Distinct transcriptional and prognostic impacts of TERT promoter mutations C228T and C250T in papillary thyroid carcinoma

TERT promoter mutations C228T and C250T are associated with disease aggressiveness and poor clinical outcomes in patients with papillary thyroid carcinomas. However, very little is known about the transcriptional consequences of these mutations and whether they both carry similar oncogenic potential. Here we characterized the transcriptional disturbances and clinical outcomes associated with the presence of each of these two mutations using data derived from The Cancer Genome Atlas. We observed that tumors harboring the C228T mutation (n = 27) exhibited a 16-fold increase in TERT mRNA levels (P = 5.3 × 10-42), whereas C250T tumors (n = 8) showed only a two-fold increase in expression (P = 0.034). The C228T mutation was associated with the activation of signaling pathways controlling the cell cycle, cellular division, and extracellular matrix degradation. Univariate analysis demonstrated that the C228T mutation was associated with older age at diagnosis, large tumor size, lymph node invasion, and distant metastases at diagnosis. The C228T mutation was also associated with worse progression-free interval (PFI) in comparison to WT tumors (HR = 5,04; P < 0.001). This association remained significant in a multivariate analysis (HR = 3.74, P = 0.003) adjusting for BRAF-V600E status and ATA risk group. Our data indicate that TERT promoter mutations C228T and C250T have distinct transcriptional consequences in papillary thyroid carcinoma (PTC), suggesting a greater oncogenic potential for the C228T mutation. TERT promoter mutation C228T may be a useful prognostic marker to identify patients at high risk of distant recurrence. Clinical data for the C250T mutation is still limited, with no evidence up to date to confirm its prognostic significance.