Genetic Landscape of Peripheral T-Cell Lymphoma

Genetic alterations in mature B- and T-cell lymphomas - a practical guide to WHO-HAEM5

The identification of recurrent genomic alterations in tumour cells has a significant role in the classification of mature B- and T-cell lymphomas. Following the development of new technologies, such as next generation sequencing and the improvement of classical technologies such as conventional and molecular cytogenetics, a huge catalogue of genomic alterations in lymphoid neoplasms has been established. These alterations are relevant to refine the taxonomy of the classification of lymphomas, to scrutinize the differential diagnosis within different lymphoma entities and to help assessing the prognosis and clinical management of the patients. Consequently, here we describe the key genetic alterations relevant in mature B- and T-cell lymphomas.

Genome-wide methylation profiling of Peripheral T-cell lymphomas identifies TRIP13 as a critical driver of tumor proliferation and survival

Cytosine methylation of genomic DNA contributes to the regulation of gene expression and is involved in normal development including hematopoiesis in mammals. It is catalyzed by the family of DNA methyltransferases (DNMTs) that include DNMT1, DNMT3A, and DNMT3B. Peripheral T-cell lymphomas (PTCLs) represent a diverse group of aggressive mature T-cell malignancies accounting for approximately 10-15% of non-Hodgkin lymphoma cases in the US. PTCLs exhibit a broad spectrum of clinical, histological, and immunophenotypic features with poor prognosis and inadequately understood molecular pathobiology. To better understand the molecular landscape and identify candidate genes involved in disease maintenance, we used high-resolution Whole Genome Bisulfite Sequencing (WGBS) and RNA-seq to profile DNA methylation and gene expression of PTCLs and normal T-cells. We found that the methylation patterns in PTCLs are deregulated and heterogeneous but share 767 hypo- and 567 hypermethylated differentially methylated regions (DMRs) along with 231 genes up- and 91 genes downregulated in all samples suggesting a potential association with tumor development. We further identified 39 hypomethylated promoters associated with increased gene expression in the majority of PTCLs. This putative oncogenic signature included the TRIP13 (thyroid hormone receptor interactor 13) gene whose both genetic and pharmacologic inactivation, inhibited cellular growth of PTCL cell lines by inducing G2-M arrest accompanied by apoptosis suggesting that such an approach might be beneficial in human lymphoma treatment. Altogether we show that human PTCLs are characterized by a large number of recurrent methylation alterations, and demonstrated that TRIP13 is critical for PTCL maintenance in vitro .

Liquid biopsy in T-cell lymphoma: biomarker detection techniques and clinical application

T-cell lymphoma is a highly invasive tumor with significant heterogeneity. Invasive tissue biopsy is the gold standard for acquiring molecular data and categorizing lymphoma patients into genetic subtypes. However, surgical intervention is unfeasible for patients who are critically ill, have unresectable tumors, or demonstrate low compliance, making tissue biopsies inaccessible to these patients. A critical need for a minimally invasive approach in T-cell lymphoma is evident, particularly in the areas of early diagnosis, prognostic monitoring, treatment response, and drug resistance. Therefore, the clinical application of liquid biopsy techniques has gained significant attention in T-cell lymphoma. Moreover, liquid biopsy requires fewer samples, exhibits good reproducibility, and enables real-time monitoring at molecular levels, thereby facilitating personalized health care. In this review, we provide a comprehensive overview of the current liquid biopsy biomarkers used for T-cell lymphoma, focusing on circulating cell-free DNA (cfDNA), circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), Epstein-Barr virus (EBV) DNA, antibodies, and cytokines. Additionally, we discuss their clinical application, detection methodologies, ongoing clinical trials, and the challenges faced in the field of liquid biopsy.

Peripheral T-Cell Lymphoma in a Patient Previously Diagnosed With Sarcoidosis

Sarcoidosis is a multisystem disorder characterized by granulomatous inflammation on histopathological evaluation. Diagnosis of sarcoidosis requires thorough elimination of malignancy and alternative causes of noncaseating granulomatous inflammation. Sarcoidosis and several subtypes of lymphoma have similar clinical presentations and can potentially have similar histopathological findings. Patients with a histopathology-confirmed diagnosis of sarcoidosis are at higher risk of developing malignancies. In this report, we present a case of a 64-year-old male diagnosed with sarcoidosis 2 years before presenting to the emergency department with a 4-month history of generalized weakness, cough, and very high fever. After a thorough workup involving cervical lymph node biopsy and bone marrow biopsy, he was diagnosed with peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS). Due to the patient's current lymphoma diagnosis and features noted on pathology, a retrospective review of the prior biopsy specimen was performed, finding similar hematopathological features on both initial lymph node biopsy diagnosing sarcoidosis and current biopsies diagnosing lymphoma. Given these findings, our patient likely had early manifestation of PTCL misdiagnosed as sarcoidosis. In summary, lymphoma should be considered in all patients with suspected sarcoidosis, especially those who do not respond to treatment or who present with persistent hematological abnormalities.

