The anti-tumorigenic properties of peroxisomal proliferator-activated receptor alpha are arachidonic acid epoxygenase-mediated.

Prevalence and mortality make cancer a health challenge in need of effective and better tolerated therapeutic approaches, with tumor angiogenesis identified as a promising target for drug development. The epoxygenase products, the epoxyeicosatrienoic acids, are pro-angiogenic, and down-regulation of their biosynthesis by peroxisomal proliferator-activated receptor alpha (PPARalpha) ligands reduces tumor angiogenesis and growth. Endothelial cells lacking a Cyp2c44 epoxygenase, a PPARalpha target, show reduced proliferative and tubulogenic activities that are reversed by the enzyme's metabolites. In a mouse xenograft model of tumorigenesis, disruption of the host Cyp2c44 gene causes marked reductions in tumor volume, mass, and vascularization. The relevance of these studies to human cancer is indicated by the demonstration that: (a) activation of human PPARalpha down-regulates endothelial cell CYP2C9 epoxygenase expression and blunts proliferation and tubulogenesis, (b) in a PPARalpha-humanized mouse model, activation of the receptor inhibits tumor angiogenesis and growth, and (c) the CYP2C9 epoxygenase is expressed in the vasculature of human tumors. The identification of anti-angiogenic/anti-tumorigenic properties of PPARalpha points to a role for the receptor and its epoxygenase regulatory target in the pathophysiology of cancer, and for its ligands as candidates for the development of a new generation of safer and better tolerated anti-cancer drugs.

Spatial and temporal alterations of phospholipids determined by mass spectrometry during mouse embryo implantation.

Molecular events involved in successful embryo implantation are not well understood. In this study, we used MALDI imaging mass spectrometry (IMS) technologies to characterize the spatial and temporal distribution of phospholipid species associated with mouse embryo implantation. Molecular images showing phospholipid distribution within implantation sites changed markedly between distinct cellular areas during days 4-8 of pregnancy. For example, by day 8, linoleate- and docosahexaenoate-containing phospholipids localized to regions destined to undergo cell death, whereas oleate-containing phospholipids localized to angiogenic regions. Arachidonate-containing phospholipids showed different segregation patterns depending on the lipid class, revealing a strong correlation of phosphatidylethanolamines and phosphatidylinositols with cytosolic phospholipase A(2alpha) and cyclooxygenase-2 during embryo implantation. LC-ESI-MS/MS was used to validate MALDI IMS phospholipid distribution patterns. Overall, molecular images revealed the dynamic complexity of lipid distributions in early pregnancy, signifying the importance of complex interplay of lipid molecules in uterine biology and implantation.

Solvent-free matrix dry-coating for MALDI imaging of phospholipids.

A fast and simple, solvent-free matrix deposition protocol was developed for positive ionization mode phospholipid analysis in tissues. Finely ground 2,5-dihydroxybenzoic acid was deposited onto sagittal mouse brain sections using a dry-coating technique, in which solid matrix particles were filtered directly onto the tissue through a 20-microm stainless steel sieve. Phospholipid signals were obtained directly off these sections, allowing acquisition of high-resolution MS images. These images were compared to those from serial sections that were spray-coated with a thin-layer chromatography (TLC) reagent sprayer. Signals obtained from the dry matrix deposition method were comparable to those from spray-coated sections, producing identical localization patterns with a simpler and faster sample preparation with virtually no analyte delocalization. This approach was found to yield highly reproducible results, eliminating much of the variance caused by operator differences, and making it an attractive alternative to the currently used matrix application methods.