Abstract 242: Evaluation of apoptosis-related microRNAs in salivary gland tumors

Abstract

Abstract MicroRNAs (miRNAs) are a class of short non-coding RNAs that regulates gene expression post-transcriptionally, being important modulators of several cellular functions such as proliferation, apoptosis, differentiation, and cell signaling. Salivary gland tumors comprise a heterogeneous group of lesions with different histologic features and diverse clinical behavior accounting for about 3% of all head and neck tumors. The low incidence of salivary gland tumors, coupled with the large amount of different lesions present in this group, makes the diagnosis a challenging activity. Therefore, the identification of molecular markers for diagnosis and prognosis is so important, especially for this group of neoplasms. Apoptosis plays an important role during during morphogenesis of glandular structures, including salivary gland development and recent studies demonstrated that several miRNAs are involved in the control of apoptosis. The aim of the present study was to determine the expression of apoptosis-related miRNAs in salivary gland tumors. With this goal, 60 samples have been selected: 25 pleomorphic adenomas (most common benign tumor), 25 mucoepidermoid carcinomas (most common malignant tumor) and 10 normal salivary gland samples. miRNA expression was examined by Real Time RT-PCR (qPCR) using TaqMan miRNA Assays (miR-15a, miR-16, miR-17-5p, miR-20a, miR-21, miR-29 and miR-34). The relative microRNA expression level was normalized based on the expression of RNU48. Experiments were performed in duplicate for each data point. Considering up- or down-regulation as a 2-fold difference in expression relative to the normal tissue, we observed up-regulation of miR-15a, miR-16, miR-17-5p, miR-21, miR-29 and miR-34a in 76.0%, 60.0%, 47.8%, 80.0%, 84.0% and 96.0% of the pleomorphic adenoma samples, respectively. Down-regulation of miR-20a was observed in 75.0% of the pleomorphic adenoma samples. Normal expression of miR-15a, miR-16, miR-17-5p and miR-29 was observed in the mucoepidermoid carcinoma samples. Down-regulation of miR-20a was observed in 56.5% of the mucoepidermoid samples. An increased expression if miR-21 was observed in 90.9% of these samples. miR-34a is up-regulated in 73.9% of the mucoepidermoid carcinoma samples, suggesting an important role in the pathogenesis of these salivary gland tumor. Our study provides evidence of alterations in the expression of apoptosis-regulating miRNAs in salivary gland tumors, suggesting a possible involvement of these microRNAs in salivary gland tumorigenesis. Citation Format: Bianca T. Flores, Silvia V. Lourenço, Maria A. Nagai, Luiz Paulo Kowalski, Fernando A. Soares, Cláudia Coutinho-Camillo. Evaluation of apoptosis-related microRNAs in salivary gland tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 242. doi:10.1158/1538-7445.AM2015-242