Abstract

Acute myeloid leukemia (AML) is generally considered a poorly immunogenic malignancy, displaying a “non-inflamed” leukemia microenvironment (LME), leading to T cell tolerance. However, the immune landscape of AML is much more heterogeneous. Since B7 expression is regarded as a consequence of an interferon-mediated “inflammatory” phenotype, we have investigated by flow cytometry the B7 checkpoint ligands B7.1, B7.2, programmed death ligand 1 (PD-L1), PD-L2, ICOS-L, B7-H3, and B7-H4 on the AML blasts of 30 newly diagnosed patients and their corresponding receptors [cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed death 1 (PD-1), and inducible T cell costimulator (ICOS)] on bone marrow (BM) T cell maturation populations. We could thus evidence B7-negative and B7-positive leukemias either with an isolated expression or part of eight different checkpoint ligand “signatures” that always included an inhibitory B7 molecule. B7-positive AMLs encompassed intermediate and adverse European Leukemia Net (ELN) risk cases and displayed mainly central memory CD4+ T cells with high ICOS levels and effector CD8+ T cells with high PD-1 expression. B7-negative cases were rather classified as AML with recurrent genetic anomalies and displayed predominantly naive T cells, with the exception of NPM1 mutated AMLs, which expressed B7-H3. These different B7 immune profiles suggest that specific immunotherapies are required to target the distinct immune evasion strategies of this genetically heterogeneous disease.

Highlights

  • The last decade has witnessed dramatic advances in the field of cancer immunotherapy

  • Well-beyond investigating the expression of isolated molecules, our study aims to simultaneously evaluate the B7 checkpoint ligand phenotype of Acute myeloid leukemia (AML) blasts (B7.1, B7.2, programmed death ligand 1 (PD-L1), PD-L2, ICOS-L, B7-H3, B7-H4) and the expression of immune checkpoint receptors (ICRs) [inducible T cell costimulator (ICOS), programmed death 1 (PD-1), cytotoxic T lymphocyte-associated protein 4 (CTLA-4)] on helper and cytotoxic T cell maturation populations and to correlate these data to standard prognostic factors

  • AML diagnosis was established according to the WHO diagnostic criteria [34], and patients were risk-stratified in accordance with the 2017 European Leukemia Net (ELN) recommendations [35]

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Summary

Introduction

The last decade has witnessed dramatic advances in the field of cancer immunotherapy. Immune checkpoint blockade (ICB) is reshaping the treatment paradigm of solid tumors [1] and hematologic cancers, such as Hodgkin lymphoma [2]. Gene expression profiling (GEP) of tumor immune microenvironments is revolutionizing our understanding of cancer-immune interactions. Several recurrent pan-cancer immune profiles have been identified and could serve as biomarkers for predicting clinical responses to immunotherapy or for tailoring personalized treatment strategies [7, 8]. Tumors with inflamed type I and II interferon (IFN)-driven immune microenvironments (informally designated as “hot”) are ICB responsive, while “cold” “immune-desert” tumors would rather benefit from adoptive cell transfer or tumor–peptide vaccination [9]

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