Table S15: Relative quantification by lipid class

Table S12: gene signatures used to analyze RNA-seq data from patients with AML before/after GILT

Table S2: EnrichR analysis of FLT3 gene signatures

Supplementary materials and methods

Table S4: GSEA results in FLT3-ITD PDX AML cells ex vivo-treated with QUIZ or Veh.

Table S8: Multimodal analysis of shCEBPA versus shCTL MOLM14 cell line

Table S14: PUFA/MUFA ratios in phospholipids

Table S7: Transcriptomics analysis of shCEBPA#2 versus shCTL

Supplemental figures S1-S22: Supplementary Figure S1 shows lipid metabolism dependency in FLT3-mutant AML, Supplementary Figure S2 shows anti-leukemic activity of GILT across a panel of AML PDX, Supplementary Figure S3 shows mechanisms of post-translational regulation of C/EBPα expression, Supplementary Figure S4 shows inhibition of C/EBPα phosphorylation and protein expression by FLT3i, Supplementary Figure S5 shows the implication of Ser-21 phosphorylation in post-translational regulation of C/EBPα expression, Supplementary Figure S6 shows that FLT3-ITD regulates the expression of C/EBPα and of proteins related to lipid biosynthesis in AML cell lines, Supplementary Figure S7 shows that FLT3-ITD regulates the expression of genes related to lipid biosynthesis in AML cell lines, Supplementary Figure S8 shows that C/EBPα directly regulates the transcription of lipid biosynthesis genes in AML, Supplementary Figure S9 shows the correlation between CEBPA mRNA expression and FLT3-ITD mutations, Supplementary Figure S10 shows scRNA-seq analysis from PDXTUH84, Supplementary Figure S11 shows scRNA-seq analysis from PDXTUH110, Supplementary Figure S12 shows the evolution of CEBPA_UP and FLT3-ITD_UP signatures in patients with AML treated with GILT, Supplementary Figure S13 shows that C/EBPα regulates rate-limiting lipid biosynthetic enzymes downstream of FLT3-ITD, Supplementary Figure S14 shows that C/EBPα controls lipid amount in FLT3-ITD cell lines, Supplementary Figure S15 shows that FLT3 inhibitors induce a lipid switch increasing neutral lipids dependent on C/EBPα, Supplementary Figure S16 shows that FLT3 inhibitor inhibits fatty acid synthesis fueled by glucose and glutamine, Supplementary Figure S17 shows that FLT3 inhibition decreases monounsaturated fatty acid dependent on C/EBPα, Supplementary Figure S18 shows that FLT3 inhibition increases PUFA/MUFA ratio dependent on C/EBPα, Supplementary Figure S19 shows that ferroptotic cell death induced by FLT3i is mediated by inhibition of SCD-dependent mono-unsaturated FA synthesis, Supplementary Figure S20 shows that FLT3 inhibitors unmask a vulnerability of FLT3-mutant leukemic cells to ferroptosis, Supplementary Figure S21 shows that lipid redox stress induction by GPX4 inhibition primed FLT3i activity in FLT3-ITD AML cells and Supplementary Figure S22 shows combined treatment with GILT and APR-246 in preclinical AML models in vivo.

Table S13: lipidomic results by lipid species in dox-inducible and constitutives shRNAs and siRNA CTL/CEBPA, empty vector/CEBPA-OE and vehicle/QUIZ conditions in MOLM-14 cells

Table S3: Clinical characteristics of samples from patients with AML used in PDX assays

Table S6: Proteomic analysis of FLT3-ITD AML cell lines treated with vehicle or QUIZ

Table S1: Transcriptome analysis of FLT3-ITD cell lines after FLT3 inhbition

Table S5: GSEA results in FLT3-ITD PDX AML cells in vivo-treated with GILT or Veh.

