OPEN Exhaled volatile organic compounds as SUBJECT AREAS: lung cancer biomarkers during one-lung CANCER TUMOUR BIOMARKERS ventilation Changsong Wang1, Ran Dong1, Xiaoyang Wang1, Ailing Lian1, Chunjie Chi1, Chaofu Ke2, Lei Guo1, Received Shanshan Liu1, Wei Zhao1, Guowang Xu3 & Enyou Li1 1 July 2014 Accepted 1Department of Anesthesiology, the First Affiliated Hospital of Harbin Medical University, Harbin, China, 2Department of 13 November 2014 Biostatistics, School of Public Health, Harbin Medical University, Harbin, China, 3CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China. Published 8 December 2014 In this study, single-lung ventilation was used to detect differences in the volatile organic compound (VOCs) profiles between lung tissues in healthy and affected lungs. In addition, changes that occurred after lung Correspondence and cancer resection in both the VOCs profiles of exhaled breath from ipsilateral and contralateral lungs and the VOCs profiles of exhaled breath and blood sample headspaces were also determined. Eighteen patients with requests for materials non-small cell carcinoma were enrolled. Alveolar breath samples were taken separately from healthy and should be addressed to diseased lungs before and after the tumor resection. Solid phase microextraction–gas chromatography/mass E.L. (enyouli@aliyun. spectrometry was used to assess the exhaled VOCs of the study participants. The VOCs exhibited significant com) differences between the contralateral and ipsilateral lungs before surgery, the contralateral and ipsilateral lungs after surgery, the ipsilateral lungs before and after surgery, and the blood samples from before and after surgery; 12, 19, 12 and 5 characteristic metabolites played decisive roles in sample classification, respectively. 2,2-Dimethyldecane, tetradecane, 2,2,4,6,6-pentamethylheptane, 2,3,4-trimethyldecane, nonane, 3,4,5,6-tetramethyloctane, and hexadecane may be generated from lipid peroxidation during surgery. Caprolactam and propanoic acid may be more promising exhaled breath biomarkers for lung cancer. he analysis of volatile organic compounds (VOCs) in exhaled air is a newly developed method for screening and diagnosing diseases. This approach has drawn increasing attention from researchers because of its T advantages of convenience, non-invasiveness, and good patient tolerance. The analysis of a number of different VOCs in the exhaled breaths of lung cancer (LC) patients has revealed that LC-specific VOCs can be detected not only in the exhaled breaths of these patients but also in the headspaces of blood from LC patients, LC tissues, and LC cells1–10. In most studies addressing the exhaled breath of LC patients, the exhaled breath samples typically con- sisted of mixed gas from both lungs (without separating the air from the ipsilateral and contralateral lungs). In addition, sample comparisons were performed between healthy individuals and patients (rather than samples from the same individual), and a few comparisons have been made of the VOC differences between the exhaled breath and the headspace of blood cells2–4. As previously established, the optimal method to validate or determine the pathophysiologic pathways of LC VOCs is to compare VOC profiles from different sources (organs or clinical samples) in the same LC patient11. Within this approach, the simplest starting point would be a comparison between VOC profiles collected from the headspace of the LC tumor, the (headspace of) blood samples, and the breath samples. In this study, we used a double-lumen endobronchial tube to separate the contralateral and ipsilateral lungs. Using this approach, we sought to perform single-lung ventilation to detect differences in VOC profiles between the lung tissues in healthy and affected lungs. In addition, changes that occurred after LC resection in both the VOC profiles of exhaled breath from ipsilateral and contralateral lungs and the VOC profiles of exhaled breath and blood sample headspaces were deter- mined, enabling the identification of LC-specific VOC profiles of exhaled breath and the explanation of both the pathophysiological pathways involved in the generation of LC VOCs and the characteristics of changes in these VOCs. SCIENTIFIC REPORTS | 4 : 7312 | DOI: 10.1038/srep07312 1 www.nature.com/scientificreports Results exhaled breath profile of the contralateral lung did not change after In total, 18 LC patients participated in this study, including 13 male tumor resection. patients and 5 female patients. The average age of these patients was In the corresponding PCA score plot, the preoperative and post- 58.67 6 6.34 years. Using the TNM (tumor, node, and metastasis) operative exhaled breath samples from the ipsilateral