Increased tryptophan degradation in patients with bronchus carcinoma

Myeloid-derived suppressor cells and plasmacytoid dendritic cells are associated with oncogenesis of oral squamous cell carcinoma

Myeloid-derived suppressor cells (MDSCs) help establish the tumor microenvironment by suppressing T-cell response in tumor-bearing hosts. Plasmacytoid dendritic cells (pDCs) activate antigen-specific T cells, thereby, maximizing their antitumor effects. IDO1 is associated with both MDSCs and pDCs and plays a major role in the formation of the tumor-mediated immunosuppressive environment. We utilized immunohistochemistry to examine the involvement of IDO1 in oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMDs, precancerous lesions). We examined the expression of MDSC markers, CD11b and CD33, as well as pDC markers, CD303 and IDO1, in 60 OSCC and 45 precancerous lesion specimens and analyzed their association with clinicopathological parameters. Expression of these biomarkers identifying MDSCs and pDCs was high in precancerous lesions in patients with severe dysplasia and OSCC. While detecting pDCs, high CD303 and IDO1 expression levels were frequently observed in moderately or poorly differentiated OSCCs. CD11b, CD33, and CD303 levels were significantly correlated with the mode of invasion; CD33 was correlated with OSCC invasion depth while the other three markers tended to be highly expressed in superficial cancer cases showing microinvasion. Expression levels of all four biomarkers were significantly associated with the cancerization of OPMDs to OSCCs. We show, for the first time, that the infiltration of MDSCs and pDCs is significantly associated with progression of premalignant lesions to OSCC. This suggests that these cells may act as prognostic biomarkers for premalignant lesion progression and that immunotherapeutic approaches that control each of these immunosuppressive cells may protect against progression to malignancy.

Information entropy of quantitative chemometric endogenous fluorescence improves photonic lung cancer diagnosis

Quantitative chemometric widefield endogenous fluorescence microscopy (CFM) maps the endogenous absolute chromophore concentration and spatial distribution in cells and tissue sections label-free from fluorescence color images under broadband excitation and detection. By quantifying the endogenous chromophores, including tryptophan, elastin, reduced nicotinamide adenine dinucleotide [NAD(P)H], and flavin adenine dinucleotide (FAD), CFM reveals the biochemical environment and subcellular structure. Here we show that the chromophore information entropy, marking its spatial distribution pattern of quantitative chemometric endogenous fluorescence at the microscopic scale, improves photonic lung cancer diagnosis with independent diagnostic power to the cellular metabolism biomarker. NAD(P)H and FAD's information entropy is found to decrease from normal to perilesional to cancerous tissue, whereas the information entropy for the redox ratios [FAD/tryptophan and FAD/NAD(P)H] is smaller for the normal tissue than both perilesional and cancerous tissue. CFM imaging of the specimen's inherent biochemical and structural properties eliminates the dependence on measurement details and facilitates robust, accurate diagnosis. The synergy of quantifying absolute chromophore concentration and information entropy achieves high accuracies for a three-class classification of lung tissue into normal, perilesional, and cancerous ones and a three-class classification of lung cancers into grade 1, grade 2, and grade 3 using a support vector machine, outperforming the chromophore concentration biomarkers.

Chromatographic method for the determination of inflammatory biomarkers and uric acid in human saliva

Determination of concentration of biomarkers of the activation of immune system, uric acid, and creatinine in the saliva can be useful tool for the diagnosis and monitoring of early manifestations of diseases such as malignant, inflammatory, and periodontal disorders. We have developed and validated a high-performance liquid chromatographic method coupled with fluorescence and diode array detection for the separation and quantification of neopterin, tryptophan, creatinine, uric acid, and kynurenine in the human saliva. A separation of these analytes was achieved within 9 min by using second-generation monolithic stationary phase and elution with phosphate buffer. The present method involves very simple sample preparation requiring small amount of sample matrix. The internal standard 3-nitro-l-tyrosine was used for a more precise quantification. The sensitivity of the present method was demonstrated with lower limits of quantification of 0.6 × 10^-3 μmol/L for neopterin, 0.725 μmol/L for tryptophan, 0.12 μmol/L for creatinine, 0.18 μmol/L for uric acid, and 0.135 μmol/L for kynurenine. The method was validated with 67 real-life saliva samples collected from patients suffering from breast, ovarian, colorectal, and renal cancer, and 19 saliva samples from patients with periodontal diseases and allowed monitoring of inflammatory response.

