Modulation of splicing catalysis for therapeutic targeting of leukemia with mutations in genes encoding spliceosomal proteins

Abstract

Mutations in spliceosomal genes are commonly found in patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML)1–3. These mutations occur at highly recurrent amino acid residues and perturb normal splice site and exon recognition4–6. Spliceosomal mutations are always heterozygous and rarely co-occur with one another, suggesting that cells may only tolerate a partial deviation from normal splicing activity. To test this hypothesis, we engineered mice that express the SRSF2P95H mutation, which commonly occurs in MDS and AML, in an inducible hemizygous manner in hematopoietic cells. These mice developed lethal bone marrow failure, demonstrating that Srsf2-mutant cells depend on the wildtype Srsf2 allele for survival. In the context of leukemia, treatment with the spliceosome inhibitor E71077,8 resulted in significant reductions in leukemic burden specifically in isogenic mouse leukemias and patient-derived xenograft (PDX) AMLs carrying spliceosomal mutations. While in vivo E7107 exposure resulted in widespread intron retention and cassette exon skipping regardless of Srsf2 genotype, the magnitude of splicing inhibition following E7107 treatment was greater in Srsf2-mutant versus wildtype leukemias, consistent with its differential effect on survival in these two genotypes. Collectively, these data provide genetic and pharmacologic evidence that leukemias with spliceosomal mutations are preferentially susceptible to additional splicing perturbations in vivo compared with wildtype counterparts. Modulation of spliceosome function may provide a novel therapeutic avenue in genetically defined subsets of MDS and AML patients.

The NLRP3 inflammasome functions as a driver of the myelodysplastic syndrome phenotype

“…52 Comparative transcriptome analysis also shows that S100A8/9 is highly upregulated in Srsf2 P95H mutant as well as Ezh2-deleted mouse models. 53,54 Additionally, our findings that catalytically active pyroptotic ASC specks are released from the cytosol into the extracellular space suggests that specks may further reinforce bystander inflammation in the microenvironment in a non-cell-autonomous fashion. 25,55 Importantly, NOX1/4 inhibition suppressed activation of the inflammasome and b-catenin both in MDS patient-derived BM-MNCs and in cells harboring varied classes and types of MDS founder gene mutations.…”

CMML: Clinical and molecular aspects

“…The recent advances in the molecular deciphering of the disease have led to renewed collaborative efforts in this disease. Current basic and translational research aims at better understanding how the specific clonal architecture of CMML drives its clinical phenotype, identify therapeutic strategies to eradicate ancestral mutations such as those in the spliceosome [73], and derive relevant pre-clinical models to allow unbiased therapeutic screens. Clinical studies are ongoing to derive uniform risk stratification and therapeutic evaluation tools.…”

Splicing-factor alterations in cancers

“…For example, SF3B1 inhibitors, such as spliceostatin A, pladienolide-B, GEX1A, and E1707, partially inhibit splicing in cultured cells and animal models, and show selective action, i.e., greater potency, on tumor cells (for review, see Ohe and Hagiwara 2015). Thus SF3B1 inhibitors are currently being evaluated in the context of splicing-factor mutations in preclinical models of MDS (Lee et al 2016).…”