In support of our findings, it has been documented that Smad3 and Smad4, but not Smad2, are required for transcriptional regulation of several TGF‐β target genes, such as plasminogen activator inhibitor‐type 1,60 Smad7,61 collagen type VII α1 chain,62 inhibitor of DNA binding 1,63 tenascin‐C,64 and selenoprotein P.65In addition, although a recent study documented that PSG1 expression correlates with the expression of TGF‐β in cervical cancer tissues,66 no information is currently available about whether PSG9 induces secretion and activation of TGF‐β1 in human cancer cells. Here, ID1 is linked to cancer.