IL15 and neoplasm: TGF-β exerts its effects largely via the SMAD signalling pathway and the regulation of gene expression [22], [24], [25]; TGF-β treatment of IL-15 stimulated NK cells for 48 hours mimicked the results of the tumour cell-NK cell co-cultures by reducing the cell surface expression of NKp30, NKG2D and DNAM-1, but not NKp46 (Figure 2A).