Clonal germinal center B cells function as a niche for T-cell lymphoma

Targeting the cGAS-STING Pathway Inhibits Peripheral T-cell Lymphoma Progression and Enhances the Chemotherapeutic Efficacy

Peripheral T-cell lymphoma (PTCL) is a highly heterogeneous group of mature T-cell malignancies. The efficacy of current first-line treatment is dismal, and novel agents are urgently needed to improve patient outcomes. A close association between the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway and tumor promotion exists, revealing prospective therapeutic targets. This study, investigates the role of the cGAS-STING pathway and its underlying mechanisms in PTCL progression. Single-cell RNA sequencing showes that the cGAS-STING pathway is highly expressed and closely associated with PTCL proliferation. cGAS inhibition suppresses tumor growth and impaires DNA damage repair. Moreover, Cdc2-like kinase 1 (CLK1) is critical for residual tumor cell survival after treatment with cGAS inhibitors, and CLK1 suppression enhances sensitivity to cGAS inhibitors. Single-cell dynamic transcriptomic analysis indicates reduced proliferation-associated nascent RNAs as the underlying mechanism. In first-line therapy, chemotherapy-triggered DNA damage activates the cGAS-STING pathway, and cGAS inhibitors can synergize with chemotherapeutic agents to kill tumors. The cGAS-STING pathway is oncogenic in PTCL, whereas targeting cGAS suppresses tumor growth, and CLK1 may be a sensitivity indicator for cGAS inhibitors. These findings provide a theoretical foundation for optimizing therapeutic strategies for PTCL, especially in patients with relapsed/refractory disease.

Tumor heterogeneity and immune-evasive T follicular cell lymphoma phenotypes at single-cell resolution

T follicular helper (TFH) cell lymphomas (TFHLs) are characterized by TFH-like properties and accompanied by substantial immune-cell infiltration into tumor tissues. Nevertheless, the comprehensive understanding of tumor-cell heterogeneity and immune profiles of TFHL remains elusive. To address this, we conducted single-cell transcriptomic analysis on 9 lymph node (LN) and 16 peripheral blood (PB) samples from TFHL patients. Tumor cells were divided into 5 distinct subclusters, with significant heterogeneity observed in the expression levels of TFH markers. Copy number variation (CNV) and trajectory analyses indicated that the accumulation of CNVs, together with gene mutations, may drive the clonal evolution of tumor cells towards TFH-like and cell proliferation phenotypes. Additionally, we identified a novel tumor-cell-specific marker, PLS3. Notably, we found a significant increase in exhausted CD8+ T cells with oligoclonal expansion in TFHL LNs and PB, along with distinctive immune evasion characteristics exhibited by infiltrating regulatory T, myeloid, B, and natural killer cells. Finally, in-silico and spatial cell-cell interaction analyses revealed complex networking between tumor and immune cells, driving the formation of an immunosuppressive microenvironment. These findings highlight the remarkable tumor-cell heterogeneity and immunoevasion in TFHL beyond previous expectations, suggesting potential roles in treatment resistance.

Advances in the pathogenesis and therapeutic strategies of angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive subtype of peripheral T-cell lymphomas with its cell origin determined to be follicular helper T-cells. AITL is characterized by a prominent tumor microenvironment involving dysregulation of immune cells, signaling pathways, and extracellular matrix. Significant progress has been made in the molecular pathophysiology of AITL, including genetic mutations, immune metabolism, hematopoietic-derived microenvironment, and non-hematopoietic microenvironment cells. Early diagnosis, detection of severe complications, and timely effective treatment are crucial for managing AITL. Treatment typically involves various combination chemotherapies, but the prognosis is often poor, and relapsed and refractory AITL remains challenging, necessitating improved treatment strategies. Therefore, this article provides an overview of the pathogenesis and latest advances in the treatment of AITL, with a focus on potential therapeutic targets, novel treatment strategies, and emerging immunotherapeutic approaches.

Composite Angioimmunoblastic T-Cell Lymphoma and Diffuse Large B-Cell Lymphoma Presenting with Distributive Shock

Diffuse large B-cell lymphoma (DLBCL) and angioimmunoblastic T-cell lymphoma (AITL) are two subtypes of non-Hodgkin lymphoma (NHL). The simultaneous occurrence of DLBCL and AITL in a composite lymphoma is very rare, and there are no established treatment regimens. We present the case of an 85-year-old male admitted to the intensive care unit with distributive shock, lymphocytosis, and lymphadenopathy, who was subsequently diagnosed with composite AITL and DLBCL, and treated with brentuximab vedotin (BV) and rituximab. To our knowledge, this is the first case of composite lymphoma presenting with distributive shock and treated with BV and rituximab, with successful resolution of shock.

