DNA Methylation and Gene Expression of the Cysteinyl Leukotriene Receptors as a Prognostic and Metastatic Factor for Colorectal Cancer Patients.

Colorectal cancer (CRC), one of the leading causes of cancer-related deaths in the western world, is the third most common cancer for both men and women. As a heterogeneous disease, colon cancer (CC) is caused by both genetic and epigenetic changes. The prognosis for CRC is affected by a variety of features, including late diagnosis, lymph node and distant metastasis. The cysteinyl leukotrienes (CysLT), as leukotriene D and C (LTD and LTC), are synthesized from arachidonic acid via the 5-lipoxygenase pathway, and play an important role in several types of diseases such as inflammation and cancer. Their effects are mediated via the two main G-protein-coupled receptors, CysLTR and CysLTR. Multiple studies from our group observed a significant increase in CysLTR expression in the poor prognosis group, whereas CysLTR expression was higher in the good prognosis group of CRC patients. Here, we systematically explored and established the role of the CysLTRs, cysteinyl leukotriene receptor 1( and cysteinyl leukotriene receptor 2 ( gene expression and methylation in the progression and metastasis of CRC using three unique in silico cohorts and one clinical CRC cohort. Primary tumor tissues showed significant upregulation compared with matched normal tissues, whereas it was the opposite for the . Univariate Cox proportional-hazards (CoxPH) analysis yielded a high expression of and accurately predicted high-risk patients in terms of overall survival (OS; hazard ratio (HR) = 1.87, = 0.03) and disease-free survival [DFS] Hazard ratio [HR] = 1.54, = 0.05). Hypomethylation of the gene and hypermethylation of the gene were found in CRC patients. The M values of the CpG probes for are significantly lower in primary tumor and metastasis samples than in matched normal samples, but those for are significantly higher. The differentially upregulated genes between tumor and metastatic samples were uniformly expressed in the high- group. Two epithelial-mesenchymal transition (EMT) markers, E-cadherin () and vimentin () were significantly downregulated and upregulated in the high- group, respectively, but the result was opposite to that of expression in CRC. expression was high in patients with less methylated but low in those with more methylated . The EMT-associated observations were also validated in CC SW620 cell-derived colonospheres, which showed decreased E-cadherin expression in the LTD stimulated cells, but not in the CysLTR knockdown SW620 cells. The methylation profiles of the CpG probes for CysLTRs significantly predicted lymph node (area under the curve [AUC] = 0.76, < 0.0001) and distant (AUC = 0.83, < 0.0001) metastasis. Intriguingly, the CpG probes cg26848126 (HR = 1.51, = 0.03) for , and cg16299590 (HR = 2.14, = 0.03) for significantly predicted poor prognosis in terms of OS, whereas the CpG probe cg16886259 for significantly predicts a poor prognosis group in terms of DFS (HR = 2.88, = 0.03). The and gene expression and methylation results were successfully validated in a CC patient cohort. In this study, we have demonstrated that CysLTRs' methylation and gene expression profile are associated with the progression, prognosis, and metastasis of CRC, which might be used for the assessment of high-risk CRC patients after validating the result in a larger CRC cohort.