NK cell defects: implication in acute myeloid leukemia

Natural killer cells in combination with the inhibition of telomerase induced apoptosis in Acute Myeloid Leukemia cells

Background

Recent trends in developing new treatments for cancers, highlight the use of immune cells particularly Natural Killer (NK) cells, as promising therapeutic strategies. While NK cells exhibit significant anti-tumor effects, their effectiveness is often limited. This study investigated the impact of BIBR1532, a human telomerase reverse transcriptase (hTERT) inhibitor, on improving the cytotoxicity of NK cells against Acute Myeloid Leukemia (AML) cells.

Methods

Primary AML cells and Kg-1a cell lines were cultured and treated with the half-maximal inhibitory concentration (IC50) of BIBR1532 for 48 h. The treated cells were then co-cultured with NK cells, after which cytotoxicity, cell proliferation, and apoptosis were assessed using Annexin V/7-AAD and Ki-67 expression analysis. Finally, apoptosis-related genes and proteins, hTERT gene and caspase 3/7 activity were studied.

Results

The Telomerase Inhibition (TI) in primary AML and Kg-1a cells with IC50 values of 38.75 μM and 57.64 μM, respectively, sensitized the AML cells and enhanced the anti-proliferative effects of NK cells. The combination of BIBR1532 and NK cells led to increased apoptosis, as indicated by the upregulation of the Bax and Bad genes, an increased Bax/Bcl-2 ratio, caspase 3/7 activity, Bax protein and a downregulation of mRNA expression levels of Bcl-2, Bcl-xl and decreased Bcl-2 protein.

Conclusion

The findings of this study demonstrate that the concurrent application of BIBR1532 and NK cells promotes apoptosis and reduces proliferation by targeting apoptosis-related genes and proteins such as Bax and Bcl-2.

Unlocking the Potential of CAR-NK Cell Therapy: Overcoming Barriers and Challenges in the Treatment of Myeloid Malignancies

Myeloid malignancies include various types of cancers that arise from the abnormal development or proliferation of myeloid cells within the bone marrow. Chimeric antigen receptor (CAR) T cell treatments, which show great potential for B cell and plasma cell cancers, face major challenges when used for myeloid malignancies. CAR natural killer (NK) cell-based immunotherapy encounters several challenges in treating myeloid cancers, including (i) poor gene transfer efficiency and expansion platforms in vitro, (ii) limited proliferation and persistence in vivo, (iii) antigenic heterogeneity, and (iv) an immunosuppressive tumor microenvironment. Despite these hurdles, "off-the-shelf" CAR-NK treatments showed encouraging results, marked by enhanced proliferation, prolonged persistence, enhanced tumor infiltration, and improved adaptability. This review offers a summary of the biological traits and cellular sources of NK cells along with a discussion of contemporary CAR designs. Furthermore, it addresses the challenges observed in preclinical research and clinical trials related to CAR-NK cell therapy for myeloid cancers, suggesting enhancement strategies.

Maintenance Therapy in AML: What Is the Future Potential?

Over the last decade, there have been significant advancements in the treatment for patients with acute myeloid leukemia (AML) including the addition of novel, targeted agents to intensive or nonintensive chemotherapy regimens. However, despite this, the majority of patients will still ultimately relapse and long-term survival remains poor. While the use of maintenance therapy has emerged as a potential strategy to maintain more durable remissions and improve overall survival, the optimal use of these therapies has not yet been clearly defined. In this review, we provide a comprehensive overview of the evolution of maintenance strategies in AML and present a commentary on the future of maintenance therapy, including the pressing, unmet needs in this field.

CD56neg CD16+ cells represent a distinct mature NK cell subset with altered phenotype and are associated with adverse clinical outcome upon expansion in AML

Introduction

Acute myeloid leukemia (AML) is a rare haematological cancer with poor 5-years overall survival (OS) and high relapse rate. Leukemic cells are sensitive to Natural Killer (NK) cell mediated killing. However, NK cells are highly impaired in AML, which promote AML immune escape from NK cell immune surveillance. We made the first report of CD56neg CD16+ NK cells expansion in AML. This unconventional subset has been reported to expand in some chronic viral infections. Although it is unclear whether CD56neg NK cells expansion mechanism is common across diseases, it seems more relevant than ever to further investigate this subset, representing a potential therapeutic target.

Methods

We used PBMCs from AML patients and HV to perform mass cytometry, spectral flow cytometry, bulk RNA-seq and in vitro assays in order to better characterize CD56neg CD16+ NK cells that expand in AML.

