Wang Y, et al. – The correlation between the clinical parameters, responses to chemotherapy, and indoleamine 2,3–dioxygenase (IDO) activity was examined to provide a theoretical basis for the clinical application of IDO inhibitors to improve the suppression status and poor prognosis in cancer patients. Results revealed increased IDO activity in lung cancer patients. The cancer cells’ resistance to chemotherapy was induced and the efficacy of chemotherapy was decreased by higher IDO activity correlated with histological types and disease stages of lung cancer patients.

Methods

• High-performance liquid chromatography estimated the serum concentrations of Trp and Kyn in 252 patients with stage IIIB or IV non-small-cell lung cancer, and 55 healthy controls.
• By calculating the serum Kyn-to-Trp (Kyn/Trp) ratio, the IDO activity was determined.

Results

• As compared to the controls, the IDO activity was significantly higher in the lung cancer patients (median 0.0389 interquartile range [0.0178–0.0741] vs 0.0111 [0.0091–0.0133], respectively; P<0.0001).
• Data displayed higher IDO activity in patients with adenocarcinoma than patients with nonadenocarcinoma (0.0449 [0.0189–0.0779] vs 0.0245 [0.0155–0.0563], respectively; P=0.006).
• In comparison to patients with stage IV disease, patients with stage IIIB disease had higher IDO activity (0.0225 [0.0158–0.0595] vs 0.0445 [0.0190–0.0757], respectively; P=0.012).
• A significant difference was observed between the partial response (PR) patients and the stable disease (SD) and progressive disease (PD) patients (0.0240 [0.0155–0.0381] vs 0.0652 [0.0390–0.0831] vs 0.0868 [0.0209–0.0993], respectively, P<0.0001).