Direct Comparison of Metastasis-Related miRNAs Expression Levels in Circulating Tumor Cells, Corresponding Plasma, and Primary Tumors of Breast Cancer Patients.

Background: Circulating tumor cells (CTCs) and microRNAs (miRNAs) are important in liquid biopsies in which peripheral blood is used to characterize the evolution of solid tumors. We evaluated the expression levels of miR-21, miR-146a, miR-200c, and miR-210 in CTCs of breast cancer patients with verified metastasis and compared their expression levels in corresponding plasma and primary tumors.

Methods: Expression levels of the miRNAs were quantified by quantitative reverse transcription PCR (RT-qPCR) in (a) 89 primary breast tumors and 30 noncancerous breast tissues and (b) CTCs and corresponding plasma of 55 patients with metastatic breast cancer and 20 healthy donors.

Quantification of circulating miRNAs in plasma: effect of preanalytical and analytical parameters on their isolation and stability.

Circulating miRNAs are intensively evaluated as promising blood-based biomarkers. This growing interest in developing assays for circulating miRNAs necessitates careful consideration of the effects of preanalytical and analytical parameters on the isolation, stability, and quantification of circulating miRNAs. By using quantitative stem-loop RT-PCR, we compared the relative efficiencies of four miRNA isolation systems and different storage conditions.