Highly prevalent TERT promoter mutations in aggressive thyroid cancers

Abstract

Mutations 1 295 228 C>T and 1 295 250 C>T (termed C228T and C250T respectively), corresponding to -124 C>T and -146 C>T from the translation start site in the promoter of the telomerase reverse transcriptase (TERT) gene, have recently been reported in human cancers, but not in thyroid cancers yet. We explored these mutations in thyroid cancers by genomic sequencing of a large number of primary tumor samples. We found the C228T mutation in 0 of 85 (0.0%) benign thyroid tumors, 30 of 257 (11.7%) papillary thyroid cancers (PTC), 9 of 79 (11.4%) follicular thyroid cancers (FTC), 3 of 8 (37.5%) poorly differentiated thyroid cancers (PDTC), 23 of 54 (42.6%) anaplastic thyroid cancers (ATC), and 8 of 12 (66.7%) thyroid cancer cell lines. The C250T mutation was uncommon, but mutually exclusive with the C228T mutation, and the two mutations were collectively found in 11 of 79 (13.9%) FTC, 25 of 54 (46.3%) ATC, and 11 of 12 (91.7%) thyroid cancer cell lines. Among PTC variants, the C228T mutation was found in 4 of 13 (30.8%) tall-cell PTC (TCPTC), 23 of 187 (12.3%) conventional PTC, and 2 of 56 (3.6%) follicular variant PTC samples. No TERT mutation was found in 16 medullary thyroid cancer samples. The C228T mutation was associated with the BRAF V600E mutation in PTC, being present in 19 of 104 (18.3%) BRAF mutation-positive PTC vs 11 of 153 (7.2%) the BRAF mutation-negative PTC samples (P=0.0094). Conversely, BRAF mutation was found in 19 of 30 (63.3%) C228T mutation-positive PTC vs 85 of 227 (37.4%) C228T mutation-negative PTC samples (P=0.0094). We thus for the first time, to our knowledge, demonstrate TERT promoter mutations in thyroid cancers, that are particularly prevalent in the aggressive thyroid cancers TCPTC, PDTC, ATC and BRAF mutation-positive PTC, revealing a novel genetic background for thyroid cancers.

Keywords: BRAF V600E mutation; TERT promoter mutations; telomerase reverse transcriptase; thyroid cancers; thyroid tumorigenesis.

Figure 1

Sequencing of the human TERT promoter electropherograms. Representative electropherograms of the genomic DAN sequencing of the human TERT promoter for the two indicated mutations are shown. (A) The sense DNA strand obtained using the sense primer for sequencing, displaying TERT promoter mutations C228T and C250T in various thyroid cancer cell lines and thyroid cancer samples. (B) The antisense DNA strand obtained using the antisense primer for sequencing, displaying TERT promoter mutations G228A and G250A in various thyroid cancer cell lines and thyroid cancer samples. (A and B) WRO cell line is used to show the wild-type human TERT promoter. PTC, papillary thyroid cancer; FTC, follicular thyroid cancer; ATC, anaplastic thyroid cancer; PDTC, poorly differentiated thyroid cancer.