PPIB and breast cancer: In MDA-MB-231 and MCF-7 breast cancer model calcitriol supports NK cells to fight against breast cancer cells partly by reducing miR-302c and miR-520c expression in breast cancer cells and consequently upregulating the activating receptor natural killer group 2, member D (NKG2D) ligands, major histocompatibility complex class I chain-related proteins A and B (MICA/B), and unique long UL16-binding protein 2 (ULBP2) [281].