Impact of molecular alterations of BRAF in the pathogenesis of thyroid cancer

BRAF alterations represent a novel indicator of the progression and aggressiveness of thyroid carcinogenesis. So, the main aim of the study was to elucidate the involvement of BRAF gene mutations and its expression in Kashmiri (North India) patients and investigate their association with clinico-pathological characteristics. Mutational analysis of BRAF gene was performed by polymerase chain reaction followed by DNA sequencing, whereas analysis of BRAF protein expression was done by western blotting. Overall mutations in BRAF was found to be 25% (15 of 60) and all of them were transversions (T > A) affecting codon 600 (valine to glutamine), restricted only to papillary thyroid cancer and well-differentiated grade. Patients with well-differentiated disease and in particular elevated thyroid-stimulating hormone levels were significantly associated with BRAF mutations (P < 0.05). Overall, 90% (54 of 60) of thyroid cancer cases showed increased expression of BRAF and non-smokers being significantly associated with BRAF over-expression. Totally, 86.7% (13 of 15) of BRAF mutation-positive patients were having over-expression of BRAF protein, whereas 91.2% (41 of 45) of patients with wild-type BRAF status were having over-expressed BRAF protein (P > 0.05). We conclude that both mutational events as well as over-expression of BRAF gene is highly implicated in pathogenesis of thyroid cancer and the BRAF protein over-expression is independent of the BRAF mutational status of thyroid cancer patients.