The immunotherapeutic role of indoleamine 2,3-dioxygenase in head and neck squamous cell carcinoma: A systematic review

BACKGROUND

Novel cancer immunotherapy seeks to harness the body's own immune system and tip the balance in favour of antitumour activity. The intracellular enzyme indoleamine 2,3-dioxygenase (IDO) is a critical regulator of the tumour microenvironment (TME) via tryptophan metabolism. The potential immunotherapeutic role of IDO in head and neck squamous cell carcinoma (HNSCC) requires further exploration. We aim to assess the evidence on IDO in HNSCC.

METHODS

A systematic review of literature and clinical trials databases.

RESULTS

We included 40 studies: seven involved cell lines: eight assessed tumour immunohistochemistry: ten measured IDO gene transcription: 15 reported on clinical trials. Increased cell line IDO expression was postulated to adversely affect tumour metabolism and apoptosis. Immunohistochemical IDO expression correlated with worse survival. Gene transcription studies associated IDO with positive PD-L1 and human papillomavirus (HPV) status. Phase I/II clinical trials showed (a) overall response (34%-55%) and disease control rates (62%-70%) for IDO1 inhibitor in combination with a PD-1 inhibitor, (b) similar safety profiles when both are used in combination therapy compared to each as monotherapies and (c) IDO gene expression as a predictive biomarker for response to PD-L1 therapy.

CONCLUSIONS

IDO expression is increased in the TME of HNSCC, which correlates with poor prognosis. However, the exact mechanism of IDO-driven immune modulation in the TME is an enigma. Future translational studies should map IDO activity during HNSCC treatment and elucidate its precise role in the TME, such research will underpin the development of clinical trials establishing the efficacy of IDO inhibitors in HNSCC.

What is the prospect of indoleamine 2,3-dioxygenase 1 inhibition in cancer? Extrapolation from the past

Indoleamine 2,3-dioxygenase 1 (IDO1), a monomeric heme-containing enzyme, catalyzes the first and rate-limiting step in the kynurenine pathway of tryptophan metabolism, which plays an important role in immunity and neuronal function. Its implication in different pathophysiologic processes including cancer and neurodegenerative diseases has inspired the development of IDO1 inhibitors in the past decades. However, the negative results of the phase III clinical trial of the would-be first-in-class IDO1 inhibitor (epacadostat) in combination with an anti-PD1 antibody (pembrolizumab) in patients with advanced malignant melanoma call for a better understanding of the role of IDO1 inhibition. In this review, the current status of the clinical development of IDO1 inhibitors will be introduced and the key pre-clinical and clinical data of epacadostat will be summarized. Moreover, based on the cautionary notes obtained from the clinical readout of epacadostat, strategies for the identification of reliable predictive biomarkers and pharmacodynamic markers as well as for the selection of the tumor types to be treated with IDO1inhibitors will be discussed.

High indoleamine-2,3-dioxygenase 1 (IDO) activity is linked to primary resistance to immunotherapy in non-small cell lung cancer (NSCLC)

Background

Metabolic profiling in non-small cell lung cancer (NSCLC) may identify key metabolic vulnerabilities and shows enormous discovery potential. Preclinical studies showed that metabolic rewiring in cancer plays an essential role in modulation of immunotherapy response. However, this situation is understudied in the clinical setting. Therefore, we aimed to evaluate the plasma metabolic profile of immune checkpoint inhibitor (CI) responding versus non-responding NSCLC patients. The aim of this project is to identify potential predictive biomarkers for CI response.

Methods

Plasma samples from CI treated NSCLC patients were analysed at baseline and at the first follow up scan by using a broad targeted metabolomics mass spectrometry panel, and were compared to healthy controls. For further validation of identified key alterations high-performance liquid chromatography (HPLC) for tryptophan (Trp) and kynurenine (Kyn) as indicator of IDO-activity was performed.

Results

Sixty-seven metabolites were significantly altered in NSCLC patients compared to healthy controls. The metabolic profile of patients with primary CI resistance showed an increase in indoleamine-2,3-dioxygenase (IDO) and a decrease in branched-chain amino acids (BCAA) compared to baseline concentrations. Deregulated IDO activity was validated by additional HPLC measurements, which revealed that baseline Trp levels were predictive for CI response. According to receiver operating characteristic (ROC)-analysis baseline Trp levels ≥49.3 µmol/L predicted disease control at the first follow up scan with a sensitivity of 89% and a specificity of 71%.

