mRNA and miRNA analyses in cytologically positive endobronchial ultrasound-guided transbronchial needle aspiration: Implications for molecular staging in lung cancer patients

BACKGROUND Lung cancer is highly aggressive and tends to metastasize early. Therefore, accurate mediastinal staging is important for therapeutic decision making. Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has emerged as a minimally invasive procedure for mediastinal lymph node sampling and cancer staging. Classical EBUS-TBNA cytology has been combined with molecular staging techniques to improve sensitivity and specificity. This study aimed to assess mRNA integrity in samples acquired by EBUS-TBNA in the clinics. As proof-of-principle experiments, we also investigated whether stable miRNA could be detected in these samples. METHODS Integrity of mRNA isolated from tumor-positive EBUS-TBNA samples was assessed by calculating the RNA integrity number (RIN). In addition, 4 microRNAs were investigated (miRNA 21, miRNA 155, miRNA 200c, and miRNA 34a) because their relation to lung cancer has been documented recently. A group of patients with benign mediastinal lymphadenopathy served as a control. RESULTS mRNA isolated from EBUS-TBNA samples was nearly completely degraded if handled under clinical conditions (RIN <5). Intact miRNA was detected in all samples, with no nonspecific amplification in negative control samples. miRNA 21 and miRNA 200c levels were significantly higher in tumor-positive than in control samples (miRNA 21: median, 325,678 [range, 34,822-583,502] vs. 801,430 (range, 17,013-5,362,145]; P < .05; miRNA 200c: median, 9,198 [range, 610-211,121] vs. 42,870 [range, 0-926,252]; P < .05). CONCLUSIONS Under clinical conditions, mRNA detection is likely unsuitable for improving sensitivity of EBUS-TBNA-facilitated cancer staging. In contrast, detection of miRNA combined with EBUS-TBNA cytology may improve staging sensitivity. Cancer (Cancer Cytopathol) 2014;122:292-298. (c) 2014 American Cancer Society.