TGFB1 and cancer: Because it is unclear whether the platelet-derived fraction is relevant for cancer biology, we developed a statistical model to assess both the component of TGF-β1 and VEGF associated with platelet degranulation (captured by PF4) and the remaining component unrelated to platelets (estimated using the residuals from the linear regression models of TGF-β1 and VEGF on PF4).