Recurrent mutations in epigenetic regulators, RHOA and FYN kinase in peripheral T cell lymphomas

Peripheral T-cell lymphoma: From biology to practice to the future

Recent advancements in comprehending peripheral T-cell lymphomas (PTCLs) validate and broaden our perspective, highlighting their diverse nature and the varying molecular mechanisms underlying the entities. Based on a comprehensive accumulated understanding, the PTCLs currently overcome the most challenging features of any disease: rarity, incredible heterogeneity, and a lack of any established standard of care. The treatments deployed in the front-line are extrapolated from regimens developed for other diseases. The recent approval of the three drugs brentuximab vedotin (BV), pralatrexate, and belinostat for patients with relapsed or refractory disease has provided clues about pathophysiology and future directions, though challenges satisfying post-marketing requirements (PMR) for those accelerated approvals have led to one of those drugs being withdrawn and put the other two in jeopardy. Edits of the front-line regimens, often called CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone)-plus approaches, look more like CHOP-minus strategies, as the toxicity of five-drug regimens often reduces the dose intensity of the added 'novel' drug, nullifying any hope of an advance. The turmoil in the field produced by the aforementioned, coupled with an ever-changing classification, has left the field uncertain about the path forward. Despite these challenges, empiric findings from studies of novel drug approaches, coupled with a logic emerging from studies of PTCL lymphomagenesis, have begun to illuminate, albeit faintly for some, a potential direction. The empiric finding that drugs targeting the discrete components of the PTCL epigenome, coupled with the description of multiple mutations in genes that govern epigenetic biology, offers, at the very least, an opportunity to finally be hypothesis-driven. The most recent recognition that the only combination of drugs shown to markedly improve progression-free survival (PFS) in patients with relapsed disease is one based on dual targeting of different and discrete components of that epigenetic biology has established a possibility that circumnavigating chemotherapy addition studies is both plausible, feasible, and likely the best prospect for a quantum advance in this disease. Herein, we analyze PTCL through a 2025 lens, highlighting and underscoring walls that have impeded progress. We will critically explore all the clues and the panoramic view of PTCL research.

Function of a complex of p-Y42 RhoA GTPase and pyruvate kinase M2 in EGF signaling pathway in glioma cells

Epidermal growth factor (EGF) is known to be a critical stimulant for inducing the proliferation of glioma cancer cells. In our study, we observed that GST-RhoA binds to pyruvate kinase M2 (PKM2) in vitro. While EGF reduced the levels of RhoA protein, it significantly increased p-Y42 RhoA, as well as PKM1 and PKM2 in LN18 glioma cell line. We determined that RhoA undergoes degradation through ubiquitination involving SCF1 and Smurf1. Interestingly, we observed that p-Y42 RhoA binds to PKM2, while the dephosphomimetic form, RhoA Y42F, did not. Additionally, our observation revealed that PKM2 stabilized both RhoA and p-Y42 RhoA. Importantly, RhoA, p-Y42 RhoA, and PKM2, but not RhoA-GTP, were localized in the nucleus upon EGF stimulation. Knockdown of RhoA with siRNA resulted in the reduced levels of phosphoglycerate kinase1 (PGK1) and microtubule affinity-regulating kinase 4 (MARK). Furthermore, we found that the promoter of PGK1 was associated with β-catenin and YAP. Notably, p-Y42 RhoA and PKM2 co-immunoprecipitated with β-catenin and YAP. Based on these findings, we proposed a novel mechanism by which p-Y42 RhoA and PKM2, in conjunction with β-catenin and YAP, regulate PGK1 expression, contributing to the progression of glioma upon EGF.

