BRAF V600E Mutated Gene Variant as a Circulating Molecular Marker in Metastatic Melanoma Patients

Abstract

Cutaneous metastatic melanoma management has recently approached the age of individualized therapy (Romano et al., 2011). The discovery that the 1799T>A point mutation in the BRAF oncogene (BRAFV600E) occurs in ~50% of melanoma lesions and that melanoma cells bearing the mutation are oncogene addicted, i.e., strictly dependent upon BRAFV600E activity for growth and survival, have pointed to BRAFV600E as a promising target for therapy. Drugs targeting BRAF have been developed, and several clinical trials are currently ongoing. Phase I-II results recently reported remarkable tumor regression in the great majority of patients bearing disseminated BRAFV600E mutated melanoma disease after treatment with BRAFV600E-specific inhibitors. In these trials, BRAF mutational status is determined to select patients who may benefit from therapy. However, melanoma specimens are not always available to perform this analysis; moreover, a negative result in a single tumor biopsy may cover the presence of mutation-positive tumor lesions. Because blood has been proven to represent a valuable alternative source of tumor-derived cells as well as of tumor-derived DNA, several technical approaches have been studied to detect BRAFV600E in RNA/DNA extracted from bloodderived circulating tumor cells and in circulating free DNA isolated from plasma or serum. For these reasons, circulating BRAFV600E has the potential as both a specific melanoma molecular marker and a monitoring factor to be used to evaluate clinical response. In this chapter, we summarize the clinical and biological features of BRAF mutation in melanoma. Furthermore, we report a new BRAFV600E detection assay developed in our lab that shows high sensitivity and specificity.