Saturday, November 21, 2015

PCR testing for melanoma

Polymerase chain reaction (PCR) is a technique that is used to amplify trace amounts of DNA (and in some instances, RNA) located in or on almost any liquid or surface where DNA strands may be deposited.  It is an exceedingly sensitive technique to detect molecules.  In everyday medicine it can be used to check for the presence of a wide variety of substances - pertussis from a nasal swab, chlamydia and gc in urine, viral load of HIV patients from their blood sample, fungus in skin scrapings, and even genetic mutations.  It would be super cool if we could utilize this technique to accurately identify the presence and characteristics of melanoma cells....both for diagnosis as well as monitoring effects of treatment.  Here are some peeps who are working on it:

SNPase-ARMS qPCR:  Ultrasensitive Mutation-Based Detection of Cell-Free Tumor DNA in Melanoma Patients.  PLoS One. 2015 Nov 12.  Stadler, Eder, Pratscher, et al.

"Cell-free circulating tumor DNA in the plasma of cancer patients has become a common point of interest as indicator of therapy options and treatment response in clinical cancer research. Especially patient- and tumor-specific single nucleotide variants that accurately distinguish tumor DNA from wild type DNA are promising targets. The reliable detection and quantification of these single-base DNA variants is technically challenging. Currently, a variety of techniques is applied, with no apparent "gold standard". Here we present a novel qPCR protocol that meets the conditions of extreme sensitivity and specificity that are required for detection and quantification of tumor DNA. By consecutive application of two polymerases, one of them designed for extreme base-specificity, the method reaches unprecedented sensitivity and specificity. Three qPCR assays were tested with spike-in experiments, specific for point mutations BRAF V600E, PTEN T167A and NRAS Q61L of melanoma cell lines. It was possible to detect down to one copy of tumor DNA per reaction , at a background of up to 200 000 wild type DNAs. To prove its clinical applicability, the method was successfully tested on a small cohort of BRAF V600E positive melanoma patients."

Still needs to be tested on a greater scale...but sounds like progress. - c

No comments:

Post a Comment