Supersulfide metabolome of exhaled breath condensate applied as diagnostic biomarkers for esophageal cancer

Early detection of esophageal cancer is essential for esophagogastroduodenoscopy and histopathological diagnosis. However, endoscopic examinations are sometimes invasive, which limits their clinical application and compliance, and traditional blood tumor markers are unsuitable for cancer screening. The current study aimed to evaluate the usefulness of sulfur metabolites as new biomarkers for esophageal cancer using blood samples and exhaled breath condensate (EBC), which can be readily obtained and is non-invasive. We collected EBC and plasma samples from 50 patients with esophageal cancer and 30 healthy controls. Sulfur metabolome analysis using tandem mass spectrometry was performed to compare the metabolic profile between the two groups. Supersulfide metabolic profiles were different between the two cohorts. Supersulfide metabolome analysis showed that cysteine hydropersulfide (CysSSH) and homocysteine hydropersulfide (HomoCysSSH) were increased in the plasma of patients with esophageal cancer. Elevated levels of HomoCysSSH could distinguish patients with esophageal cancer from healthy subjects (area under the curve [AUC]: 0.93, sensitivity: 89%, specificity: 96%). Interestingly, we also detected an elevation of supersulfides in the EBC analysis. CysSSH levels significantly increased in the EBC recovered from patients with esophageal cancer (AUC: 0.71, sensitivity: 60%, specificity: 96%). In addition, the observed level was correlated with that of HomoCysSSH in the plasma (r = 0.27). Supersulfides, such as CysSSH and HomoCysSSH, are potential biomarkers for detecting esophageal cancer. CysSSH from EBC may serve as a valuable non-invasive biomarker with similar detection ability but with superior precision and convenience compared with the currently available blood biomarkers.