Routine sequencing in CLL has prognostic implications and provides new insight into pathogenesis and targeted treatments

Chronic lymphocytic leukaemia (CLL) is a genetically heterogeneous disease characterised by genomic alterations and gene mutations that may portend worse survival or resistance to treatments. A total of 680 blood or bone marrow samples underwent targeted sequencing of 29 genes previously identified as being mutated in CLL, which were correlated to known prognostic clinical characteristics. Overall, 400 (59%) patients were treatment-naive (TN) and 280 (41%) were relapsed/refractory (R/R). Most patients (70%) had 1 mutation, with TP53 (22%), SF3B1 (18%), NOTCH1 (13%) and ATM (13%) being the most commonly mutated genes. A higher proportion of R/R patients had mutations in SF3B1 (P=001) and TP53 (P<0001). Patients with mutated IGHVCLL more often had mutations in KLHL6 (P=0001) and MYD88 (P<0001). Pairwise associations showed mutational co-occurrences in the TN group including SF3B1/ATM [false discovery rate (FDR)<005] and NOTCH1/POT1 (FDR<001). Recurrent mutations resulting in premature truncation prior to the ubiquitination domains of NOTCH1 in its PEST domain and BIRC3 in its RING domain can produce proteins that constitutively activate CLL. Frequent missense mutations, such as K700E in SF3B1 and E571K in XPO1, have unknown function but are most likely to be activating mutations. Future directions include using these mutations to identify pathways for therapeutic targeting and rational drug design.