Genetic analysis of patients with leukemic transformation of myeloproliferative neoplasms shows recurrent SRSF2 mutations that are associated with adverse outcome

Abstract

Leukemic transformation (LT) of myeloproliferative neoplasms (MPNs) is associated with a poor prognosis and resistance to therapy. Although previous candidate genetic studies have identified mutations in MPN patients who develop acute leukemia, the complement of genetic abnormalities in MPN patients who undergo LT is not known nor have specific molecular abnormalities been shown to have clinical relevance in this setting. We performed high-throughput resequencing of 22 genes in 53 patients with LT after MPN to characterize the frequency of known myeloid mutations in this entity. In addition to JAK2 and TET2 mutations, which occur commonly in LT after MPN, we identified recurrent mutations in the serine/arginine-rich splicing factor 2 (SRSF2) gene (18.9%) in acute myeloid leukemia (AML) transformed from MPNs. SRSF2 mutations are more common in AML derived from MPNs compared with LT after myelodysplasia (4.8%) or de novo AML (5.6%), respectively (P=.05). Importantly, SRSF2 mutations are associated with worsened overall survival in MPN patients who undergo LT in univariate (P=.03; HR, 2.77; 95% CI, 1.10-7.00) and multivariate analysis (P<.05; HR, 2.11; 95% CI, 1.01-4.42). These data suggest that SRSF2 mutations contribute to the pathogenesis of LT and may guide novel therapeutic approaches for MPN patients who undergo LT.

Figure 1

Distribution of mutations among patients with AML derived from a MPN. Pre-exisitng MPN diagnosis and cytogenetic risk category as defined by Slovak et al is listed as well.

Figure 2

Mutations found with TA cloning. (A) TA cloning found a novel, heterozygous in-frame insertion of 2 amino acids in the region of the previously described recurrent mutation in U2AF1. (B) In addition, a single occurrence of a somatic homozygous SRSF2 P95H mutation was seen as well as a novel missense SRSF2 P96S mutation adjacent to the previously described recurrent heterozygous point mutation at codon P95. (C) A novel, heterozygous 24 nucleotide in-frame deletion in SRSF2 was also found. (D) Multiple previously undescribed mutations were also found in ZRSR2, including several nonsense mutations, N-terminal insertions/deletions that resulted in premature stop codons, as well as in-frame insertions/deletions in the Arginine-serine rich domain.

Figure 3

multiple genetic abnormalities at LT found with comprehensive sequencing. Comprehensive sequencing of paired MPN samples that later transformed to AML found multiple genetic abnormalities at transformation as shown by (A) paired MPN/AML mutational diagram as well as (B-D) 3 illustrative cases. For instance, gain of TET2 and KRas mutations (B), loss of JAK2 mutation and acquisition of IDH2 and TP53 mutations (C), and loss of the JAK2 mutation but acquisition of activating mutation in FLT3 could all be observed by comparing chronic MPN and leukemic states. SRSF2 mutations when present in the AML state were always present in the paired antecedent MPN sample. Mutations in c-kit, EZH2, WT1, KRas, HRas, IDH1, U2AF1, SF3B1, ZRSR2, PTEN, RUNX1, and DNMT3a were not seen in either state in this set of patients and hence are not displayed here.

Figure 4

Mutations in SRSF2 are associated with worsened OS in AML derived from MPNs.