Integrative single-cell expression and functional studies unravels a sensitization to cytarabine-based chemotherapy through HIF pathway inhibition in AML leukemia stem cells.

Relapse remains a major challenge in the clinical management of acute myeloid leukemia (AML) and is driven by rare therapy-resistant leukemia stem cells (LSCs) that reside in specific bone marrow niches. Hypoxia signaling maintains cells in a quiescent and metabolically relaxed state, desensitizing them to chemotherapy. This suggests the hypothesis that hypoxia contributes to the chemoresistance of AML-LSCs and may represent a therapeutic target to sensitize AML-LSCs to chemotherapy. Here, we identify HIFhigh and HIFlow specific AML subgroups (inv(16)/t(8;21) and MLLr, respectively) and provide a comprehensive single-cell expression atlas of 119,000 AML cells and AML-LSCs in paired diagnostic-relapse samples from these molecular subgroups. The HIF/hypoxia pathway signature is attenuated in AML-LSCs compared with more differentiated AML cells but is more expressed than in healthy hematopoietic cells. Importantly, chemical inhibition of HIF cooperates with standard-of-care chemotherapy to impair AML growth and to substantially eliminate AML-LSCs in vitro and in vivo. These findings support the HIF pathway in the stem cell-driven drug resistance of AML and unravel avenues for combinatorial targeted and chemotherapy-based approaches to specifically eliminate AML-LSCs.

CD155/PVR determines acute myeloid leukemia targeting by Delta One T cells.

ABSTRACT: Relapsed or refractory acute myeloid leukemia (AML) remains a major therapeutic challenge. We have recently developed a Vδ1+ γδ T cell-based product for adoptive immunotherapy, named Delta One T (DOT) cells, and demonstrated their cytolytic capacity to eliminate AML cell lines and primary blasts in vitro and in vivo. However, the molecular mechanisms responsible for the broad DOT-cell recognition of AML cells remain poorly understood. Here, we dissected the role of natural killer (NK) cell receptor ligands in AML cell recognition by DOT cells. Screening of multiple AML cell lines highlighted a strong upregulation of the DNAM-1 ligands, CD155/pulmonary vascular resistance (PVR), CD112/nectin-2, as well as the NKp30 ligand, B7-H6, in contrast with NKG2D ligands. CRISPR-mediated ablation revealed key nonredundant and synergistic contributions of PVR and B7-H6 but not nectin-2 to DOT-cell targeting of AML cells. We further demonstrate that PVR and B7-H6 are critical for the formation of robust immunological synapses between AML and DOT cells. Importantly, PVR but not B7-H6 expression in primary AML samples predicted their elimination by DOT cells. These data provide new mechanistic insight into tumor targeting by DOT cells and suggest that assessing PVR expression levels may be highly relevant to DOT cell-based clinical trials.

Engineered T cells secreting anti-BCMA T cell engagers control multiple myeloma and promote immune memory in vivo.

Multiple myeloma is the second most common hematological malignancy in adults and remains an incurable disease. B cell maturation antigen (BCMA)-directed immunotherapy, including T cells bearing chimeric antigen receptors (CARs) and systemically injected bispecific T cell engagers (TCEs), has shown remarkable clinical activity, and several products have received market approval. However, despite promising results, most patients eventually become refractory and relapse, highlighting the need for alternative strategies. Engineered T cells secreting TCE antibodies (STAb) represent a promising strategy that combines the advantages of adoptive cell therapies and bispecific antibodies. Here, we undertook a comprehensive preclinical study comparing the therapeutic potential of T cells either expressing second-generation anti-BCMA CARs (CAR-T) or secreting BCMAxCD3 TCEs (STAb-T) in a T cell-limiting experimental setting mimicking the conditions found in patients with relapsed/refractory multiple myeloma. STAb-T cells recruited T cell activity at extremely low effector-to-target ratios and were resistant to inhibition mediated by soluble BCMA released from the cell surface, resulting in enhanced cytotoxic responses and prevention of immune escape of multiple myeloma cells in vitro. These advantages led to robust expansion and persistence of STAb-T cells in vivo, generating long-lived memory BCMA-specific responses that could control multiple myeloma progression in xenograft models, outperforming traditional CAR-T cells. These promising preclinical results encourage clinical testing of the BCMA-STAb-T cell approach in relapsed/refractory multiple myeloma.

