Cells expressing FLT3/ITD mutations exhibit elevated repair errors generated through alternative NHEJ pathways:...

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• FMS-like tyrosine kinase-3 (FLT3) internal tandem duplication (ITD) mutations are linked to poor prognosis in acute myeloid leukemia (AML).
• DNA double-strand breaks (DSBs) are primarily repaired by the DNA-PK-dependent nonhomologous end-joining (NHEJ) pathway.
• Alternative NHEJ pathways, utilizing microhomology, contribute to genomic instability and cancer progression.

Purpose of the Study:

• To investigate the role of microhomology-mediated end-joining in FLT3/ITD-driven DNA deletions.
• To examine the impact of FLT3/ITD mutations on DNA repair pathway components.
• To assess the therapeutic potential of targeting FLT3 signaling and DNA ligase IIIα.

Main Methods:

• Analysis of FLT3/ITD-expressing cell lines and bone marrow mononuclear cells from knock-in mice.
• Quantification of Ku proteins and DNA ligase IIIα levels.
• Assessment of DNA deletions and DSB repair following FLT3 inhibitor treatment.

Main Results:

• FLT3/ITD expression leads to DSB repair at microhomologous sequences, causing frequent DNA deletions.
• Ku protein levels are decreased, while DNA ligase IIIα levels are increased in FLT3/ITD cells.
• FLT3 inhibition reduces DNA ligase IIIα levels and DNA deletions, indicating FLT3 signaling regulates DSB repair pathways.

Conclusions:

• FLT3/ITD signaling promotes genomic instability by favoring error-prone microhomology-mediated end-joining.
• Targeting FLT3 signaling or DNA ligase IIIα may represent a therapeutic strategy to reduce repair errors in AML.
• Understanding DSB repair mechanisms in FLT3-mutated AML is crucial for developing effective treatments.