CXCL8 and esophageal squamous cell carcinoma: Through the use of an in vitro indirect co-culture system between ESCC cell lines and macrophages derived from peripheral blood monocytes (PBMos), we identified several factors that mediate their interaction, including growth differentiation factor (GDF) 15 [7], interleukin (IL)-8 [8], C-C motif chemokine ligand (CCL) 1 [9], and CCL3 [10].