Liquid biopsy of gastric cancer patients: Circulating tumor cells and cell-free nucleic acids

Abstract

To improve the clinical outcomes of cancer patients, early detection and accurate monitoring of diseases are necessary. Numerous genetic and epigenetic alterations contribute to oncogenesis and cancer progression, and analyses of these changes have been increasingly utilized for diagnostic, prognostic and therapeutic purposes in malignant diseases including gastric cancer (GC). Surgical and/or biopsy specimens are generally used to understand the tumor-associated alterations; however, those approaches cannot always be performed because of their invasive characteristics and may fail to reflect current tumor dynamics and drug sensitivities, which may change during the therapeutic process. Therefore, the importance of developing a non-invasive biomarker with the ability to monitor real-time tumor dynamics should be emphasized. This concept, so called “liquid biopsy”, would provide an ideal therapeutic strategy for an individual cancer patient and would facilitate the development of “tailor-made” cancer management programs. In the blood of cancer patients, the presence and potent utilities of circulating tumor cells (CTCs) and cell-free nucleic acids (cfNAs) such as DNA, mRNA and microRNA have been recognized, and their clinical relevance is attracting considerable attention. In this review, we discuss recent developments in this research field as well as the relevance and future perspectives of CTCs and cfNAs in cancer patients, especially focusing on GC.

Keywords: Gastric cancer; Biomarker; Liquid biopsy; Circulating tumor cells; Cell-free nucleic acids; MicroRNA

Core tip: The potent utilities of circulating tumor cells and cell-free nucleic acids have recently attracted attention toward their clinical application in therapeutic management of cancer patients. The concept of “liquid biopsy” can allow for repeated samplings and real-time monitoring of tumor dynamics in each individual patient and consequently would facilitate the development of “tailor-made” cancer management programs. Before translating this novel diagnostic and prognostic assay into the clinical settings, further large-scale studies with well-established methods are required to validate its clinical relevance.