Arachidonic acid and its metabolites in breast cancer: a transcriptomic approach to elucidate their biological significance

ANA FERNANDA CASTILLO; ULISES ORLANDO; MELINA A. DATTILO; CECILIA PODEROSO; ANGELA SOLANO; PAULA MALOBERTI; ERNESTO J. PODESTA

Busan

Congreso; 45th World Chemistry Congress; 2015

IUPAC

Arachidonic acid (AA, (5Z,8Z,11Z,14Z)-5,8,11,14-Eicosatetraenoic acid) is a polyunsaturated omega-6 fatty acid 20:4(ω-6) which represents one of the major polyunsaturated fatty acid in the mammalian cell membranes. It is the precursor of the eicosanoids, an important group of biologically active compounds. AA can be enzymatically metabolized by three main enzymatic activities: lipoxygenases (LOXs), cyclooxygenases (COXs) and epoxygenase-cytochrome P450. AA and its eicosanoid metabolites play critical role in the development and progression of breast cancer (1). The compartmentalization of AA has been proposed as a mechanism to control its levels and metabolism by LOX and COX-2 (1, 2). We have described a mechanism which regulates AA levels in mitochondria. The key enzyme in this mechanism is acyl-CoA synthetase 4 (ACSL4), which has high specificity for AA esterification to produce araquidonoil-CoA (AA-CoA). AA-CoA is substrate of an acyl-CoA thioesterase, generating intramitochondrial AA for the eicosanoids production (3). ACSL4 is increased in breast cancer, colon and hepatocellular carcinoma. We have demonstrated a positive correlation of ACSL4 expression and aggressiveness in breast cancer cells, both in vitro and in vivo. The sole transfection of MCF-7 cells, a model of non-aggressive breast cancer cells, with ACSL4 cDNA transforms them into a highly aggressive phenotype (1, 2). The mechanism involved in this effect has yet to be fully elucidated. The goal of this work was to study the molecular networks triggered by ACSL4 overexpression which mediate increased aggressiveness that could be considered as potential targets in therapeutic strategies.RNA-sequencing (RNA-Seq) analysis was performed to compare the transcriptome of control (MCF-7 Tet-Off) and ACSL4-overexpressing (MCF-7 Tet-Off/ACSL4) human breast cancer cell lines. Real-time RT-PCR was used to further validate the gene-expression changes found. From 32247 successfully sequenced loci, 3944 were significantly and differentially expressed in MCF-7 Tet-Off/ACSL4 samples. Among them, 2501 were up-regulated, and 1443 were down-regulated. Bioinformatics analysis using IPA (Ingenuity Pathway Analysis) revealed altered regulation in key pathways implicated in cancer-related biofunctions such as increased cell movement, migration and proliferation. Enriched canonical pathways analysis revealed that the mTOR and the signaling of molecular mechanisms of cancer were among the top canonical pathways triggered by ACSL4 with the lowest p-values. Furthermore, IPA revealed that the transcriptomic profiles were also consistent with some chemical compounds effects that partially mimic ACSL4 signature.We have demonstrated that inhibition of ACSL4 activity with Rosiglitazone, a drug belonging to the thiazolidinedione family, in combination with 5-LOX and COX-2 inhibitors reduced tumor growth in doses that were ineffective when used alone (2). Here, the identification of specific ACSL4-altered pathways can lead to the discovery of new therapeutic targets to be use in combination with Rosiglitazone. Moreover, it will promote the design of compounds with dual activity, in order to improve the management of a significant proportion of cancer patients.