Analysis of Kynurenine/Tryptophan ratio and expression of IDO1 and 2 mRNA in tumour tissue of cervical cancer patients

• IDO1 expression is elevated in cervical cancer patients' tumour tissue.
• K/T ratio is greater than 1 in the tumour tissue, and is significantly correlated with IDO1 levels.
• IDO1 and not IDO2 may play an important role in tryptophan catabolism and cervical tumourigenesis.

ObjectivesIndoleamine 2,3-Dioxygenase (IDO) catalyses the degradation of the essential amino acid tryptophan leading to the production of immunosuppressive Kynurenine. In the present study, we developed a modified method for measurement of Kynurenine/tryptophan (K/T) ratio in the cervical tissue using HPLC and investigated its relationship with the expression of IDO1 and 2 genes in the cervical tumour milieu.Design and MethodsCervical cancer punch biopsy samples of 27 women who presented at the Cancer Institute (WIA) were used for detection of K/T ratio by HPLC as well as expression of IDO1 and 2 at the mRNA level by Realtime PCR after obtaining Institutional ethical committee approval.ResultsThe K/T ratio was elevated significantly in cancer cervix samples compared to normal cervix (p < 0.05). IDO1 mRNA levels were up-regulated whereas IDO2 mRNA levels were down-regulated in cancer cervix compared to the normal cervix. A positive correlation was observed between IDO1 and K/T (p < 0.05) indicating that IDO1 was responsible for the increase in K/T ratio.ConclusionOur preliminary data indicates that the K/T ratio at the tissue level may be investigated reliably using HPLC, as an indirect measure of IDO1 gene expression and activity.

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