title: Increased NFk-B activity in HCT116 colorectal cancer cell line harboring TLR4 Asp299Gly variant.
abstract: Toll-Like Receptor 4 (TLR4), considered one of the most important TLR, recognizes lipopolysaccharide of Gram-negative bacteria.  Recognition of ligands by TLRs induces signaling pathways resulting in activation of transcriptional factors such as NF-κB which are involved in the expression of inflammatory cytokines and chemokines. To prevent an inappropriate immune response, a complex network of molecules negatively regulates TLRs and their associated signaling pathways. Two cosegregating single nucleotide polymorphisms of the human TLR4 gene, namely Asp299Gly and Thr399Ile, have been associated with hyporesponsiveness to inhaled LPS.  The purpose of this study was to determine the impact of TLR4 gene variant on NF-κB activity in colorectal cancer cell line. HCT116 cells were transfected with wild-type and mutants Flag-CMV1-TLR4 expression vectors. Western blot analysis was performed to evaluate selected molecules involved in TLR4 signaling.  NF-κB activity was assessed by dual-luciferase reporter assay and cytokine profiles were evaluated byELISA  and Cytometric Bead Array method. Results showed that the activity of pNF-κB was higher in cells harboring TLR4 D299G compared to the other cells. However, the activity of pAKT, pERK1 and pIRAK was higher in wild-type. The results of cytokine measurements showed about four fold higher level of IL-8 in cells with wild-type TLR4. This study suggest that TLR4 Asp299Gly gene variant has an impact on TLR4 signaling and potentially on intestinal homeostasis due to impaired control signals at the epithelial cell level which may lead to chronic intestinal inﬂammation and interrupted intestinal homeostasis and may eventually lead to colorectal cancer.
authors: Golestan University of Medical Sciences, Gorgan, Iran.
authors: Homa
authors: H
authors: Davoodi
authors: Seyed Reza
authors: SR
authors: Hashemi
authors: Heng Fong
authors: HF
authors: Seow
mesh_terms: D001224:Aspartic Acid; D015153:Blotting, Western; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D017930:Genes, Reporter; D005998:Glycine; D045325:HCT116 Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D053592:Interleukin-1 Receptor-Associated Kinases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D020641:Polymorphism, Single Nucleotide; D020033:Protein Isoforms; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation
chemical_list: D016207:Cytokines; D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D020033:Protein Isoforms; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D001224:Aspartic Acid; D008156:Luciferases; D053592:Interleukin-1 Receptor-Associated Kinases; D051057:Proto-Oncogene Proteins c-akt; D048052:Mitogen-Activated Protein Kinase 3; D005998:Glycine