Aug 2026· Cancer Cell· Vol 44, pp. 1779-1798.e14· 1 citation· 111 references
Medicine
TL;DR
TFiT (tumor-reactive features in T cells), a transcriptional classifier that identifies tumor-reactive T cells and stratifies immunotherapy, but not chemotherapy, response across independent MM and AML cohorts, supporting its specificity for T cell-mediated tumor control.
Abstract
T cell-mediated immune surveillance is critical for cancer control, yet its role in bone marrow malignancies remains poorly understood. Here, we integrate TCR profiling, HLA immunopeptidomics, and functional screening to characterize tumor-reactive T cells in the bone marrow of patients with multiple myeloma (MM) and acute myeloid leukemia (AML). These cells are transcriptionally defined by a conserved effector program distinct from the exhausted phenotype of tumor-reactive T cells in solid cancers. Immunopeptidomic profiling reveals a partially shared antigen landscape enriched for noncanonical peptides driving convergent TCR responses. We develop TFiT (tumor-reactive features in T cells), a transcriptional classifier that identifies these cells and stratifies immunotherapy, but not chemotherapy, response across independent MM and AML cohorts, supporting its specificity for T cell-mediated tumor control. These findings reveal a latent but activatable anti-tumor T cell compartment in bone marrow malignancies and provide a framework for engaging endogenous immunity in MM and AML.
Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by the clonal expansion of myeloid blasts and the persistence of leukemic stem cells (LSCs) within a profoundly remodeled bone marrow (BM) microenvironment. Despite advances in molecular stratification and the introduction of targeted agents, long-term outcomes remain unsatisfactory, particularly in older and high-risk patients. Increasing evidence indicates that leukemogenesis and treatment resistance are critically sustained by a permissive immune milieu, in which LSCs, myeloid-derived suppressor cells, leukemia-associated macrophages, and dysfunctional T and NK cells shape an immunosuppressive “leukemic niche.” This evolving understanding has renewed interest in immune-based strategies capable of restoring effective antitumor immunity. Bispecific antibodies (bsAbs) are engineered molecules designed to engage AML-associated antigens while simultaneously recruiting and activating immune effector cells, most commonly T cells or NK cells. By promoting immune synapse formation independently of major histocompatibility complex expression and conventional co-stimulatory pathways, bsAbs can overcome several mechanisms of immune escape. In this review, we summarize the biological rationale for immunotherapy in AML, with a focus on the role of the BM microenvironment and immune dysregulation. We then discuss the structural and functional properties of IgG-like and non-IgG-like bsAbs, key antigenic targets such as CD33, CD123, CD70 and others, and the main T-cell- and NK-cell-engaging platforms under clinical investigation. Finally, we highlight emerging clinical data, principal toxicities, and the challenges of integrating bsAbs into existing treatment algorithms, including combinations with hypomethylating agents, BCL-2 inhibitors, and allogeneic stem cell transplantation. A deeper understanding of AML immune biology and antigen expression patterns will be essential to optimize bsAb design, maximize therapeutic benefit, and minimize on-target off-tumor toxicity.
A. Bruzzese, E. Martino, Santino Caserta et al.· Antibodies· 0 citations
Chimeric antigen receptor (CAR) T cells are capable to eliminate cancer cells in the treatment of hematologic malignancies, yet the efficacy is frequently inconsistent and limited by cancer cell resistance and antigen-loss resulting in early tumor relapses. While CAR T cells are deemed to be the primary effectors in controlling the tumor, maturing evidence indicates that therapeutic outcomes are shaped by a broader immune cell network involving both the endogenous adaptive and innate immunity. In this review, we reframe CAR T cell therapy as the induction of a multi-system immune response rather than a uni-directional cytotoxic cell-autonomous intervention. We discuss the respective contributions of CAR T cells, innate immune cells, and host adaptive immunity in controlling tumor progression and outline strategies to recruit innate immunity using TRUCKs, armored CAR T cells, as well as immunological adjuvants to surmount current limitations. Finally, we address the risks associated with excessive innate immune activation and propose that a calibrated, broad immune cell activation should be viewed as design principle for next-generation CAR T cell therapies.
