Identification of circulating long non-coding RNA GAS5 as a potential biomarker for non-small cell lung cancer diagnosisnon-small cell lung cancer, long non-coding RNA, plasma, GAS5, biomarker.

Non-small cell lung cancer (NSCLC) is one of the most malignant cancers in the world. Early diagnosis of NSCLC has become especially important for patient treatment and prognosis. Increasing evidence suggest that long non-coding RNA GAS5 plays vital roles in cancer proliferation and differentiation in NSCLC. However, its clinical value in the diagnosis of NSCLC is unclear. The objective of this study was to evaluate the importance of circulating GAS5 as a biomarker for NSCLC diagnosis. In our study, quantitative real-time PCR (QRT-PCR) was applied to detect the GAS5 expression level in 80 pairs of cancer tissues and 57 pairs of plasma samples of NSCLC patients. Further analysis was performed to study the differential expression of circulating GAS5 in 111 NSCLC patients and 78 healthy controls in our study. The results showed that GAS5 decreased in NSCLC tissues compared to noncancerous tissues (P<0.001). Furthermore, the GAS5 expression level was statistically declined in early stage of NSCLC before surgery compared with healthy controls (P<0.05) and sharply increased in postoperative groups (P=0.026). ROC curve analysis for early stage of NSCLC with the combination of GAS5, CEA and CA199 showed that the area under the ROC curve (AUC) was 0.734 (95% CI, 0.628‑0.839; P<0.0005). In conclusion, circulating GAS5 could be functioned as a potential combined biomarker for screening NSCLC and patient monitoring after surgical treatment.