Necessity Is the Mother of Invention: The Development of Digital Genomics.

Abstract

Featured Article: Vogelstein B, Kinzler KW. Digital PCR. Proc Nat Acad Sci USA 1999;96:9236–41.3 An oft-cited proverb is that “necessity is the mother of invention,” and that is certainly the case for the development of digital PCR and the advent of digital genomics. In the early 1990s, we were exploring the use of released tumor DNA as a clinical biomarker. Tumor DNA can be readily distinguished from normal DNA by the presence of somatic driver gene mutations. We had already demonstrated that released tumor DNA could be detected in the urine or stool of patients with bladder or colorectal cancers, respectively, and sought to apply this approach to other bodily fluids, particularly plasma. However, the success of this approach was limited by the small amounts of tumor DNA and the large excess of DNA from normal cells in such clinical samples. How could one maximize the analytical specificity and sensitivity for the detection of rare mutant DNA molecules released from tumors? This question prompted the realization that maximum specificity could be achieved by genetically characterizing one molecule at a time. The featured article described the manifestation of this realization, called digital PCR. The increased signal-to-noise ratio obtained by this approach is conceptually identical to the increased signal-to-noise ratio associated with digital as compared to analog technologies in electronics. Digital PCR introduced the concept of digital genomics. With digital PCR, individual DNA template molecules are separately amplified and genetically characterized. This was achieved by optimizing the amplification of individual DNA templates in confined spaces (initially, in wells of a 384-well plate) in …