A panel of promoter methylation markers for invasive and noninvasive early detection of NSCLC using a quantum dots-based FRET approach

Non-small-cell lung cancer (NSCLC) leads to a significant proportion of cancer-related deaths, and early detection of NSCLC can significantly increase cancer survival rates. A promising approach has been studied to exploit DNA methylation, which is closely correlated to early cancer diagnosis. Herein, in order to realize the early detection of NSCLC, we utilized the developed quantum dots-based (QDs-based) fluorescence resonance energy transfer (FRET) nanosensor technique to analyze the promoter methylation in early stage NSCLC tissue samples and noninvasive bronchial brushing specimens. Using this method, the methylation levels can be quantitatively determined by measuring the signal amplification during FRET. A panel of three tumor suppressor genes (PCDHGB6, HOXA9 and RASSF1A) was assessed in 50 paired early stage NSCLC and their adjacent nontumorous tissue (NT) samples, and 50 early stage NSCLC bronchial brushing and normal specimens. The combined detection was able to identify not only tissue samples but noninvasive bronchial brushing specimens from control cases with a high degree of sensitivity of 92% (AUC=0.977, P<0.001) and 80% (AUC=0.907, P<0.001) respectively, indicating the versatility of promoter expression in invasive and noninvasive NSCLC samples. Therefore this approach can be used to sensitively analyze the methylation levels of cancer-related genes, which might be a potential tool for noninvasive early clinical diagnosis of cancers.