CBFA2T3-GLIS2 oncogenic fusion is sufficient for leukemic transformation

Abstract

Fusion oncoproteins are the initiating event in AML pathogenesis, although they are thought to require additional cooperating mutations for leukemic transformation. CBFA2T3-GLIS2 (C/G) fusion occurs exclusively in infants and is associated with highly aggressive disease1-4. Here we report that lentiviral transduction of C/G fusion is sufficient to induce malignant transformation of human cord blood hematopoietic stem and progenitor cells (CB HSPCs) that fully recapitulates C/G AML. Engineered CB HSPCs co-cultured with endothelial cells undergo complete malignant transformation with identical molecular, morphologic, phenotypic and disease characteristics observed in primary C/G AML. Interrogating the transcriptome of engineered cells identified a library of C/G fusion-specific targets that are candidates for chimeric antigen receptor (CAR) T cell therapy. We developed CAR-T cells directed against one of the targets, FOLR1, and demonstrated the pre-clinical efficacy against C/G AML while sparing normal hematopoiesis. Our findings underscore the role of the endothelial niche in promoting leukemic transformation of C/G-transduced CB HSPCs. Moreover, 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.

Targeting FOLR1 in high-risk CBF2AT3-GLIS2 pediatric AML with STRO-002 FOLR1–antibody-drug conjugate

“… 7 We have previously demonstrated cell surface expression of FOLR1 in primary CBF/GLIS patient samples. 8 In addition, we also showed that cord blood cells that were transduced with a CBF/GLIS expression construct acquired high levels of FOLR1 expression, suggesting that FOLR1 expression is induced by the CBF/GLIS fusion oncoprotein. 8 Thus, FOLR1 may provide a promising and specific antigen target for CBF/GLIS AML.…”

“… 8 In addition, we also showed that cord blood cells that were transduced with a CBF/GLIS expression construct acquired high levels of FOLR1 expression, suggesting that FOLR1 expression is induced by the CBF/GLIS fusion oncoprotein. 8 Thus, FOLR1 may provide a promising and specific antigen target for CBF/GLIS AML. Here, we present preclinical studies on the efficacy of STRO-002, a FOLR1-directed antibody-drug conjugate (ADC), developed by Sutro Biopharma for solid malignancies, 9 against CBF/GLIS AML.…”

“…Then, we evaluated the preclinical efficacy of STRO-002 in CBF/GLIS AML, using CBF/GLIS-transduced CB HPSCs (CBF/GLIS-CB), a cell line we previously generated that models the molecular and cellular properties of primary CBF/GLIS AML 8 and WSU-AML, a CBF/GLIS AML cell line with endogenous expression of FOLR1. Consistent with previous studies, CBF/GLIS-CB demonstrated bright cell surface expression of FOLR1 by using flow cytometry ( Figure 1 D).…”

“…Consistent with this hypothesis, we previously showed that FOLR1-directed chimeric antigen receptor T cells do not affect cell viability, self-renewal, and multilineage differentiation of normal hematopoietic stem/progenitor cells. 8 However, FOLR1 is expressed at low levels in other tissues, including the luminal epithelial surface of the kidney, lung, and choroid plexus. 7 Although severe pulmonary toxicity has been reported with a FOLR1 T-cell bispecific antibody in nonhuman primates, 11 ongoing phase 1 clinical trials of STRO-002 in patients with advanced ovarian cancer have shown the drug to be well tolerated without significant toxicity.…”

Advances in molecular characterization of pediatric acute megakaryoblastic leukemia not associated with Down syndrome; impact on therapy development

“…Upregulated molecules or pathways Downregulated molecules or pathways CBFA2T3::GLIS2 pathways: Hippo/TNF, TGFβ/BMP, Hedgehog, ECM-receptor interaction, Super Enhancers (Smith et al, 2020;Benbarche et al, 2022) molecules: cell-adhesion and cell-surface markers (e.g., CD56, CD44, ITGA2); RTKs (e.g., ROR1, MET, NTRK1); TAM family kinases (e.g., TYRO3, AXL); others (e.g., GLIS2, BMP2, HHIP, PTCH1, DHH, GLI1, RAB23, WNT9A, WNT11, ERG, DNMT3B, SLITRK5, KIT, PDGFRA, FOLR1) (Smith et al, 2020;Benbarche et al, 2022;Le et al, 2022) molecules: CD38, CD45, HLA-DRA, HLA-DRB1, HLA-DRB5, HLA-DRB6, CASP1, TRAIL-R2, GLIPR1, PER2, GATA1 (Smith et al, 2020) miRNAs : miR-203a-3p, miR-452-3p, miR-452-5p, miR-135a-3p, miR-5683, miR-224-5p, miR-224-3p, miR-6507-5p, miR-130a-3p, miR-181b-5p (Smith et al, 2020) miRNAs : miR-6503-5p, miR-196b-3p, miR-196b-5p, miR-133a-3p, and miR-5584-5p (Smith et al, 2020) KMT2Ar pathway: CDK6 (Placke et al, 2014;Schmoellerl et al, 2020) molecules: HOX cluster and others, such as HOXA9, MEIS1, S100A9, S100A8 (de Rooij et al, 2017;Milan et al, 2022) molecules: associated with stem cell phenotype, including CD34, GPR56, MN1 (de Rooij et al, 2017) (Milan et al, 2022) NUP98::KDM5A pathways: JAK-STAT, CDK6 (Cardin et al, 2019;Schmoellerl et al, 2020) pathways: Myc (Noort et al, 2021) molecules: HOXA cluster, HOXB cluster, MEIS1, MEIS2, E2F targets, FLT3 targets, STAT5 targets, NF1 targets, NOTCH1 targets, NEO1, MPIG6B, SELP (de Rooij et al, 2017;Cardin et al, 2019;Noort et al, 2021) molecules: RB1 (compared to all AMKL), TP53 Frontiers in Cell and Developmental Biology frontiersin.org along the granulocytic-monocytic lineages at the expense of erythroid-megakaryocytic differentiation (Chyla et al, 2008). GLIS2 is a member of the GLIS subfamily of Kru€ppel-like zinc finger transcription factors closely related to the GLI and ZIC subfamilies (Scoville et al, 2017).…”