Serum MicroRNA Profiles As Novel Biomarkers For Post-operative Evaluation Of Non-small Cell Lung Cancer

Background and ObjectiveLung cancer is the leading cause of cancer mortality worldwide, accounting for12.7%of new cases and18.2%of death of all solid tumors. About80%of lung cancers are non-small cell lung cancers (NSCLCs) and surgery is the most important and effective management so far. Despite potentially curative surgery,40%of NSCLC patients will relapse within5years. Therefore, it is of crucial importance to develop biomarkers for post-operative evaluation to improve the prognosis. The use of miRNAs as novel biomarkers has gained growing interest in the last few years. MicroRNAs (MiRNAs) are a class of endogenous single-stranded non-coding RNAs of about22nucleotides in length. They can pair with sites in the3’-UTR of their target mRNAs. regulating gene expression through mRNA cleavage or translational inhibition at post-transcriptional level. Several studies indicated that some miRNAs up-regulated in pre-operative serum of patients with esophageal cancer, gastric cancer, and colorectal cancer were significantly reduced after surgical resection of primary tumor. These miRNAs may derived from tumor cells. However, a serum miRNA signature that can predict the effect of operation in NSCLC patients has not been found so far.The aim of this study was to explore the differentially expressed miRNAs in serum collected after operation compared to before in NSCLC patients with regular clinical follow-up, which may be potential biomarkers for post-operative evaluation of NSCLC patients.MethodsA total of45NSCLC patients with clinical pathological diagnosis were enrolled in this study. The blood samples were collected both before any treatment and7-10days after operation. In the initial biomarker screening stage,18samples from patients with stage Ⅰ, Ⅱ and Ⅲ (6each) were pooled together. Total RNAs were extracted and subjected to TaqMan Low Density Array (TLDA) to select miRNAs whose expression was altered before and after operation. Some of those differentially expressed miRNAs were selected to be verified in the subsequent experimental procedure (45NSCLC patients) using TaqMan probe-based RT-qPCR assay. The follow-up consisted of clinical examination at3-month intervals by the patients’ primary doctors. ResultsA total of754miRNAs were detected in TLDA, of which266miRNAs were present in the two pooled samples.180miRNAs were down-regulated and22miRNAs were up-regulated after operation compared to before. Based on previous research achievements in our lab and other published literature20miRNAs were selected to be verified in the RT-qPCR phase. Finally,5miRNAs were identified to be significantly down-regulated after operation, including miR-24, miR-34a, miR-155, miR-199a-5p and miR-221. In patients whose CEA were normal before operation, there was a trend that miR-24, miR-155, and miR-199a-5p were associated with disease-free survival (DFS) though statistical analysis was not significant. Additionally, miR-24, and miR-199a-5p were associated with DFS in adenocarcinoma (AC) patients and there was also a trend that miR-24. miR-155, and miR-199a-5p were associated with DFS in AC patients though statistical analysis was not significant.ConclusionsAfter TLDA detection phase and an experimental procedure using RT-qPCR assay, this study found5miRNAs were down-regulated in the serum of NSCLC patients collected after operation, which may be related with tumor load of NSCLC patients. The5miRNAs may serve as potential novel non-invasive biomarkers for post-operative evaluation of NSCLC patients, miR-24, miR-155, and miR-199a-5p for that of patients whose CEA were not up-regulated before operation, and miR-24. miR-155and miR-199a-5p for that of AC patients. These miRNA biomarkers might be powerful and useful for confirming the completeness of tumor resection and their expression level would provide useful information for the treatment after operation.