Salivary gland tumors exhibit distinct miRNA signatures involved in Wnt/β-Catenin signaling in formalin fixed paraffin embedded tissue samples

Advances in high-throughput genomic technologies have enabled the identification of numerous selective tumor markers. However, adapting these newly identified markers to clinical practice is not always possible because most RNA molecules, including mRNAs of protein-coding genes and long non-coding RNAs, are not stable under laboratory conditions, making their testing a major challenge. In contrast to long RNA molecules, miRNAs offer a great advantage in that they are relatively stable due to their small size. Accordingly, herein we aimed to determine the expression levels of miRNAs that are involved in Wnt/β-catenin signaling pathway in formalin fixed paraffin embedded (FFPE) tissue samples of patients with salivary gland tumors. A total of 42 patients with salivary gland tumors were included in the study. The miRNA expression signatures were evaluated using the RT-qPCR. As a result, β-catenin positivity was observed in all salivary gland tumors without distinguishing between benign and malignant phenotypes. Remarkably, we found that miR-200a and miR-373 were significantly upregulated whereas miR-30c were downregulated in tissues of patients with salivary gland tumors, compared to adjacent healthy tissue samples. In addition, distinct expression signatures of these miRNAs were significantly associated with the clinicopathological findings of patients such as perineural invasion and lymph node metastasis. Additionally, miR-145 and miR-30a were found to be specifically downregulated in a mucoepidermoid carcinoma. Also, miR-26b was selectively increased in pleomorphic adenomas of the salivary gland. Collectively, our findings suggest that these miRNAs may play chief roles in the differential diagnosis of salivary gland tumors.