The genomic DNA of toll-like receptor (TLR) 2, TLR4, radioprotective 105, TLR6, and TLR9 were examined for mutations in 48 patients with gastric cancer. Of these, 22 had well-differentiated and 20 had poorly-differentiated adenocarcinomas, the latter group including 10 with signet ring cell carcinomas. The remaining 6 had gastric adenomas. Ten healthy volunteers with no family history of malignant diseases served as controls. DNA was extracted from peripheral blood and subjected to electrophoresis using PCR oligonucleotide primers. The resultant gel was analyzed with a DNA sequencer. None of the healthy volunteers, patients with gastric adenomas or those with well-differentiated gastric adenocarcinomas showed mutations. However, 8 of the 20 with poorly-differentiated gastric adenocarcinoma showed heterozygosity at the 135th position of the amino acid sequence of TLR4, and a mutation from threonine to alanine was found at this site. Analysis of the entire available amino acid sequence of TLR4 revealed that this mutation occurred at a leucine-rich repeat corresponding to one of its extracellular components. This suggests a disturbance in the protein phosphorylation reaction of TLR4, and that this disturbance is related to the development of poorly-differentiated gastric adenocarcinomas.

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