engleski

Frequency of BRAF V600E mutated alleles in patients with papillary thyroid cancer and its association with metastatic status

BRAF V600E mutations are the most common genetic alteration in patients with papillary thyroid cancer. Their prognostic value and association with aggressive features in patients with papillary thyroid cancer have been extensively studied but with conflicting results. Based on clonal evolution model and confirmed intralesional heterogeneity of thyroid papillary cancer we hypothesize that frequency of BRAF V600E mutated alleles might be associated with aggressiveness of thyroid papillary cancer. The aim of this study was to determine the frequency of BRAF V600E mutated alleles in patients with thyroid papillary cancer and to determine if it is associated with metastatic status. In this study we analysed thyroid papillary cancer samples from 72 patients (27 with localised disease, 35 with lymph node metastases, and 10 with distant metastases). DNA was isolated from formalin-fixed paraffin-embedded tissue and assessed for presence of BRAF V600E mutation using competitive allele-specific TaqMan polymerase chain reaction. Validated assay for BRAF V600E mutation and BRAF reference assay were used enabling us to calculate percentage of mutated alleles. To determine accurate frequency of mutated alleles in cancer cells, percentage of mutated alleles was normalized to the percentage of cancer cells in samples. This research was funded by Croatian Science Foundation project IP- 2019-04-1130. BRAF V600E mutation was found in 47 (65, 3%) out of 72 patients ; 19 out of 27 (70, 4%) patients with localised disease, 24 out of 35 (68, 6%) patients with lymph node metastases, and 4 out of 10 (40%) patients with distant metastases. There was no significant difference between these groups of patients regarding presence of BRAF V600E mutation (p=0, 15). Among patients with mutation, frequency of mutated alleles varied significantly, from 1% to 99%. Out of 47 patients with BRAF V600E mutation, 32 (68%) had frequency of mutated alleles < 30%, 11 (23%) had 30-60% mutated alleles which corresponds to heterozygous BRAF status, while 4 patients (8, 5%) had frequency of mutated alleles >60%. There was no significant difference in frequency of BRAF mutated alleles between groups of patients without metastases, with lymph node metastases and with distant metastases (p=0, 71). Our results indicate significant clonal heterogeneity in papillary thyroid cancer lesions regarding BRAF mutation status. No association was found between frequency of BRAF mutated alleles and metastatic status.

thyroid cancer ; prognostic markers ; BRAF mutations

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