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A bivalent molecular glue linking lysine acetyltransferases to oncogene-induced cell death.

Developing cancer therapies that induce specific death of malignant cells is critical for preventing relapse. Highly effective strategies, such as immunotherapy, exemplify this principle. Here, we provide the mechanistic basis for a small-molecule approach that leverages chemically induced proximity (CIP) to kill diffuse large B cell lymphoma, the most common non-Hodgkin lymphoma. We developed lysine acetyltransferase (KAT)-based TCIPs (transcriptional/epigenetic chemical inducers of proximity), or KAT-TCIPs, which redirect p300/CREB-binding protein (CBP) to activate cell-death networks repressed by the oncogenic driver BCL6. Our lead KAT-TCIP reprograms the epigenome to initiate apoptosis. The crystal structure of the chemically induced p300-BCL6 complex reveals how chance protein-protein interactions may be exploited to confer the potency and selectivity of KAT-TCIPs. Thus, oncogenic drivers can be co-opted to activate robust cell death. Consistent with their gain-of-function mechanism, TCIPs recruiting different transcriptional activators-p300, BRD4, or CDK9-produce distinct genomic responses, suggesting specialized therapeutic uses.

Humans

TGF-β and IL-2 differentially shape T follicular regulatory cell differentiation and stability in vitro.

T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells play critical roles in regulating the activity of the germinal center (GC), which is essential for the generation of high-affinity antibodies. In the GC, Tfh cells help B cells to proliferate and to differentiate into memory B cells and long-lived plasma cells. In contrast, Tfr cells, a specialized subset of regulatory T cells (Tregs), modulate the humoral immune response by suppressing excessive or autoreactive B-cell activity. Here, we established an in vitro differentiation protocol for mouse CD4⁺ T cells that yielded CXCR5⁺FoxP3⁺ Tfr cells that exhibited a Bcl6hiPD-1hiCD25loGITRint phenotype and were distinct from Treg and Tfh cells. Functionally, in vitro-generated Tfr cells potently suppressed Tfh cell-driven B-cell class switching to IgG1 and downregulated the expression of B-cell costimulatory ligands. While in vitro-generated Bcl6-deficient Tfh cells were impaired in providing help to B cells for efficient class switching to IgG1, in vitro-generated Bcl6-deficient Tfr cells failed to inhibit Tfh cell-driven B-cell class switching to IgG1. Mechanistically, we showed that Tfr cells emerged from FoxP3+ precursors in low-IL-2 environments through a TGF-β- and c-Maf-dependent pathway, allowing for reprogramming and reinforcement of the follicular regulatory cell program in CD4+ T cells in vitro.

Animals

Uterine Sarcomas With Recurrent KDM2B Gene Fusions: Three Cases of a Possible Novel Subtype of High-Grade Endometrial Stromal Sarcoma.

