In situ expression of the CCL20-CCR6 axis in lymphocyte-rich gastric cancer and its potential role in the formation of lymphoid stroma.

Lymphocyte-rich gastric cancer (Ly-rich GC) is characterized by lymphoid stroma. To understand its formation, we studied the expression of a chemokine ligand (CCL)20 and its receptor CCR6 in 36 and 37 cases of Ly-rich- and conventional GC, respectively. Lymphoid tissues in the alimentary tract were studied in parallel. By quantitative polymerase chain reaction, Ly-rich GC contained CCL20 and CCR6 mRNAs at higher levels than conventional GC. By immunohistochemistry, CCL20 was expressed by cancer cells more frequently in Ly-rich GC than in conventional GC. This was comparable with its expression in epithelial cells of the alimentary tract lymphoid tissues. CCR6 was mostly expressed by dendritic cells (DC) and B cells in Ly-rich GC, which was also comparable with its expression in the alimentary tract lymphoid tissues. Cancer cells also expressed CCR6. However, its expression did not differ between Ly-rich- and conventional GC, nor was it related to the stage of cancer. Given that the CCL20-CCR6 axis is involved in the formation of alimentary tract lymphoid tissue, the similarity between the lymphoid stroma of Ly-rich GC and the alimentary tract lymphoid tissues supports the notion that it plays a significant role in the formation of lymphoid stroma in Ly-rich GC.