The diagnostic chronic lymphocytic leukaemia genome by nanopore sequencing

Abstract

Chronic lymphocytic leukaemia (CLL) is characterised by considerable clinical and biological heterogeneity, with specific recurrent genomic alterations, including TP53 mutations, deletions of chromosome 17p, and IgHV mutational status, impacting on response to chemo-immunotherapy and targeted agents. Consequently, diagnostic screening for these predictive biomarkers is recommended in both national and international clinical guidelines. Current conventional methods, including fluorescent in-situ hybridisation and Sanger sequencing, exhibit shortcomings in terms of cost, speed and sensitivity, and even second-generation sequencing methods encounter technical limitations imposed by short-read lengths and bio-informatics analysis. The MinION platform from Oxford Nanopore Technologies generates exceptionally long (1-100kbp) read lengths in a short period of time and at low cost, making it a good candidate for diagnostic testing. In this paper, we present a nanopore-based CLLspecific screening assay, to simultaneously screen for both TP53 mutations and del17p13.1, as well as determining the IgHV mutation status for a single patient in one sequencing run. We sequenced 11 CLL patients and were able to generate a full diagnostic dataset for all. We identified somatic SNVs and indels in the coding region of TP53, and demonstrate that, following error correction of the data, we could accurately define the somatically hypermutated IgHV region in all patients. We also demonstrated the ability of the MinION platform to detect large-scale genomic deletions through low-coverage whole-genome sequencing. We conclude that nanopore sequencing has the potential to provide accurate, low-cost and rapid diagnostic information, which could be applied to other cancer types.