Prognostic significance of cytogenetic abnormalities in T-cell prolymphocytic leukemia

Morphology, immunophenotype, and suggested diagnostic criteria of TCL1 family-negative T-prolymphocytic leukemia

OBJECTIVES

We sought to investigate the morphologic and immunophenotypic characteristics of TCL1 family-negative T-cell prolymphocytic leukemia (T-PLL).

METHODS

Twenty cases of TCL1 family-negative T-PLL were studied.

RESULTS

The doubling time of leukemic cells ranged from less than 2 days to more than 5 years, with a median of 5.5 months. Leukemic cells were small to medium-sized, with round to irregular nuclei, variably condensed chromatin, and small amounts of agranular cytoplasm. A visible nucleolus was identified in 11 (55%) cases. Cytoplasmic blebs/protrusions were identified in all cases, but their occurrence was highly variable from case to case. Bone marrow biopsy showed an interstitial pattern in 90% of cases and a diffuse pattern in the remaining 10% of cases. Flow cytometric immunophenotypic analysis showed that the leukemic cells in all cases were CD4 positive; 3 (15%) also showed concurrent CD8 expression. All cases were positive for CD2 and CD5. Surface CD3 and CD7 were positive in 19 of 20 (95%) cases, and all CD3-positive cases expressed the T-cell receptor αβ. Compared with prototypic T-PLL cases, these 2 groups shared many immunophenotypic findings, except CD8 and CD26, both of which were more commonly expressed in prototypic T-PLL cases.

CONCLUSIONS

TCL1 family-negative T-PLL cases have morphologic and immunophenotypic features that are similar to prototypic T-PLL. They are characterized by neoplastic proliferation of small to medium-sized mature T cells with CD4-positive T-cell receptor αβ phenotype. Tumor cells frequently maintain pan-T antigen expression. Recognizing these morphologic and immunophenotypic features will aid in accurately diagnosing this rare subset of T-PLL.

Predictive and prognostic molecular biomarkers in lymphomas

Recent advances in molecular diagnostics have markedly expanded our understanding of the genetic underpinnings of lymphomas and catalysed a transformation in not just how we classify lymphomas, but also how we treat, target, and monitor affected patients. Reflecting these advances, the World Health Organization Classification, International Consensus Classification, and National Comprehensive Cancer Network guidelines were recently updated to better integrate these molecular insights into clinical practice. We summarise here the molecular biomarkers of lymphomas with an emphasis on biomarkers that have well-supported prognostic and predictive utility, as well as emerging biomarkers that show promise for clinical practice. These biomarkers include: (1) diagnostic entity-defining genetic abnormalities [e.g., B-cell acute lymphoblastic leukaemia (B-ALL) with KMT2A rearrangement]; (2) molecular alterations that guide patients' prognoses (e.g., TP53 loss frequently conferring worse prognosis); (3) mutations that serve as the targets of, and often a source of acquired resistance to, small molecular inhibitors (e.g., ABL1 tyrosine kinase inhibitors for B-ALL BCR::ABL1, hindered by ABL1 kinase domain resistance mutations); (4) the growing incorporation of molecular measurable residual disease (MRD) in the management of lymphoma patients (e.g., molecular complete response and sequencing MRD-negative criteria in multiple myeloma). Altogether, our review spans the spectrum of lymphoma types, from the genetically defined subclasses of precursor B-cell lymphomas to the highly heterogeneous categories of small and large cell mature B-cell lymphomas, Hodgkin lymphomas, plasma cell neoplasms, and T/NK-cell lymphomas, and provides an expansive summary of our current understanding of their molecular pathology.

