• genes
• neoplasm
• genetics
• medical oncology

Telomerase reverse transcriptase (TERT) promoter mutations, resulting in increased TERT activity, are known to be associated with many different cancer types, including among 70%–80% of glioblastomas and 60% each of bladder carcinomas and hepatocellular carcinomas.1–3 Increased TERT activity has also been associated with several molecular features including rare rearrangements, duplications and amplifications.1 However, of all the molecular changes, mutations in the TERT promoter region are known to be the most frequent. They are often restricted to two hotspots, 124 and 146 base pairs upstream of the transcription start sites, often referred to as C228T and C250T.1 2 The presence of these promoter mutations increases the similarity of these sites to the erythroblast transformation-specific (ETS) binding region, serving as a de novo binding site for ETS family transcription factors. Over time these mutations have assumed greater importance as markers of prognostication.4 In a recent study, Kikuchi et al 4 have clearly demonstrated that glioblastomas with TERT promoter mutations had a shorter progression-free survival (7 months vs 10 months; p=0.015) and overall survival (16 months vs 24 months; p=0.017) as compared with TERT wild-type glioblastomas. Such studies emphasise the need for accurate laboratory assays to detect these TERT promoter mutations. However, detection of TERT promoter mutation can be challenging in tissues with low tumour cellularity, high heterogeneity and poor DNA quality, especially if they are formalin-fixed.3 The problem is further compounded by the high guanine-cytosine (GC) content of the region (~80%) that can form strong secondary structures impairing strand denaturation.

Validated assays that amplify GC-rich regions often use additives like the Q solution and locked nucleic acids (LNA)4 on a droplet digital PCR …