Intratumoral heterogeneity can affect the competitive fitness and chemoresistance of individual cancer cells. In acute myeloid leukemia (AML), both genetic and functional heterogeneity contribute to chemoresistance, resulting in relapse. Whereas the role of cell-extrinsic factors has been described for AML relapse, whether interactions between cancer cells affect chemoresistance is not fully known. In this study, we demonstrated that a dominant leukemic fraction can suppress the proliferation and expansion of other leukemic cells and that this suppression is reversible. This suppression is mediated in part by both type I and type II intra-leukemic interferon signaling and dependent on BST2. Importantly, blocking antibodies to type II interferon receptor activated the cycling of this suppressed cell fraction and sensitized the cells to subsequent chemotherapy treatment. Our findings suggest that interactions between functionally heterogeneous leukemic fractions can affect competitive fitness and treatment response, highlighting interferon signaling as a potential therapeutic target to counter chemoresistance. SIGNIFICANCE:AML presents a significant challenge in clinical management due to its poor prognosis and high rates of relapse following chemotherapy. Using multiple models of primary human AML, we demonstrate that competitive interactions between leukemia cells affect clonal dynamics and therapy resistance, thereby identifying a potential strategy to improve patient outcomes. See related commentary by Papaioannou and Aifantis, p. 18.

Supplementary Table 1 shows List of genes for gene set enrichment analysis Supplementary Table 2 shows Sequences of gRNA Supplementary Table 3 shows List of antibody Supplementary Table 4 shows Sequences of primers and probes

Supplementary Figure 1 shows Suppressed leukemia cells maintain disease-initiating capacity. Supplementary Figure 2 shows iAML isogenic competition model with fluorescent G0 reporter. Supplementary Figure 3 shows Oxidative phosphorylation does not account for suppression Supplementary Figure 4 shows IFN signaling inhibits suppressed samples Supplementary Figure 5 shows BST2 contributes to IFN-mediated AML suppression. Supplementary Figure 6 shows IFN signaling is associated with chemoresistance in experimental models. Supplementary Figure 7 shows IFN signaling is associated with chemoresistance in primary AML patient samples. Supplementary Figure 8 shows Blocking IFN signaling affects cycling and chimerism of patient samples.

Primary B-ALL-derived TR-APCs activate T cells in an MHC-restricted manner according to the inflammatory milieu

In vivo doxycycline administration results in significant TR-APC induction throughout tumors

Primary B-ALL TR-APCs can be generated via exogenous cytokine stimulation

TR-APC induction in solid tumor models attenuates tumor growth kinetics and prolongs survival

In vivo TR-APC induction results in expansion of activated and memory T cells, and decreased frequency of Tregs

Summary of clinical features of primary B-ALL specimens

Table S1 showing AML primary cell details for metabolomics

In vivo TR-APC induction results in no observable off-target toxicity

In vivo TR-APC induction drives oligoclonal T cell expansion

TR-APC induction results in inflammatory rewiring of the tumor microenvironment.

In vitro re-exposure of T cells from surviving mice demonstrates TR-APC-mediated generation of tumor-specific memory.

Benchmarking antigen presentation by TR-APCs

Supplementary Figure file showing Figures S1-S7

Therapeutic cancer vaccination seeks to elicit activation of tumor-reactive T cells capable of recognizing tumor-associated antigens (TAA) and eradicating malignant cells. Here, we present a cancer vaccination approach utilizing myeloid-lineage reprogramming to directly convert cancer cells into tumor-reprogrammed antigen-presenting cells (TR-APC). Using syngeneic murine leukemia models, we demonstrate that TR-APCs acquire both myeloid phenotype and function, process and present endogenous TAAs, and potently stimulate TAA-specific CD4+ and CD8+ T cells. In vivo TR-APC induction elicits clonal expansion of cancer-specific T cells, establishes cancer-specific immune memory, and ultimately promotes leukemia eradication. We further show that both hematologic cancers and solid tumors, including sarcomas and carcinomas, are amenable to myeloid-lineage reprogramming into TR-APCs. Finally, we demonstrate the clinical applicability of this approach by generating TR-APCs from primary clinical specimens and stimulating autologous patient-derived T cells. Thus, TR-APCs represent a cancer vaccination therapeutic strategy with broad implications for clinical immuno-oncology. SIGNIFICANCE:Despite recent advances, the clinical benefit provided by cancer vaccination remains limited. We present a cancer vaccination approach leveraging myeloid-lineage reprogramming of cancer cells into APCs, which subsequently activate anticancer immunity through presentation of self-derived cancer antigens. Both hematologic and solid malignancies derive significant therapeutic benefit from reprogramming-based immunotherapy. This article is highlighted in the In This Issue feature, p. 1027.