Biological insights into the role of TET2 in T cell lymphomas

Peripheral T cell lymphomas (PTCL) are a heterogenous group of mature T cell lymphomas with an overall poor prognosis. Understanding the molecular heterogeneity in PTCL subtypes may lead to improved understanding of the underlying biological mechanisms driving these diseases. Mutations in the epigenetic regulator TET2 are among the most frequent mutations identified in PTCL, with the highest frequency in angioimmunoblastic T cell lymphomas and other nodal T follicular helper (TFH) lymphomas. This review dissects the role of TET2 in nodal TFH cell lymphomas with a focus on emerging biological insights into the molecular mechanism promoting lymphomagenesis and the potential for epigenetic therapies to improve clinical outcomes.

Advances in single-cell RNA sequencing and its applications in cancer research

Cancers are a group of heterogeneous diseases characterized by the acquisition of functional capabilities during the transition from a normal to a neoplastic state. Powerful experimental and computational tools can be applied to elucidate the mechanisms of occurrence, progression, metastasis, and drug resistance; however, challenges remain. Bulk RNA sequencing techniques only reflect the average gene expression in a sample, making it difficult to understand tumor heterogeneity and the tumor microenvironment. The emergence and development of single-cell RNA sequencing (scRNA-seq) technologies have provided opportunities to understand subtle changes in tumor biology by identifying distinct cell subpopulations, dissecting the tumor microenvironment, and characterizing cellular genomic mutations. Recently, scRNA-seq technology has been increasingly used in cancer studies to explore tumor heterogeneity and the tumor microenvironment, which has increased the understanding of tumorigenesis and evolution. This review summarizes the basic processes and development of scRNA-seq technologies and their increasing applications in cancer research and clinical practice.

SOHO State of the Art Updates and Next Questions | New Pathways and New Targets in PTCL: Staying on Target

While the peripheral T-cell lymphomas (PTCL) remain a therapeutic challenge, and increasingly account for a disproportionate number of lymphoma-related deaths, improved understanding of disease pathogenesis and classification, and the development of novel therapeutic agents over the past decade, all provide reasons for a more optimistic outlook in the next. Despite their genetic and molecular heterogeneity, many PTCL are dependent upon signaling input provided by antigen, costimulatory, and cytokine receptors. While gain-of-function alterations effecting these pathways are recurrently observed in many PTCL, more often than not, signaling remains ligand-and tumor microenvironment (TME)-dependent. Consequently, the TME and its constituents are increasingly recognized as "on target". Utilizing a "3 signal" model, we will review new-and old-therapeutic targets that are relevant for the more common nodal PTCL subtypes.

TET2, tumor control, and CAR T cell hyperproliferation

A recent study by Jain et al. published in Nature followed up on evidence suggesting that depletion of 5-methylcytosine dioxygenase TET2 in chimeric antigen receptor CAR T cells could enhance their expansion, persistence, and antitumor efficacy. Their findings are cautionary, but offer hope of a path forward.

DNMT3AR882H accelerates angioimmunoblastic T-cell lymphoma in mice

DNA methylation-related genes, including TET2, IDH2, and DNMT3A are highly frequently mutated in angioimmunoblastic T-cell lymphoma (AITL), an aggressive malignancy of T follicular helper (Tfh) cells associated with aberrant immune features. It has been shown that TET2 loss cooperates with RHOA^G17V to promote AITL in mice but the functional role of DNMT3A mutations in AITL remains unclear. Here, we report that DNMT3A^R882H, the most common mutation of DNMT3A in AITL, accelerates the development of Tet2^-/-; RHOA^G17V AITL in mice, indicated by the expansion of malignant Tfh cells and aberrant B cells, skin rash, and significantly shortened disease-free survival. To understand the underlying cellular and molecular mechanisms, we performed single-cell transcriptome analyses of lymph nodes of mice transplanted with Tet2^-/-, Tet2^-/-; RHOA^G17V or DNMT3A^R882H; Tet2^-/-; RHOA^G17V hematopoietic stem and progenitor cells. These single-cell landscapes reveal that DNMT3A mutation further activates Tfh cells and leads to rapid and terminal differentiation of B cells, probably through enhancing the interacting PD1/PD-L1, ICOS/ICOSL, CD28/CD86, and ICAM1/ITGAL pairs. Our study establishes the functional roles of DNMT3A mutation in AITL and sheds light on the molecular mechanisms of this disease.

