Plasma Endoglin is Associated with Favorable Outcome for Pemetrexed-Based Therapy in Advanced Non-Small Cell Lung Cancer

PURPOSE: Pemetrexed-based chemotherapy (Pem-C) is the first-line chemotherapy for advanced non-squamous non-small cell lung cancer (NSCLC). However, limited tumor-associated proteins in blood are available to predict pemetrexed response and/or survival. PATIENTS AND METHODS: Plasma samples from three responders and three nonresponders with stage IIIB–IV NSCLC were collected prior to Pem-C and analyzed using Proteome Profiler(TM) Human XL Oncology Array to detect 84 oncology-related proteins. The plasma concentrations of cathepsin S, endoglin (ENG), and matrix metalloproteinases 3 and 9 in 71 patients with advanced NSCLC treated with Pem-C were further measured using enzyme-linked immunosorbent assay based on the remarkable differences in the four proteins between responders and nonresponders in the array results. RESULTS: Pem-C responders had significantly higher ENG levels but not the other three markers than nonresponders (mean ENG level: 27.1 ± 7.4 vs 22.3 ± 6.9, p < 0.01). High ENG concentration was correlated with improved progression-free survival (hazard ratio [HR]: 0.52, 95% confidence interval [CI]: 0.31–0.86, p < 0.01) and overall survival (HR: 0.55, 95% CI: 0.32–0.94, p < 0.05) in patients treated with Pem-C, and the ENG level was an independent factor in our cohort (HR: 0.54, 95% CI: 0.33–0.89, p < 0.05). ENG concentration in Pem-C responders also significantly increased at the time of best response (p < 0.05). CONCLUSION: Cumulatively, this study reveals that ENG is correlated with Pem-C responsiveness in patients, which indicates the potential use of plasma ENG levels as a non-invasive biomarker for pemetrexed-based treatment in patients with non-squamous NSCLC.