Mis-splicing of Mitotic Regulators Sensitizes SF3B1-Mutated Human HSCs to CHK1 Inhibition

Area of Science:

• Hematology
• Molecular Biology
• Cancer Genomics

Background:

• SF3B1 mutations are common in myeloid neoplasms, affecting hematopoietic stem cells (HSCs).
• The precise impact of SF3B1 mutations on human HSCs and progenitors (HSPCs) is not fully understood.
• Understanding these effects is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the molecular and functional consequences of SF3B1 mutations in human HSPCs.
• To identify the mis-splicing program induced by SF3B1 mutations as a potential therapeutic vulnerability.
• To evaluate the efficacy of CHK1 inhibition in targeting SF3B1-mutant HSPCs.

Main Methods:

• Precise gene editing of SF3B1 K700E mutations in primary CD34+ cells.
• Analysis of gene expression and splicing patterns in engineered HSPCs.
• Assessment of cell cycle progression, differentiation, and sensitivity to CHK1 inhibition (CHK1i).
• In vivo studies using prexasertib, a clinical CHK1 inhibitor.

Main Results:

• Mutant SF3B1 induced widespread mis-splicing and reduced expression of genes involved in mitosis and genome maintenance.
• SF3B1-mutant HSPCs exhibited altered differentiation, delayed G2/M progression, and enhanced sensitivity to CHK1i.
• Mis-splicing of BUBR1 and CDC27 contributed to delayed G2/M transit and CHK1i sensitivity.
• Clinical CHK1 inhibitor prexasertib selectively targeted SF3B1-mutant HSCs and impaired their engraftment in vivo.

Conclusions:

• The mis-splicing program in SF3B1-mutant HSPCs represents a targetable vulnerability.
• Pharmacological CHK1 inhibition, specifically with prexasertib, can selectively target and eliminate SF3B1-mutant HSPCs.
• These findings provide a rationale for using CHK1 inhibitors in treating SF3B1-mutant myeloid neoplasms.