lungs could be staging approach, the examined LC cases included 13 cases of stage I separated into two different categories (R2X50.865 and Q250.6; LC, 4 cases of stage II LC, and 1 case of stage IV LC. Figure 3A). To provide a more detailed explanation, PLSDA was In the corresponding PCA score plot, the exhaled air samples performed, leading to the establishment of a prediction model con- from contralateral and ipsilateral lungs before lung tumor resection taining two components (R2X50.375, R2Y50.818, and Q250.544; could be separated into two different categories (R2X50.869 and Figure 3B). After 100 iterations of permutation testing, the intercept Q250.601; Figure 1A). To provide a more detailed explanation, for R2 was 0.334, and the intercept for Q2 was 20.274 (Figure 3C). PLSDA was performed. Using three orthogonal components, a pre- The PLSDA model identified 12 characteristic metabolites for which diction model was obtained (R2X50.56, R2Y50.9, and Q250.624; the VIP values were .1 and P,0.05 in the t-tests (Table 1). Figure 1B). After 100 iterations of permutation testing, the intercept In the corresponding PCA score plot, R2X was 0.84 and Q2 was for R2 was 0.458, and the intercept for Q2 was 20.362 (Figure 1C). In 0.414 for the blood samples from before and after surgery the PLSDA model, 12 characteristic metabolites played decisive roles (Figure 4A). PLSDA was performed using a single main component. in the sample classification, as indicated by VIP values .1 and In the prediction model that was obtained, R2X50.112, R2Y50.715, P,0.05 in the t-tests (Table 1). and Q250.426 (Figure 4B). In addition, 100 iterations of permuta- In the corresponding PCA score plot, the exhaled air samples from tion testing produced an R2 intercept of 0.277 and a Q2 intercept of contralateral and ipsilateral lungs after surgery could be separated 20.13 (Figure 4C). The PLSDA model identified five characteristic into two different categories (R2X50.692 and Q250.471; metabolites for which VIP values were .1 and P,0.05 in the t-tests Figure 2A). PLSDA was performed, and a prediction model was (Table 2). established (R2X50.486, R2Y50.952, and Q250.815; Figure 2B). After 100 iterations of permutation testing, the intercept for R2 Discussion was 0.486, and the intercept for Q2 was 20.435 (Figure 2C). In the To the best of our knowledge, Sabine et al. first applied the single- PLSDA model, there were 19 characteristic metabolites for which the lung ventilation technique for collecting exhaled breath in order to VIP values were .1 and P,0.05 in the t-tests (Table 1). separate exhaled breath from the contralateral and ipsilateral lungs, In the corresponding PCA score plot, there were no significant thereby providing a new method for the more accurate collection of differences between the preoperative and postoperative exhaled alveolar air12. In this study, we also used the single-lung ventilation breath samples; thus, the PCA score plot could not be divided into technique. However, in contrast with Sabine et al., we directly placed two categories (R2X50.729 and Q250.561). PLSDA was performed, a specially designed gas collection tube on the tracheal bifurcation, and a model was established (R2X50.331, R2Y50.316, and Q25 thereby enabling the maximal exclusion of dead space gas and ensur- 20.21). These PCA and PLSDA examinations revealed that the ing that the collected gas was alveolar gas. Sabine et al. observed the Figure 1 | (A): PCA results for exhaled breath samples from contralateral and ipsilateral lungs before lung tumor resection (8 components, R2X50.869, Q250.601). (B): PLSDA results for exhaled breath samples from contralateral and ipsilateral lungs before lung tumor resection (3 components, R2X50.56, R2Y50.9, Q250.624). (C): Y-intercepts: R25(0.0, 0.458), Q25(0.0, 20.362). SCIENTIFIC REPORTS | 4 : 7312 | DOI: 10.1038/srep07312 2 SCIENTIFIC REPORTS | 4 : 7312 | DOI: 10.1038/srep07312 Table 1 | Potential biomarkers in exhaled breath samples from contralateral and ipsilateral lungs Preoperative contralateral vs. ipsilateral Postoperative contralateral vs. ipsilateral Ipsilateral lung preoperative vs. postoperative Potential biomarker RT p-value FC VIP p-value FC VIP p-value FC VIP Cyclopentanone 3.94 0.000201 3.85 1.3522 2-Butanone 5.29 0.00341 3.65 1.2879 4-Methyltoluene 5.59 5.68E-05 3.95 1.6122 Cyclohexanone 6.14 0.00291 21.75 1.407 0.000246 22.44 1.216 Butyl glycol 6.35 0.00257 20.85 1.3227 0.00376 1.57 1.1917 0.0027 1.26 1.4783 Isopropylbenzene 6.81 0.003739 4.59 1.1221 Ethylene carbonate 7.58 0.0096 1.93 1.107 2,2-Dimethyldecane 8.31 0.000566 5.65 1.327 0.00376 1.99 1.1814 0.000108 22.13 2.1988 2,2,4,6,6-Pentamethylheptane 8.35 3.66E-05 22.12 1.004 0.000133 22.2 2.1969 Ethylhexanol