Cytogenetics in the management of mature T-cell and NK-cell neoplasms: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Mature T-cell and natural killer (NK)-cell neoplasms (MTNKNs) are a highly heterogeneous group of lymphomas that represent 10-15 % of lymphoid neoplasms and have usually an aggressive behavior. Diagnosis can be challenging due to their overlapping clinical, histological and immunophenotypic features. Genetic data are not a routine component of the diagnostic algorithm for most MTNKNs. Indeed, unlike B-cell lymphomas, the genomic landscape of MTNKNs is not fully understood. Only few characteristic rearrangements can be easily identified with conventional cytogenetic methods and are an integral part of the diagnostic criteria, for instance the t(14;14)/inv(14) or t(X;14) abnormality harbored by 95 % of patients with T-cell prolymphocytic leukemia, or the ALK gene translocation observed in some forms of anaplastic large cell lymphoma. However, advances in molecular and cytogenetic techniques have brought new insights into MTNKN pathogenesis. Several recurrent genetic alterations have been identified, such as chromosomal losses involving tumor suppressor genes (SETD2, CDKN2A, TP53) and gains involving oncogenes (MYC), activating mutations in signaling pathways (JAK-STAT, RAS), and epigenetic dysregulation, that have improved our understanding of these pathologies. This work provides an overview of the cytogenetics knowledge in MTNKNs in the context of the new World Health Organization classification and the International Consensus Classification of hematolymphoid tumors. It describes key genetic alterations and their clinical implications. It also proposes recommendations on cytogenetic methods for MTNKN diagnosis.

T-Cell Prolymphocytic Leukemia: Diagnosis, Pathogenesis, and Treatment

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells. Most patients with T-PLL present with lymphocytosis, anemia, thrombocytopenia, and hepatosplenomegaly. Correct identification of T-PLL is essential because treatment for this disease is distinct from that of other T-cell neoplasms. In 2019, the T-PLL International Study Group (TPLL-ISG) established criteria for the diagnosis, staging, and assessment of response to treatment of T-PLL with the goal of harmonizing research efforts and supporting clinical decision-making. T-PLL pathogenesis is commonly driven by T-cell leukemia 1 (TCL1) overexpression and ATM loss, genetic alterations that are incorporated into the TPLL-ISG diagnostic criteria. The cooperativity between TCL1 family members and ATM is seemingly unique to T-PLL across the spectrum of T-cell neoplasms. The role of the T-cell receptor, its downstream kinases, and JAK/STAT signaling are also emerging themes in disease pathogenesis and have obvious therapeutic implications. Despite improved understanding of disease pathogenesis, alemtuzumab remains the frontline therapy in the treatment of naïve patients with indications for treatment given its high response rate. Unfortunately, the responses achieved are rarely durable, and the majority of patients are not candidates for consolidation with hematopoietic stem cell transplantation. Improved understanding of T-PLL pathogenesis has unveiled novel therapeutic vulnerabilities that may change the natural history of this lymphoproliferative neoplasm and will be the focus of this concise review.

Haploidentical Stem Cell Transplantation Using Post-Transplant Cyclophosphamide for T-Cell Prolymphocytic Leukemia after Alemtuzumab Induction Therapy: A Case Report

T-cell prolymphocytic leukemia (T-PLL) is a rare aggressive disease with a poor prognosis. Allogeneic stem cell transplantation (allo-SCT) followed by alemtuzumab administration is the most promising treatment for T-PLL but is associated with a high risk of infections as alemtuzumab strongly suppresses cellular immunity, leading to high transplant-related mortality and unsatisfactory survival rates. In addition, for patients without human leukocyte antigen-matched donors, haploidentical stem cell transplantation (haplo-SCT) using post-transplant cyclophosphamide (PTCy) has been used because of the ready availability of donors and achievement of results comparable to those of transplantation with human leukocyte antigen-matched donors. However, there are no reports on the efficacy and safety, including infectious complications, of haplo-SCT with PTCy after alemtuzumab therapy in patients with. Here, we describe a 66-year-old Japanese male patient with T-PLL treated successfully with haplo-SCT after induction therapy of alemtuzumab for T-PLL. Approximately 3 months after the achievement of complete remission with alemtuzumab for T-PLL, haplo-SCT with reduced-intensity conditioning and PTCy was performed. Infectious complications were improved by early therapeutic interventions, and peripheral T cell counts gradually recovered. The patient was alive for more than 16 months after allo-SCT with no signs of relapse. Thus, haplo-SCT using PTCy should be considered as an option after alemtuzumab treatment for T-PLL.