Tumor-derived RHOA mutants interact with effectors in the GDP-bound state

RHOA mutations are found at diverse residues in various cancer types, implying mutation- and cell-specific mechanisms of tumorigenesis. Here, we focus on the underlying mechanisms of two gain-of-function RHOA mutations, A161P and A161V, identified in adult T-cell leukemia/lymphoma. We find that RHOAA161P and RHOAA161V are both fast-cycling mutants with increased guanine nucleotide dissociation/association rates compared with RHOAWT and show reduced GTP-hydrolysis activity. Crystal structures reveal an altered nucleotide association in RHOAA161P and an open nucleotide pocket in RHOAA161V. Both mutations perturb the dynamic properties of RHOA switch regions and shift the conformational landscape important for RHOA activity, as shown by 31P NMR and molecular dynamics simulations. Interestingly, RHOAA161P and RHOAA161V can interact with effectors in the GDP-bound state. 1H-15N HSQC NMR spectra support the existence of an active population in RHOAA161V-GDP. The distinct interaction mechanisms resulting from the mutations likely favor an RHOAWT-like "ON" conformation, endowing GDP-bound state effector binding activity.

Single-cell landscape reveals the immune heterogeneity of bone marrow involvement in peripheral T-cell lymphoma

The prognosis of patients with peripheral T-cell lymphoma (PTCL) depends on bone marrow involvement (BMI). The bone marrow (BM) tumor microenvironment in PTCL remains unclear. We performed single-cell RNA sequencing (scRNA-seq) on 11 fresh BM samples from patients with BMI to reveal the associations of immune landscape and genetic variations with the prognosis of PTCL patients. Compared with PTCL not otherwise specified (NOS), angioimmunoblastic T-cell lymphoma (AITL) had a higher number of T cells, lower number of lymphocytes, and greater inflammation. Immune heterogeneity in AITL is associated with prognosis. In particular, specific T-cell receptor (TCR) T cells are enriched in patients with good response to anti-CD30 therapy. We observed RhoA mutation-associated neoantigens. Chidamide-treated patients had a higher number of CD4+ regulatory cells and a better treatment response compared with other patients. In the nonresponder group, T-cell enrichment progressed to secondary B-cell enrichment and subsequently diffuse large B-cell lymphoma. Moreover, AITL patients with lymphoma-associated hemophagocytic syndrome had more T follicular helper (Tfh) cells with copy number variations in CHR5. To our knowledge, this study is the first to reveal the single-cell landscape of BM microenvironment heterogeneity in PTCL patients with BMI. scRNA-seq can be used to investigate the immune heterogeneity and genetic variations in AITL associated with prognosis.

Chidamide plus prednisone, cyclophosphamide, and thalidomide for relapsed or refractory peripheral T-cell lymphoma: A multicenter phase II trial

BACKGROUND

Although the treatment of peripheral T-cell lymphoma (PTCL) has undergone advancements during the past several years, the response rate and long-term effects with respect to patients with PTCL remain unsatisfactory-particularly for relapsed or refractory (R/R) patients. This phase II trial was designed to explore the efficacy and safety of an all-oral regimen of chidamide plus prednisone, cyclophosphamide, and thalidomide (CPCT) for R/R PTCL patients who could not tolerate the standard chemotherapy for a variety of reasons.

METHODS

We conducted a multicenter phase II clinical trial in which we combined chidamide (30 mg twice weekly) with prednisone (20 mg daily after breakfast), cyclophosphamide (50 mg daily after lunch), and thalidomide (100 mg daily at bedtime) (the CPCT regimen) for a total of fewer than 12 cycles as an induction-combined treatment period, and then applied chidamide as single-drug maintenance. Forty-five patients were ultimately enrolled from August 2016 to April 2021 with respect to Chinese patients at nine centers. Our primary objective was to assess the overall response rate (ORR) after the treatment with CPCT.

RESULTS

Of the 45 enrolled patients, the optimal ORR and complete response (CR)/CR unconfirmed (CRu) were 71.1% (32/45) and 28.9% (13/45), respectively, and after a median follow-up period of 56 months, the median progression-free survival (PFS) and overall survival (OS) were 8.5 months and 17.2 months, respectively. The five-year PFS and OS rates were 21.2% (95% confidence interval [CI], 7.9-34.5%) and 43.8% (95% CI, 28.3-59.3%), respectively. The most common adverse event was neutropenia (20/45, 44.4%), but we observed no treatment-related death.

CONCLUSION

The all-oral CPCT regimen was an effective and safe regimen for R/R PTCL patients who could not tolerate standard chemotherapy for various reasons.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT02879526.

