Circulating microRNAs as potential cancer biomarkers: the advantage and disadvantage

Abstract

MicroRNAs are endogenous single-stranded non-coding small RNA molecules that can be secreted into the circulation and exist stably. They usually exhibit aberrant expression under different physiological and pathological conditions. Recently, differentially expressed circulating microRNAs were focused on as potential biomarkers for cancer screening. We herein review the role of circulating microRNAs for cancer diagnosis, tumor subtype classification, chemo- or radio-resistance monitoring, and outcome prognosis. Moreover, circulating microRNAs still have several issues hindering their reliability for the practical clinical application. Future studies need to elucidate further potential application of circulating microRNAs as specific and sensitive markers for clinical diagnosis or prognosis in cancers.

Keywords: Biomarker; Cancer; Circulating microRNA; Diagnosis; Prognosis.

Fig. 1

The potential clinical applications of circulating miRNAs as tumor biomarkers for NSCLC. Diverse circulating miRNAs functioned at various aspects of clinical screening. In NSCLC patient for example, some differentially expressed miRNAs facilitated cancer diagnosis and prognosis while others contributed to treatment strategy selection by distinguishing tumor subtypes, monitoring tumor progression, or predicting the drug resistance. The expression levels of these cell-free miRNAs could be significantly differentiated at early stage, during the tumor progression, or until the late stage. Red color indicated increased expressed miRNAs in peripheral blood of NSCLC patients, while blue color indicated decreased ones

Fig. 2

Screening for potential circulating miRNA biomarkers for clinical applications. A great number of differentially expressed miRNAs were identified in laboratory investigations to constitute the candidate pool. In the further screening, candidates which had no correlation with individual characteristics were retained, as well as those with high specificity and sensitivity in order to distinguish cancer patients from healthy people accurately. They were considered as potential clinical biomarkers for large-scale validation