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

Computational gene expression analysis reveals distinct molecular subgroups of T-cell prolymphocytic leukemia

T-cell prolymphocytic leukemia (T-PLL) is a rare blood cancer with poor prognosis. Overexpression of the proto-oncogene TCL1A and missense mutations of the tumor suppressor ATM are putative main drivers of T-PLL development, but so far only little is known about the existence of T-PLL gene expression subtypes. We performed an in-depth computational reanalysis of 68 gene expression profiles of one of the largest currently existing T-PLL patient cohorts. Hierarchical clustering combined with bootstrapping revealed three robust T-PLL gene expression subgroups. Additional comparative analyses revealed similarities and differences of these subgroups at the level of individual genes, signaling and metabolic pathways, and associated gene regulatory networks. Differences were mainly reflected at the transcriptomic level, whereas gene copy number profiles of the three subgroups were much more similar to each other, except for few characteristic differences like duplications of parts of the chromosomes 7, 8, 14, and 22. At the network level, most of the 41 predicted potential major regulators showed subgroup-specific expression levels that differed at least in comparison to one other subgroup. Functional annotations suggest that these regulators contribute to differences between the subgroups by altering processes like immune responses, angiogenesis, cellular respiration, cell proliferation, apoptosis, or migration. Most of these regulators are known from other cancers and several of them have been reported in relation to leukemia (e.g. AHSP, CXCL8, CXCR2, ELANE, FFAR2, G0S2, GIMAP2, IL1RN, LCN2, MBTD1, PPP1R15A). The existence of the three revealed T-PLL subgroups was further validated by a classification of T-PLL patients from two other smaller cohorts. Overall, our study contributes to an improved stratification of T-PLL and the observed subgroup-specific molecular characteristics could help to develop urgently needed targeted treatment strategies.

Mature T-Cell leukemias: Challenges in Diagnosis

T-cell clones can frequently be identified in peripheral blood. It can be difficult to appreciate whether these are benign and transient or whether they signify a clonal disorder. We review factors that aid in understanding the relevance of T-cell clones. Conversely, obvious pathological T-cell clones can be detected in blood, but there is uncertainty in how to categorize this clonal T cell population, thus, we adopt a multidisciplinary review of the clinical features, diagnostic material and radiology before making the diagnosis. In this review we shall discuss some of these challenges faced when diagnosing mature T-cell leukemias.

Genetic Landscape of Peripheral T-Cell Lymphoma

Peripheral T-Cell lymphoma (PTCL) comprises a heterogenous group of uncommon lymphomas derived from mature, post-thymic or “peripheral” T- and natural killer cells. The World Health Organization (WHO) emphasizes a multiparameter approach in the diagnosis and subclassification of these neoplasms, integrating clinical, morphologic, immunophenotypic, and genetic features into the final diagnosis. Clinical presentation is particularly important due to histologic, immunophenotypic and genetic variations within established subtypes, and no convenient immunophenotypic marker of monoclonality exists. In recent years, widespread use of gene expression profiling and next-generation sequencing (NGS) techniques have contributed to an improved understanding of the pathobiology in PTCLs, and these have been incorporated into the 2016 revised WHO classification of mature T- and NK-cell neoplasms which now encompasses nearly 30 distinct entities. This review discusses the genetic landscape of PTCL and its role in subclassification, prognosis, and potential targeted therapy. In addition to discussing T-Cell lymphoma subtypes with relatively well-defined or relevant genetic aberrancies, special attention is given to genetic advances in T-Cell lymphomas of T follicular helper cell (TFH) origin, highlighting genetic overlaps between angioimmunoblastic T-Cell lymphoma (AITL), follicular T-Cell lymphoma, and nodal peripheral T-Cell lymphoma with a TFH phenotype. Furthermore, genetic drivers will be discussed for ALK-negative anaplastic large cell lymphomas and their role in differentiating these from CD30+ peripheral T-Cell lymphoma, not otherwise specified (NOS) and primary cutaneous anaplastic large cell lymphoma. Lastly, a closer look is given to genetic pathways in peripheral T-Cell lymphoma, NOS, which may guide in teasing out more specific entities in a group of T-Cell lymphomas that represents the most common subcategory and is sometimes referred to as a “wastebasket” category.