D. Harrer, Markus Barden, H. Abken· Frontiers in Immunology· 0 citations
BACKGROUND
Acute myeloid leukemia (AML) is a malignancy characterized by abnormal myeloid proliferation. Despite therapeutic advances, relapse is frequent. Understanding the tumor microenvironment (TME), particularly the dysfunction and interactions of natural killer (NK) cells, is essential for improving immunotherapeutic strategies such as chimeric antigen receptor T-cell (CAR-T) and chimeric antigen receptor natural killer cell (CAR-NK) therapies.
OBJECTIVES
This study aimed to characterize the AML TME using single-cell RNA sequencing (scRNA-seq), focusing on NK cell dysfunction and their interactions with immunosuppressive cell populations.
MATERIAL AND METHODS
We investigated single-cell RNA sequencing data from 59 samples, comprising 40 AML and 19 healthy donor (HD) samples, obtained from public sources and processed using standard methods. After quality control and doublet removal, 284,687 high-quality cells were retained. Acute myeloid leukemia malignant cells were identified using cluster-specific occupancy scores and inferred copy number variations. Batch effects were corrected with Harmony, followed by clustering and cell-type annotation using SingleR and established markers. We performed pathway activity profiling with gene set variation analysis (GSVA), explored intercellular communication using CellChat, and inferred cellular trajectories with Monocle3. Functional characteristics of NK cell subsets were evaluated using curated gene sets, and transcriptional regulation was assessed with pySCENIC.
RESULTS
Single-cell RNA sequencing of 40 AML and 19 HD samples identified 76 cell clusters, including patient-specific malignant cells with elevated copy number variations (CNVs). Acute myeloid leukemia samples showed altered immune composition, with increased plasma cells and hematopoietic stem cell (HSC)/progenitor populations. T-cell analysis revealed higher proportions of exhausted CD8+T_LAG3 and immunosuppressive CD4+T_FOXP3 cells in AML, while CD4+T_GZMK cells were more abundant in HD samples. Natural killer (NK) cells exhibited AML-specific subtypes, notably NK_CD56dim_DNAJB1, characterized by terminal exhaustion and high stress scores. Myeloid analysis showed elevated LAMP3+ dendritic cells and macrophages in AML. Notably, enhanced interactions between NK_CD56dim_DNAJB1 and CD8+ T cells via TGFB1-TGFBR signaling suggest key immunoregulatory mechanisms in AML progression.
CONCLUSIONS
This study highlights the cellular heterogeneity and complex immune interactions within the AML microenvironment, offering insights into immune evasion and informing future immunotherapeutic and targeted treatment strategies.
Junyi Li, Huoyan Zhu, Chaoqiong Ye et al.· Advances in Clinical and Exp...· 0 citations
Solid tumors are populated with functional, non-circulating virus-specific CD8+ T cells, primed for rapid response to re-infection. Immunosurveillance by these memory T cells is evident across multiple tissues and solid tumors. Activation of these bystander cells triggers clearance of poorly immunogenic tumors in mice and is phenocopied in human tumor explants through unknown mechanisms — putatively involving the adjuvanting of tumor-specific T cell responses — providing the basis for a Phase I immunotherapy trial termed peptide alarm therapy (PAT).
To define mechanisms of PAT mediated tumor clearance in murine models, we used single-cell multi-omics, targeted immune cell depletions, and genetic manipulations. We mapped how viral peptides influence antiviral T cell states and by what axes they signal to activate the innate and adaptive immune system to mount an effective response against malignant cells. We validated our multi-omic approach via in vivo studies to measure treatment efficacy in the context of key immune cell depletion and pathway inhibitions.
We initially hypothesized that tumors were cleared in an antigen-specific manner; however, PAT cured without conventional recognition-dependent mechanisms and in the absence of any tumor-specific TCRab T cell. Mechanistically, robust T cell activation recruited immune cells, utilized innate leukocytes, and triggered a tumoricidal combination of effector molecules and panoptotic pathways, resulting in tumor-specific clearance independent of conventional T cell mechanisms. IFN-γ, TNF, and NO induced caspase-dependent death, recapitulating melanoma cures in mice or human melanoma cell death in vitro. Gene expression signatures of immune and tumor cell types involved in this panoptotic pathway were predictive of survival among human melanoma patients.