CD58 Alterations Govern Antitumor Immune Responses by Inducing PDL1 and IDO in Diffuse Large B-Cell Lymphoma

Recurrent abnormalities in immune surveillance-related genes affect the progression of diffuse large B-cell lymphoma (DLBCL) and modulate the response to therapeutic interventions. CD58 interacts with the CD2 receptor on T cells and NK cells and is recurrently mutated and deleted in DLBCL, suggesting that it may play a role in regulating antitumor immunity. In this study, we comprehensively analyzed the genomic characteristics of CD58 through targeted next-generation sequencing, RNA sequencing (RNA-seq), whole-exome sequencing, and single-cell RNA-seq in patients with newly diagnosed DLBCL. The CD58 mutation rate was 9.1%, and the copy number loss rate was 44.7% among all enrolled patients with DLBCL. Notably, CD58 genetic alterations, along with low CD58 expression, significantly correlated with reduced rates of response to R-CHOP therapy and inferior progression-free survival and overall survival. Single-cell RNA-seq revealed that CD58 expression in tumor cells was negatively correlated with CD8+ T-cell exhaustion/dysfunction status. Insufficient T-cell activation resulting from CD58 alterations could not be attributed solely to CD2 signaling. CD58 inhibited the activity of the JAK2/STAT1 pathway by activating the LYN/CD22/SH2 domain-containing phosphatase 1 (SHP1) axis, thereby limiting PDL1 and IDO expression. Elevated PDL1 and IDO expression in CD58-deficient DLBCL cells led to immune evasion and tumor-intrinsic resistance to chimeric antigen receptor T-cell therapy. Direct activation of CD58-CD2 costimulatory signaling in combination with anti-PDL1 blockade or IDO inhibitor sensitized CD58-deficient DLBCL to chimeric antigen receptor T-cell therapy. Collectively, this work identified the multiple roles of CD58 in regulating antitumor immune responses in DLBCL. Significance: Loss of CD58 mediates immune evasion and therapy resistance in diffuse large B-cell lymphoma by upregulating PDL1 and IDO through LYN/CD22/SHP1 signaling, providing potential targets and therapeutic strategies to improve patient treatment.

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.

DNA methylation in human diseases

Aberrant epigenetic modifications, particularly DNA methylation, play a critical role in the pathogenesis and progression of human diseases. The current review aims to reveal the role of aberrant DNA methylation in the pathogenesis and progression of diseases and to discuss the original data obtained from international research laboratories on this topic. In the review, we mainly summarize the studies exploring the role of aberrant DNA methylation as diagnostic and prognostic biomarkers in a broad range of human diseases, including monogenic epigenetics, autoimmunity, metabolic disorders, hematologic neoplasms, and solid tumors. The last section provides a general overview of the possibility of the DNA methylation machinery from the perspective of pharmaceutic approaches. In conclusion, the study of DNA methylation machinery is a phenomenal intersection that each of its ways can reveal the mysteries of various diseases, introduce new diagnostic and prognostic biomarkers, and propose a new patient-tailored therapeutic approach for diseases.

Novel clinical risk stratification and treatment strategies in relapsed/refractory peripheral T-cell lymphoma

Peripheral T cell lymphoma (PTCL) represents a group of heterogeneous hematological malignancies, which are notoriously challenging to treat and outcomes are typically poor. Over the past two decades, clinical prognostic indices for patient risk stratification have evolved, while several targeted agents are now available to complement combination chemotherapy in the frontline setting or as a salvage strategy. With further understanding of the molecular pathobiology of PTCL, several innovative approaches incorporating immunomodulatory agents, epigenetic therapies, oncogenic kinase inhibitors and immunotherapeutics have come to the forefront. In this review, we provide a comprehensive overview of the progress in developing clinical prognostic indices for PTCL and describe the broad therapeutic landscape, emphasizing novel targetable pathways that have entered early phase clinical studies.

