S100A8 and esophageal squamous cell carcinoma: Among the genes upregulated in co-cultured ESCC cells, we reported that S100 calcium-binding proteins A8 and A9 (S100A8/A9), interleukin-7 receptor (IL-7R), and matrix metalloproteinase 9 (MMP9) are involved in tumor progression and poor prognosis [20,21,22].