CR1 and esophageal squamous cell carcinoma: We first examined the expression of CR-1 in two human ESCC cell lines EC109 and TE-1, and found that both of the two cell lines expressed CR-1 at mRNA and protein levels, and the expression level of EC109 cells was approximately 2 ~ 3 fold higher than that of TE-1 cells (Additional file 1: Figure S1A and S1B).