SMAD2 and clear cell renal carcinoma: This hypothesis is supported by the recent finding that clear cell renal cell carcinoma exosomes [145], as well as pancreatic cancer exosomes [123], interact with TGFβ receptors on human PBMCs-derived NK cells and human NK-92 cell line, respectively, activate the TGFβ-Smad2/3 pathway and, consequently, induce the phosphorylation Smad2/3, suppressing the activation of NK cells.