Analysis of salivary protein SPLUNC2 from head and neck cancer patients

Abstract

Patients with head and neck cancer are commonly treated by surgical resection with or without the use of radiotherapy. Dental or voice prostheses are frequently part of rehabilitation following surgical treatment and can improve patients’ quality of life. An obturator prosthesis, made from acrylic resin and sometimes covered with a silicone liner, is used by patients who have undergone tumour resection of the hard palate for neoplasms in the paranasal sinuses or superior aspect of the oral cavity. Voice prostheses of medical grade silicone are used for patients who have had total laryngectomy as treatment for laryngeal cancer.

Patients undergoing treatment for head and neck cancer often require radiotherapy, chemotherapy, or both, to ensure total elimination of the cancer cells, rendering individuals immunocompromised. Candida albicans is a commensal yeast normally present asyptomatically in the oral cavity, but in the immunocompromised, it can be an opportunistic pathogen causing superficial and systemic infections ranging from denture stomatitis to potentially life-threatening, deep-seated or disseminated candidiasis. Furthermore, patients' prostheses may rapidly become colonized with a microbial biofilm in which C. albicans is often a major constituent. Radiation therapy to the salivary glands leads to loss of salivary gland function, and xerostomia is a common side-effect. Clinically, reduced salivary flow post-radiotherapy may lead to an overgrowth of Candida, increasing the risk of oral candidiasis. For voice prostheses, the biofilm impairs the function of the valves often necessitating frequent replacement of the device. Recently, a salivary protein, SPLUNC2 (Short Palate Lung Nasal Clone 2), has been reported to bind to both denture acylic and silicone and act as a recptor for C. albicans adherence. The initial aim of this study was to develop a method to quantify SPLUNC2 in saliva wash samples. The major aim of this study was to investigate whether there is an increased presence of SPLUNC2 in saliva from a group of patients who had received radiation therapy for head and neck cancer, compared to a control group. Such an increase might explain the reported increase in C. albicans colonisation in head and neck cancer patients. The study recruited patients from Christchurch and Dunedin, as well as controls matched for age, sex and smoking history. Following determination of salivary flow rates, salivary wash samples were collected and stored frozen for immunoblot analysis. Blots were probed for two salivary proteins, SPLUNC2 and IgA, and relative concentrations determined by use of internal controls and image analysis of the blots. IgA was detected in all samples and there was no significant difference between the relative amounts detected in patient and control samples. In control samples, amounts of SPLUNC2 and IgA were correlated. Thus, IgA was confirmed as a suitable control for the relative determination of SPLUNC2 presence. However, SPLUNC2 was only detected in 6 of 15 patient samples and was never present at higher levels than in control samples. It was concluded that head and neck cancer, or its treatment, may reduce the production of SPLUNC2 in saliva. Thus the presence of SPLUNC2 is probably not linked to susceptibility to C. albicans colonisation.