Allele specific Taqman-based real-time PCR assay to quantify circulating BRAFV600E mutated DNA in plasma of melanoma patients

BackgroundBRAF is the most frequently mutated oncogene in melanoma with BRAF^V600E mutation accounting for 92% of all BRAF variants. As this event occurs early in melanoma progression, the quantification of BRAF-mutated alleles in plasma may represent a useful biomarker for noninvasive diagnosis and prediction of response to therapy.MethodsWe propose an assay based on the use of a locked nucleic acid probe and an allele specific primer to measure plasma-circulating BRAF^V600E concentration in patients affected by cutaneous melanoma (n = 55) and non-melanoma skin cancers (n = 13) as well as 18 healthy subjects. The assay is highly sensitive and accurate in detecting down to 0.3% of mutated allele in plasma.ResultsA significant difference between the control group and invasive melanomas (p < 0.01) was evidenced in BRAF^V600E concentration, either as relative percentage or absolute values. ROC curve indicated that BRAF^V600E absolute concentration has the maximal diagnostic relevance with 97% sensitivity and 83% specificity. Comparison of the results obtained in plasma with those found in the corresponding tissues indicated an 80% concordance.ConclusionsThe allele specific Taqman-based real-time PCR assay allows the sensitive, accurate and reliable measurement of BRAF^V600E mutated DNA in plasma.