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SF3B1 mutation-mediated sensitization to H3B-8800 splicing inhibitor in chronic lymphocytic leukemia
Irene López-Oreja1,2,3,4, André Gohr2, Heribert Playa-Albinyana1,4
1Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain.
Abstract:
Splicing factor 3B subunit 1 (SF3B1) is involved in pre-mRNA branch site recognition and is the target of antitumor-splicing inhibitors. Mutations in SF3B1 are observed in 15% of patients with chronic lymphocytic leukemia (CLL) and are associated with poor prognosis, but their pathogenic mechanisms remain poorly understood. Using deep RNA-sequencing data from 298 CLL tumor samples and isogenic SF3B1 WT and K700E-mutated CLL cell lines, we characterize targets and pre-mRNA sequence features associated with the selection of cryptic 3' splice sites upon SF3B1 mutation, including an event in the MAP3K7 gene relevant for activation of NF-κB signaling. Using the H3B-8800 splicing modulator, we show, for the first time in CLL, cytotoxic effects in vitro in primary CLL samples and in SF3B1-mutated isogenic CLL cell lines, accompanied by major splicing changes and delayed leukemic infiltration in a CLL xenotransplant mouse model. H3B-8800 displayed preferential lethality towards SF3B1-mutated cells and synergism with the BCL2 inhibitor venetoclax, supporting the potential use of SF3B1 inhibitors as a novel therapeutic strategy in CLL.
Insights
SF3B1 mutations in chronic lymphocytic leukemia (CLL) drive cryptic splice site selection. Splicing modulator H3B-8800 shows efficacy against SF3B1-mutated CLL cells, offering a new therapeutic avenue.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Splicing factor 3B subunit 1 (SF3B1) is crucial for pre-mRNA splicing and a target for cancer therapies.
- SF3B1 mutations are found in 15% of chronic lymphocytic leukemia (CLL) patients and are linked to poor prognosis, but their role is unclear.
Purpose of the Study:
- To investigate the pathogenic mechanisms of SF3B1 mutations in CLL.
- To characterize the impact of SF3B1 mutations on splicing patterns and identify therapeutic strategies.
Main Methods:
- Deep RNA-sequencing of 298 CLL tumor samples and isogenic SF3B1 wild-type (WT) and K700E-mutated CLL cell lines.
- Utilized the H3B-8800 splicing modulator in in vitro and in vivo CLL models.
- Assessed cytotoxic effects, splicing alterations, and leukemic infiltration in a xenotransplant mouse model.
Main Results:
- SF3B1 mutations lead to cryptic 3' splice site selection, including in the MAP3K7 gene, affecting NF-κB signaling.
- H3B-8800 demonstrated in vitro cytotoxicity in primary CLL and isogenic cell lines, inducing significant splicing changes.
- H3B-8800 showed preferential lethality against SF3B1-mutated cells and synergized with venetoclax, delaying leukemic infiltration in vivo.
Conclusions:
- SF3B1 mutations contribute to CLL pathogenesis through aberrant splicing.
- H3B-8800 exhibits potent anti-CLL activity, particularly against SF3B1-mutated cells.
- SF3B1 inhibitors represent a promising novel therapeutic strategy for CLL, especially in combination therapies.