The advent of widespread genomic testing of uterine mesenchymal tumors has led to novel insights into the biology of these diverse tumors, and many genomically defined entities have been described in recent years. During a larger study of endometrial stromal sarcomas and unclassified uterine sarcomas, we identified 3 tumors harboring KDM2B gene fusions. Patients were 32, 61, and 67 years old, and all initially underwent incomplete sampling via laparoscopic myomectomy (n = 1), laparoscopic biopsy (n = 1), or hysteroscopic myomectomy (n = 1). One patient's tumor was densely adherent to the pelvic sidewall; she was treated with chemotherapy and died of widely metastatic disease at 29 weeks. Another underwent a subsequent recent hysterectomy with the tumor confined to the uterus and minimal follow-up to date. The final patient refused further treatment and was alive at 28 weeks, although the status of the disease progression was unknown. On microscopic examination, 2 tumors showed infiltrative borders, whereas interface with the myometrium was not present in the third. The tumors were variably cellular with alternating hypercellular and hypocellular zones in a myxoid to loosely collagenous stroma. The hypercellular areas contained round to ovoid cells in diffuse (n = 3) and sex cord-like arrangements, including cords (n = 3), nests (n = 2), and tubules (n = 1); 2 also contained occasional spindled cells arranged in vague fascicles. These cells showed moderate atypia with open chromatin, numerous mitoses (8, 24, and 25 per 10 high-power fields), and frequent apoptosis. The hypocellular areas contained sparse, ovoid-to-spindled cells with minimal atypia. All tumors were diffusely positive for cyclin D1, whereas BCL6 corepressor was diffusely positive in 1 and negative in 2; desmin and caldesmon were negative in all 3 neoplasms. All harbored KDM2B gene fusions; partner genes included EPC1, EP400, and CITED1. MDM2 amplification was also noted in 2. Clustering analysis based on RNA expression profiling revealed tight clustering of all 3 tumors within the broad group of high-grade endometrial stromal sarcomas. Based on the overall clinicopathologic and genomic features, we suggest that these tumors may represent a novel subtype of uterine sarcoma and may be best classified as high-grade endometrial stromal sarcoma, although additional confirmatory studies are needed.

Humans

Testicular aggressive B-cell lymphoma with plasmablastic morphology harboring concurrent IGH::MYC and IGH::BCL2 rearrangements.

BACKGROUND: Aggressive B-cell lymphomas with plasmablastic morphology are uncommon neoplasms that may exhibit overlapping morphologic, immunophenotypic, and genetic features of plasmablastic lymphoma (PBL) and double-hit lymphoma (DHL). Concurrent IGH::MYC and IGH::BCL2 rearrangements are rarely encountered in this setting, particularly in the testis. Here, we describe an unusual case presenting significant diagnostic challenges at the interface between PBL and DHL. CASE PRESENTATION: We report a 66-year-old, immunocompetent man presenting with a 5 cm left testicular mass. Histologic examination revealed diffuse proliferation of large atypical lymphoid cells with plasmablastic morphology. Immunohistochemically, the tumor expressed CD138, CD38, and MUM1, with focal BCL2, c-MYC protein, and CD79a positivity, while CD20, CD19, PAX5, CD10, BCL6, and ALK were negative. EBV-encoded RNA in situ hybridization was negative. Fluorescence in situ hybridization identified IGH::MYC [t(8;14)] rearrangement in 45% and IGH::BCL2 [t(14;18)] rearrangement in 21% of analyzed nuclei. Next-generation sequencing additionally revealed BRAF V600E mutation, CDKN2A deletion, and human leukocyte antigen class I genomic alterations. CONCLUSION: This case highlights a rare testicular aggressive B-cell lymphoma with plasmablastic morphology and concurrent IGH::MYC and IGH::BCL2 rearrangements, representing a diagnostically challenging neoplasm at the interface between PBL and DHL. Our findings underscore the value of integrated morphologic, immunophenotypic, cytogenetic, and molecular analyses in evaluating aggressive B-cell lymphomas with plasmablastic features arising in immune-privileged sites.

Humans

Exploring the Genetic Landscape of Primary Marginal Zone Lymphoma of the Urinary Bladder.

