CBFA2T3-GLIS2 model of pediatric acute megakaryoblastic leukemia identifies FOLR1 as a CAR T cell target
Quy Le, … , Keith R. Loeb, Soheil Meshinchi
Quy Le, … , Keith R. Loeb, Soheil Meshinchi
Published September 22, 2022
Citation Information: J Clin Invest. 2022;132(22):e157101. https://doi.org/10.1172/JCI157101.
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Research Article Oncology

CBFA2T3-GLIS2 model of pediatric acute megakaryoblastic leukemia identifies FOLR1 as a CAR T cell target

Abstract

The CBFA2T3-GLIS2 (C/G) fusion is a product of a cryptic translocation primarily seen in infants and early childhood and is associated with dismal outcome. Here, we demonstrate that the expression of the C/G oncogenic fusion protein promotes the transformation of human cord blood hematopoietic stem and progenitor cells (CB HSPCs) in an endothelial cell coculture system that recapitulates the transcriptome, morphology, and immunophenotype of C/G acute myeloid leukemia (AML) and induces highly aggressive leukemia in xenograft models. Interrogating the transcriptome of C/G-CB cells and primary C/G AML identified a library of C/G-fusion-specific genes that are potential targets for therapy. We developed chimeric antigen receptor (CAR) T cells directed against one of the targets, folate receptor α (FOLR1), and demonstrated their preclinical efficacy against C/G AML using in vitro and xenograft models. FOLR1 is also expressed in renal and pulmonary epithelium, raising concerns for toxicity that must be addressed for the clinical application of this therapy. Our findings underscore the role of the endothelial niche in promoting leukemic transformation of C/G-transduced CB HSPCs. Furthermore, this work has broad implications for studies of leukemogenesis applicable to a variety of oncogenic fusion-driven pediatric leukemias, providing a robust and tractable model system to characterize the molecular mechanisms of leukemogenesis and identify biomarkers for disease diagnosis and targets for therapy.

Authors

Quy Le, Brandon Hadland, Jenny L. Smith, Amanda Leonti, Benjamin J. Huang, Rhonda Ries, Tiffany A. Hylkema, Sommer Castro, Thao T. Tang, Cyd N. McKay, LaKeisha Perkins, Laura Pardo, Jay Sarthy, Amy K. Beckman, Robin Williams, Rhonda Idemmili, Scott Furlan, Takashi Ishida, Lindsey Call, Shivani Srivastava, Anisha M. Loeb, Filippo Milano, Suzan Imren, Shelli M. Morris, Fiona Pakiam, Jim M. Olson, Michael R. Loken, Lisa Brodersen, Stanley R. Riddell, Katherine Tarlock, Irwin D. Bernstein, Keith R. Loeb, Soheil Meshinchi

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Figure 4

Integrative transcriptomics of primary samples and C/G-CB identify FOLR1 therapeutic target.

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Integrative transcriptomics of primary samples and C/G-CB identify FOLR1...
(A) Diagram of computational workflow to identify C/G-specific CAR targets. See Methods and Supplemental Figure 6 for details. Normal tissues include bulk bone marrow (BM) samples and peripheral blood (PB) CD34+ samples. (B and C) Expression of C/G-specific CAR targets in primary-fusion-positive patients versus normal BM (NBM) (B) and C/G-CB versus GFP-CB cells (C). CBFA2T3-GLIS2 primary samples (n = 39); NBM samples (n = 68). For cultured cells, n = 4 technical replicates for C/G-CB cells in EC coculture at week; n = 3 technical replicates for all other groups. (D) Top: Gating strategies used to identify AML cells and normal lymphocytes, monocytes, and myeloid cells in 4 representative patients based on CD45 expression and SSC. Bottom: FOLR1 expression in the AML blast subpopulation versus normal cells. (E) Quantification of FOLR1 expression (geometric mean fluorescent intensity, MFI) among AML blasts and their normal counterparts across n = 15 patients. Autofluorescence was used as control. ****P < 0.00005 by 1-way ANOVA. (F and G) Expression of FOLR1 (F) and quantification of FOLR1+ cells (G) among GFP-CB and C/G-CB over weeks in EC coculture. Data presented as mean ± SD from 3 technical replicates.