Circulating cell-free DNAs and miRNAs as promising non-invasive biomarkers for early detection of gastric cancer.

Early diagnosis of gastric cancer is critical to decrease the mortality of this globally fatal disease. Currently, endoscopic biopsy is the gold standard for diagnosis of gastric cancer. However, invasiveness and high expense limit its application. Hence, non-invasive and cost-effective biomarkers for early detection and subsequent management are crucial steps to monitor gastric cancer. Recent studies suggest that circulating cell-free nucleic acids, including circulating tumor DNAs and microRNAs (miRNAs), are promising for various applications. Development of such blood-based biomarkers is expected to facilitate detection, predict prognosis, monitor chemotherapeutic response and manage recurrence of human cancers. In this review, the characteristics of circulating cell-free DNAs and miRNAs will be elucidated, including their origin and dysregulation. Mutations and hypermethylation of circulating DNAs, abnormal alternations of expression of circulating miRNAs will be revealed as aberrant changes indicating gastric cancer. The roles of circulating DNAs and miRNAs for early detection of gastric cancer will be focused on, as well as the challenges of developing circulating nucleic acids as biomarkers.