Baseline Plasma Proteomic Analysis to Identify Biomarkers that Predict Radiation-Induced Lung Toxicity in Patients Receiving Radiation for Non-small Cell Lung Cancer
Journal of Thoracic Oncology
Purpose: To identify new plasma proteomic markers before radiotherapy start to predict later grade Ն2 radiation-induced lung toxicity (RILT2). Methods: Fifty-seven patients with non-small cell lung cancer received radiotherapy (RT) were eligible. Forty-eight patients with minimum follow-up of 1 year, nine with RILT2 with tumor stage matched to 39 without RILT2, were enrolled for this analysis. Platelet-poor plasma was obtained within 2 weeks before radiotherapy. The plasma proteomes were
... oteomes were compared using a multiplexed quantitative proteomics approach involving ExacTag labeling, reverse-phase high-performance liquid chromatography, and nano liquid chromatography electrospray ionization tandem mass spectrometry. Z scores and Bonferroni-adjusted p values for the twosample mean comparison were used to identify the differential protein expression between patients with and without RILT2. Results: More than 200 proteins were identified and quantified. After excluding proteins that were not detected in at least 40% of the 48 patient samples, C4b-binding protein alpha chain and vitronectin had significantly higher (p Ͻ 0.001 and p ϭ 0.02) expression levels in patients with RILT2 compared with patients without RILT2. These two proteins were validated by Western blot. Ingenuity pathway analysis revealed that they both play important roles in the inflammatory response and are associated with the known pathways of radiation-induced lung damage. Conclusions: This proteomic approach demonstrates new plasma protein biomarkers before treatment for future studies on RILT2 prediction. FIGURE 2. Plasma protein expressions in patients with RILT2 (RILT2) and without RILT2 (RILT1/0). All p values are after Bonferroni correction. RILT2, grade Ն2 radiation-induced lung toxicity. FIGURE 3. Validation of the proteomic approaches by Western blotting. Lanes 1 to 4 are from the samples with lower levels of VTN and C4BPA from patients without RILT2, and lanes 5 to 8 are from the samples with higher levels of VTN detected by proteomic approaches. C4BPA, C4b-binding protein alpha chain; RILT2, grade Ն2 radiation-induced lung toxicity; VTN, vitronectin. FIGURE 4. ROC curves with AUC values of five predictive models for grade Ն2 radiation-induced lung toxicity. ROC, receiver operating characteristic; AUC, area under the curve; C4BPA, C4b-binding protein alpha chain; VTN, vitronectin; MLD, mean lung dose. Cai et al.