HCP5 and cancer: Histocompatibility leukocyte antigen complex P5 (HCP5) is a momentous lncRNA located between MHC class I polypeptide related sequence A (MICA) and MHC class I polypeptide related sequence B (MICB) genes in the MHC class I chain-related gene (MHCI) region, involving many autoimmune diseases and malignant tumors (25).