MicroRNA Expression Profling of Salivary Duct Carcinoma and Pleomorphic Adenomas of the Parotid Gland
RR Seethala, L Aspden, YE Nikiforov, MN Nikiforova. University of Pittsburgh, Pittsburgh, PA
Background: Salivary duct carcinoma (SDCA) is a rare but highly aggressive salivary gland malignancy that may either arise de novo or from pleomorphic adenomas (PA) for which pathogenesis is still largely unclear. MicroRNAs (miRNAs) are small non-coding RNA molecules that function as negative regulators of coding gene expression that have been shown to be differentially expressed between normal tissues and tumor at other organ sites. To improve the molecular understanding of these tumors, we evaluate the miRNA expression pattern parotid SDCA and PA.
Design: Human mature miRNA expresion was studied in 4 normal parotid tissues, 11 PA, and 9 SDCA (5 de novo, 4 SDCA ex PA) . Total RNA was extracted from frozen tissue using Trizol reagent (Invitrogen). RNA quality was evaluated on 2100 Bioanalyzer (Agilent). First, 4 salivary duct carcinomas, 4 pleomorphic adenomas and 4 normal parotids were analyzed for 328 human mature miRNAs using Flexmir MicroRNA Human Panel (Exiqon) on Luminex 200. Analysis of miRNA expression was performed using Luminex IS software v.2.3 (Luminex) relative to normal tissue. Subsequently, expression of selected miRNAs was validated and extended to include all selected samples by real-time PCR on ABI 7500 (Applied Biosystems).
Results: The miRNA expression in both SDCA and PA was different as compared to normal tissue. MiRNAs strongly upregulated (> 24 folds) in tumors vs normal tissue included miR-181d, miR-501, and miR-25, while the miRNAs most downregulated included miR-32, miR-153, miR-380-3p. While SDCA and PA showed similar levels in many miRNAs, a few miRNAs were differentially expressed between SDCA and PA: miR-154 was upregulated (>11 folds) in PA vs. SDCA, while miR-99b was upregulated (>10 folds) in SDCA vs PA and normal tissue. Interestingly, miR-424, which was upregulated in PA (77 folds vs normal), was still higher in SDCA x PA (40 folds) than in SDCA de novo (2 folds). A search of MiRanda and PicTar databases for miRNA target prediction demonstrated PLAG1, known to be commonly altered in PA, as one potential target gene for miR-424.
Conclusions: Both SDCA and PA show differential miRNA expression with respect to normal parotid tissue. Despite a similar miRNA expression profile, there are several key miRNA that are differentially expressed between SDCA and PA. MiR-424 expression is one key difference between SDCA ex PA and SDCA de novo. A miRNA database search raises the possibility that miR-424 may affect PLAG1 regulation.
Category: Head & Neck
Monday, March 9, 2009 1:00 PM
Poster Session II # 158, Monday Afternoon