Oral azacitidine compared with standard therapy in patients with relapsed or refractory follicular helper T-cell lymphoma (ORACLE): an open-label randomised, phase 3 study

BACKGROUND

Follicular helper T-cell lymphomas (TFHL) harbour frequent alterations in genes that regulate DNA methylation. Preliminary reports suggest that treatment with 5-azacitidine has clinical activity in patients with relapsed or refractory TFHL. We aimed to compare the oral form of azacitidine with investigator's choice standard therapy (ICT; ie, gemcitabine, bendamustine, or romidepsin) in patients with relapsed or refractory TFHL.

METHODS

Patients older than 18 years with relapsed or refractory TFHL (angioimmunoblastic T-cell lymphoma, follicular lymphoma, or nodal T-cell lymphoma with phenotype, ie, positive with two or more markers among CD10, BCL6, CXCL13, PD1, or ICOS) based on the 2017 WHO classification of haematological neoplasms, with an Eastern Cooperative Oncology Group performance status score of 0-3, were recruited in university hospitals from five European countries and from Japan. Patients were randomly assigned 1:1 to treatment with either azacitidine given at a dose of 300 mg once a day (200 mg in Japanese patients) for 14 days in a 28-day cycle or gemcitabine, bendamustine, or romidepsin according to the investigator's choice. Random assignment was stratified by the number of previous lines of therapy and by the presence of previous or concomitant myeloid malignancy. The primary endpoint was investigator-assessed progression-free survival, presented in the intention-to-treat population. This Article is the final analysis of this trial, registered at ClinicalTrials.gov (Europe NCT03593018 and Japan NCT03703375).

FINDINGS

86 patients (median age 69 years [IQR 62-76], 50 patients were male, 36 were female) were enrolled between Nov 9, 2018, to Feb 22, 2021; 42 in the azacitidine group and 44 in the ICT group. With a median follow-up of 27·4 months (IQR 20·2-32·9), the median progression-free survival was 5·6 months (95% CI 2·7 -8·1) in the azacitidine group versus 2·8 months (1·9-4·8) in the ICT group (hazard ratio of 0·63 (95% CI 0·38-1·07); 1-sided p=0·042). Grade 3-4 adverse events were reported in 32 (76%) of 42 patients in the azacitidine group versus 42 (98%) of 43 patients in the ICT group. The most adverse grade 3 or worse adverse events were haematological (28 [67%] of 42 patients vs 40 [93%] of 43 patients), infection (8 [19%] and 14 [33%]), and gastrointestinal (5 [12%] vs 1 [2%] for azacitidine and ICT, respectively). There were two treatment-related deaths in the azacitidine group (one endocarditis and one candidiasis) and three in the ICT group (one heart failure, one COVID-19, and one cause unknown).

INTERPRETATION

Although the pre-specified primary outcome of the trial was not met, the favourable safety profile suggests that azacitidine could add to the treatment options in these difficult to treat diseases especially in combination with other drugs. Trials with combination are in preparation in a platform trial.

FUNDING

Bristol-Myers Squibb.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Enhancer of Zeste Homolog 2 Inhibitor SHR2554 in Relapsed or Refractory Peripheral T-cell Lymphoma: Data from the First-in-Human Phase I Study

PURPOSE

Patients with peripheral T-cell lymphomas (PTCL) in the relapsed or refractory (r/r) setting have only a limited number of therapies available, and the prognosis is extremely poor. SHR2554 is an oral inhibitor against EZH2, a rational therapeutic target for lymphomas.

PATIENTS AND METHODS

This was a multicenter, two-part, phase I study of SHR2554 in r/r mature lymphoid neoplasms. In part I, 350 mg twice daily was established as the recommended phase II dose (RP2D) based on the findings during dose escalation and expansion; subsequently, selected lymphoma subtypes were recruited in clinical expansion cohorts to receive SHR2554 at RP2D. Here, we provide an in-depth assessment of SHR2554 at RP2D in subpopulation with r/r PTCL.

