Mitochondrial damage-associated molecular patterns (mtDAMPs) include proteins, lipids, metabolites, and DNA and have various context-specific immunoregulatory functions. Cell-free mitochondrial DNA (mtDNA) is recognized via pattern recognition receptors and is a potent activator of the innate immune system. Cell-free mtDNA is elevated in the circulation of trauma patients and patients with cancer; however, the functional consequences of elevated mtDNA are largely undefined. Multiple myeloma (MM) relies upon cellular interactions within the bone marrow (BM) microenvironment for survival and progression. Here, using in vivo models, we describe the role of MM cell-derived mtDAMPs in the protumoral BM microenvironment and the mechanism and functional consequence of mtDAMPs in myeloma disease progression. Initially, we identified elevated levels of mtDNA in the peripheral blood serum of patients with MM compared with those of healthy controls. Using the MM1S cells engrafted into nonobese diabetic severe combined immunodeficient gamma mice, we established that elevated mtDNA was derived from MM cells. We further show that BM macrophages sense and respond to mtDAMPs through the stimulator of interferon genes (STING) pathway, and inhibition of this pathway reduces MM tumor burden in the KaLwRij-5TGM1 mouse model. Moreover, we found that MM-derived mtDAMPs induced upregulation of chemokine signatures in BM macrophages, and inhibition of this signature resulted in egress of MM cells from the BM. Here, we demonstrate that malignant plasma cells release mtDNA, a form of mtDAMPs, into the myeloma BM microenvironment, which in turn activates macrophages via STING signaling. We establish the functional role of these mtDAMP-activated macrophages in promoting disease progression and retaining MM cells in the protumoral BM microenvironment.

With growing indications for chimeric antigen receptor (CAR) T-cell therapy, toxicity profiles are evolving. There is an urgent and unmet need of approaches to optimally manage emerging adverse events that extend beyond the standard paradigm of cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (ICANS). Although management guidelines exist for ICANS, there is little guidance on how to approach patients with neurologic comorbidities, and how to manage rare neurotoxicity presentations, such as CAR T-cell therapy-related cerebral edema, severe motor complications or late-onset neurotoxicity. In this study, we present 3 scenarios of patients treated with CAR T cells who develop unique types of neurotoxicity, and we describe an approach for the evaluation and management based on experience because objective data are limited. The goal of this study is to develop an awareness of emerging and unusual complications, discuss treatment approaches, and help institutions and health care providers establish frameworks to navigate how to best address unusual neurotoxicities to ultimately improve patient outcomes.

Therapeutic targeting of CDK7 has proven beneficial in preclinical studies, yet the off-target effects of currently available CDK7 inhibitors make it difficult to pinpoint the exact mechanisms behind MM cell death mediated by CDK7 inhibition. Here, we show that CDK7 expression positively correlates with E2F and MYC transcriptional programs in cells from patients with multiple myeloma (MM); its selective targeting counteracts E2F activity via perturbation of the cyclin-dependent kinases/Rb axis and impairs MYC-regulated metabolic gene signatures translating into defects in glycolysis and reduced levels of lactate production in MM cells. CDK7 inhibition using the covalent small-molecule inhibitor YKL-5-124 elicits a strong therapeutic response with minimal effects on normal cells, and causes in vivo tumor regression, increasing survival in several mouse models of MM including a genetically engineered mouse model of MYC-dependent MM. Through its role as a critical cofactor and regulator of MYC and E2F activity, CDK7 is therefore a master regulator of oncogenic cellular programs supporting MM growth and survival, and a valuable therapeutic target providing rationale for development of YKL-5-124 for clinical use.

The communication of talin-activated integrin αIIbβ3 with the cytoskeleton (integrin outside-in signaling) is essential for platelet aggregation, wound healing, and hemostasis. Filamin, a large actin crosslinker and integrin binding partner critical for cell spreading and migration, is implicated as a key regulator of integrin outside-in signaling. However, the current dogma is that filamin, which stabilizes inactive αIIbβ3, is displaced from αIIbβ3 by talin to promote the integrin activation (inside-out signaling), and how filamin further functions remains unresolved. Here, we show that while associating with the inactive αIIbβ3, filamin also associates with the talin-bound active αIIbβ3 to mediate platelet spreading. Fluorescence resonance energy transfer-based analysis reveals that while associating with both αIIb and β3 cytoplasmic tails (CTs) to maintain the inactive αIIbβ3, filamin is spatiotemporally rearranged to associate with αIIb CT alone on activated αIIbβ3. Consistently, confocal cell imaging indicates that integrin α CT-linked filamin gradually delocalizes from the β CT-linked focal adhesion marker-vinculin likely because of the separation of integrin α/β CTs occurring during integrin activation. High-resolution crystal and nuclear magnetic resonance structure determinations unravel that the activated integrin αIIb CT binds to filamin via a striking α-helix→β-strand transition with a strengthened affinity that is dependent on the integrin-activating membrane environment containing enriched phosphatidylinositol 4,5-bisphosphate. These data suggest a novel integrin αIIb CT-filamin-actin linkage that promotes integrin outside-in signaling. Consistently, disruption of such linkage impairs the activation state of αIIbβ3, phosphorylation of focal adhesion kinase/proto-oncogene tyrosine kinase Src, and cell migration. Together, our findings advance the fundamental understanding of integrin outside-in signaling with broad implications in blood physiology and pathology.

