Role of indoleamine 2,3-Dioxygenase 1 in modulating the malignant biological behavior of cervical cancer cells through the Tryptophan-Kynurenine pathway.

Objective: The aim of this study is to evaluate the influence of altered expression of indoleamine 2,3-dioxygenase 1 (IDO1) on key enzymes and metabolites within the tryptophan-kynurenine pathway, as well as to assess the resulting effects on the malignant biological behavior of cervical cancer cells, including proliferation, invasion and migration.

Methods: IDO1 expression was assessed in cervical cancer and normal cervical tissues via immunohistochemistry and western blot (WB) analysis. Four human cervical cancer cell lines (HeLa, C33A, SiHa, CaSki) were cultured, and HeLa and SiHa cells-characterized by elevated IDO1 expression-were selected for further experimentation. IDO1 was silenced using RNA interference techniques. Quantitative real-time polymerase chain reaction and WB were used to detect the messenger RNA and protein expression levels of IDO2, tryptophan 2,3-dioxygenase (TDO), kynurenine 3-monooxygenase (KMO), and aryl hydrocarbon receptor (AhR). Targeted metabolomics analysis based on liquid chromatography-tandem mass spectrometry was conducted to quantify tryptophan, N-formylkynurenine (NFK), and L-kynurenine (L-KYN) in cell culture supernatants. Cell proliferation, apoptosis, and migratory capacity were evaluated via flow cytometry and scratch assays.

Results: IDO1 expression was significantly elevated in cervical cancer tissues compared to normal cervical tissues, with the highest levels observed in samples positive for human papillomavirus types 16 or 18. Silencing of IDO1 in cervical cancer cells resulted in downregulation of IDO2, TDO, KMO, and AHR expression. Correspondingly, reduced metabolic activity in the tryptophan-kynurenine pathway was observed, evidenced by decreased levels of NFK and L-KYN. These molecular alterations were associated with G1 phase cell cycle arrest, diminished cellular proliferation, migration and invasion, and increased apoptotic activity.

Conclusion: IDO1 mediates the malignant biological behavior of cervical cancer cells through the tryptophan-kynurenine pathway, suggesting its potential as a therapeutic target in cervical malignancies.