RESULTS

Twenty-eight patients were included for analysis (17 angioimmunoblastic T-cell lymphoma and 11 not otherwise specified). Eighteen (64%) patients had received ≥2 lines of previous anticancer therapies. The objective response rate was 61% [95% confidence interval (CI), 41-78]. Responses were still ongoing in 59% (10/17) of the responders; estimated median duration of response was 12.3 months (95% CI, 7.4-not reached). Median progression-free survival was 11.1 months (95% CI, 5.3-22.0), and 12-month overall survival rate was 92% (95% CI, 72-98). The most common grade 3 or 4 treatment-related adverse events were decreased platelet count [nine (32%)] as well as decreased white blood cell count, decreased neutrophil count, and anemia [four (14%) for each]. No treatment-related deaths were reported.

CONCLUSIONS

This extended follow-up analysis further supports SHR2554 as a therapeutic opportunity for patients with r/r PTCL.

Clinicopathologic analysis of nodal T-follicular helper cell lymphomas, a multicenter retrospective study from China

Background

Nodal T-follicular helper cell lymphomas (nTFHLs) represent a new family of peripheral T-cell lymphomas (PTCLs), and comparative studies of their constituents are rare.

Methods

This study retrospectively enrolled 10 patients with nTFHL-F and 30 patients with nTFHL-NOS diagnosed between December 2017 and October 2023 at six large comprehensive tertiary hospitals; 188 patients with nTFHL-AI were diagnosed during the same period at the First Affiliated Hospital of Zhengzhou University for comparison.

Results

Compared with nTFHL-AI, nTFHL-NOS patients exhibited better clinical manifestations, lower TFH expression levels, and a lower Ki-67 index. However, no differences in clinicopathological features were observed between nTFHL-F and nTFHL-AI patients as well as nTFHL-NOS patients. According to the survival analysis, the median OS for patients with nTFHL-NOS, nTFHL-AI, and nTFHL-F were 14.2 months, 10 months, and 5 months, respectively, whereas the median TTP were 14 months, 5 months, and 3 months, respectively. Statistical analysis revealed differences in TTP among the three subtypes(P=0.0173). Among the population of patients receiving CHOP-like induction therapy, there were significant differences in the OS and TTP among the nTFHL-NOS, nTFHL-AI, and nTFHL-F patients (P=0.0134, P=0.0205). Both the GDPT and C-PET regimens significantly improved the ORR, OS, and PFS in nTFHL patients.

Conclusion

There are significant differences in the clinical manifestations, pathology, and survival outcomes among the three subtypes of nTFHLs. However, further research with a larger sample size, and involving clinical pathology and molecular genetics is needed to determine the distinctive biological characteristics of these tumors.

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.

Clinicopathological implications of immunohistochemical expression of TBX21, CXCR3, GATA3, CCR4, and TCF1 in nodal follicular helper T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified

BACKGROUND

The classification of nodal peripheral T-cell lymphoma (PTCL) has evolved according to histology, cell-of-origin, and genetic alterations. However, the comprehensive expression pattern of follicular helper T-cell (Tfh) markers, T-cell factor-1 (TCF1), and Th1- and Th2-like molecules in nodal PTCL is unclear.

METHODS

Eighty-two cases of nodal PTCL were classified into 53 angioimmunoblastic T-cell lymphomas (AITLs)/nodal T-follicular helper cell lymphoma (nTFHL)-AI, 18 PTCLs-Tfh/nTFHL-not otherwise specified (NOS), and 11 PTCLs-NOS according to the revised 4th/5th World Health Organization classifications. Immunohistochemistry for TCF1, TBX21, CXCR3, GATA3, and CCR4 was performed.

RESULTS

TCF1 was highly expressed in up to 68% of patients with nTFHL but also in 44% of patients with PTCL-NOS (p > .05). CXCR3 expression was higher in AITLs than in non-AITLs (p = .035), whereas GATA3 expression was higher in non-AITL than in AITL (p = .007) and in PTCL-Tfh compared to AITL (p = .010). Of the cases, 70% of AITL, 44% of PTCLTfh/ nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the TBX21 subtype; and 15% of AITL, 38% of PTCL-Tfh/nTFHL-NOS, and 36% of PTCL-NOS were subclassified as the GATA3 subtype. The others were an unclassified subtype. CCR4 expression was associated with poor progression-free survival (PFS) in patients with PTCL-Tfh (p < .001) and nTFHL (p = .023). The GATA3 subtype showed poor overall survival in PTCL-NOS compared to TBX21 (p = .046) and tended to be associated with poor PFS in patients with non-AITL (p = .054).

