Abstract
PURPOSE: Tryptophan 2,3-dioxygenase (TDO), encoded by the gene TDO2, is an enzyme that catalyses the first and rate-limiting step of tryptophan (Try) degradation in the kynurenine (Kyn) pathway in the liver. Recently, TDO has been demonstrated to be expressed in various human tumours, especially hepatocellular carcinoma (HCC). However, the role of TDO in HCC is still not very clear. Here, we studied the role of TDO in HCC. METHODS: We demonstrated that TDO is overexpressed in human HCC tissues and is significantly correlated with malignant phenotype characteristics, including tumour size, tumour differentiation, vascular invasion, etc. Kaplan-Meier analysis showed a poor overall survival rate in patients with TDO-overexpressing tumours. In addition, the effects of TDO on HCC tumour growth and metastasis were detected both in vivo and in vitro. TDO overexpression facilitated HCC cell growth, invasion and migration. CONCLUSION: Our results suggest that TDO positively regulates HCC proliferation and invasion and acts as a new prognostic biomarker of HCC.