title: Inhibition of Fatty Acid Synthase (FASN) synergistically enhances the efficacy of 5-fluorouracil in breast carcinoma cells.
abstract: The lipogenic enzyme fatty acid synthase (FASN) is differentially overexpressed and hyperactivated in a biologically aggressive subset of breast carcinomas and minimally in most normal adult tissues, rendering it an interesting target for anti-neoplastic therapy development. We previously reported that the FASN blockade can induce a synergistic chemosensitization of breast cancer cells to microtubule interfering agents (MIAs) such as docetaxel, paclitaxel and vinorelbine. Upon pharmacological inhibition of FASN activity using the natural antibiotic cerulenin [(2S,3R)-2,3-epoxy-4-oxo-7E,10E-dodecadienamide], we evaluated the role of FASN-catalyzed endogenous fatty acid biogenesis on the sensitivity of SK-Br3, MCF-7 and MDA-MB-231 breast cancer cell lines to the anti-metabolite 5-fluorouracil (5-FU). Cells were exposed simultaneously to cerulenin and 5-FU, sequentially to 5-FU followed by cerulenin or cerulenin followed by 5-FU. Cell viability was determined by MTT assays and the increase in 5-FU-induced cell growth inhibition was measured by dividing 5-FU IC30 and IC50 values (i.e., 30% and 50% inhibitory concentrations, respectively) that were obtained in the absence of cerulenin by those in its presence. Co-exposure to cerulenin enhanced 5-FU efficacy up to 20-, 81-, and 58-times in SK-Br3, MCF-7 and MDA-MB-231 cells, respectively. Pre-treatment with cerulenin followed by the addition of 5-FU increased 5-FU efficacy up to 31-, 87-, and 126-times in SK-Br3, MCF-7 and MDA-MB-231 cells, respectively. Pre-treatment with 5-FU followed by the addition of cerulenin augmented 5-FU efficacy up to 107-, 20-, and 18-times in SK-Br3, MCF-7 and MDA-MB-231 cells, respectively. When isobologram transformations of multiple dose-response analyses were performed to detect in vitro synergy, we concluded that the nature of the interaction between cerulenin and 5-FU in individual breast cancer cells lines generally exhibited sequence-dependency. Thus, while synergism was mainly observed when breast cancer cells were exposed to 5-FU prior to cerulenin, moderate synergism or additive interactions was obtained either when the chemical FASN blocker preceded 5-FU or when both drugs were concurrently administered. Of note, no antagonist interactions occurred upon any schedule of combined treatment with cerulenin and 5-FU. Our current findings revealing a schedule-dependent synergistic interaction between 5-FU and cerulenin represents, to the best of our knowledge, the first evidence that FASN-catalyzed de novo FA biogenesis plays a key role in regulating breast cancer cell response to antimetabolite-based therapies.
authors.affiliation: Catalan Institute of Oncology-Health Services Division of Catalonia, 17007 Girona, Catalonia, Spain.
authors.forename: Alejando
authors.initials: A
authors.lastname: Vazquez-Martin
authors.forename: Santiago
authors.initials: S
authors.lastname: Ropero
authors.forename: Joan
authors.initials: J
authors.lastname: Brunet
authors.forename: Ramon
authors.initials: R
authors.lastname: Colomer
authors.forename: Javier A
authors.initials: JA
authors.lastname: Menendez
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects*; D002569:Cerulenin / Q000494:pharmacology*; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D054890:Fatty Acid Synthase, Type I / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D014407:Tumor Cells, Cultured / Q000187:drug effects