Results

We confirmed that CD56neg CD16+ NK cells represent a unique NK cell subset coexpressing Eomes and T-bet. CD56neg CD16+ NK cells could recover CD56 expression in vitro where they displayed unaltered NK cell functions. We previously demonstrated that CD56neg CD16+ NK cells expansion at diagnosis was associated with adverse clinical outcome in AML. Here, we validated our findings in a validation cohort of N=38 AML patients. AML patients with CD56neg CD16+ NK cells expansion at diagnosis had decreased overall survival (HR[CI95]=5.5[1.2-24.5], p=0.0251) and relapse-free survival (HR[CI95]=13.1[1.9-87.5], p=0.0079) compared to AML patients without expansion after 36 months follow-up. RNA-seq unveiled that CD56neg CD16+ NK cells were mature circulating NK cells with functional capacities. Upon expansion, CD56neg CD16+ NK cells from AML patients showed altered proteomic phenotype, with increased frequency of terminally mature CD56neg CD16+ NK cells expressing TIGIT along with decreased frequency of Siglec-7+ CD56neg CD16+ NK cells.

Discussion

Taken together, our results suggest that we could harness CD56neg CD16+ NK cells cytotoxic potential in vitro to restore NK cell anti-tumor response in AML patients with CD56neg CD16+ NK cells expansion and improve patients' prognosis. To conclude, CD56neg CD16+ NK cells represent a relevant target for future NK-cell-based immunotherapies in AML.

Single-cell transcriptomics reveals heterogeneity and prognostic markers of myeloid precursor cells in acute myeloid leukemia

Background

Acute myeloid leukemia (AML) is a hematologic tumor with poor prognosis and significant clinical heterogeneity. By integrating transcriptomic data, single-cell RNA sequencing data and independently collected RNA sequencing data this study aims to identify key genes in AML and establish a prognostic assessment model to improve the accuracy of prognostic prediction.

Materials and methods

We analyzed RNA-seq data from AML patients and combined it with single-cell RNA sequencing data to identify genes associated with AML prognosis. Key genes were screened by bioinformatics methods, and a prognostic assessment model was established based on these genes to validate their accuracy.

Results

The study identified eight key genes significantly associated with AML prognosis: SPATS2L, SPINK2, AREG, CLEC11A, HGF, IRF8, ARHGAP5, and CD34. The prognostic model constructed on the basis of these genes effectively differentiated between high-risk and low-risk patients and revealed differences in immune function and metabolic pathways of AML cells.

Conclusion

This study provides a new approach to AML prognostic assessment and reveals the role of key genes in AML. These genes may become new biomarkers and therapeutic targets that can help improve prognostic prediction and personalized treatment of AML.

Antitumor progestins activity: Cytostatic effect and immune response

Progestins are used to treat some hormone-sensitive tumors. This review discusses the mechanisms of progestins' effects on tumor cells, the differences in the effects of progesterone and its analogs on different tumor types, and the influence of progestins on the antitumor immune response. Progestins cause a cytostatic effect, but at the same time they can suppress the antitumor immune response, and this can promote the proliferation and metastasis of tumor cells. Such progestins as dienogest, megestrol acetate and levonorgestrel increase the activity of NK-cells, which play a major role in the body's fight against tumor cells. The use of existing progestins and the development of new drugs with gestagenic activity may hold promise in oncotherapy.

Finding potential targets in cell-based immunotherapy for handling the challenges of acute myeloid leukemia

Acute myeloid leukemia (AML) is a hostile hematological malignancy under great danger of relapse and poor long-term survival rates, despite recent therapeutic advancements. To deal with this unfulfilled clinical necessity, innovative cell-based immunotherapies have surfaced as promising approaches to improve anti-tumor immunity and enhance patient outcomes. In this comprehensive review, we provide a detailed examination of the latest developments in cell-based immunotherapies for AML, including chimeric antigen receptor (CAR) T-cell therapy, T-cell receptor (TCR)-engineered T-cell therapy, and natural killer (NK) cell-based therapies. We critically evaluate the unique mechanisms of action, current challenges, and evolving strategies to improve the efficacy and safety of these modalities. The review emphasizes how promising these cutting-edge immune-based strategies are in overcoming the inherent complexities and heterogeneity of AML. We discuss the identification of optimal target antigens, the importance of mitigating on-target/off-tumor toxicity, and the need to enhance the persistence and functionality of engineered immune effector cells. All things considered, this review offers a thorough overview of the rapidly evolving field of cell-based immunotherapy for AML, underscoring the significant progress made and the ongoing efforts to translate these innovative approaches into more effective and durable treatments for this devastating disease.

Proteasome inhibition enhances the anti-leukemic efficacy of chimeric antigen receptor (CAR) expressing NK cells against acute myeloid leukemia

BACKGROUND

Relapsed and refractory acute myeloid leukemia (AML) carries a dismal prognosis. CAR T cells have shown limited efficacy in AML, partially due to dysfunctional autologous T cells and the extended time for generation of patient specific CAR T cells. Allogeneic NK cell therapy is a promising alternative, but strategies to enhance efficacy and persistence may be necessary. Proteasome inhibitors (PI) induce changes in the surface proteome which may render malignant cells more vulnerable to NK mediated cytotoxicity. Here, we investigated the potential benefit of combining PIs with CAR-expressing allogeneic NK cells against AML.

