TDO2 and neoplasm: Meanwhile, a higher tumorigenic rate of TDO2 overexpression SMC-7721 cells was found in immunodeficient mice (Fig. 1F), and TDO2 overexpression SMC-7721 revealed strengthened cell proliferation capability (Fig. 1G) and rapid tumor growth in vivo (Fig. 1H), when compared to the SMC-7721 vector group.