MicroRNA-132 is frequently down-regulated in ductal carcinoma in situ (DCIS) of breast and acts as a tumor suppressor by inhibiting cell proliferation

Ductal carcinoma in situ (DCIS) is the most common type of non-invasive breast cancer. The currently accepted step-wise model suggests that breast cancer progressed in the following manner: normal breast cell → usually ductal hyperplasia (UDH) → atypical ductal hyperplasia (ADH) → DCIS → invasive ductal carcinoma (IDC). Therefore, DCIS can serve as a good model to analyze the mechanism underlying invasive breast cancer occurrence. MicroRNAs (miRNAs) are a novel class of small non-coding RNAs (∼22 nt) involved in the regulation of various biological processes. Altered miRNA expression could also contribute to the origination of cancer, including breast cancer. Here, by using miRNA microarray and real time PCR, we analyzed the miRNA expression profile in 21 DCIS and the corresponding normal tissues. miR-10b, miR-125b, miR-132, miR-145, miR-154-3p, miR-382-5p and miR-409-3p were found to be significantly deregulated in DCIS. Results from CCK-8 assay showed that the overexpression of miR-132 could inhibit the proliferation of breast cancer cell line. High expression of miR-132 could also inhibit the colony formation. Our findings will lead to further understanding of the development of breast cancer.