TDO2 and lung adenocarcinoma: In addition, we performed a comprehensive analysis of the five prognostic characteristics to determine their correlations with prognosis, clinical features, immunity, and metabolism, and finally, we performed a series of experimental validation of PTTG1, demonstrating that knockdown of PTTG1 reduced the proliferation and migration ability of lung adenocarcinoma cells while increasing apoptosis, and found that the transcription of the key enzyme of tryptophan metabolism, TDO2, was down-regulation after PTTG1 down-regulation (Figure 1).