Gene expression profiling of endobronchial ultrasound (EBUS)‐derived cytological fine needle aspirates from hilar and mediastinal lymph nodes in non‐small cell lung cancer

Abstract

Endobronchial ultrasound (EBUS) allows minimally invasive sampling of hilar and mediastinal lymph nodes and has an established role in non-small cell lung cancer (NSCLC) diagnosis and staging. Molecular biomarkers are being explored increasingly in lung cancer research. Gene expression profiling (GEP) is a microarray-based technology that comprehensively assesses genome-wide changes in gene expression that can provide tumour-specific molecular signatures with the potential to predict prognosis and treatment responsiveness. We assessed the feasibility of using EBUS-derived aspirates from benign and tumour-infiltrated lymph nodes for GEP. RNA was extracted from EBUS-directed transbronchial fine needle aspiration samples in routine clinical practice. GEP was subsequently performed in six patients with NSCLC, three of whom had tumour-infiltrated nodes and three who had benign lymph nodes; the differences in gene expression were then compared. RNA was successfully extracted in 29 of 32 patients, 12 of whom were diagnosed with NSCLC. RNA yield (median, 12.1 μg) and RNA integrity (median, 6.3) were sufficient after amplification for GEP. Benign and malignant nodes in adenocarcinoma were discriminated by principal component analysis and hierarchical clustering with different expression patterns between malignant and benign nodes. We have demonstrated the feasibility of RNA extraction and GEP on EBUS-derived transbronchial fine needle aspirates from benign and tumour-infiltrated lymph nodes in patients with known NSCLC in routine clinical practice. Further studies on larger patient cohorts are required to identify expression profiles that robustly differentiate benign from malignant lymph nodes in NSCLC.