METHODS

We established the IC50 concentrations for Bortezomib and Carfilzomib against several AML cell lines. Surface expression of class-I HLA molecules and stress-associated proteins upon treatment with proteasome inhibitors was determined by multiparameter flow cytometry. Using functional in vitro assays, we explored the therapeutic synergy between pre-treatment with PIs and the anti-leukemic efficacy of NK cells with or without expression of AML-specific CAR constructs against AML cell lines and primary patient samples. Also, we investigated the tolerability and efficacy of a single PI application strategy followed by (CAR-) NK cell infusion in two different murine xenograft models of AML.

RESULTS

AML cell lines and primary AML patient samples were susceptible to Bortezomib and Carfilzomib mediated cytotoxicity. Conditioned resistance to Azacitidine/Venetoclax did not confer primary resistance to PIs. Treating AML cells with PIs reduced the surface expression of class-I HLA molecules on AML cells in a time-and-dose dependent manner. Stress-associated proteins were upregulated on the transcriptional level and on the cell surface. NK cell mediated killing of AML cells was enhanced in a synergistic manner. PI pre-treatment increased effector-target cell conjugate formation and Interferon-γ secretion, resulting in enhanced NK cell activity against AML cell lines and primary samples in vitro. Expression of CD33- and CD70-specific CARs further improved the antileukemic efficacy. In vivo, Bortezomib pre-treatment followed by CAR-NK cell infusion reduced AML growth, leading to prolonged overall survival.

CONCLUSIONS

PIs enhance the anti-leukemic efficacy of CAR-expressing allogeneic NK cells against AML in vitro and in vivo, warranting further exploration of this combinatorial treatment within early phase clinical trials.

STAT3 in acute myeloid leukemia facilitates natural killer cell-mediated surveillance

Acute myeloid leukemia (AML) is a heterogenous disease characterized by the clonal expansion of myeloid progenitor cells. Despite recent advancements in the treatment of AML, relapse still remains a significant challenge, necessitating the development of innovative therapies to eliminate minimal residual disease. One promising approach to address these unmet clinical needs is natural killer (NK) cell immunotherapy. To implement such treatments effectively, it is vital to comprehend how AML cells escape the NK-cell surveillance. Signal transducer and activator of transcription 3 (STAT3), a component of the Janus kinase (JAK)-STAT signaling pathway, is well-known for its role in driving immune evasion in various cancer types. Nevertheless, the specific function of STAT3 in AML cell escape from NK cells has not been deeply investigated. In this study, we unravel a novel role of STAT3 in sensitizing AML cells to NK-cell surveillance. We demonstrate that STAT3-deficient AML cell lines are inefficiently eliminated by NK cells. Mechanistically, AML cells lacking STAT3 fail to form an immune synapse as efficiently as their wild-type counterparts due to significantly reduced surface expression of intercellular adhesion molecule 1 (ICAM-1). The impaired killing of STAT3-deficient cells can be rescued by ICAM-1 overexpression proving its central role in the observed phenotype. Importantly, analysis of our AML patient cohort revealed a positive correlation between ICAM1 and STAT3 expression suggesting a predominant role of STAT3 in ICAM-1 regulation in this disease. In line, high ICAM1 expression correlates with better survival of AML patients underscoring the translational relevance of our findings. Taken together, our data unveil a novel role of STAT3 in preventing AML cells from escaping NK-cell surveillance and highlight the STAT3/ICAM-1 axis as a potential biomarker for NK-cell therapies in AML.

Recent Advances in Immune-Based Therapies for Acute Myeloid Leukemia

Despite advancements, acute myeloid leukemia (AML) remains unconquered by current therapies. Evidence of immune evasion during AML progression, such as HLA loss and T-cell exhaustion, suggests that antileukemic immune responses contribute to disease control and could be harnessed by immunotherapy. In this review, we discuss a spectrum of AML immunotherapy targets, encompassing cancer cell-intrinsic and surface antigens as well as targeting in the leukemic milieu, and how they can be tailored for personalized approaches. These targets are overviewed across major immunotherapy modalities applied to AML: immune checkpoint inhibitors, antibody-drug conjugates, therapeutic vaccines, bispecific/trispecific antibodies, and chimeric antigen receptor (CAR)-T and CAR-NK cells. Significance: Immune therapies in AML treatment show evolving promise. Ongoing research aims to customize approaches for varied patient profiles and clinical scenarios. This review covers immune surveillance mechanisms, therapy options like checkpoint inhibitors, antibodies, CAR-T/NK cells, and vaccines, as well as resistance mechanisms and microenvironment considerations.

