BRAF mutation in papillary thyroid cancer (#194)
Introduction: Mutations in the BRAF oncogene have been linked to papillary thyroid cancer (PTC) in various populations, giving it potential as a tumourigenic marker. The most common mutation is V600E which leads to activation of MAPK and uncontrolled cellular growth. PCR based methods are used to detect the BRAF mutation but their detection sensitivity and accuracy has not been examined. This study compares the utility of three methods of detection of the V600E mutation in a Sydney PTC cohort.
Methods DNA was extracted from histologically confirmed cancer and non cancer thyroid tissue from17 patients who had a thyroidectomy at RPA Hospital. Evidence for the BRAF mutation was examined in all samples using the BRAF ACE kit(1) and melt curve analysis by Light Cycler(R) 480(2) and results were confirmed by direct sequencing. HT29 cells, containing the BRAF mutation were used as positive control and for determination of assay sensitivity.
Results: The assays used between 10 and 30ng of DNA and had similar sensitivities (~70%). By direct sequencing 11 patients were BRAF positive but only 10 were detected by either Melt curve analysis or BRAF ACE kit. There were no mutations found in the normal tissues by any method. Compared with Melt curve analysis the BRAF ACE kit is labour intensive (2 vs 0.5 days) and uses the largest amount of sample (30 vs 10ng DNA).
Conclusion: Similar to other studies, the incidence of BRAF mutation in this cohort is 65 %. At present, direct sequencing remains the most reliable method for detection of BRAF mutation. However melt curve analysis has potential utility and may be readily adaptable as a routine test. As clinical decisions are now being made on samples obtained by fine needle biopsy the development of reliable and sensitive techniques using smaller amounts of DNA are essential.
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