Abstract Therapeutic cancer vaccination seeks to elicit activation of tumor-reactive T cells capable of recognizing tumor-associated antigens (TAA) and eradicating malignant cells. Here, we present a cancer vaccination approach utilizing myeloid-lineage reprogramming to directly convert cancer cells into tumor-reprogrammed antigen-presenting cells (TR-APC). Using syngeneic murine leukemia models, we demonstrate that TR-APCs acquire both myeloid phenotype and function, process and present endogenous TAAs, and potently stimulate TAA-specific CD4+ and CD8+ T cells. In vivo TR-APC induction elicits clonal expansion of cancer-specific T cells, establishes cancer-specific immune memory, and ultimately promotes leukemia eradication. We further show that both hematologic cancers and solid tumors, including sarcomas and carcinomas, are amenable to myeloid-lineage reprogramming into TR-APCs. Finally, we demonstrate the clinical applicability of this approach by generating TR-APCs from primary clinical specimens and stimulating autologous patient-derived T cells. Thus, TR-APCs represent a cancer vaccination therapeutic strategy with broad implications for clinical immuno-oncology. Significance: Despite recent advances, the clinical benefit provided by cancer vaccination remains limited. We present a cancer vaccination approach leveraging myeloid-lineage reprogramming of cancer cells into APCs, which subsequently activate anticancer immunity through presentation of self-derived cancer antigens. Both hematologic and solid malignancies derive significant therapeutic benefit from reprogramming-based immunotherapy.

Supplementary Figure S1: SIRPabodies bind to CD20 and CD47 with weak affinity for CD47

Abstract Isocitrate dehydrogenase 1 and 2 (IDH) are mutated in multiple cancers and drive production of (R)-2-hydroxyglutarate (2HG). We identified a lipid synthesis enzyme [acetyl CoA carboxylase 1 (ACC1)] as a synthetic lethal target in mutant IDH1 (mIDH1), but not mIDH2, cancers. Here, we analyzed the metabolome of primary acute myeloid leukemia (AML) blasts and identified an mIDH1-specific reduction in fatty acids. mIDH1 also induced a switch to b-oxidation indicating reprogramming of metabolism toward a reliance on fatty acids. Compared with mIDH2, mIDH1 AML displayed depletion of NADPH with defective reductive carboxylation that was not rescued by the mIDH1-specific inhibitor ivosidenib. In xenograft models, a lipid-free diet markedly slowed the growth of mIDH1 AML, but not healthy CD34+ hematopoietic stem/progenitor cells or mIDH2 AML. Genetic and pharmacologic targeting of ACC1 resulted in the growth inhibition of mIDH1 cancers not reversible by ivosidenib. Critically, the pharmacologic targeting of ACC1 improved the sensitivity of mIDH1 AML to venetoclax. Significance: Oncogenic mutations in both IDH1 and IDH2 produce 2-hydroxyglutarate and are generally considered equivalent in terms of pathogenesis and targeting. Using comprehensive metabolomic analysis, we demonstrate unexpected metabolic differences in fatty acid metabolism between mutant IDH1 and IDH2 in patient samples with targetable metabolic interventions. See related commentary by Robinson and Levine, p. 266. This article is highlighted in the In This Issue feature, p. 247