Related Experiment Video
Updated: Jan 16, 2026
Comet Assay to Quantify DNA Damage in FLT3 Mutant-expressing 32D Cells after Exposure to Type I and Type II FLT3 Inhibitors
Published on: October 17, 2025
FLT3-ITD Induces CMTM6 and Enhances Immune Escape in Acute Myeloid Leukemia
Melissa Zwick1,2, Bastian Zinkel1,2, Corinna Spohr3
1Department of Medicine I, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Abstract:
FMS-like tyrosine kinase-3 internal tandem duplication (FLT3-ITD) mutations are frequent in acute myeloid leukemia (AML) and are associated with a high risk of relapse. CKLF-like MARVEL transmembrane domain containing member 6 (CMTM6) stabilizes PD-L1 surface expression and modulates tumor immunity in solid cancer. In this study, we found a role for FLT3-induced CMTM6 in hematologic malignancies. FLT3 drove CMTM6 and PD-L1 expression in AML cells, whereas FLT3 inhibition reduced expression of CMTM6 and PD-L1. In three distinct allogeneic hematopoietic cell transplantation mouse models, transplantation of Cmtm6-deficient FLT3-ITD+ leukemia cells resulted in prolonged survival, reduced leukemia burden, enhanced T-cell effector function, and decreased expression of T-cell exhaustion markers compared with Cmtm6-proficient FLT3-ITD+ leukemia cells. Furthermore, combination therapy with anti-PD-L1 and tandutinib significantly improved survival, suppressed leukemia cell expansion, and augmented the anti-leukemia T-cell response in mice bearing FLT3-ITD+ leukemia. Mechanistically, protein-protein interaction of FLT3 and CMTM6 within their transmembrane domains, which was not phosphorylation dependent, enhanced CMTM6 stability in leukemia cells, whereas FLT3-ITD did not increase CMTM6 and PD-L1 expression at the RNA level. Furthermore, CMTM6 upregulation and protein interaction with FLT3 were validated in primary leukemia cells from two independent cohorts of patients with FLT3-ITD+ AML. Collectively, these findings uncover FLT3-mediated stabilization of CMTM6 in AML cells, which results in enhanced PD-L1 cell surface expression and leukemia immune escape.
Significance:
Activation of the CMTM6/PD-L1 axis in FLT3-ITD-driven acute myeloid leukemia mediates immunosuppression, providing the basis for potential inhibition of this pathway to harness antitumor immunity.
Insights
FMS-like tyrosine kinase-3 internal tandem duplication (FLT3-ITD) drives CKLF-like MARVEL transmembrane domain containing member 6 (CMTM6) stabilization in acute myeloid leukemia (AML) cells. This interaction enhances PD-L1 expression, promoting immune escape and relapse risk in AML patients.
Area of Science:
- Oncology
- Immunology
- Hematology
Background:
- FMS-like tyrosine kinase-3 internal tandem duplication (FLT3-ITD) mutations are common in acute myeloid leukemia (AML) and linked to poor prognosis.
- CKLF-like MARVEL transmembrane domain containing member 6 (CMTM6) is known to stabilize PD-L1 expression in solid tumors, impacting tumor immunity.
Purpose of the Study:
- To investigate the role of FLT3-induced CMTM6 in hematological malignancies, specifically AML.
- To elucidate the mechanism by which FLT3 influences CMTM6 and PD-L1 expression in AML.
- To evaluate the therapeutic potential of targeting the FLT3-CMTM6-PD-L1 axis in FLT3-ITD+ AML.
Main Methods:
- Utilized mouse models of allogeneic hematopoietic cell transplantation with Cmtm6-deficient and proficient FLT3-ITD+ leukemia cells.
- Administered combination therapy involving anti-PD-L1 and tandutinib in FLT3-ITD+ leukemia mouse models.
- Analyzed protein-protein interactions between FLT3 and CMTM6, and their expression levels at RNA and protein levels.
- Validated findings in primary leukemia cells from FLT3-ITD+ AML patient cohorts.
Main Results:
- FLT3 drove CMTM6 and PD-L1 expression in AML cells; FLT3 inhibition reduced these expressions.
- Transplantation of Cmtm6-deficient FLT3-ITD+ leukemia cells led to prolonged survival, reduced leukemia burden, and enhanced T cell function in mice.
- Combination therapy with anti-PD-L1 and tandutinib significantly improved survival and augmented anti-leukemia T cell responses.
- FLT3 and CMTM6 interact via their transmembrane domains, stabilizing CMTM6 protein without altering RNA levels; this was confirmed in patient samples.
Conclusions:
- FLT3 signaling stabilizes CMTM6 protein in AML cells, leading to increased PD-L1 surface expression and promoting immune evasion.
- Targeting the FLT3-CMTM6 interaction and PD-L1 represents a promising therapeutic strategy for FLT3-ITD+ AML.