Molecular characterization of Novel ATM fusions in chronic lymphocytic leukemia and T-cell prolymphocytic leukemia

ATM deletions and/or mutations are recurrent in lymphoid neoplasms while rearrangements are rare. In this study, we used mate pair sequencing (MPseq) technology to characterize two novel ATM rearrangements in one patient with chronic lymphocytic leukemia (CLL) and one patient with T-prolymphocytic leukemia (T-PLL). Both patients showed chromosome 11q22 aberrations encompassing ATM by conventional karyotype and fluorescence in situ hybridization: isolated t(11;13)(q22;q14) in CLL and a complex karyotype with apparent 11q deletion and unbalanced der(14)t(11;14)(q22;p11.2) in T-PLL. MPseq identified ATM-LINC00371 fusion in CLL and ATM-USP28 in T-PLL, both of which led to ATM inactivation, confirmed by loss of immunohistochemical protein expression. Next-generation sequencing mutation analysis detected concurrent ATM mutation(s) CLL patient, while T-PLL lacked ATM mutation. ATM rearrangements, not apparently detectable using standard laboratory technologies, represent another mechanism of loss-of-function. Recent high-throughput technologies such as MPseq can uncover novel pathogenic gene fusions and resolve complex chromosomal rearrangements in hematologic malignancies.

Advanced Pathogenetic Concepts in T-Cell Prolymphocytic Leukemia and Their Translational Impact

T-cell prolymphocytic leukemia (T-PLL) is the most common mature T-cell leukemia. It is a typically aggressively growing and chemotherapy-resistant malignancy with a poor prognosis. T-PLL cells resemble activated, post-thymic T-lymphocytes with memory-type effector functions. Constitutive transcriptional activation of genes of the T-cell leukemia 1 (TCL1) family based on genomic inversions/translocations is recognized as a key event in T-PLL's pathogenesis. TCL1's multiple effector pathways include the enhancement of T-cell receptor (TCR) signals. New molecular dependencies around responses to DNA damage, including repair and apoptosis regulation, as well as alterations of cytokine and non-TCR activation signaling were identified as perturbed hallmark pathways within the past years. We currently witness these vulnerabilities to be interrogated in first pre-clinical concepts and initial clinical testing in relapsed/refractory T-PLL patients. We summarize here the current knowledge on the molecular understanding of T-PLL's pathobiology and critically assess the true translational progress around this to help appraisal by caregivers and patients. Overall, the contemporary concepts on T-PLL's pathobiology are condensed in a comprehensive mechanistic disease model and promising interventional strategies derived from it are highlighted.

Current Progress in Investigating Mature T- and NK-Cell Lymphoma Gene Aberrations by Next-Generation Sequencing (NGS)

Despite efforts to abrogate the severe threat to life posed by the profound malignancy of mature natural killer/T-cell lymphoma (NKTCL), therapeutic advances still require further investigation of its inherent regulatory biochemical processes. Next-generation sequencing (NGS) is an increasingly developing gene detection technique, which has been widely used in lymphoma genetic research in recent years. Targeted therapy based on the above studies has also generated a series of advances, making genetic mutation a new research hotspot in lymphoma. Advances in NKTCL-related gene mutations are reviewed in this paper.

B and T cell prolymphocytic leukaemia

Prolymphocytic leukaemias B-PLL and T-PLL are rare disorders, typically with an aggressive clinical course and poor prognosis. Combining morphology, immunophenotyping, cytogenetic and molecular diagnostics reliably separates B-PLL and T-PLL from one another and other disorders. In T-PLL discovery of frequent mutations in the JAK-STAT pathway have increased understanding of disease pathogenesis. Alemtuzumab (anti-CD52) produces excellent response rates but long-term remissions are only achieved in a minority following consolidation with allogeneic stem cell transplant. Molecular abnormalities in B-PLL are less understood. Disruption of TP53 is a key finding, conveying chemotherapy resistance requiring novel therapies such as B-cell receptor inhibitors (BCRi). Both conditions require improved pathobiological knowledge to identify new treatment targets and guide therapy with novel pathway inhibitors.

