leukotriene-d4 and Adenocarcinoma

The abnormal activation of the Wnt/β-catenin pathway frequently occurs in colorectal cancer. The nuclear translocation of β-catenin activates the transcription of target genes that promote cell proliferation, survival, and invasion. The pro-inflammatory mediator leukotriene D4 (LTD4) exerts its effects through the CysLT1 receptor. We previously reported an upregulation of CysLT1R in patients with colon cancer, suggesting the importance of leukotrienes in colon cancer. The aim of this study was to investigate the impact of LTD4 on Wnt/β-catenin signaling and its effects on proliferation and migration of colon cancer cells. LTD4 stimulation led to an increase in β-catenin expression, β-catenin nuclear translocation and the subsequent transcription of MYC and CCND1. Furthermore, LTD4 significantly reduced the expression of E-cadherin and β-catenin at the plasma membrane and increased the migration and proliferation of HCT116 colon cancer cells. The effects of LTD4 can be blocked by the inhibition of CysLT1R. Furthermore, LTD4 induced the inhibition of glycogen synthase kinase 3 (GSK)-3β activity, indicating a crosstalk between the G-protein-coupled receptor CysLT1 and the Wnt/β-catenin pathway. In conclusion, LTD4, which can be secreted from macrophages and leukocytes in the tumor microenvironment, induces β-catenin translocation and the activation of β-catenin target genes, resulting in the increased proliferation and migration of colon cancer cells.

Topics: Adenocarcinoma; beta Catenin; Cell Movement; Colonic Neoplasms; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; HCT116 Cells; HT29 Cells; Humans; Inflammation Mediators; Leukotriene D4; Phosphorylation; Protein Transport; Subcellular Fractions

Searching for a link between inflammation and colon cancer, we have found that the inflammatory mediator leukotriene D(4) (LTD(4)), via its receptor CysLT(1), induces cyclooxygenase-2 expression, survival, and proliferation in intestinal epithelial cells. In conjunction with our previous observation that CysLT(1) receptor expression is increased in colorectal adenocarcinomas, we here found an increased nuclear localization of the CysLT(1) receptor in colorectal adenocarcinomas. This novel discovery of CysLT(1) receptors in the nucleus was further analyzed. It was found to be located in the outer nuclear membrane in colon cancer cells and in the nontransformed epithelial cell line Int 407 cells by Western blot and electron microscopy. Cancer cells displayed higher amounts of the nuclear CysLT(1) receptor, but prolonged LTD(4) exposure induced its nuclear translocation in nontransformed cells. Truncation of a nuclear localization sequence abrogated this translocation as well as the LTD(4)-induced proliferative response. In accordance, nuclear CysLT(1) receptors exhibited proliferative extracellular signal-regulated kinase 1/2 signaling. The significance of these experimental findings is supported by the observed correlation between the proliferative marker Ki-67 and nuclear CysLT(1) receptor localization in colorectal adenocarcinomas. The present findings indicate that LTD(4) cannot only be synthesized but also signal proliferation through nuclear CysLT(1) receptors, stressing the importance of leukotrienes in inflammation-induced colon carcinogenesis.

Topics: Adenocarcinoma; Amino Acid Sequence; Arachidonate 5-Lipoxygenase; Caco-2 Cells; Cell Line, Tumor; Cell Membrane; Cell Nucleus; Colorectal Neoplasms; Epithelial Cells; Gene Expression Regulation, Neoplastic; Humans; Leukotriene D4; Membrane Proteins; Molecular Sequence Data; Nuclear Localization Signals; Receptors, Leukotriene; Up-Regulation