Abstract
The composite word “liquid biopsy” first appears in the medical literature in 1974 according to a PubMed search of the term. Sorrells (1974) published an article entitled Synovioanalysis (“liquid biopsy”) in the Journal of the Arkansas Medical Society. Talk about being ahead of your time! The next such use of the term does not occur until 1989, with reference to bronchoalveolar lavage (Sato and Chida, 1989). The modern usage of the term began in earnest during 2010 when it was associated with the characterization of circulating tumor cells (Lianidou et al., 2010; Chimonidou et al., 2011; Pachmann et al., 2011). Since that time >1900 publications have included this nomenclature in their titles, abstracts, or key word designations. Clearly, this technology has reached a “tipping point,” and is here to stay.
This special issue of Genetic Testing and Molecular Biomarkers was capably assembled by guest editor Ying-Hsiu Su, a specialist in this technology and a faculty member within my home department here at Drexel University and a member of the Baruch S. Blumberg Institute. Please see Dr. Su's Perspective piece “An Old Concept with a New Twist” for a state-of-the-art review of the field.
In this issue, assembled from contributions of scientific teams hailing from four different continents, we have selected articles that collectively cover a broad spectrum of liquid biopsy specimen types; nucleic acids; and technical approaches—to provide our readers with multiple windows into this burgeoning field of diagnostics and theranostics. We have articles using various blood fractions, urine specimens, and saliva specimens; we have research on naked DNAs, exosomal RNAs, and differentially methylated DNAs; and evaluations utilizing sequencing, quantitative means, and structural features.
In our lead research article by Teng et al., 2019, the authors characterize long non-coding (lnc) RNAs from plasma exosomes as a means to develop biomarkers for squamous cell lung cancer (SCLC 2019). Using this approach, they demonstrated that not only was the lncRNA SOX2-OT an informative SCLC biomarker, but also that its levels were correlated with tumor size, stage, and metastasis. In the next article by Burjanivova et al., 2019, a research team from Slovakia demonstrated that they were able to use droplet digital polymerase chain reaction to identify BGRAFV600E mutations associated with malignant melanoma directly from circulating tumor DNA, and suggest that this technology could be used to follow patients' response to treatment. Also in this issue, Zhang et al. (2019) from China use differential methylation of fetal and maternal circulating DNAs to diagnose trisomy 21. In this approach, methylation-sensitive restriction enzymes are coupled with quantitative polymerase chain reaction to determine the number of copies of fetal chromosome 21 that are circulating in the mothers' blood.
We invite you to learn and be stimulated as you go through this special “Liquid Biopsy” issue.