Leukotriene D4 (LTD4) is a cysteinyl leukotriene. Cysteinyl leukotrienes (CysLTs) are a family of potent inflammatory mediators that appear to contribute to the pathophysiologic features of allergic rhinitis. LTD4 is a pro-inflammatory mediator known to mediate its effects through specific cell-surface receptors belonging to the G-protein-coupled receptor family, namely the high-affinity CysLT1 (cysteinyl leukotriene 1) receptor. LTD4 is present at high levels in many inflammatory conditions, and areas of chronic inflammation have an increased risk for subsequent cancer development. LTD4 is associated with the pathogenesis of several inflammatory disorders, such as asthma and inflammatory bowel disease. Exposure to LTD4 increases survival and proliferation in intestinal epithelial cells. CysLT1 regulator is up-regulated in colon cancer tissue and LTD4 signalling facilitates the survival of cancer cells. LTD4 could reduce apoptosis in non-transformed epithelial cells. LTD4 causes up-regulation of beta-catenin through the CysLT1 receptor, PI3K (phosphoinositide 3-kinase), and GSK-3β (glycogen synthase kinase 3β). LTD4 induces beta-catenin translocation to the nucleus and activation of TCF/LEF family of transcription factors. LTD4 causes accumulation of free beta-catenin in non-transformed intestinal epithelial cells through the CysLT1 receptor, and this accumulation is dependent upon the activation of PI3K as well as GSK-3β inactivation (PMID: 16042577, 12607939). Leukotrienes are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent and are able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis through receptor-mediated G-protein linked signaling pathways.