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.