SMAD3 and cancer: Previous study has demonstrated that RTKs could promote cell proliferation via phosphatidylinositol 3‐kinase/protein kinase B (PI3K/AKT) and mitogen activated protein kinase (MAPK) pathway,[15] and TGF‐β signaling pathway could promote cancer invasion via inducing Smad3 phosphorylation and subsequently epithelial‐mesenchymal transition (EMT).[16] In accordance with these studies, we found that HITTERS knockdown significantly decreased phosphorylation of AKT, ERK1/2, and Smad3 (Figure S3E, Supporting Information).