Increased tryptophan degradation in patients with bronchus carcinoma

Abstract

ENGIN A.B., OZKAN Y., FUCHS D. & YARDIM‐AKAYDIN S. (2009) European Journal of Cancer CareIncreased tryptophan degradation in patients with bronchus carcinoma Expression of tryptophan‐degrading enzyme indoleamine (2,3)‐dioxygenase in tumour tissue is proposed to represent an important tumour immunoescape mechanism. To further investigate the potential role of activated indoleamine (2,3)‐dioxygenase in bronchus carcinoma, we examined serum tryptophan and kynurenine concentrations in nine patients with small cell lung cancer and in 27 patients with non‐small cell lung cancer. Tryptophan metabolic changes were compared with markers of inflammation and immune activation namely C‐reactive protein (CRP), erythrocyte sedimentation rate (ESR) and neopterin. Compared with controls, patients presented with lower tryptophan concentrations (P < 0.01) and with higher serum kynurenine to tryptophan ratios (P < 0.01), an index of tryptophan degradation. Also ESR and CRP and neopterin concentrations were increased in the patients (all P < 0.001), and there was a weak correlation between kynurenine to tryptophan ratio and ESR, CRP and neopterin concentrations. We conclude that in the majority of patients with non‐small cell lung cancer and small cell lung cancer, enhanced tryptophan degradation can be observed. It seems to relate to an inflammatory response and may reflect activation of indoleamine (2,3)‐dioxygenase at the tumour site. The capacity of the tumour to escape normal host immune defence may be influenced by tryptophan degradation. Results of this pilot study deserve further confirmation.