Differential Expression Levels of Plasma-derived MiR-146b and MiR-155 in Papillary Thyroid Cancer

Background: Specific circulating microRNAs (miRNAs) in each organ may contribute to the diagnosis and prognosis in some cancers. miRNA from papillary thyroid cancer (PTC) may be released into the bloodstream. This study was performed to detect miRNAs in the plasma and estimate their diagnostic usefulness for discriminating between benign and malignant lesions.

Methods: Patients who underwent thyroidectomy for benign thyroid nodules or PTC were enrolled in this study. The patients were divided into three groups: benign, PTC without lymph node metastasis (LNM), and PTC with LNM. The levels of miR-146b, miR-221, miR-222, and miR-155miRNA expression in blood samples before surgery were evaluated.

Results: Of 89 patients enrolled in this study, 19 and 70 had benign lesions (21.3%) and PTC (78.7%), respectively. The mean levels of miR-146b and miR-155 expression were higher in the PTC group than the benign group. For discrimination between benign and PTC lesions, the area under the ROC curve (AUC) for miR-146b was 0.649 with 61.4% sensitivity and 57.9% specificity. The AUC for miR-155 was 0.695 with 74.3% sensitivity and 63.2% specificity (P<0.05). The levels of miR-146b, miR-221, and miR-222 were slightly higher in the N1 group than the N0 group. The levels of miR-146b, miR-155, and miR-222 increased in proportion to tumor size.

Conclusions: miR-146b and miR-155 helped to discriminate between benign and malignant lesions. Circulating miRNA is likely a useful alternate serological marker for PTC. This preliminary study suggested that circulating miRNAs may be useful as follow-up tools as well as diagnostic tools.