Steroid-refractory chronic graft-versus-host disease (cGVHD) after allogeneic transplant remains a significant cause of morbidity and mortality. Abatacept is a selective costimulation modulator, used for the treatment of rheumatologic diseases, and was recently the first drug to be approved by the US Food and Drug Administration for the prophylaxis of acute graft-versus-host disease. We conducted a phase 2 study to evaluate the efficacy of abatacept in steroid-refractory cGVHD. The overall response rate was 58%, seen in 21 out of 36 patients, with all responders achieving a partial response. Abatacept was well tolerated with few serious infectious complications. Immune correlative studies showed a decrease in interleukin -1α (IL-1α), IL-21, and tumor necrosis factor α as well as decreased programmed cell death protein 1 expression by CD4+ T cells in all patients after treatment with abatacept, demonstrating the effect of this drug on the immune microenvironment. The results demonstrate that abatacept is a promising therapeutic strategy for the treatment of cGVHD. This trial was registered at www.clinicaltrials.gov as #NCT01954979.

Coagulation factor V (fV) is the precursor of activated fV (fVa), an essential component of the prothrombinase complex required for the rapid activation of prothrombin in the penultimate step of the coagulation cascade. In addition, fV regulates the tissue factor pathway inhibitor α (TFPIα) and protein C pathways that inhibit the coagulation response. A recent cryogenic electron microscopy (cryo-EM) structure of fV has revealed the architecture of its A1-A2-B-A3-C1-C2 assembly but left the mechanism that keeps fV in its inactive state unresolved because of an intrinsic disorder in the B domain. A splice variant of fV, fV short, carries a large deletion of the B domain that produces constitutive fVa-like activity and unmasks epitopes for the binding of TFPIα. The cryo-EM structure of fV short was solved at 3.2 Å resolution and revealed the arrangement of the entire A1-A2-B-A3-C1-C2 assembly. The shorter B domain stretches across the entire width of the protein, making contacts with the A1, A2, and A3 domains but suspended over the C1 and C2 domains. In the portion distal to the splice site, several hydrophobic clusters and acidic residues provide a potential binding site for the basic C-terminal end of TFPIα. In fV, these epitopes may bind intramolecularly to the basic region of the B domain. The cryo-EM structure reported in this study advances our understanding of the mechanism that keeps fV in its inactive state, provides new targets for mutagenesis and facilitates future structural analysis of fV short in complex with TFPIα, protein S, and fXa.

The treatment landscape of relapsed/refractory (R/R) classic Hodgkin lymphoma (cHL) has evolved significantly over the past decade after the approval of brentuximab vedotin (BV) and the programmed death-1 (PD-1) inhibitors. We evaluated how outcomes and practice patterns have changed for patients with R/R cHL who underwent autologous hematopoietic cell transplantation (AHCT) at our institution from 2011 to 2020 (N = 183) compared with those from 2001 to 2010 (N = 159) and evaluated prognostic factors for progression-free survival (PFS) and overall survival (OS) in both eras. OS was superior in the modern era with a trend toward lower nonrelapse mortality beyond 2 years after transplant. Among patients who progressed after AHCT, 4-year postprogression survival increased from 43.3% to 71.4% in the modern era, reflecting increasing use of BV and the PD-1 inhibitors. In multivariable analysis for patients that underwent transplant in the modern era, age ≥45 years, primary refractory disease, and lack of complete remission pre-AHCT were associated with inferior PFS, whereas receipt of a PD-1 inhibitor-based regimen pre-AHCT was associated with superior PFS. Extranodal disease at relapse was associated with inferior OS. Our study demonstrates improved survival for R/R cHL after AHCT in the modern era attributed to more effective salvage regimens allowing for better disease control pre-AHCT and improved outcomes for patients who progressed after AHCT. Excellent outcomes were observed with PD-1 inhibitor-based salvage regimens pre-AHCT and support a randomized trial evaluating immunotherapy in the second line setting.