Conclusions

We showed that NSCLC patients are characterized by a distinct metabolic profile compared to healthy controls. Moreover, metabolic changes during CI therapy were observed. Of those IDO metabolism seemed to play an important role in primary CI resistance. Trp as a surrogate parameter of IDO activity is a promising biomarker in patients undergoing treatment with CIs and might be a future marker in trials investigating IDO inhibitors.

Indoleamine 2,3-Dioxygenase Activity-Induced Acceleration of Tumor Growth, and Protein Kinases-Related Novel Therapeutics Regimens

Indoleamine 2,3-dioxygenase (IDO) is overexpressed in response to interferon-gamma (IFN-γ). IDO-mediated degradation of tryptophan (Trp) along the kynurenine (Kyn) pathway by immune cells is associated with the anti-microbial, and anti-tumor defense mechanisms. In contrast, IDO is constitutively expressed by various tumors and creates an immunosuppressive microenvironment around the tumor tissue both by depletion of the essential amino acid Trp and by formation of Kyn, which is immunosuppressive metabolite of Trp. IDO may activate its own expression in human cancer cells via an autocrine aryl hydrocarbon receptor (AhR)- interleukin 6 (IL-6)-signal transducer and activator of transcription 3 (STAT3) signaling loop. Although IDO is not a unique marker, in many clinical trials serum IDO activity is suggested to be an important parameter in the pathogenesis of cancer development and growth. Measuring IDO activity in serum seems to be an indicator of cancer growth rate, however, it is controversial whether this approach can be used as a reliable guide in cancer patients treated with IDO inhibitors. Thus, IDO immunostaining is strongly recommended for the identification of higher IDO producing tumors, and IDO inhibitors should be included in post-operative complementary therapy in IDO positive cancer cases only. Novel therapies that target the IDO pathway cover checkpoint protein kinases related combination regimens. Currently, multi-modal therapies combining IDO inhibitors and checkpoint kinase blockers in addition to T regulatory (Treg) cell-modifying treatments seem promising.

Inflammation-Induced Tryptophan Breakdown is Related With Anemia, Fatigue, and Depression in Cancer

Many patients with cancer suffer from anemia, depression, and an impaired quality of life (QoL). These patients often also show decreased plasma tryptophan levels and increased kynurenine concentrations in parallel with elevated concentrations of Th1 type immune activation marker neopterin. In the course of anti-tumor immune response, the pro-inflammatory cytokine interferon gamma (IFN-γ) induces both, the enzyme indoleamine 2,3-dioxygenase (IDO) to degrade tryptophan and the enzyme GTP-cyclohydrolase I to form neopterin. High neopterin concentrations as well as an increased kynurenine to tryptophan ratio (Kyn/Trp) in the blood of cancer patients are predictive for a worse outcome. Inflammation-mediated tryptophan catabolism along the kynurenine pathway is related to fatigue and anemia as well as to depression and a decreased QoL in patients with solid tumors. In fact, enhanced tryptophan breakdown might greatly contribute to the development of anemia, fatigue, and depression in cancer patients. IDO activation and stimulation of the kynurenine pathway exert immune regulatory mechanisms, which may impair anti-tumor immune responses. In addition, tumor cells can degrade tryptophan to weaken immune responses directed against them. High IDO expression in the tumor tissue is associated with a poor prognosis of patients. The efficiency of IDO-inhibitors to inhibit cancer progression is currently tested in combination with established chemotherapies and with immune checkpoint inhibitors. Inflammation-mediated tryptophan catabolism and its possible influence on the development and persistence of anemia, fatigue, and depression in cancer patients are discussed.

The status of immunosuppression in patients with stage IIIB or IV non-small-cell lung cancer correlates with the clinical characteristics and response to chemotherapy

BACKGROUND

Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step of tryptophan (Trp) degradation via the kynurenine (Kyn) pathway, which inhibits the proliferation of T cells and induces the apoptosis of T cells, leading to immune tolerance. Therefore, IDO has been considered as the most important mechanism for tumor cells to escape from immune response. Previous studies suggested that IDO might be involved in the progression of tumor and resistance to chemotherapy. Several preclinical and clinical studies have proven that IDO inhibitors can regulate IDO-mediated tumor immune escape and potentiate the effect of chemotherapy. Thus, the present study investigated the correlation between the clinical parameters, responses to chemotherapy, and IDO activity to provide a theoretical basis for the clinical application of IDO inhibitors to improve the suppression status and poor prognosis in cancer patients.