Thus, triggering productive T cell activation within tumors can be sufficient for immunotherapy, without needing to induce or rescue cancer-specific responses.
F30CA253992, R01CA238439, DP1238659
Computational and Systems Immunology (COMP)
Tyler Dao, Noah V. Gavil, M. Geller et al.· Journal of Immunology· 0 citations
The immunosuppressive bone marrow microenvironment is an important contributor to the limited success of immunotherapy in acute myeloid leukemia (AML), but the cellular interactions underlying AML immune evasion are incompletely understood. We therefore generated a single-cell spatial transcriptomic and proteomic atlas using 148 bone biopsies from 113 individuals comprising pediatric and adult AML at diagnosis and non-leukemic controls. We observed an expansion of regulatory T cells (Tregs) in AML, with stronger colocalization between Tregs and macrophages compared to non-leukemic bone marrow. Distinct cellular neighborhoods were enriched for myeloid progenitor-like cells together with macrophages and T cells, which correlated with higher macrophage and T cell immune checkpoint expression. Moreover, these neighborhoods were associated with specific AML subtypes, especially KMT2A-rearranged and RUNX1::RUNX1T1 AML. These spatial patterns were validated by identification of malignant cells via in situ fusion detection in RUNX1::RUNX1T1 cases. Functional experiments revealed that macrophages and AML cells not only actively recruit Tregs, but also promote naïve T cell differentiation into Tregs. Spatially informed ligand-receptor analysis predicted the involvement of the Galectin-9 – CD44/TIM-3 axis in this immunosuppressive crosstalk, which was supported by in vitro inhibition of CD44 and/or TIM-3 preventing macrophage- and AML-induced Treg differentiation. Collectively, this comprehensive spatial map of the AML bone marrow identified tripartite crosstalk between AML, macrophages, and T cells mediated by the Galectin-9 – CD44/TIM-3 axis as a key component of the immunosuppressive microenvironment. Targeting Galectin-9 – CD44/TIM-3 interactions may be a promising strategy to overcome immune evasion and enhance immunotherapeutic success in AML. Highlights Spatial transcriptomic and proteomic atlas of pediatric and adult acute myeloid leukemia (AML) bone marrow Increased colocalization of macrophages and regulatory T cells (Tregs) in AML Macrophages and AML cells induce differentiation of naïve T cells to Tregs in vitro, which can be prevented by inhibition of CD44 or TIM-3
M. van der Meulen, Emma S. Pool, A. Perzolli et al.· bioRxiv· 0 citations
Bone metastasis can remodel the bone marrow microenvironment, yet how metastatic tumors reshape hematopoiesis and immunity across marrow regions remains poorly defined. Here, we profile a cross-cancer single-cell atlas with 126,986 cells by integrating bone marrow samples (tumor, involved, and distal sites) from liver, prostate, and kidney cancer bone metastases, as well as benign controls, resolving 7 major lineages and 66 subpopulations. We identified coordinated immune suppression and niche remodeling that innate cells rose in peri-tumoral marrow but dropped in tumor sites, while adaptive T/B cells progressively depleted and stromal/epithelial compartments expanded. We further revealed a shift in myelopoiesis toward immunosuppressive monocyte/macrophage states with GMP-level lineage bias, alongside impaired erythropoiesis and B lymphopoiesis driven by myeloid-like reprogramming of precursors. Tumor sites were enriched with exhausted/stressed T cells, linked to inhibitory progenitor-T cell interactions (e.g., LGALS9-HAVCR2 and CLEC2-KLRB1). Non-hematopoietic support signals (CXCL12-CXCR4, ICAM1-SPN) were attenuated, and tumor programs included a marrow-specific metaprogram with IGFBP3/NAMPT signaling predicted to further destabilize the HSC niche. Overall, our study offers an integrated framework for decoding the metastatic marrow ecosystem by jointly targeting hematopoietic distortion, stromal collapse, and immune dysfunction.
