Clinical significance of circulating miR-126 quantification in malignant mesothelioma patients

OBJECTIVES: Aim of this study was to evaluate the accuracy and precision of the detection of individual miRNA as clinical biomarkers in the serum. DESIGN AND METHODS: miRNA-126 was quantified in serum using endogenous and exogenous controls for normalization and the accuracy and precision of the method evaluated. The diagnostic value of serum miRNA-126 was evaluated in malignant mesothelioma (MM) and non-small-cell lung cancer (NSCLC) patients using both relative and absolute qRT-PCR methods. RESULTS: The use of endogenous invariant and exogenous synthetic controls as well sample dilution markedly improves the accuracy and precision of the assay. The inter- and intra-assay analyses revealed that relative qRT-PCR is a more reliable method. Circulating miR-126 detected in the serum by relative qRT-PCRs was found low-expressed in both malignancies, significantly differentiated MM patients from healthy controls and NSCLC from MM, but do not discriminate NSCLC patients from control subjects. Kaplan-Meier analysis revealed that low level of circulating miR-126 in MM patients was strongly associated with worse prognosis. CONCLUSIONS: We propose that this approach can be adopted for accurate analysis of other suitable circulating miRNA markers of different types of cancer.