Data of patients and samples from TCGA

RNA expression data (level 3) were downloaded from The Cancer Genome Atlas (TCGA; https://cancergenome.nih.gov) database, which provides normalized data by the RNASeq v2 system. The exclusion criteria were as follows: i) histological diagnosis revealed that the tissue was not CRC; ii) patients suffered malignancies other than CRC; iii) samples without enough data for analysis; and iv) patients that have received preoperative radiotherapy and chemotherapy. Subsequently, a total of 337 tumor tissues were used in the study.