Potential diagnostic value of miR-155 in serum from lung adenocarcinoma patients

Recent studies have demonstrated that microRNAs (miRNAs) are stably detectable in plasma/serum. The expression profile of miR-21 and miR-155 was evaluated in the present study, since miR-21 is frequently reported as highly expressed in several types of cancers, while miR-155 was also found to be significantly expressed in lung cancer cell lines. Using in vitro studies, we found that miR-155 could be a candidate plasmatic biomarker for diagnosing lung cancer. We assessed the differences in levels of miR-21, miR-155, carcinoembryonic antigen (CEA) and carbohydrate antigen 125 (CA-125) expression in serum samples between lung cancer patients and healthy controls. We estimating the clinical diagnostic value of miR-155 independently and combined with CA-125 and/or CEA levels. The present study consisted of three parts: i) confirmation of the stable expression of miR-155 in the patient serum samples using quantitative PCR; ii) confirmation of higher miR-155, CEA and CA-125 levels in the patient serum samples when compared with levels in the normal controls by quantitative PCR; iii) evaluation of miR-155, CEA and CA-125 concentrations in serum sampes for tumor diagnosis of lung adenocarcinoma via ROC (receiver-operating characteristic) analysis. The results showed that i) expression of miR-155 was significantly higher in the serum of lung adenocarcinoma patients than that in normal controls (P<0.05); ii) testing results of serum miR-155 levels showed a much higher sensitivity (0.722) than that for CA-125 or CEA; iii) CEA associated with CA-125 had the highest Youden's index (0.639) in all terms of combinations; and iv) combined with CA-125 testing, miR-155 received a competitive sensitivity (0.889) and specificity (0.688) for diagnosing lung adenocarcinoma (OOP=14.88). In conclusion, endogenous miR-155 stably existed in patient serum and could be sensitively and specifically measured. Overexpression of miR-155 in serum specimens could constitute a diagnostic marker for the early detection of lung adenocarcinoma.