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

Objectives: Indoleamine 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 Methods: Cervical 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. Results: The 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. Conclusion: Our 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. (C) 2016 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.