Extranodal marginal zone B-cell lymphoma (MZL) of mucosa-associated lymphoid tissue is the most frequent primary lymphoma of the urinary bladder. Although MZLs from various anatomical sites are often associated with autoimmune disorders, infections, and site-characteristic genetic alterations, the molecular foundations and potential infectious triggers of urinary bladder MZL remain poorly understood. To elucidate the disease etiology and correlation with MZLs arising in other locations, we examined a cohort of 17 cases (11 women and 6 men) diagnosed with primary bladder MZL between 2005 and 2025. Immunohistochemical analysis confirmed the literature, with all samples testing positive for the pan B-cell markers CD20 and CD79a and negative for CD5 (except 1), cyclin D1, and SOX11. Thirteen samples exhibited secretory differentiation and displayed immunoglobulin light chain restriction (9 κ and 4 λ). No gene rearrangements in BCL2, BCL6, BCL10, IRF4, MALT1, and MYC were detected. High-throughput sequencing identified 31 pathogenic/likely pathogenic somatic mutations across 18 genes, with TBL1XR1 (n = 8), MAP2K1 (n = 4), and TNFAIP3 (n = 2) being the most frequently mutated ones. Additionally, all cases included variants of unknown significance. The sample of 1 patient tested positive for Chlamydia trachomatis, human betaherpesvirus 6B, and Epstein-Barr virus. Escherichia coli was detected in 5 samples. We provide compelling evidence that urinary bladder MZL is a point mutation-driven disease rather than gene fusion-driven disease and that E coli is present in approximately one-third of tumor biopsies. These tumors frequently harbor pathogenic mutations in genes encoding components regulating plasma cell differentiation and the pleiotropic MAPK/ERK signaling pathway. TBL1XR1, which was unexpectedly frequently mutated, is generally linked to more aggressive variants of MZL and diffuse large B-cell lymphoma; however, its prognostic significance in urinary bladder MZL remains to be determined. Comparative analysis highlighted partial overlap of urinary bladder MZL mutational profiles with those found in salivary gland MZL.

Humans

Venetoclax added to dose-adjusted EPOCH-R for newly diagnosed double-hit lymphomas: phase 2 results from ALLIANCE A051701, an open-label, randomised, controlled, phase 2-3 trial.

BACKGROUND: High-grade B-cell lymphoma with rearrangements of MYC and BCL2 and/or BCL6, known as double-hit lymphoma, is a highly aggressive malignancy with poor outcomes after standard chemoimmunotherapy. We aimed to study whether the addition of the BCL2-inhibitor venetoclax to chemoimmunotherapy in patients with double-hit lymphoma resulted in superior efficacy compared with chemotherapy alone. METHODS: ALLIANCE A051701 is an open-label, randomised, controlled, phase 2-3 trial in separate cohorts of patients with double-hit lymphoma and patients with double-expressor lymphoma. In this analysis, we report phase 2 results from the double-hit lymphoma cohort. Patients aged 18-80 years with newly diagnosed double-hit lymphoma and Eastern Cooperative Oncology Group (ECOG) performance status 0-2 were recruited from 41 hospitals and outpatient clinics in the USA. Patients were randomly assigned (1:1) to receive DA-EPOCH-R (dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab) either alone (DA-EPOCH-R group) or with venetoclax (DA-EPOCH-R plus venetoclax group) using permuted block randomisation schedule. All patients and investigators were aware of group assignment. DA-EPOCH-R was administered on a 21-day schedule for up to six total cycles. Venetoclax was given as 600 mg by mouth daily on days 4-8 of cycle 1 and on days 1-5 of cycles 2-6. The primary endpoint was progression-free survival in the modified intent-to-treat population inclusive of all eligible patients with centrally confirmed double-hit lymphoma. The safety analysis population consisted of all evaluable patients who received at least one dose of protocol treatment. This trial is registered with ClinicalTrials.gov (NCT03984448) and is closed to enrolment. FINDINGS: 36 patients were randomly assigned to the DA-EPOCH-R group and 37 to the DA-EPOCH-R plus venetoclax group between Oct 22, 2019, and Sept 18, 2020. Median age was 65 years (IQR 56-73) and baseline demographic factors were well balanced between groups, with 30 (45%) female and 36 (55%) male patients. Most patients (59 [89%]) were white, two (3%) were Asian, one (2%) was Black or African American, and four (6%) had unknown or unreported ethnicity. The majority of patients had MYC-BCL2 double-hit lymphoma (59 [89%] patients), advanced stage disease (57 [86%] patients), and high-intermediate/high-risk IPI score (42 [64%] patients). Median follow-up was 34·7 months (IQR 30·1-36·8). Median progression-free survival was 28·4 months (95% CI 5·2-not estimable) in the DA-EPOCH-R group (n=30) and 7·7 months (95% CI 4·7-NE) in the DA-EPOCH-R plus venetoclax group (n=36; hazard ratio [HR] 1·13, 95% CI 0·53-2·37; p=0·75). Deaths on treatment occurred in one (3%) patient in the DA-EPOCH-R group (due to dyspnoea; possibly related to treatment) and six (17%) patients in the DA-EPOCH-R plus venetoclax group (four due to sepsis [three at least possible related and one unrelated], two due to cardiac arrest [at least possibly related]), prompting early closure of the double-hit lymphoma cohort. The most common grade 3-4 non-haematological adverse event was febrile neutropenia, occurring in 15 (43%) of 35 patients in the DA-EPOCH-R plus venetoclax group and 11 (37%) of 30 patients in the DA-EPOCH-R group. The median overall survival has not been reached in either group. The 24-month overall survival estimates were 72% (95% CI 52-85) in the DA-EPOCH-R group compared with 52% (95% CI 33-68) in the DA-EPOCH-R plus venetoclax group (HR 2·49, 95% CI 1·03-6·04; p=0·038). INTERPRETATION: The addition of venetoclax to DA-EPOCH-R resulted in excess mortality, prompting early study closure. Robust accrual shows that prospective multicentre trials are feasible in double-hit lymphoma, and the outcomes in the DA-EPOCH-R group serve as a benchmark for future studies. FUNDING: National Cancer Institute of the National Institutes of Health.

