S100A8/A9 induced by interaction with macrophages in esophageal squamous cell carcinoma promotes the migration and invasion of cancer cells via Akt and p38 MAPK pathways

Tumor-associated macrophages enhance the malignant phenotypes of esophageal squamous cell carcinoma (ESCC) cells. We have previously identified several factors associated with ESCC progression using an indirect co-culture assay between ESCC cells and macrophages. Here, we newly established a direct co-culture assay between ESCC cells and macrophages which is closer to the actual cancer microenvironment than an indirect co-culture assay. To investigate the gene expression changes by co-culture with macrophages, we performed cDNA microarray analysis between mono-cultured and co-cultured ESCC cells with macrophages. We found that the expression of S100 calcium binding protein A8 and A9 (S100A8 and S100A9) was enhanced in co-cultured ESCC cells with macrophages. S100A8 and S100A9 commonly exist stable and function as a heterodimer (S100A8/A9). S100A8/A9 is widely known as an inflammation marker. It also contributes to the enhancement of malignant phenotypes in several cancers. S100A8/A9 enhances the migration and invasion of ESCC cells by activating Akt and p38 MAPK signaling pathways. The higher expression levels of S100A8/A9 were associated with poor prognosis in ESCC patients. These results suggest that S100A8/A9 contributes to the progression of ESCC. CD14 positive peripheral blood monocytes (PBMos) were selectively collected from healthy volunteers. Recombinant human macrophage colony stimulating factor (rhM-CSF) was added to induce M2 macrophages. We seeded ESCC cell line (TE-11) and direct co-cultured with the M2 macrophages. As a control, the same amount of TE-11 without macrophage was seeded and mono-cultured. We performed cDNA microarray analysis between mono-cultured TE-11 cells and co-cultured TE-11 cells with macrophages.