# FBXO3-mediated DUSP9 ubiquitination promotes leukemia stem cell maintenance and tyrosine kinase inhibitor resistance in chronic myeloid leukemia

## TL;DR

This study shows that FBXO3 helps leukemia stem cells survive and resist treatment in chronic myeloid leukemia by modifying DUSP9, suggesting a new way to target these cells.

## Contribution

FBXO3 is identified as a novel marker and therapeutic target for CML-LSCs through its role in DUSP9 ubiquitination and MAPK activation.

## Key findings

- FBXO3 is highly expressed in TKI-resistant CML stem cells and promotes their survival.
- FBXO3 mediates DUSP9 ubiquitination, activating the MAPK pathway essential for CML progression.
- Targeting FBXO3 eliminates LSCs without harming normal blood stem cells.

## Abstract

Eradicating leukemia stem cells (LSCs) and overcoming tyrosine kinase inhibitor (TKI) resistance is urgent for chronic myeloid leukemia (CML) treatment. We find that F-box protein 3 (FBXO3) is highly upregulated in CD34+ CML stem cells from TKI-resistant patients and identify it as an innovative CML-LSC marker via single-cell RNA sequencing (scRNA-seq). FBXO3 deficiency induces apoptosis and reduces proliferation of CML cell lines and LSCs in vitro and in vivo, with minimal effects on normal CD34+ hematopoietic stem cells (HSCs). Mechanistically, FBXO3 interacts with DUSP9 to promote its ubiquitination and activate the MAPK pathway, critical for CML cell activity. DUSP9 knockdown partially reverses FBXO3-deficiency-mediated LSC elimination. Furthermore, FBXO3 inhibitor monotherapy or combination with imatinib effectively eradicates CML-LSCs, overcomes TKI resistance, and spares normal hematopoiesis. Collectively, our findings highlight FBXO3’s role in CML progression and support combining FBXO3 inhibitors with TKIs for durable LSC elimination.

•FBXO3 is an innovative CML-LSC marker highly expressed in TKI-resistant CML•FBXO3 drives the ubiquitination of DUSP9 to activate MAPK signaling in CML•FBXO3 sustains LSC self-renewal and TKI resistance via MAPK-dependent pathways•FBXO3 targeting selectively eliminates LSCs without impairing normal hematopoiesis

FBXO3 is an innovative CML-LSC marker highly expressed in TKI-resistant CML

FBXO3 drives the ubiquitination of DUSP9 to activate MAPK signaling in CML

FBXO3 sustains LSC self-renewal and TKI resistance via MAPK-dependent pathways

FBXO3 targeting selectively eliminates LSCs without impairing normal hematopoiesis

Li et al. identify that FBXO3 is an innovative marker of CML-LSCs and is responsible for the survival and TKI resistance of LSCs via mediating the ubiquitination of DUSP9. These findings provide a potential target to eliminate LSCs and overcome TKI resistance in CML.