Objective MicroRNA (miRNA) is an abundant class of small noncoding RNAs that act as gene regulators. Recent studies have suggested that miRNA deregulation is associated with the initiation and progression of human cancer. However, information about cancer-related miRNA is mostly limited to tissue miRNA. The aim of this study was to find specific profiles of serum-derived miRNAs of ovarian cancer based on a comparative study using a miRNA microarray of serum, tissue, and ascites.

Methods From 2 ovarian cancer patients and a healthy control, total RNA was isolated from their serum, tissue, and ascites, respectively, and analyzed by a microarray. Under the comparative study of each miRNA microarray, we sorted out several miRNAs showing a consistent regulation tendency throughout all 3 specimens and the greatest range of alteration in serum as potential biomarkers. The availability of biomarkers was confirmed by qRT-PCR of 18 patients and 12 controls.

Results Out of 2222 kinds of total miRNAs that were identified in the microarray analysis, 95 miRNAs were down-regulated and 88 miRNAs were up-regulated, in the serum, tissue, and ascites of cancer patients. Among the miRNAs that showed a consistent regulation tendency through all specimens and showed more than a 2-fold difference in serum, 5 miRNAs (miR-132, miR-26a, let-7b, miR-145, and miR-143) were determined as the 5 most markedly down-regulated miRNAs in the serum from ovarian cancer patients with respect to those of controls. Four miRNAs (miR-132, miR-26a, let-7b, and miR-145) out of 5 selected miRNAs were significantly underexpressed in the serum of ovarian cancer patients in qRT-PCR.

Conclusions Serum miR-132, miR-26a, let-7b, and miR-145 could be considered as potential candidates as novel biomarkers in serous ovarian cancer. Also, serum miRNAs is a promising and useful tool for discriminating between controls and patients with serous ovarian cancer.