METHODS

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

RESULTS

The IDO activity was significantly higher in the lung cancer patients than in the controls (median 0.0389 interquartile range [0.0178-0.0741] vs 0.0111 [0.0091-0.0133], respectively; P<0.0001). In addition, patients with adenocarcinoma had higher IDO activity than patients with nonadenocarcinoma (0.0449 [0.0189-0.0779] vs 0.0245 [0.0155-0.0563], respectively; P=0.006). Furthermore, patients with stage IIIB disease had higher IDO activity than patients with stage IV disease (0.0225 [0.0158-0.0595] vs 0.0445 [0.0190-0.0757], respectively; P=0.012). The most meaningful discovery was that there was a significant difference 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).

CONCLUSION

IDO activity was increased in lung cancer patients. Higher IDO activity correlated with histological types and disease stages of lung cancer patients, induced the cancer cells' resistance to chemotherapy, and decreased the efficacy of chemotherapy.

Serum neopterin concentrations and tryptophan degradation pattern in patients with late stage larynx carcinoma

As the disease-free 5-year-survival of late stage laryngeal carcinoma patients is extremely low, indoleamine-2,3-dioxygenase-1 (IDO)-induced tryptophan degradation may represent an immune escape mechanism which plays an important role in cancer spreading in advanced stage laryngeal cancers. We examined whether the late stage laryngeal cancer enhances tumor immune evasion by the expression of systemic IDO activities and chronic cellular immune activation. Twenty-two of 42 male laryngeal cancer patients were classified as late stage cancer according to American Joint Committee on Cancer (AJCC) criteria. Their serum neopterin, tryptophan and kynurenine concentrations were compared with 30 cancer-free individuals. IDO activity was approved by correlation between serum neopterin and kynurenine/tryptophan. Late stage cancer patients preoperatively showed a significantly higher IDO activity compared to controls and early stage cancer cases. Six months after tumor removal, late stage cancer patients although having higher serum neopterin concentration compared to early stage patients or controls, they showed a significant decrease in IDO activity and tryptophan consumption. Increased systemic IDO activity may provoke the escape of tumor cells from the immune surveillance of the host. High IDO activity is due to the presence of tumor mass. Persistence of high serum neopterin levels despite tumor removal may indicate poor prognosis.

Tryptophan catabolism in acute exacerbations of chronic obstructive pulmonary disease

Introduction

Exacerbations are a leading cause of morbidity in COPD. The objective of this study was to identify metabolomic biomarkers of acute exacerbations of COPD (AECOPD).

Methods

We measured metabolites via mass spectrometry (MS) in plasma drawn within 24 hours of admission to the hospital for 33 patients with an AECOPD (day 0) and 30 days later and for 65 matched controls. Individual metabolites were measured via selective reaction monitoring with mass spectrometry. We used a mixed-effect model to compare metabolite levels in cases compared to controls and a paired t-test to test for differences between days 0 and 30 in the AECOPD group.

Results

We identified 377 analytes at a false discovery rate of 5% that differed between cases (day 0) and controls, and 31 analytes that differed in the AECOPD cases between day 0 and day 30 (false discovery rate: 5%). Tryptophan was decreased at day 0 of AECOPD compared to controls corresponding to an increase in indoleamine 2,3-dioxygenase activity.

Conclusion

Patients with AECOPD have a unique metabolomic signature that includes a decrease in tryptophan levels consistent with an increase in indoleamine 2,3-dioxygenase activity.

Prognostic value of indoleamine 2,3-dioxygenase activity and expression in nasopharyngeal carcinoma

Indoleamine 2,3-dioxygenase (IDO) is an enzyme with an immunosuppressive effect whose function is diverted by tumor cells to counteract immune cell functions, inducing immune escape of tumor cells. The aim of this study was to investigate the clinical significance of IDO in nasopharyngeal carcinoma (NPC). Compared to controls, NPC patients' plasma IDO activity was significantly higher, especially among patients with metastatic cancer (p=0.005). The immunohistochemical analysis revealed that high IDO expression was observed in 74% of NPC tissues and the epithelial IDO expression was inversely correlated to T-cell infiltration. Kaplan-Meier survival analysis showed that whatever the localization, intratumoral or stromal, patients with a high IDO expression and low T-cell infiltration have significantly lower survival rates. Moreover, in multivariate analysis, intratumoral and stromal IDO expression were found to be independent prognostic factors for disease-free survival (p=0.016; HR: 3.52) and overall survival (p=0.015; HR: 4.76) respectively. Our findings provide evidence that IDO is involved in tumor immune evasion of NPC, suggesting that it could be a relevant therapeutic target for NPC.

