Expression of miRNAs in adenoid cystic carcinomas of the breast and salivary glands

Abstract

Despite their similar histomorphologic appearance, adenoid cystic carcinomas of the breast and salivary glands (bACCs and sACCs, respectively) are clinically and pathologically diverse. We studied the expression levels of 18 microRNAs (miRNAs) in bACCs and sACCs and control normal breast and salivary gland tissues (bNs and sNs, respectively) by quantitative real-time polymerase chain reaction on formalin-fixed paraffin embedded tissues. miRNAs showing significant differences between the study groups were selected for target prediction. Increased expression of miR-17 and miR-20a was found in bACCs compared with bNs (p(miR-17) = 0.017 and p(miR-20a) = 0.024, respectively), while the expression level of let-7b and miR-193b was lower in sACCs compared with normal sNs (p let-7b = 0.032 and p(miR-193b) = 0.023, respectively). Expression of miR-23b and miR-27b differed between normal breast and normal salivary gland tissue (p(miR-23b) = 0.007 and p(miR-27b) = 0.024, respectively), but not between bACCs and sACCs. The potential target mRNAs CCND1 and BCL2 were identified as reported targets of let-7b, miR-193b, miR-17, and miR-20a. Expression of their corresponding proteins cyclin D1 and Bcl-2 was studied by immunohistochemistry. We found both proteins overexpressed in bACCs as well as sACCs in comparison with corresponding normal tissues. However, expression of cyclin D1 and Bcl-2 proteins was not significantly different between bACCs and sACCs or between bNs and sNs. Although no differences in miRNA levels were found between bACCs and sACCs, in both organs, miRNA expression level was highly different between tumor tissue and control tissue.