MICA and neoplasm: The intrinsic features endow tumor cells with distinct metastatic potential through epigenetic and genetic alterations, including the downregulation of NK cell activating receptor ligands due to, for example, the reduction in the expression levels of MHC-I polypeptide-related sequence A (MICA)/MICB and UL16-binding protein 2 (ULBP2) caused by the aberrant expression of oncogenic microRNA, miR-20a, and miR-34a/c in tumor cells [76,77].