FADS2 Function Loss at the Cancer Hotspot 11q13 Locus Diverts Lipid Signaling Precursor Synthesis to Unusual Eicosanoid Fatty Acids Woo Jung Park, Kumar S. D. Kothapalli*, Peter Lawrence, J. Thomas Brenna* Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America Abstract Background: Genes coding for the fatty acid desaturases (FADS1, 2, 3) localized at the cancer genomic hotspot 11q13 locus are required for the biosynthesis of 20 carbon polyunsaturated fatty acids (PUFA) that are direct eicosanoid precursors. In several cancer cell lines, FADS2 encoded D6 and D8 desaturation is not functional. Methodology/Principal Findings: Analyzing MCF7 cell fatty acids with detailed structural mass spectrometry, we show that in the absence of FADS2 activity, the FADS1 product D5-desaturase operates to produce 5,11,14–20:3 and 5,11,14,17–20:4. These PUFA are missing the 8–9 double bond of the eicosanoid signaling precursors arachidonic acid (5,8,11,14–20:4) and eicosapentaenoic acid (5,8,11,14,17–20:5). Heterologous expression of FADS2 restores D6 and D8-desaturase activity and normal eicosanoid precursor synthesis. Conclusions/Significance: The loss of FADS2-encoded activities in cancer cells shuts down normal PUFA biosynthesis, deleting the endogenous supply of eicosanoid and downstream docosanoid precursors, and replacing them with unusual butylene-interrupted fatty acids. If recapitulated in vivo, the normal eicosanoid and docosanoid cell signaling milieu would be depleted and altered due to reduction and substitution of normal substrates with unusual substrates, with unpredictable consequences for cellular communication. Citation: Park WJ, Kothapalli KSD, Lawrence P, Brenna JT (2011) FADS2 Function Loss at the Cancer Hotspot 11q13 Locus Diverts Lipid Signaling Precursor Synthesis to Unusual Eicosanoid Fatty Acids. PLoS ONE 6(11): e28186. doi:10.1371/journal.pone.0028186 Editor: Daniel Tome´, Paris Institute of Technology for Life, Food and Environmental Sciences, France Received September 16, 2011; Accepted November 2, 2011; Published November 30, 2011 Copyright: 2011 Park et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: These authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. * E-mail: ksk25@cornell.edu (KSDK); jtb4@cornell.edu (JTB) Introduction Several human cytogenetic and fine mapping studies have pin- pointed HSA 11q13 locus as a major hotspot for a number of human cancers [1,2,3,4,5]. Numerous genetic mechanisms have been reported, including 11q13 deletions, loss of heterozygosity, translocations and allelic amplification [3,5]. The fatty acid desaturase cluster (FADS), encoded by genes FADS1, FADS2, and FADS3, localize within a 100 kb region on human chromosome 11q12–13.1 [6,7]. FADS2 and FADS1 encode for critical enzymes for long chain polyunsaturated fatty acid (LCPUFA) biosynthesis, introducing double bonds between specific carbon atoms. Omega-3 (v3 or n23) and omega-6 (v6 or n26) PUFA are key nutrients linked to most of the diseases of humans, specifically cardiovascular (CVD), cancer, diabetes and metabolic syndrome, and are key structural components of neural tissue [8,9]. The LCPUFA DGLA (20:3n26), ARA (20:4n26), EPA (20:5n23) and DHA (22:6n23) are precursors for cell signaling eicosanoids and their modification by biosynthetic inhibition of downstream metabolism are very valuable drug targets, for instance, cyclooxygenase and lipoxygenase inhibitors, and more recently docosanoids that are candidate drugs [10]. The FADS2 encoded D6-desaturase catalyzes the first and rate- limiting step in the biosynthesis of LCPUFA. In several cancer cells desaturation does not occur, which may be due to inactivation of the desaturase or of upstream (e.g. CoA production) or downstream (e.g. acyl transferase) steps. The reason for this defect has been suggested to be due to extensive chromosomal deletions, but no molecular evidence is available [11,12]. The D8- desaturation substrates 20:2n26 and 20:3n23 are often detected, thus suggesting that the elongation step is functional [12,13]. Until recently, the D8-desaturation substrates 20:2n26 and 20:3n23 were widely considered dead-end products, even though they are found in human plasma and red cells as well as other tissues. We showed the first molecular evidence that FADS2 catalyzes D8- desaturation for both of these substrates, representing an alternative route to LCPUFA biosynthesis in mammals where they are converted to eicosanoid precursor LCPUFA [14]. This pathway may be available when D6-desaturase activity is compromised. The unusual loss of PUFA desaturase activity in several cancer cells prompted us to hypothesize that the primary defect resides in the desaturase itself, and not elsewhere such as in the activation of PUFA by CoA synthesis or synthesis of phospho- glycerides as acceptors of nascent LCPUFA. We confirmed that human breast cancer MCF7 cells do not possess any capacity for biosynthesis of LCPUFA because of absence of D6-desaturase activity [12]. Here we show the restoration of this metabolic PLoS ONE | www.plosone.org 1 November 2011 | Volume 6 | Issue 11 | e28186