KLRK1 and neoplasm: Importantly, IL-21 delivery modified the levels of IFN-γ and tumor necrosis factor-alpha (TNF-α) in the mouse serum, augmented natural Killer group 2D (NKG2D) and MHC class I polypeptide-related sequence A (MICA) molecule expressions in the tumor tissues, and finally downregulated β-catenin and cyclin-D1 in the tumor, which in turn, led to delayed tumor growth posttransplantation (Zhang et al., 2014).