circIARS: a potential plasma biomarker for diagnosing non-small cell lung cancer

Abstract

Non-small cell lung cancer (NSCLC) is one of the most prevalent cancers in the world, and early diagnosis can effectively improve patient survival. Here, differentially expressed circIARS genes are screened from the sequencing results, and their molecular characteristics are examined by Sanger sequencing, RNase R assay, agarose gel electrophoresis (AGE), and fluorescence in situ hybridization (FISH). Real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) is performed to detect the expression level of circIARS. The diagnostic value of the signature is analyzed using a subject operating characteristic (ROC) curve. Moreover, plasma is collected from postsurgical, chemotherapy, and relapse patients to investigate the prognostic value of circIARS in NSCLC. The expression of circIARS is greater in both the plasma and tissues of NSCLC patients than in those of healthy individuals, and could be used to distinguish NSCLC patients from patients with benign pulmonary disease (BPD), small cell lung cancer (SCLC) patients, and healthy individuals. The expression level of circIARS relatively decreases after antitumor therapy, such as chemotherapy, and relatively increases after recurrence. ROC analysis reveals that circIARS has better detection efficiency than traditional markers. In addition, circIARS expression level is strongly correlated with several clinicopathological parameters. Finally, we tentatively predict the downstream miRNAs or RBP that might bind to circIARS. Plasma circIARS is significantly greater in NSCLC patients and has good stability and specificity as a diagnostic marker, which could aid in the adjuvant diagnosis and dynamic monitoring of NSCLC.

1. Introduction

Lung cancer is the leading cause of cancer death in men and women. The burden of treatment for non-small cell lung cancer (NSCLC), the most common type of lung cancer, has become a growing concern [1]. Despite the rapidly evolving prospects for NSCLC treatment, the disease is often diagnosed by local progression or metastasis or is already advanced. In contrast, early detection and treatment of NSCLC can significantly improve survival rates [1]. Among the ancillary diagnostic methods for detecting NSCLC, chest X-ray and sputum cytology often fail to detect NSCLC early; although bronchoscopy is excellent at detecting lung tumors, it is invasive. In addition, although CT is noninvasive and highly sensitive, it is often accompanied by overdiagnosis [2,3].

Several studies have confirmed the effects of noncoding RNAs (ncRNAs) and mRNAs on the early screening and biological progression of NSCLC, such as the inhibition of growth, ING5 overexpression, miR-34c-5p/Snail1 inhibition of EMT and lung cancer cell invasion [4], and on the pseudogene DUXAP10 which contributes to gefitinib resistance in NSCLC by inhibiting OAS2 expression [5]. Therefore, the screening of simple and efficient diagnostic markers and the development of minimally invasive techniques for the diagnosis of early-stage NSCLC are of great clinical importance.

Circular RNA (circRNA) is a covalently closed loop that lacks the 5′ cap and 3′ tail and is usually formed by reverse shearing of the precursor mRNA (premRNA) [6]. circRNAs are evolutionarily conserved, highly abundant in eukaryotes, and tissue-, cell type-, or developmental stage specific. It is also more stable than other linear RNAs due to the lack of exposed ends that are easily degraded, which allows circRNAs to be detected noninvasively in body fluids [7]. This finding illustrates the natural advantages of circRNAs over other noncoding RNAs (ncRNAs) that act as molecular markers. Advances in high-throughput sequencing and related bioinformatics algorithms have facilitated not only the discovery of more types of circRNAs in multiple model organisms but also the emergence of practical applications of circRNAs, including their utilization as molecular markers for a variety of diseases [8]. In addition, circRNAs have been found to regulate tumor cell proliferation, migration, and apoptosis through multiple mechanisms [9,10]. For instance, circHIPK3 increases WEE1 expression via miR-124 in glioma and promotes cell proliferation and invasion [11]. cIARS physically interacts with ALKBH5 and positively regulates sorafenib (SF)-induced iron death by inhibiting the ALKBH5-mediated inhibition of autophagy [12]. As discussed above, circRNAs have great potential as new biomarkers and for promoting the biological progression of tumors.