Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening systemic hyperinflammatory syndrome arising in many contexts. Its underlying mechanisms are often unclear, but defective granule-mediated cytotoxicity (familial HLH) and excess interleukin-18 (IL-18; macrophage activation syndrome) provide clues. Mounting evidence suggests the causes of HLH converge on cytotoxic T lymphocyte (CTL) hyperactivation and interferon gamma (IFN-γ) overproduction. We refined an in vitro system to simultaneously quantify multiple parameters of the murine CTL immune synapse (IS). Even in haploinsufficiency, perforin deficiency prolonged IS duration and increased IFN-γ/tumor necrosis factor production. Similarly, both target cell immortalization and inhibition of apoptotic caspases impaired IS termination and increased cytokine production. Strong CTL activation, through T-cell receptor or IL-18 signaling, also increased IFN-γ secretion but accelerated target cell death. Impaired IS termination synergized with strong CTL activation in driving IFN-γ production. Visually, both typical and Prf1-/- CTL-IS terminated with apoptotic contraction. Serendipitously, we observed many IL-18-exposed CTL-IS terminated by target cell ballooning. Both IL-18-activated CTL and IFN-γ pretreatment caused up to half of target cells to die by receptor-interacting protein kinase 1 (RIPK1)-dependent necroptosis. In vivo, RIPK1 inhibition ameliorated virus-triggered HLH in Il18tg more than Prf1-/- mice. By quantifying CTL-IS duration, cytokine production, and mode of cell death, we modeled multiple HLH contributors and their interactions and identified 3 HLH mechanistic categories: impaired IS termination, intense CTL cytokine production, and inflammatory target cell death. Integrating the inputs and outcomes of a hyperinflammatory CTL-IS may provide a useful framework for understanding, predicting, or treating HLH in its many forms.

Despite the success of B-cell maturation antigen (BCMA)-targeting chimeric antigen receptor (CAR) T cells (CAR-Ts) in multiple myeloma, patients with high-risk cytogenetic features continue to relapse most quickly and are in urgent need of additional therapeutic options. Here, we identify CD70, widely recognized as a favorable immunotherapy target in other cancers, as a specifically upregulated cell surface antigen in high-risk myeloma tumors. We use a structure-guided design to define a CD27-based anti-CD70 CAR-T design that outperforms all tested single-chain variable fragment-based CARs, leading to >80-fold improved CAR-T expansion in vivo. Epigenetic analysis via machine learning predicts key transcription factors and transcriptional networks driving CD70 upregulation in high-risk myeloma. Dual-targeting CAR-Ts against either CD70 or BCMA demonstrate a potential strategy to avoid antigen escape-mediated resistance. Together, these findings support the promise of targeting CD70 with optimized CAR-Ts in myeloma as well as future clinical translation of this approach.

Immunotherapy has become standard of care in the treatment of diffuse large B-cell lymphoma (DLBCL). Changes in immunophenotypes observed at first diagnosis predict therapy outcome but little is known about the resolution of these alterations in remission. Comprehensive characterization of immune changes from fresh, peripheral whole blood revealed a functionally relevant increase of myeloid-derived suppressor cells, reduced naïve T cells, and an increase of activated and terminally differentiated T cells before treatment, which aggravated after therapy. Suggesting causal relation, injection of lymphoma in mice induced similar changes in the murine T cells. Distinct immune imprints were found in those who have survived breast cancer and acute myeloid leukemia. Identified alterations persisted beyond 5 years of ongoing complete remission and correlated with increased proinflammatory markers such as interleukin-6, β2-microglobulin, or soluble CD14 in DLBCL. The chronic inflammation was associated with functionally blunted T-cell immunity against severe acute respiratory syndrome coronavirus 2-specific peptides, and reduced responses correlated with reduced naïve T cells. Persisting inflammation was confirmed by deep sequencing and by cytokine profiles, together pointing toward a compensatory activation of innate immunity. The persisting, lymphoma-induced immune alterations in remission may explain long-term complications, have implications for vaccine strategies, and are likely relevant for immunotherapies.

