A high prevalence of the BRAF(V600E) somatic mutation was recently reported in several series of papillary thyroid carcinomas (PTC). This mutation appears to be particularly prevalent in PTC with a predominantly papillary architecture. Another BRAF mutation (K601E) was detected in a follicular adenoma and in some cases of the follicular variant of PTC. The few studies on record provided controversial data on the relationship between the occurrence of BRAF mutations and clinicopathologic parameters such as gender, age and tumour staging. In an attempt to clarify such controversies we decided to enlarge our previous series to 315 tumours or tumour-like lesions diagnosed in 280 patients, including a thorough analysis of several clinicopathologic features. The BRAF(V600E) mutation was exclusively detected in PTC with a papillary or mixed follicular/papillary architecture both of the conventional type (46%) and of other histotypes, such as microcarcinoma (43%), Warthin-like PTC (75%) and oncocytic variant of PTC (55%). The BRAF(K601E) mutation was detected in four of the 54 cases of the follicular variant of PTC (7%). The mean age of patients with conventional PTC harbouring BRAF(V600E) (46.7 years) was significantly higher (P<0.0001) than that of patients with conventional PTC without BRAF(V600E) (29.5 years). The BRAF (BRAF(V600E)) mutated PTC did not exhibit signs of higher aggressiveness (size, vascular invasion, extra-thyroid extension and nodal metastasis) and were in fact less often multicentric than PTC without the mutation.

Due to their different molecular alterations, these cell lines represent a valuable tool to study the molecular mechanisms underlying thyroid carcinogenesis. We suggest that genotypic analyses should be included as a routine procedure to guarantee the uniqueness of each cell line used in research.

Background: Cell lines are often poorly characterized from a genetic point of view, reducing their usefulness as tumor models. Our purpose was to assess the genetic background of eight commonly used human thyroid carcinoma models and to compare the findings with those reported for primary tumors of the gland.

BackgroundThyroid carcinomas show a high prevalence of mutations in the oncogene BRAF which are inversely associated with RAS or RET/PTC oncogenic activation. The possibility of using inhibitors on the BRAF pathway as became an interesting therapeutic approach. In thyroid cancer cells the target molecules, implicated on the cellular effects, mediated by inhibition of BRAF are not well established. In order to fill this lack of knowledge we studied the proliferation and survival pathways and associated molecules induced by BRAF inhibition in thyroid carcinoma cell lines harbouring distinct genetic backgrounds.MethodsSuppression of BRAF pathway in thyroid cancer cell lines (8505C, TPC1 and C643) was achieved using RNA interference (RNAi) for BRAF and the kinase inhibitor, sorafenib. Proliferation analysis was performed by BrdU incorporation and apoptosis was accessed by TUNEL assay. Levels of protein expression were analysed by western-blot.ResultsBoth BRAF RNAi and sorafenib inhibited proliferation in all the cell lines independently of the genetic background, mostly in cells with BRAFV600E mutation. In BRAFV600E mutated cells inhibition of BRAF pathway lead to a decrease in ERK1/2 phosphorylation and cyclin D1 levels and an increase in p27Kip1. Specific inhibition of BRAF by RNAi in cells with BRAFV600E mutation had no effect on apoptosis. In the case of sorafenib treatment, cells harbouring BRAFV600E mutation showed increase levels of apoptosis due to a balance of the anti-apoptotic proteins Mcl-1 and Bcl-2.ConclusionOur results in thyroid cancer cells, namely those harbouring BRAFV600Emutation showed that BRAF signalling pathway provides important proliferation signals. We have shown that in thyroid cancer cells sorafenib induces apoptosis by affecting Mcl-1 and Bcl-2 in BRAFV600E mutated cells which was independent of BRAF. These results suggest that sorafenib may prove useful in the treatment of thyroid carcinomas, particularly those refractory to conventional treatment and harbouring BRAF mutations.