Unusual Presentation of SET::NUP214-Associated Concomitant Hematological Neoplasm in a Child-Diagnostic and Treatment Struggle

Simultaneous multilineage hematologic malignancies are uncommon and associated with poorer prognosis than single-lineage leukemia or lymphoma. Here, we describe a concomitant malignant neoplasm in a 4-year-old boy. The child presented with massive lymphoproliferative syndrome, nasal breathing difficulties, and snoring. Morphological, immunocytochemical, and flow cytometry diagnostics showed coexistence of acute myeloid leukemia (AML) and peripheral T-cell lymphoma (PTCL). Molecular examination revealed a rare t(9;9)(q34;q34)/SET::NUP214 translocation as well as common TCR clonal rearrangements in both the bone marrow and lymph nodes. The disease showed primary refractoriness to both lymphoid and myeloid high-dose chemotherapy as well as combined targeted therapy (trametinib + ruxolitinib). Hence, HSCT was performed, and the patient has since been in complete remission for over a year. This observation highlights the importance of molecular techniques for determining the united nature of complex SET::NUP214-positive malignant neoplasms arising from precursor cells with high lineage plasticity.

Angioimmunoblastic T-cell lymphoma and correlated neoplasms with T-cell follicular helper phenotype: from molecular mechanisms to therapeutic advances

Angioimmunoblastic T-cell lymphoma (AITL) is the second most frequent subtype of mature T-cell lymphoma (MTCL) in the Western world. It derives from the monoclonal proliferation of T-follicular helper (TFH) cells and is characterized by an exacerbated inflammatory response and immune dysregulation, with predisposition to autoimmunity phenomena and recurrent infections. Its genesis is based on a multistep integrative model, where age-related and initiator mutations involve epigenetic regulatory genes, such as TET-2 and DNMT3A. Subsequently, driver-mutations, such as RhoA G17V and IDH-2 R172K/S promote the expansion of clonal TFH-cells ("second-hit"), that finally begin to secrete cytokines and chemokines, such as IL-6, IL-21, CXCL-13 and VEGF, modulating a network of complex relationships between TFH-cells and a defective tumor microenvironment (TME), characterized by expansion of follicular dendritic cells (FDC), vessels and EBV-positive immunoblasts. This unique pathogenesis leads to peculiar clinical manifestations, generating the so-called "immunodysplastic syndrome", typical of AITL. Its differential diagnosis is broad, involving viral infections, collagenosis and adverse drug reactions, which led many authors to use the term "many-faced lymphoma" when referring to AITL. Although great advances in its biological knowledge have been obtained in the last two decades, its treatment is still an unmet medical need, with highly reserved clinical outcomes. Outside the setting of clinical trials, AITL patients are still treated with multidrug therapy based on anthracyclines (CHOP-like), followed by up-front consolidation with autologous stem cell transplantation (ASCT). In this setting, the estimated 5-year overall survival (OS) is around 30-40%. New drugs, such as hypomethylating agents (HMAs) and histone deacetylase inhibitors (HDAi), have been used for relapsed/refractory (R/R) disease with promising results. Such agents have their use based on a biological rationale, have significant potential to improve the outcomes of patients with AITL and may represent a paradigm shift in the therapeutic approach to this lymphoma in the near future.

The fusion oncogene VAV1-MYO1F triggers aberrant T-cell receptor signaling in vivo and drives peripheral T-cell lymphoma in mice

VAV1-MYO1F is a recently identified gain-of-function fusion protein of the proto-oncogene Vav guanine nucleotide exchange factor 1 (VAV1) that is recurrently detected in T-cell non-Hodgkin's lymphoma (T-NHL) patients. However, the pathophysiological functions of VAV1-MYO1F in lymphomagenesis are insufficiently defined. Therefore, we generated transgenic mouse models to conditionally express VAV1-MYO1F in T-cells in vivo. We demonstrate that VAV1-MYO1F triggers cell autonomous activation of T-cell signaling with an activation of the ERK, JNK, and AKT pathways. VAV1-MYO1F expression induces a T-cell activation phenotype with high surface expression of CD25, ICOS, CD44, PD-1, and decreased CD62L as well as aberrant T-cell differentiation, proliferation, and neoplastic transformation. Consequently, the VAV1-MYO1F expressing T-cells induce a malignant T lymphoproliferative disease with 100% penetrance in vivo that mimics key aspects of human peripheral T-cell lymphoma. These results demonstrate that the human T-cell oncogene VAV1-MYO1F is sufficient to trigger oncogenic T-cell signaling and neoplastic transformation, and moreover, it provides a new clinically relevant mouse model to explore the pathogenesis of and treatment concepts for human T-cell lymphoma.

Rational Targets of Therapy in Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive extranodal non-Hodgkin lymphoma (NHL) with poor outcomes, particularly in advanced-stage and relapsed/refractory disease. Emerging research on molecular drivers of ENKTL lymphomagenesis by next-generation and whole genome sequencing has revealed diverse genomic mutations in multiple signaling pathways, with the identification of multiple putative targets for novel therapeutic agents. In this review, we summarize the biological underpinnings of newly-understood therapeutic targets in ENKTL with a focus on translational implications, including epigenetic and histone regulatory aberrations, activation of cell proliferation signaling pathways, suppression of apoptosis and tumor suppressor genes, changes in the tumor microenvironment, and EBV-mediated oncogenesis. In addition, we highlight prognostic and predictive biomarkers which may enable a personalized medicine approach toward ENKTL therapy.