New lessons learned in T-PLL: results from a prospective phase-II trial with fludarabine-mitoxantrone-cyclophosphamide-alemtuzumab induction followed by alemtuzumab maintenance

Clinical trials in T-cell prolymphocytic leukemia (T-PLL) are scarce. Based on a precursor study testing fludarabine, mitoxantrone, and cyclophosphamide followed by alemtuzumab (FMC-A), we aimed to improve this regimen by upfront combining subcutaneous (s.c.) alemtuzumab with FMC for four cycles followed by an alemtuzumab-maintenance (FMCA + A). This prospective multicenter phase-II trial assessed response, survival, and toxicity of that regimen administered to pretreated (n = 4) and treatment-naïve (n = 12) T-PLL patients. The best overall response rate after FMCA was 68.8% (n = 11) including five CRs (31.3%) and six PRs (37.5%). Six patients entered the alemtuzumab-maintenance. Median overall and progression-free survival was 16.7 and 11.2 months, respectively. Hematologic toxicities were the most frequent grade 3/4 side effects. A reduced incidence of CMV-reactivations was attributed to the prophylactic administration of valganciclovir. Overall, FMCA + A did not improve the efficacy of the FMC-A-regimen or of single i.v. alemtuzumab. It suggests that a chemotherapy backbone prevents efficient alemtuzumab dosing and confirms that intravenous alemtuzumab is to be preferred over its s.c. route in T-PLL. ClinicalTrials.gov identifier: NCT01186640.

Actionable perturbations of damage responses by TCL1/ATM and epigenetic lesions form the basis of T-PLL

T-cell prolymphocytic leukemia (T-PLL) is a rare and poor-prognostic mature T-cell malignancy. Here we integrated large-scale profiling data of alterations in gene expression, allelic copy number (CN), and nucleotide sequences in 111 well-characterized patients. Besides prominent signatures of T-cell activation and prevalent clonal variants, we also identify novel hot-spots for CN variability, fusion molecules, alternative transcripts, and progression-associated dynamics. The overall lesional spectrum of T-PLL is mainly annotated to axes of DNA damage responses, T-cell receptor/cytokine signaling, and histone modulation. We formulate a multi-dimensional model of T-PLL pathogenesis centered around a unique combination of TCL1 overexpression with damaging ATM aberrations as initiating core lesions. The effects imposed by TCL1 cooperate with compromised ATM toward a leukemogenic phenotype of impaired DNA damage processing. Dysfunctional ATM appears inefficient in alleviating elevated redox burdens and telomere attrition and in evoking a p53-dependent apoptotic response to genotoxic insults. As non-genotoxic strategies, synergistic combinations of p53 reactivators and deacetylase inhibitors reinstate such cell death execution.

T-cell prolymphocytic leukemia (T-PLL) is a rare malignancy with a poor prognosis. Here, the authors investigate the genomic landscape, gene expression profiles and functional mechanisms in 111 patients, highlighting TCL1 overexpression and ATM aberrations as core lesions which co-operate to impair DNA damage processing.

Discovery of novel drug sensitivities in T-PLL by high-throughput ex vivo drug testing and mutation profiling

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells with an urgent need for rationally designed therapies to address its notoriously chemo-refractory behavior. The median survival of T-PLL patients is <2 years and clinical trials are difficult to execute. Here we systematically explored the diversity of drug responses in T-PLL patient samples using an ex vivo drug sensitivity and resistance testing platform and correlated the findings with somatic mutations and gene expression profiles. Intriguingly, all T-PLL samples were sensitive to the cyclin-dependent kinase inhibitor SNS-032, which overcame stromal-cell-mediated protection and elicited robust p53-activation and apoptosis. Across all patients, the most effective classes of compounds were histone deacetylase, phosphoinositide-3 kinase/AKT/mammalian target of rapamycin, heat-shock protein 90 and BH3-family protein inhibitors as well as p53 activators, indicating previously unexplored, novel targeted approaches for treating T-PLL. Although Janus-activated kinase-signal transducer and activator of transcription factor (JAK-STAT) pathway mutations were common in T-PLL (71% of patients), JAK-STAT inhibitor responses were not directly linked to those or other T-PLL-specific lesions. Overall, we found that genetic markers do not readily translate into novel effective therapeutic vulnerabilities. In conclusion, novel classes of compounds with high efficacy in T-PLL were discovered with the comprehensive ex vivo drug screening platform warranting further studies of synergisms and clinical testing.