Radiotherapy changes acquired enamel pellicle proteome in head and neck cancer patients

Objectives: To evaluate in vivo the proteomic profile of the acquired enamel pellicle (AEP) in patients with head and neck cancer (HNC) before, during and after radiotherapy. Methods: Nine patients, after prophylaxis, had their AEPs collected before (BRT), during (DRT; 2-5 weeks) and after (ART; 3-4 months) radiotherapy. AEP was also collected from nine healthy patients (Control). The proteins were extracted in biological triplicate and processed by label-free proteomics. Results: Statherin was increased more than 9-fold and several hemoglobin subunits were increased more than 5 fold DRT compared to BRT, while lactotransferrin, proline-rich proteins, cystatins, neutrophil defensins 1 and 3 and histatin-1 were decreased. ART, there was an increase in lactotransferrin and several isoforms of histones, while statherin and alpha-amylase proteins were decreased. MOAP-1 was exclusively found ART in comparison to BRT. When compared to Control, AEP of patients BRT showed an increase in proteins related to the perception of bitter taste, mucin-7 and alpha-amylases, while cystatin-S was decreased. Conclusions: HNC and radiotherapy remarkably altered the proteome of the AEP. Antibacterial and acid-resistant proteins were decreased during radiotherapy. Clinical significance: Our results provide important information for designing more effective dental products for these patients, in addition to contributing to a better understanding of the differential protective roles of the AEP proteins during radiotherapy. Moreover, some proteins identified in the AEP after radiotherapy may serve as prognostic markers for survival of HNC patients.