SMAD2 and breast cancer: For example, GCs induce the production of reactive oxygen species/reactive nitrogen species and DNA damage through an iNOS‐mediated pathway in breast cancer.[56] As for MSC‐Exos, it has been reported that thrombospondin 1 on Exos activates TGFβ, and inhibits the proliferation, activation, and cytotoxicity of NK cells through the TGFβ/Smad2/3 signaling.[43] Additionally, MSC‐EXOs were found to modulate macrophage phenotype to regulate inflammatory microenvironment.