Lipid droplets provide metabolic flexibility for cancer progression.

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation of LDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Chromosomal instability in aneuploid acute lymphoblastic leukemia associates with disease progression.

Chromosomal instability (CIN) lies at the core of cancer development leading to aneuploidy, chromosomal copy-number heterogeneity (chr-CNH) and ultimately, unfavorable clinical outcomes. Despite its ubiquity in cancer, the presence of CIN in childhood B-cell acute lymphoblastic leukemia (cB-ALL), the most frequent pediatric cancer showing high frequencies of aneuploidy, remains unknown. Here, we elucidate the presence of CIN in aneuploid cB-ALL subtypes using single-cell whole-genome sequencing of primary cB-ALL samples and by generating and functionally characterizing patient-derived xenograft models (cB-ALL-PDX). We report higher rates of CIN across aneuploid than in euploid cB-ALL that strongly correlate with intraclonal chr-CNH and overall survival in mice. This association was further supported by in silico mathematical modeling. Moreover, mass-spectrometry analyses of cB-ALL-PDX revealed a "CIN signature" enriched in mitotic-spindle regulatory pathways, which was confirmed by RNA-sequencing of a large cohort of cB-ALL samples. The link between the presence of CIN in aneuploid cB-ALL and disease progression opens new possibilities for patient stratification and offers a promising new avenue as a therapeutic target in cB-ALL treatment.

The relapsed acute lymphoblastic leukemia network (ReALLNet): a multidisciplinary project from the spanish society of pediatric hematology and oncology (SEHOP).

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, with survival rates exceeding 85%. However, 15% of patients will relapse; consequently, their survival rates decrease to below 50%. Therefore, several research and innovation studies are focusing on pediatric relapsed or refractory ALL (R/R ALL). Driven by this context and following the European strategic plan to implement precision medicine equitably, the Relapsed ALL Network (ReALLNet) was launched under the umbrella of SEHOP in 2021, aiming to connect bedside patient care with expert groups in R/R ALL in an interdisciplinary and multicentric network. To achieve this objective, a board consisting of experts in diagnosis, management, preclinical research, and clinical trials has been established. The requirements of treatment centers have been evaluated, and the available oncogenomic and functional study resources have been assessed and organized. A shipping platform has been developed to process samples requiring study derivation, and an integrated diagnostic committee has been established to report results. These biological data, as well as patient outcomes, are collected in a national registry. Additionally, samples from all patients are stored in a biobank. This comprehensive repository of data and samples is expected to foster an environment where preclinical researchers and data scientists can seek to meet the complex needs of this challenging population. This proof of concept aims to demonstrate that a network-based organization, such as that embodied by ReALLNet, provides the ideal niche for the equitable and efficient implementation of "what's next" in the management of children with R/R ALL.

A human genome editing-based MLL::AF4 ALL model recapitulates key cellular and molecular leukemogenic features.

Cellular ontogeny and MLL breakpoint site influence the capacity of MLL-edited CD34+ hematopoietic cells to initiate and recapitulate infant patients' features in pro-B-cell acute lymphoblastic leukemia (B-ALL). We provide key insights into the leukemogenic determinants of MLL-AF4+ infant B-ALL.

GPRC5C drives branched-chain amino acid metabolism in leukemogenesis.

Leukemia stem cells (LSCs) share numerous features with healthy hematopoietic stem cells (HSCs). G-protein coupled receptor family C group 5 member C (GPRC5C) is a regulator of HSC dormancy. However, GPRC5C functionality in acute myeloid leukemia (AML) is yet to be determined. Within patient AML cohorts, high GPRC5C levels correlated with poorer survival. Ectopic Gprc5c expression increased AML aggression through the activation of NF-κB, which resulted in an altered metabolic state with increased levels of intracellular branched-chain amino acids (BCAAs). This onco-metabolic profile was reversed upon loss of Gprc5c, which also abrogated the leukemia-initiating potential. Targeting the BCAA transporter SLC7A5 with JPH203 inhibited oxidative phosphorylation and elicited strong antileukemia effects, specifically in mouse and patient AML samples while sparing healthy bone marrow cells. This antileukemia effect was strengthened in the presence of venetoclax and azacitidine. Our results indicate that the GPRC5C-NF-κB-SLC7A5-BCAAs axis is a therapeutic target that can compromise leukemia stem cell function in AML.