Uncovering the cellular and omics characteristics of natural killer cells in the bone marrow microenvironment of patients with acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a highly heterogeneous hematologic malignancy and the most frequently acute leukemia of stem cell precursors and the myeloid derivatives in adult. Longitudinal studies have indicated the therapeutic landscape and drug resistance for patients with AML are still intractable, which largely attribute to the deficiency of detailed information upon the pathogenesis.

METHODS

In this study, we compared the cellular phenotype of resident NK cells (rAML-NKs, rHD-NKs) and expanded NK cells (eAML-NKs, eHD-NKs) from bone marrow of AML patients (AML) and healthy donors (HD). Then, we took advantage of the co-culture strategy for the evaluation of the in vitro cytotoxicity of NK cells upon diverse tumor cell lines (e.g., K562, Nalm6, U937). With the aid of RNA-sequencing (RNA-SEQ) and bioinformatics analyses (e.g., GOBP analysis, KEGG analysis, GSEA, volcano plot), we verified the similarities and differences of the omics features between eAML-NKs and eHD-NKs.

RESULTS

Herein, we verified the sharp decline in the content of total resident NK cells (CD3-CD56+) in rAML-NKs compared to rHD-NKs. Differ from the expanded eHD-NKs, eAML-NKs revealed decline in diverse NK cell subsets (NKG2D+, CD25+, NKp44+, NKp46+) and alterations in cellular vitality but conservations in cytotoxicity. According to transcriptomic analysis, AML-NKs and HD-NKs showed multifaceted distinctions in gene expression profiling and genetic variations.

CONCLUSIONS

Collectively, our data revealed the variations in the cytobiological and transcriptomic features between AML-NKs and HD-NKs in bone marrow environment. Our findings would benefit the further development of novel biomarkers for AML diagnosis and NK cell-based cytotherapy in future.

Effect of low skeletal muscle mass on NK cells in patients with acute myeloid leukemia and its correlation with prognosis

The objective of this study was to analyze the correlation between skeletal muscle mass and the distribution of peripheral blood lymphocytes and natural killer (NK) cells, as well as their impact on prognosis in patients with acute myeloid leukemia (AML). A retrospective analysis was conducted on 211 newly diagnosed AML patients, evaluating skeletal muscle index (SMI), NK cell proportion, and absolute value, along with relevant clinical data. Linear regression and Spearman's correlation coefficient were used to assess the relationship between various indicators and SMI, followed by multiple linear regression for further modeling. Univariate and multivariate Cox proportional hazards regression models were used to identify independent predictors for overall survival (OS). Among the 211 AML patients, 38 cases (18.0%) were diagnosed with sarcopenia. Multiple linear regression analysis included weight, fat mass, ECOG score, body mass index, and peripheral blood NK cell proportion, constructing a correlation model for SMI (R2 = 0.745). Univariate analysis identified higher NK cell count (> 9.53 × 106/L) as a poor predictor for OS. Multivariate Cox proportional hazards regression model indicated that age ≥ 60 years, PLT < 100 × 109/L, ELN high risk, sarcopenia, and B cell count > 94.6 × 106/L were independent adverse prognostic factors for AML patients. Low skeletal muscle mass may negatively impact the count and function of NK cells, thereby affecting the prognosis of AML. However, further basic and clinical research is needed to explore the specific mechanisms underlying the relationship between NK cells and SMI in AML.

Cytokine-Induced Memory-Like NK Cells: Emerging strategy for AML immunotherapy

Acute myeloid leukemia (AML) is a heterogeneous disease developed from the malignant expansion of myeloid precursor cells in the bone marrow and peripheral blood. The implementation of intensive chemotherapy and hematopoietic stem cell transplantation (HSCT) has improved outcomes associated with AML, but relapse, along with suboptimal outcomes, is still a common scenario. In the past few years, exploring new therapeutic strategies to optimize treatment outcomes has occurred rapidly. In this regard, natural killer (NK) cell-based immunotherapy has attracted clinical interest due to its critical role in immunosurveillance and their capabilities to target AML blasts. NK cells are cytotoxic innate lymphoid cells that mediate anti-viral and anti-tumor responses by producing pro-inflammatory cytokines and directly inducing cytotoxicity. Although NK cells are well known as short-lived innate immune cells with non-specific responses that have limited their clinical applications, the discovery of cytokine-induced memory-like (CIML) NK cells could overcome these challenges. NK cells pre-activated with the cytokine combination IL-12/15/18 achieved a long-term life span with adaptive immunity characteristics, termed CIML-NK cells. Previous studies documented that using CIML-NK cells in cancer treatment is safe and results in promising outcomes. This review highlights the current application, challenges, and opportunities of CIML-NK cell-based therapy in AML.