PDIA4 and cancer: Since DNA methylation is usually associated with downregulation of gene expression and directly affects the occurrence and progression of cancers (34), we then evaluated the methylation profiles of PDIA5 and other PDI family members (e.g., P4HB, PDIA2, PDIA3, PDIA4, and PDIA6) in human cancers from the TCGA dataset by using the GSCALite platform.