ALPL-1 is a target for chimeric antigen receptor therapy in osteosarcoma.

Osteosarcoma (OS) remains a dismal malignancy in children and young adults, with poor outcome for metastatic and recurrent disease. Immunotherapies in OS are not as promising as in some other cancer types due to intra-tumor heterogeneity and considerable off-target expression of the potentially targetable proteins. Here we show that chimeric antigen receptor (CAR) T cells could successfully target an isoform of alkaline phosphatase, ALPL-1, which is highly and specifically expressed in primary and metastatic OS. The target recognition element of the second-generation CAR construct is based on two antibodies, previously shown to react against OS. T cells transduced with these CAR constructs mediate efficient and effective cytotoxicity against ALPL-positive cells in in vitro settings and in state-of-the-art in vivo orthotopic models of primary and metastatic OS, without unexpected toxicities against hematopoietic stem cells or healthy tissues. In summary, CAR-T cells targeting ALPL-1 show efficiency and specificity in treating OS in preclinical models, paving the path for clinical translation.

Low input capture Hi-C (liCHi-C) identifies promoter-enhancer interactions at high-resolution.

Long-range interactions between regulatory elements and promoters are key in gene transcriptional control; however, their study requires large amounts of starting material, which is not compatible with clinical scenarios nor the study of rare cell populations. Here we introduce low input capture Hi-C (liCHi-C) as a cost-effective, flexible method to map and robustly compare promoter interactomes at high resolution. As proof of its broad applicability, we implement liCHi-C to study normal and malignant human hematopoietic hierarchy in clinical samples. We demonstrate that the dynamic promoter architecture identifies developmental trajectories and orchestrates transcriptional transitions during cell-state commitment. Moreover, liCHi-C enables the identification of disease-relevant cell types, genes and pathways potentially deregulated by non-coding alterations at distal regulatory elements. Finally, we show that liCHi-C can be harnessed to uncover genome-wide structural variants, resolve their breakpoints and infer their pathogenic effects. Collectively, our optimized liCHi-C method expands the study of 3D chromatin organization to unique, low-abundance cell populations, and offers an opportunity to uncover factors and regulatory networks involved in disease pathogenesis.

Ruptured subcapsular liver hematoma as a rare complication of HELLP syndrome. A therapeutic challenge.

HELLP syndrome (HS), a low-incidence condition of uncertain pathogenesis associated with pregnancy hypertensive syndromes, is characterized by hemolysis, elevated liver enzymes and low platelet count. Ruptured subcapsular liver hematoma complicated with hemoperitoneum is an uncommon but very serious condition where early recognition and multidisciplinary management are key to reduce its associated maternal, infant mortality rate. Symptoms are nonspecific, characterized by por epigastric pain, nausea and vomiting; clinical suspicion and appropriate imaging studies are of crucial importance. We report the case of a 36-year-old primiparous woman at 39 weeks of gestation. She was admitted for early membrane rupture, with delivery complicated by retained placenta. During the immediate puerperium she had blood pressure > 140/90 mmHg, epigastric pain and vomiting, which required respiratory and hemodynamic support. An exploratory laparotomy was performed that revealed a massive hemoperitoneum as well as CR in the RLL with multifocal active bleeding. The left liver lobe was macroscopically normal. The patient underwent hemoperitoneum drainage and hepatic packing (HP); biopsy findings were consistent with necrosis. Polytransfusion was initiated with blood products and antihemorrhagic agents.

Efficient preclinical treatment of cortical T cell acute lymphoblastic leukemia with T lymphocytes secreting anti-CD1a T cell engagers.