The Clinical Significance and Prognostic Role of Whole-Blood Epstein-Barr Virus DNA in Lymphoma-Associated Hemophagocytic Lymphohistiocytosis

PURPOSE

To evaluate the role of circulating Epstein-Barr virus (EBV) DNA in lymphoma-associated hemophagocytic lymphohistiocytosis (HLH).

METHODS

We conducted a retrospective cohort study to explore the clinical and prognostic significance of EBV DNA in lymphoma-associated HLH. We included adult patients with combined diagnoses of lymphoma and HLH from January 2010 and November 2022 by retrieving the medical record system.

RESULTS

A total of 281 patients with lymphoma-associated HLH were identified. Elevated whole-blood EBV DNA was observed in 54.4% (153/281) of patients, and the median copy number was significantly higher in the T/NK-cell malignancies (199,500, interquartile range, 30,000-1,390,000) than that in the B-cell non-Hodgkin lymphoma (5520, interquartile range, 1240-28,400, P < 0.001). The optimum cutoff for predicting survival was 16,100 copies/mL. Compared to the patients with EBV DNA ≤ 16,100 copies/mL, those with EBV DNA > 16,100 copies/mL were younger and had more T/NK-cell malignancies, lower levels of neutrophils and fibrinogen, and higher levels of hemoglobin, alanine aminotransferase, aspartate aminotransferase, lactic dehydrogenase, and β₂-microglobulin. A higher load of EBV DNA (> 16,100 copies/mL), thrombocytopenia (< 100 × 10⁹/L), neutropenia (< 1 × 10⁹/L), hypofibrinogenemia (≤ 1.5 g/L), and elevated levels of creatinine (> 133 μmol/L) were independent adverse predictors of 60-day overall survival and overall survival. A prognostic index based on EBV DNA and the other four factors was established to categorize the patients into four groups with significantly different outcomes.

CONCLUSION

Our study identified high EBV load as a risk factor for lymphoma-associated HLH and established a prognostic index to predict outcomes.

IDH2 and TET2 mutations synergize to modulate T Follicular Helper cell functional interaction with the AITL microenvironment

Angioimmunoblastic T cell lymphoma (AITL) is a peripheral T cell lymphoma that originates from T follicular helper (Tfh) cells and exhibits a prominent tumor microenvironment (TME). IDH2 and TET2 mutations co-occur frequently in AITL, but their contribution to tumorigenesis is poorly understood. We developed an AITL mouse model that is driven by Idh2 and Tet2 mutations. Malignant Tfh cells display aberrant transcriptomic and epigenetic programs that impair TCR signaling. Neoplastic Tfh cells bearing combined Idh2 and Tet2 mutations show altered cross-talk with germinal center B cells that promotes B cell clonal expansion while decreasing Fas-FasL interaction and reducing B cell apoptosis. The plasma cell count and angiogenesis are also increased in the Idh2-mutated tumors, implying a major relationship between Idh2 mutation and the characteristic AITL TME. Our mouse model recapitulates several features of human IDH2-mutated AITL and provides a rationale for exploring therapeutic targeting of Tfh-TME cross-talk for AITL patients.

The Immunology of DLBCL

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell-cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in "immune-privileged sites"-where multiple immune-modulating mechanisms exist-shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.

Mature T-cell and NK-cell lymphomas: updates on molecular genetic features

Mature T-cell and NK-cell lymphomas are a heterogeneous group of rare and typically aggressive neoplasms. Diagnosis and subclassification have historically relied primarily on the integration of clinical, histologic, and immunophenotypic features, which often overlap. The widespread application of a variety of genomic techniques in recent years has provided extensive insight into the pathobiology of these diseases, allowing for more precise diagnostic classification, improved prognostication, and development of novel therapies. In this review, we summarize the genomic features of the most common types of mature T-cell and NK-cell lymphomas with a particular focus on the contribution of genomics to biologic insight, classification, risk stratification, and select therapies in the context of the recently published International Consensus and updated World Health Organization classification systems.