Fast and sensitive HPLC method for the determination of neopterin, kynurenine and tryptophan in amniotic fluid, malignant effusions and wound exudates

Aim: A new HPLC method for the determination of neopterin, kynurenine and tryptophan using a second-generation monolith stationary phase and high-throughput sample preparation procedure based on microplates was developed and fully validated. Materials & methods: As the stationary phase a monolithic C18 Chromolith high-resolution column with dimensions of 4.6 × 100 mm connected to a monolithic 4.6 × 10-mm security guard was used. Separation was achieved using 15 mM phosphate buffer (KH2PO4 +K2HPO4·3H2O at pH 3) and acetonitrile in gradient mode. Results: Target analytes were determined in 5.5 minutes in amniotic fluid, effusions and wound exudates with a limit of quantification (LOQ) of 1.25 nM for neopterin, 2.5 µM for tryptophan and 0.25 µM for kynurenine. Discussion: The method was applied to real clinical sample measurements, and it will be used to monitor neopterin, kynurenine and tryptophan levels in biological fluids to assess the patient response to therapy and clinical status.

Pre-treatment effects of peripheral tumors on brain and behavior: neuroinflammatory mechanisms in humans and rodents

Cancer patients suffer high levels of affective and cognitive disturbances, which have been attributed to diagnosis-related distress, impairment of quality of life, and side effects of primary treatment. An inflammatory microenvironment is also a feature of the vast majority of solid tumors. However, the ability of tumor-associated biological processes to affect the central nervous system (CNS) has only recently been explored in the context of symptoms of depression and cognitive disturbances. In this review, we summarize the burgeoning evidence from rodent cancer models that solid tumors alter neurobiological pathways and subsequent behavioral processes with relevance to affective and cognitive disturbances reported in human cancer populations. We consider, in parallel, the evidence from human clinical cancer research demonstrating that affective and cognitive disturbances are common in some malignancies prior to diagnosis and treatment. We further consider the underlying neurobiological pathways, including altered neuroinflammation, tryptophan metabolism, prostaglandin synthesis and associated neuroanatomical changes, that are most strongly implicated in the rodent literature and supported by analogous evidence from human cancer populations. We focus on the implications of these findings for behavioral researchers and clinicians, with particular emphasis on methodological issues and areas of future research.

Indoleamine 2,3-dioxygenase activity and clinical outcome following induction chemotherapy and concurrent chemoradiation in Stage III non-small cell lung cancer

Indoleamine 2,3-dioxygenase (IDO) has recently been proposed to account for tumor-induced immunosuppression by influencing the conversion of tryptophan (Trp) into kynurenine (Kyn). The objective of our study was to correlate IDO activity with disease outcome in non-small cell lung cancer (NSCLC) patients treated with multimodal combination therapy. In a single-arm Phase II trial involving induction gemcitabine and carboplatin followed by concurrent paclitaxel, carboplatin and 74 Gy thoracic radiation in stage III NSCLC patients, plasma was drawn at baseline, post-induction, and post-concurrent therapy. The mean plasma Kyn/Trp ratio was used as a surrogate indicator of IDO activity. The 33 participants were distributed as follows: 15 females, 18 males; median age = 62; median overall survival (OS) = 22.4 (95% CI 19.3-25.1) months; median progression-free survival (PFS) = 11.5 (95% CI 6.7-16.3) months. The mean Kyn/Trp ratio at baseline (4.5 ± 2.8) was higher than that of healthy controls (2.9 ± 1.9, p = 0.03) and increased after induction therapy (5.2 ± 3.2, p = 0.08) and chemoradiation (5.8 ± 3.9, p = 0.01). The post-treatment Kyn/Trp ratio and radiologic responses were not significantly associated at any time point. No significant correlation was found between baseline Kyn/Trp ratios and OS (HR = 1.1, 95% CI 0.45-2.5) or PFS (HR = 0.74, 95% CI 0.30-1.82). A post-induction chemotherapy increase in IDO activity portended worse OS (HR = 0.43, 95% CI 0.19-0.95, p = 0.037) and PFS (HR = 0.47, 95% CI 0.22-1.0, p = 0.055). This observed increase in IDO transcription may be a means for tumors to evade immunosurveillance.

Interferon-γ-induced inflammatory markers and the risk of cancer: the Hordaland Health Study

BACKGROUND

It has been reported that interferon-γ (IFN-γ)-induced inflammatory markers, such as circulating neopterin and kynurenine-to-tryptophan ratio (KTR), are increased in patients with cancer and are also a predictor of poor prognosis. However, whether baseline levels of these makers are associated with subsequent cancer risk in the general population remains unknown.

