Molecular markers in salivary gland tumours

Salivary gland tumours are uncommon neoplasms of the head and neck. The increase of precise pre-operative diagnosis is crucial for their correct management and the identification of molecular markers would surely improve the required accuracy. With this aim we studied the proteins and the microRNAs expressed from salivary gland neoplasms in order to identify tumour markers able to preoperatively distinguish these neoplasms. We performed a proteomic analysis of fine needle aspiration fluids of malignant tumours in order to draw their proteomic profiles and to point out their significant features. Twenty patients affected by a malignant salivary gland neoplasm and submitted to parotidectomy were included in the study. For comparison, fine needle aspiration citology was performed on 37 pleomorphic adenoma and 14 warthin’s tumour, which are known to be the most frequent histologies among the benign salivary gland neoplasms. Fine needle aspiration samples were processed using a two-dimensional electrophoresis/mass spectrometry-based approach. Ingenuity software was used to search the biological processes to which these proteins belong and to construct potential networks. Fourteen differentially expressed proteins were identified between malignant samples and pleomorphic adenomas, while 22 differentially expressed proteins were identified in malignant tumours compared to warthin’s tumours. The western blot validation of selected differentially expressed proteins was performed on fine needle aspiration fluid and paraffin tissues in order to verify the results. Intriguingly, up-regulated Ig subunits were confirmed to characterize Warthin’s tumour, as suggested in our previous experience. The expression profiling of 798 microRNAs was performed on paraffin section. microRNA expression profiles were detected in 24 salivary gland tumors (14 malignant tumors and 10 benign tumors namely pleomorphic adenoma) by using an highly reproducible and sensitive method, NanoString Technologies. Thirty-two microRNAs were found to be down-regulated in malignant neoplasms compared to benign ones, whereas a significant overexpression of 29 microRNAs was reported in malignant compared to benign lesions. Hierarchical clustering according to differentially expressed microRNAs was performed using nSolver Analysis software with Pearson correlation. The signature of the differentially expressed microRNAs was perfectly able to discriminate benign from malignant lesions. Although further studies are needed in order to improve the accuracy of the tumour markers identified, our research suggests the use of biomarker in salivary gland tumours in order to improve diagnosis. Better diagnosis of salivary gland tumours will allow better clinical decision-making with more appropriate treatment