Humans

LymphGen-Sig: Integrating Genetic and Transcriptional States to Predict Therapeutic Response in Diffuse Large B-Cell Lymphoma.

PURPOSE: Genetic classification may advance precision medicine in diffuse large B-cell lymphoma (DLBCL), but existing tools like LymphGen (LG) are limited by complexity and incomplete classification and do not incorporate nongenetic features that affect disease biology and therapeutic outcomes. To address these limitations, we developed LG-sig (LGsig), a gene expression-based platform that classifies all DLBCLs and harmonizes both genetic and nongenetic dimensions of the disease. METHODS: LGsig was built on the distinct subtype-specific gene expression signature of each LG class using paired genomic and transcriptomic data (National Cancer Institute/British Columbia Cancer Agency; N = 764). Model development was restricted to DLBCLs classified into MYD88L265P and CD79B mutations (MCD), BCL6 translocation and NOTCH2 mutations (BN2), EZH2 mutations and BCL2 translocation (EZB), or SGK1 and TET2 mutations (ST2). Gene features were selected by differential gene expression, with 294 genes being optimal for classification using a nearest shrunken centroid classifier. LGsig classifications were designated as MCDsig, BN2sig, ST2sig, and EZBsig. The final model was applied to RNAseq from archival samples from the POLARIX trial (N = 678) to assess outcomes after polatuzumab vedotin-R-CHP (pola-R-CHP) or rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) for each LGsig subtype. RESULTS: LGsig accurately identified LG subtypes using transcriptional data alone and extended assignments to all previously LG-unclassified cases. Importantly, LG-unclassified DLBCLs reassigned by LGsig mirrored the transcriptional and clinical features of their corresponding LG counterparts, supporting their reclassification. In addition, LGsig reassigned LG A53 DLBCLs, characterized by aneuploidy and TP53 alterations, into more biologically and therapeutically relevant LGsig clusters. Finally, LGsig improved the performance of LG as a biomarker in the POLARIX study, by identifying distinct DLBCL subtypes exhibiting a survival benefit with pola-R-CHP over R-CHOP in both LG-classified and LG-unclassified cases. CONCLUSION: LGsig expands molecular classification beyond current genetic classifiers in DLBCL by integrating both genetic and transcriptional dimensions of the disease to better inform subtype-specific therapeutic strategies.

Journal Article