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Adenoid cystic carcinoma (ACC) is a malignant tumor of the salivary glands but identical tumors can also arise from the breast. Despite their similar histomorphological appearance the salivary gland- and the breast-derived forms differ in their clinical features: while ACC of the salivary glands (sACC) have an aggressive clinical course, the breast-derived form (bACC) shows a very favourable clinical outcome. To date no exact molecular alterations have yet been identified which would explain the diverse clinical features of the ACCs of different origin. In our pilot experiment we investigated the post-transcriptional features of ACC cases by performing microRNA-profiling on 2-2 bACC and sACC tissues and on 1-1 normal breast and salivary gland tissue. By comparing the microRNA-profiles of the investigated samples we identified microRNAs which were expressed differently in bACC and sACC cases according to their normal controls: 7 microRNAs were overexpressed in sACC cases and downexpressed in bACC tumors (let-7b, let-7c, miR-17, miR-20a, miR-24, miR-195, miR-768-3) while 9 microRNAs were downexpressed in sACC cases and overexpressed in bACC tissues (let-7e, miR-23b, miR-27b, miR-193b, miR-320a, miR-320c, miR-768-5p, miR-1280 and miR-1826) relative to their controls. We also identified 8 microRNAs which were only expressed in sACCs and one microRNA (miR-1234) which was only absent in sACC cases. By target predictor online databases potential targets of the these microRNAs were detected to identify genes that may play central role in the diverse clinical outcome of bACC and sACC cases.

Introduction: Adenoid cystic carcinoma is a salivary gland-derived malignant tumor, but rarely it can originate from the breast, too. The salivary gland-derived form shows a very aggressive clinical outcome, while adenoid cystic carcinoma of the breast has mostly a very good prognosis., Aim: The aim of the authors was to compare the miRNA-expression profile of breast- and salivary gland-derived cases., Method: The miRNA-profiles of two salivary gland derived and two breast-derived adenoid cystic carcinoma tissues as well as one normal breast and one salivary gland tissues were analysed using the Affymetrix® Gene Chip., Results: The expression of some miRNAs differed in the tumor tissues compared to their controls: the let-7b was overexpressed in salivary gland-derived adenoid cystic carcinoma, while decreased in breast-derived adenoid cystic carcinoma. In addition, the miR-24 was decreased in salivary gland-derived but overexpressed in breast-derived adenoid cystic carcinomas. The miR-181a-2* was only detected in salivary gland-derived adenoid cystic carcinomas., Conclusions: Through post-transcriptional regulation of the genes, the diverse expression of some miRNAs may partially explain the diverse clinical outcome of salivary gland-derived and breast-derived adenoid cystic carcinomas.