Table S10: EnrichR analysis of CEBPA_UP signature

Abstract While transcription factor C/AAT-enhancer binding protein a (C/EBPa) is critical for normal and leukemic differentiation, its role on cell and metabolic homeostasis is largely unknown in cancer. Here, multi-omics analyses uncovered a coordinated activation of C/EBPa and Fms-like tyrosine kinase 3 (FLT3) that increased lipid anabolism in vivo and in patients with FLT3-mutant acute myeloid leukemia (AML). Mechanistically, C/EBPa regulated FASN-SCD axis to promote fatty acid (FA) biosynthesis and desaturation. We further demonstrated that FLT3 or C/EBPa inactivation decreased mono-unsaturated FA incorporation to membrane phospholipids through SCD downregulation. Consequently, SCD inhibition enhanced susceptibility to lipid redox stress that was exploited by combining FLT3 and glutathione peroxidase 4 inhibition to trigger lipid oxidative stress, enhancing ferroptotic death of FLT3-mutant AML cells. Altogether, our study reveals a C/EBPa function in lipid homeostasis and adaptation to redox stress, and a previously unreported vulnerability of FLT3-mutant AML to ferroptosis with promising therapeutic application

Background:Immunotherapy-based regimens have considerably improved the survival rate of B-cell non-Hodgkin lymphoma (B-NHL) patients in the last decades; however, most disease subtypes remain almost incurable. TG-1801, a bispecific antibody that targets CD47 selectively on CD19+ B-cells, is under clinical evaluation in relapsed/refractory (R/R) B-NHL patients either as a single-agent or in combination with ublituximab, a new generation CD20 antibody.Methods:A set of eight B-NHL cell lines and primary samples were cultured in vitro in the presence of bone marrow-derived stromal cells, M2-polarized primary macrophages, and primary circulating PBMCs as a source of effector cells. Cell response to TG-1801 alone or combined with the U2 regimen associating ublituximab to the PI3Kδ inhibitor umbralisib, was analyzed by proliferation assay, western blot, transcriptomic analysis (qPCR array and RNA sequencing followed by gene set enrichment analysis) and/or quantification of antibody-dependent cell death (ADCC) and antibody-dependent cell phagocytosis (ADCP). CRISPR-Cas9 gene edition was used to selectively abrogate GPR183 gene expression in B-NHL cells. In vivo, drug efficacy was determined in immunodeficient (NSG mice) or immune-competent (chicken embryo chorioallantoic membrane (CAM)) B-NHL xenograft models.Results:Using a panel of B-NHL co-cultures, we show that TG-1801, by disrupting the CD47-SIRPα axis, potentiates anti-CD20-mediated ADCC and ADCP. This led to a remarkable and durable antitumor effect of the triplet therapy composed by TG-1801 and U2 regimen, in vitro, as well as in mice and CAM xenograft models of B-NHL. Transcriptomic analysis also uncovered the upregulation of the G protein-coupled and inflammatory receptor, GPR183, as a crucial event associated with the efficacy of the triplet combination. Genetic depletion and pharmacological inhibition of GPR183 impaired ADCP initiation, cytoskeleton remodeling and cell migration in 2D and 3D spheroid B-NHL co-cultures, and disrupted macrophage-mediated control of tumor growth in B-NHL CAM xenografts.Conclusions:Altogether, our results support a crucial role for GPR183 in the recognition and elimination of malignant B cells upon concomitant targeting of CD20, CD47 and PI3Kδ, and warrant further clinical evaluation of this triplet regimen in B-NHL.

Targeted therapies have considerably improved the survival rate of B-cell non-Hodgkin lymphoma (B-NHL) patients in the last decade; however, most subtypes remain incurable. TG-1801, a bispecific antibody that targets CD47 selectively on CD19+ B-cells, is under clinical evaluation in relapsed/refractory B-NHL patients either as a single-agent or in combination with ublituximab, a CD20 antibody, which is also being combined with the PI3Kδ/CK1e inhibitor, umbralisib (“U2”-regimen). In this study, we demonstrated that TG-1801 potentiates ublituximab-mediated antibody-dependent cell death (ADCC) and antibody-dependent cell phagocytosis (ADCP), leading to an additive anti-tumour effect of the TG-1801/U2 combination in B-NHL co-cultures. Accordingly, in a B-NHL xenotransplant model, the triplet achieved a 93% tumour growth inhibition, with 40% of the animals remaining tumour-free 35 days after the last dosing. Transcriptomic analysis further uncovered the upregulation of the G protein-coupled receptor, GPR183, as a crucial event associated with TG-1801/U2 synergism, while pharmacological blockade or genetic depletion of this factor impaired ADCP initiation, as well as cytoskeleton remodelling and cell migration, in B-NHL cultures exposed to the drug combination. Thus, our results set the preclinical rationale and support a combination strategy of TG-1801 with PI3Kδ- and CD20-targeting agents in patients with B-NHL.