This study analyzed the genetics of classic Hodgkin lymphoma (cHL) by using circulating tumor DNA (ctDNA). Two genetic subtypes were identified, differing in genetic instability mechanisms: one subtype (64% of cases) showed a higher mutation load and a higher fraction of mutations associated with activation-induced cytidine deaminase and microsatellite instability signatures, whereas the other subtype (36% of cases) exhibited chromosomal instability with more somatic copy number alterations. Whole-genome duplication was more common in cHL compared with other B-cell tumors and emerged as a prognostic biomarker for patients undergoing Adriamycin (doxorubicin)-bleomycin-vinblastine-dacarbazine-based therapy. Noncoding regulatory mutations, similar to those in diffuse large B-cell lymphoma, were highly prevalent in 86% of cHL. A recurrent somatic expression quantitative trait locus (seQTL) involving the BCL6 gene was found in 30% of cases. The seQTL of BCL6 aligned with accessible chromatin and increased H3K27 acetylation in cHL, disrupted PRDM1 binding, and co-occurred with BCL6 expression in cHL cells. Weak to strong expression of BCL6 was observed in 68% of cases, and BCL6 expression associated with gene repression similarly in cHL and germinal center B cells. After BCL6 degradation, the core set of genes directly bound and regulated by BCL6 was derepressed in cHL, and proliferation was impaired. The number and clonality of neoantigens was associated with tumor microenvironment type and response to checkpoint blockade. Finally, ctDNA analysis was suggested as a tool to distinguish ambiguous positron emission tomography/computed tomography-positive lesions after treatment.

Coagulation factor V (FV) is a key protein in maintaining the hemostatic balance, with abnormal plasma levels associated with both thrombotic and hemorrhagic conditions. We propose a comprehensive bioinformatic analysis integrating large-scale proteogenomics and transcriptomic data from original and public data sets. We identify a biological fingerprint of 26 new proteins and loci involved in the regulation of plasma FV levels. Furthermore, the messenger RNA expression levels of 10 of these components demonstrate strong correlation in the liver. In addition, we provide experimental evidence for the involvement of one of the newly identified players (CLEC4M) in the clearance of FV. This work opens new avenues for a better understanding of the physiological processes involved in thrombotic and bleeding disorders.

Rare thrombotic events associated with ChAdOx1 nCoV-19 (ChAdOx1) vaccination have raised concerns; however, the underlying mechanisms remain elusive. Here, we report a novel biophysical mechanism by which ChAdOx1 directly interacts with platelets under arterial shear conditions, potentially contributing to postvaccination arterial thrombosis. Using microfluidic post assays, we demonstrate that ChAdOx1 induces shear-dependent platelet aggregation, distinct from conventional von Willebrand factor-mediated adhesion. This interaction is mediated by platelet integrin αIIbβ3 and requires biomechanical activation, explaining the absence of significant binding under static conditions. Molecular dynamics simulations and docking studies reveal preferential binding of ChAdOx1's penton arginine-glycine-aspartic acid (RGD) motif to the activated conformation of αIIbβ3. Inhibiting integrin αIIbβ3 completely abolishes ChAdOx1-induced platelet aggregation, whereas blocking glycoprotein (GP) Ib has minimal effect, confirming a mechanism that bypasses the conventional GPIb-dependent platelet adhesion pathway. Mutagenesis of the RGD motif to AAA eliminates platelet binding, verifying the specificity of this interaction. These findings provide a potential explanation for the association between ChAdOx1 vaccination and arterial thrombotic events, distinct from vaccine-induced immune thrombotic thrombocytopenia. Our results highlight the importance of considering biomechanical factors in vaccine-related thrombotic complications and suggest that shear-dependent integrin activation may be another determinant in the pathogenesis of these rare adverse events.

