosis during S phase, whereas TOFA did not. Moreover, application of TOFA 2 h before C75 blocked the C75 induced apoptosis, whereas etomoxir did not. Taken together these data indicate that FAS inhibition and its downstream inhibition of phospholipid production is a necessary part of the mechanism of action of C75. CPT-1 stimulation does not likely play a role in the cytotoxic response. The continued ability of TOFA to rescue cancer cells from C75 cytotoxicity implies a proapoptotic role for malonyl-CoA independent of CPT-1 that selectively targets cancer cells as they progress into S phase.
Zhou
Weibo
W
Department of Pathology, The Johns Hopkins University School of Medicine, Hopkins Bayview Medical Center, 4940 Eastern Avenue, Baltimore, MD 21205, USA.
Simpson
P Jeanette
PJ
McFadden
Jill M
JM
Townsend
Craig A
CA
Medghalchi
Susan M
SM
Vadlamudi
Aravinda
A
Pinn
Michael L
ML
Ronnett
Gabriele V
GV
Kuhajda
Francis P
FP
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004347:Drug Interactions; D004852:Epoxy Compounds / Q000494:pharmacology; D064429:Fatty Acid Synthases / Q000037:antagonists & inhibitors*; D005663:Furans / Q000494:pharmacology*; D006801:Humans; D008563:Membrane Lipids / Q000096:biosynthesis / Q000378:metabolism; D010743:Phospholipids / Q000096:biosynthesis; D016196:S Phase / Q000187:drug effects / Q000502:physiology
C406734:4-methylene-2-octyl-5-oxofuran-3-carboxylic acid; D004852:Epoxy Compounds; D005663:Furans; D008563:Membrane Lipids; D010743:Phospholipids; C014289:5-(tetradecyloxy)-2-furancarboxylic acid; D002334:Carnitine O-Palmitoyltransferase; D064429:Fatty Acid Synthases; C054207:etomoxir; D015107:4-Butyrolactone