Salivary proteins as markers of radiation-related oral mucositis

Objectives The aim of this study was to characterize the salivary proteomic profile of patients treated for head and neck cancers (HNCs) and correlate it with the risk of developing severe radiation-related oral mucositis (OM). Study Design Forty-one patients with oral squamous cell carcinoma (OSCC) who underwent adjuvant radiotherapy (RT) or chemoradiotherapy (CRT) were included. All patients were submitted to dental conditioning protocols prior to RT. OM and OM-related pain were evaluated daily during RT and graded according to the Common Toxicity Criteria for Adverse Events (National Cancer Institute, version 4.0, 2010) and the visual analogue scale (VAS). For the molecular analysis, whole saliva was collected immediately before RT and subjected to proteomic analysis by means of liquid chromatography–mass spectrometry (LTQ Orbitrap Velos MS; Thermo Fisher Scientific, Bremen, Germany) and label-free protein quantification. The results obtained from the targeted proteomic analysis were compared with OM clinical outcomes. Statistical analysis was performed by using Wilcoxon's test. Results Of the study patients, 73% presented with stage III/IV OSCC; 58% were submitted to CRT protocols, with a mean RT dose of 66 Gy. Most of the patients (66%) had visible tumor areas at the time of saliva collection; 43.9% had grade 2 and 31.7% had grade 3 as the highest OM grade during RT, with a mean highest reported VAS score of 3.53. For the target proteomics analysis, a total of 65 proteins were observed to be mostly related to biologic processes, such as immune responses, peptidase inhibitor activity, and the inflammatory system. The macrophage migration inhibitory factor (MIF HUMAN) was statistically significant when correlated with OM grade. MIF was observed in patients with grades 1 to 4 OM and showed higher abundance for OM grades 3 and 4 compared with grades 1 and 2 (P = .04). Conclusions The correlation of MIF with the severity of OM is compatible with the role of MIF as a proinflammatory protein. This seems to be the first study to describe this association; therefore, future prospective studies would be ideal to observe pre- and post-RT alterations in salivary MIF levels to validate this result and better understand the role of MIF in the pathogenesis of OM.