DPP4 and hepatocellular carcinoma: In combination with the expression data of these genes in a larger cohort of HCC samples from The Cancer Genome Atlas (TCGA) and RNA-seq data (Additional files 5: Fig. S3), we further narrowed down Snail-regulated genes by excluding COL1A1, COLEC11, CXCL12, and MBL2, and found that DPP4, PDGFB and CSPP1 might be candidate genes involved in snail-mediated immunosuppression (Fig. 5e), which was further tested by the dual-luciferase reporter assay.