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Diagnostic utility of droplet digital PCR to detect TERT promoter mutations among glioblastoma samples using 7-deaza-dGTP
  1. Rajadurai Abarna1,
  2. Rachel Nancy1,
  3. Ari Chacko2,
  4. Geeta Chacko1,
  5. Rekha Pai1
  1. 1Pathology, Christian Medical College, Vellore, Tamil Nadu, India
  2. 2Division of Neurosciences, Christian Medical College, Vellore, Tamil Nadu, India
  1. Correspondence to Dr Rekha Pai, Pathology, Christian Medical College Vellore, Vellore, Tamil Nadu, India; rekhapai{at}cmcvellore.ac.in

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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 al4 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 (ddPCR) …

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Footnotes

  • Handling editor Dhirendra Govender.

  • Contributors RA helped with the design and standardisation of the TERT assay. RN helped with the completion of lab work. AC is the neurosurgeon who treated these patients and helped to design the study. GC helped with the design, diagnostic pathology, IHC-related work and interpretation of results. RP helped with the design of the study, assay standardisation, analysis and manuscript writing.

  • Funding This work was supported partly through the funds received from the institutional review board.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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