Insufficient eradication of cancer cells and survival of drug tolerant clones are major relapse driving forces. Underlying molecular mechanisms comprise activated prosurvival and antiapoptotic signaling, leading to insufficient apoptosis and drug resistance. The identification of programmed cell death pathways alternative to apoptosis opens up possibilities to antagonize apoptosis escape routes. We have earlier shown that acute lymphoblastic leukemia (ALL) harbors a distinct propensity to undergo cell death by receptor-interacting protein kinase 1 (RIPK1)-dependent necroptosis, activated by small-molecule second mitochondria-derived activators of caspase (SMAC) mimetics. Despite demonstrated safety and tolerability of SMAC mimetics in clinical trials, their efficacy as single agent seems still limited, highlighting the need for combinatorial treatments. Here, we investigate so far unexplored regulatory mechanisms of necroptosis and identify targets for interference to augment the necroptotic antileukemia response. Ex vivo drug response profiling in a model of the bone marrow microenvironment reveals powerful synergy of necroptosis induction with histone deacetylase (HDAC) inhibition. Subsequent transcriptome analysis and functional in vivo CRISPR screening identify gene regulatory circuitries through the master transcription regulators specificity protein 1 (SP1), p300, and HDAC2 to drive necroptosis. Although deletion of SP1 or p300 confers resistance to necroptosis, loss of HDAC2 sensitizes cells to RIPK1-dependent cell death by SMAC mimetics. Consequently, our data inform strong in vivo antileukemic activity of combinatorial necroptosis induction and HDAC inhibition in patient-derived human leukemia models. Thus, transcriptional dependency of necroptosis activation is a key regulatory mechanism that identifies novel targets for interference, pointing out a strategy to exploit alternative nonapoptotic cell death pathways to eradicate resistant disease.

After the introduction of tyrosine kinase inhibitors (TKIs), the number of patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) for chronic phase chronic myeloid leukemia (CP-CML) has dramatically decreased. Imatinib was the first TKI introduced into the clinical arena, predominantly used in the first-line setting. In cases of insufficient response, resistance, or intolerance, patients with CML can subsequently be treated with a second-, third-, or fourth-generation TKI. However, despite the approval of first-, second-, third-, and fourth-generation TKIs, allo-HSCT still remains indicated for a minority of patients with CML. Here, we discuss the indications in the era of TKIs through different cases representing the clinical situations for which allo-HSCT remains the best option. We also propose our transplant strategy to decrease transplant-related morbidity, particularly graft-versus-host disease, and mortality in the particular context of CML, a disease that is one of the most sensitive to immune cellular therapy, allowing the use of a combination of donor lymphocyte infusion and TKIs for posttransplant molecular progression.

In 2013, we published a Perspective titled "The myth of the second remission of acute leukemia in the adult," which underscored the dismal outcomes of relapsed acute leukemia in adults. We emphasized that only a few patients achieved second complete remission (CR2) after relapse and were subsequently eligible to receive a potentially curative allogeneic hematopoietic stem cell transplantation (HSCT). Hence, we urged the leukemia community not to delay HSCT in first complete remission if indicated to avoid dire outcomes. Historically, poor outcomes resulted from suboptimal frontline therapy, inadequate risk stratification, and lack of effective agents to achieve CR2. In the past decade, remarkable progress has been made in the treatment paradigm of acute leukemia, most evidently in B-cell acute lymphoblastic leukemia. Key advancements include refinement of frontline treatment, incorporation of early immunotherapy, improved disease risk stratification based on molecular profiling and assessment of measurable residual disease, and discovery of highly effective salvage immunotherapies. These innovations have led to a high rate of cure by frontline therapy, precise selection for HSCT in first complete remission for high-risk patients, and the reality of HSCT for patients in CR2. Here, we re-evaluate the myth of CR2 given the progress in the field.