An overview on the methods of determining the activity of Indoleamine 2, 3-Dioxygenase 1.

Immune escape plays an important hallmark of cancer. The tryptophan-catabolizing enzyme indoleamine 2, 3-dioxygenase 1 (IDO1) is involved in the immune escape mechanism of human tumours, the expression of which is associated with a poor prognosis in cancer and correlated with tumour progression clinically. Therefore, finding the inhibitors targeting IDO1 may be an impellent approach that can reverse the complicated processes in tumour immune escape and induce an antitumor response as well. Here, we summarised and compared some methods of determining the activity of IDO1 and they can be used to screen IDO1 inhibitors as well, including HPLC, fluorescence detection, cell-based assay, NFK GreenScreen and absorbance assay. Each determining method possesses special advantages and disadvantages, so we need to have a comprehensive view of these methods and select the most suitable one for further research.