BACKGROUND: The dismal clinical outcome of relapsed/refractory (R/R) T cell acute lymphoblastic leukemia (T-ALL) highlights the need for innovative targeted therapies. Although chimeric antigen receptor (CAR)-engineered T cells have revolutionized the treatment of B cell malignancies, their clinical implementation in T-ALL is in its infancy. CD1a represents a safe target for cortical T-ALL (coT-ALL) patients, and fratricide-resistant CD1a-directed CAR T cells have been preclinically validated as an immunotherapeutic strategy for R/R coT-ALL. Nonetheless, T-ALL relapses are commonly very aggressive and hyperleukocytic, posing a challenge to recover sufficient non-leukemic effector T cells from leukapheresis in R/R T-ALL patients. METHODS: We carried out a comprehensive study using robust in vitro and in vivo assays comparing the efficacy of engineered T cells either expressing a second-generation CD1a-CAR or secreting CD1a x CD3 T cell-engaging Antibodies (CD1a-STAb). RESULTS: We show that CD1a-T cell engagers bind to cell surface expressed CD1a and CD3 and induce specific T cell activation. Recruitment of bystander T cells endows CD1a-STAbs with an enhanced in vitro cytotoxicity than CD1a-CAR T cells at lower effector:target ratios. CD1a-STAb T cells are as effective as CD1a-CAR T cells in cutting-edge in vivo T-ALL patient-derived xenograft models. CONCLUSIONS: Our data suggest that CD1a-STAb T cells could be an alternative to CD1a-CAR T cells in coT-ALL patients with aggressive and hyperleukocytic relapses with limited numbers of non-leukemic effector T cells.

ABO gene editing for the conversion of blood type A to universal type O in Rhnull donor-derived human-induced pluripotent stem cells.

The limited availability of red cells with extremely rare blood group phenotypes is one of the global challenges in transfusion medicine that has prompted the search for alternative self-renewable pluripotent cell sources for the in vitro generation of red cells with rare blood group types. One such phenotype is the Rhnull , which lacks all the Rh antigens on the red cell membrane and represents one of the rarest blood types in the world with only a few active blood donors available worldwide. Rhnull red cells are critical for the transfusion of immunized patients carrying the same phenotype, besides its utility in the diagnosis of Rh alloimmunization when a high-prevalence Rh specificity is suspected in a patient or a pregnant woman. In both scenarios, the potential use of human-induced pluripotent stem cell (hiPSC)-derived Rhnull red cells is also dependent on ABO compatibility. Here, we present a CRISPR/Cas9-mediated ABO gene edition strategy for the conversion of blood type A to universal type O, which we have applied to an Rhnull donor-derived hiPSC line, originally carrying blood group A. This work provides a paradigmatic example of an approach potentially applicable to other hiPSC lines derived from rare blood donors not carrying blood type O.

Generation and proof-of-concept for allogeneic CD123 CAR-Delta One T (DOT) cells in acute myeloid leukemia.

BACKGROUND: Chimeric antigen receptor (CAR)-T cells have emerged as a breakthrough treatment for relapse/refractory hematological tumors, showing impressive complete remission rates. However, around 50% of the patients relapse before 1-year post-treatment. T-cell 'fitness' is critical to prolong CAR-T persistence and activity. Allogeneic T cells from healthy donors are less dysfunctional or exhausted than autologous patient-derived T cells; in this context, Delta One T cells (DOTs), a recently described cellular product based on MHC/HLA-independent Vδ1+γδ T cells, represent a promising allogeneic platform. METHODS: Here we generated and preclinically validated, for the first time, 4-1BB-based CAR-DOTs directed against the interleukin-3α chain receptor (CD123), a target antigen widely expressed on acute myeloid leukemia (AML) blasts. RESULTS: CD123CAR-DOTs showed vigorous, superior to control DOTs, cytotoxicity against AML cell lines and primary samples both in vitro and in vivo, even on tumor rechallenge. CONCLUSIONS: Our results provide the proof-of-concept for a DOT-based next-generation allogeneic CAR-T therapy for AML.

Hyaluronic acid-GPRC5C signalling promotes dormancy in haematopoietic stem cells.

Bone marrow haematopoietic stem cells (HSCs) are vital for lifelong maintenance of healthy haematopoiesis. In inbred mice housed in gnotobiotic facilities, the top of the haematopoietic hierarchy is occupied by dormant HSCs, which reversibly exit quiescence during stress. Whether HSC dormancy exists in humans remains debatable. Here, using single-cell RNA sequencing, we show a continuous landscape of highly purified human bone marrow HSCs displaying varying degrees of dormancy. We identify the orphan receptor GPRC5C, which enriches for dormant human HSCs. GPRC5C is also essential for HSC function, as demonstrated by genetic loss- and gain-of-function analyses. Through structural modelling and biochemical assays, we show that hyaluronic acid, a bone marrow extracellular matrix component, preserves dormancy through GPRC5C. We identify the hyaluronic acid-GPRC5C signalling axis controlling the state of dormancy in mouse and human HSCs.