UBE2E3 and liver cancer: In addition, the interaction between the beta‐transducin repeat‐containing E3 ubiquitin protein ligase (βTrCP) and the SMAD‐specific E3 ubiquitin protein ligase 1 through the WD40‐repeat domains [7 × tryptophan (W) aspartic acid (D)] of βTrCP is relatively resistant to the proliferative capacity of liver cancer cells and may be useful for oncotherapy in patients with liver cancer.39