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Rapamycin Pretreatment Rescues the Bone Marrow AML Cell Elimination Capacity of CAR-T Cells
Zhigang Nian1,2, Xiaohu Zheng3,2, Yingchao Dou1,2
1Hefei National Laboratory for Physical Sciences at Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China.
Purpose:
Ongoing clinical trials show limited efficacy for Chimeric antigen receptor (CAR) T treatment for acute myeloid leukemia (AML). The aim of this study was to identify potential causes of the reported limited efficacy from CAR-T therapies against AML.
Experimental Design:
We generated CAR-T cells targeting Epithelial cell adhesion molecule (EpCAM) and evaluated their killing activity against AML cells. We examined the impacts of modulating mTORC1 and mTORC2 signaling in CAR-T cells in terms of CXCR4 levels. We examined the effects of a rapamycin pretreatment of EpCAM CAR-T cells (during ex vivo expansion) and assessed the in vivo antitumor efficacy of rapamycin-pretreated EpCAM CAR-T cells (including CXCR4 knockdown cells) and CD33 CAR-T cells in leukemia xenograft mouse models.
Results:
EpCAM CAR-T exhibited killing activity against AML cells but failed to eliminate AML cells in bone marrow. Subsequent investigations revealed that aberrantly activated mTORC1 signaling in CAR-T cells results in decreased bone marrow infiltration and decreased the levels of the rapamycin target CXCR4. Attenuating mTORC1 activity with the rapamycin pretreatment increased the capacity of CAR-T cells to infiltrate bone marrow and enhanced the extent of bone marrow AML cell elimination in leukemia xenograft mouse models. CXCR4 knockdown experiments showed that CXCR4 contributes to the enhanced bone marrow infiltration capacity of EpCAM CAR-T cells and the observed reduction in bone marrow AML cells.
Conclusions:
Our study reveals a potential cause for the limited efficacy of CAR-T reported from current AML clinical trials and illustrates an easy-to-implement pretreatment strategy, which enhances the anti-AML efficacy of CAR-T cells.See related commentary by Maiti and Daver, p. 5739.
Insights
Chimeric antigen receptor (CAR) T-cell therapy shows limited efficacy in acute myeloid leukemia (AML). Pretreating CAR-T cells with rapamycin enhances their ability to infiltrate bone marrow and eliminate AML cells, improving treatment outcomes.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Chimeric antigen receptor (CAR) T-cell therapy has shown limited efficacy in clinical trials for acute myeloid leukemia (AML).
- Understanding the mechanisms behind this limited efficacy is crucial for improving CAR-T cell therapy outcomes in AML.
- Epithelial cell adhesion molecule (EpCAM) and CD33 are targeted by CAR-T cells in AML treatment.
Purpose of the Study:
- To identify potential causes for the limited efficacy of CAR-T cell therapy in acute myeloid leukemia (AML).
- To investigate the role of mTORC1 and mTORC2 signaling in CAR-T cell function against AML.
- To evaluate a rapamycin pretreatment strategy to enhance CAR-T cell anti-AML efficacy.
Main Methods:
- Generated EpCAM-targeted CAR-T cells and assessed their activity against AML cells.
- Examined the impact of modulating mTORC1/mTORC2 signaling on CXCR4 levels in CAR-T cells.
- Evaluated the in vivo antitumor efficacy of rapamycin-pretreated EpCAM CAR-T cells and CXCR4 knockdown cells in leukemia xenograft mouse models.
Main Results:
- EpCAM CAR-T cells showed killing activity but failed to eliminate AML in bone marrow.
- Aberrant mTORC1 signaling in CAR-T cells decreased bone marrow infiltration and CXCR4 levels.
- Rapamycin pretreatment of EpCAM CAR-T cells enhanced bone marrow infiltration and AML cell elimination.
- CXCR4 knockdown impaired bone marrow infiltration and AML cell reduction.
Conclusions:
- Aberrant mTORC1 signaling contributes to limited CAR-T cell efficacy in AML by reducing bone marrow infiltration.
- Rapamycin pretreatment is a potential strategy to enhance CAR-T cell anti-AML efficacy.
- CXCR4 plays a role in CAR-T cell bone marrow infiltration and anti-leukemic activity in AML.