METHODS

We conducted a prospective analysis of the Hordaland Health Study in 6594 adults without known cancer at baseline who were enrolled between April 1998 and June 1999. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using multivariate Cox proportional hazards regression models adjusted for sex, age, body mass index, smoking status, and renal function.

RESULTS

A total of 971 incident cancer cases (507 men and 464 women) were identified over a median follow-up time of 12 years. Baseline plasma neopterin, KTR and C-reactive protein (CRP) were significantly associated with an increased risk of overall cancer in models adjusted for covariates (P for trend across quartiles = .006 for neopterin, .022 for KTR, and .005 for CRP). The multivariate-adjusted HR (95% CI) per SD increment in similar models were 1.09 (1.03-1.16) for neopterin, 1.07 (1.01-1.14) for KTR, and 1.04 (0.98-1.10) for CRP. The associations between the inflammatory markers and risk of major specific cancer types were also provided.

CONCLUSIONS

Our findings indicate that plasma neopterin, KTR, and CRP are associated with a significantly increased risk of overall cancer. Our study revealed novel evidence regarding the role of IFN-γ-induced inflammation in human carcinogenesis.

Circulating biomarkers of tryptophan and the kynurenine pathway and lung cancer risk

BACKGROUND

Imbalances in tryptophan metabolism have been linked to cancer-related immune escape and implicated in several cancers, including lung cancer.

METHODS

We conducted a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) that included 893 incident lung cancer cases and 1,748 matched controls. Circulating levels of tryptophan and six of its metabolites were measured and evaluated in relation to lung cancer risk.

RESULTS

Tryptophan (Ptrend = 2 × 10(-5)) and the kynurenine/tryptophan ratio (KTR; Ptrend = 4 × 10(-5)) were associated with lung cancer risk overall after adjusting for established risk factors. The ORs comparing the fifth and first quintiles (OR5th vs. 1st) were 0.52 [95% confidence interval (CI), 0.37-0.74] for tryptophan and 1.74 (95% CI, 1.24-2.45) for KTR. After adjusting for plasma methionine (available from previous work, which was strongly correlated with tryptophan), the associations of tryptophan (adjusted Ptrend = 0.13) and KTR (Ptrend = 0.009) were substantially attenuated. KTR was positively associated with squamous cell carcinoma, the OR5th vs. 1st being 2.83 (95% CI, 1.62-4.94, Ptrend = 3 × 10(-5)) that was only marginally affected by adjusting for methionine.

CONCLUSIONS

This study indicates that biomarkers of tryptophan metabolism are associated with subsequent lung cancer risk. Although this result would seem consistent with the immune system having a role in lung cancer development, the overall associations were dependent on methionine, and further studies are warranted to further elucidate the importance of these metabolites in lung cancer etiology.

IMPACT

This is the first prospective study investigating the tryptophan pathway in relation to lung cancer risk.

Clinical significance of simultaneous determination of serum tryptophan and tyrosine in patients with lung cancer

BACKGROUND

To explore the clinical significance of serum tyrosine (Tyr) and tryptophan (Trp) in patients with lung cancer, we used a simple and efficient method of high-performance liquid chromatography with fluorescence detection (HPLC-FD) that simultaneously measured serum Trp and Tyr contents.

METHODS

The concentrations of Tyr and Trp were measured simultaneously by HPLC-FD in the sera of 80 patients with lung cancer and 120 healthy controls.

RESULTS

Trp concentrations were significantly lower in patients with lung cancer than in healthy controls (39.26±5.44 vs. 49.93±5.43 µmol/l, respectively; P<0.01), whereas in Tyr concentrations there were no differences with healthy controls (65.38±7.94 vs.66.40±8.55 µmol/l, respectively; P>0.05). In addition, patients in the adenocarcinoma group had significantly lower Trp and Tyr concentrations than those in squamous cell carcinoma group. There was no difference between the early stage and advanced stage of lung cancer.

CONCLUSIONS

Determination of serum Trp and Tyr concentrations can be employed to assist the diagnosis of the histotypes of lung cancer and tumor stage. Tyr and Trp as indexes on the lung cancer diagnostic sensitivity, specificity were 54.9, 62.9% and 82.4, 92.1%, Trp is an important and special index for lung cancer diagnosis of which the specificity of diagnosis of lung cancer is more than 92%.