CONCLUSIONS

The TBX21 subtype was more prevalent than the GATA3 subtype in AITL. The GATA3 subtype was associated with poor prognosis in patients with non-AITL and PTCL-NOS.

Genomic and transcriptomic profiling of peripheral T cell lymphoma reveals distinct molecular and microenvironment subtypes

Peripheral T cell lymphoma (PTCL) is a heterogeneous group of non-Hodgkin's lymphomas varying in clinical, phenotypic, and genetic features. The molecular pathogenesis and the role of the tumor microenvironment in PTCL are poorly understood, with limited biomarkers available for genetic subtyping and targeted therapies. Through an integrated genomic and transcriptomic study of 221 PTCL patients, we delineate the genetic landscape of PTCL, enabling molecular and microenvironment classification. According to the mutational status of RHOA, TET2, histone-modifying, and immune-related genes, PTCL is divided into 4 molecular subtypes with discrete patterns of gene expression, biological aberrations, and vulnerabilities to targeted agents. We also perform an unsupervised clustering on the microenvironment transcriptional signatures and categorize PTCL into 4 lymphoma microenvironment subtypes based on characteristic activation of oncogenic pathways and composition of immune communities. Our findings highlight the potential clinical rationale of future precision medicine strategies that target both molecular and microenvironment alterations in PTCL.

Angioimmunoblastic T-cell lymphoma and Kaposi sarcoma: A fortuitous collision?

AIMS

Follicular helper T-cell (TFH) lymphoma of the angioimmunoblastic-type (AITL), one of the most prevalent T-cell lymphomas, typically encompasses proliferation of high endothelial venules and Epstein-Barr virus-positive immunoblasts, but neither infection with HHV8 nor association with Kaposi's sarcoma (KS) have been described. The aims of this study are to characterise the association between AITL and HHV8 infection or KS.

METHODS AND RESULTS

Three male patients aged 49-76 years, HIV-negative, with concurrent nodal involvement by AITL and KS, were identified from our files and carefully studied. Two patients originated from countries where endemic KS occurs, including one with cutaneous KS. The lymphomas featured abundant vessels, expanded follicular dendritic cells and neoplastic TFH cells [PD1+ (three of three), ICOS+ (three of three), CXCL13+ (three of three), CD10+ (two of three), BCL6 (two of three)] but lacked EBV+ immunoblasts. The foci of KS consisted of subcapsular proliferations of ERG+, CD31+ and/or CD34+ , HHV8+ spindle cells. High-throughput sequencing showed AITL-associated mutations in TET2 (three of three), RHOA (G17V) (three of three) and IDH2 (R172) (two of three), which were absent in the microdissected KS component in two cases. Relapses in two patients consisted of AITL, without evidence of KS. No evidence of HHV8 infection was found in a control group of 23 AITL cases.

CONCLUSION

Concurrent nodal involvement by AITL and KS is rare and identification of both neoplastic components may pose diagnostic challenges. The question of whether the association between AITL and KS may be fortuitous or could reflect the underlying immune dysfunction in AITL remains open.

Therapeutic challenges in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare and heterogeneous group of hematological malignancies. Compared to our knowledge of B-cell tumors, our understanding of T-cell leukemia and lymphoma remains less advanced, and a significant number of patients are diagnosed with advanced stages of the disease. Unfortunately, the development of drug resistance in tumors leads to relapsed or refractory peripheral T-Cell Lymphomas (r/r PTCL), resulting in highly unsatisfactory treatment outcomes for these patients. This review provides an overview of potential mechanisms contributing to PTCL treatment resistance, encompassing aspects such as tumor heterogeneity, tumor microenvironment, and abnormal signaling pathways in PTCL development. The existing drugs aimed at overcoming PTCL resistance and their potential resistance mechanisms are also discussed. Furthermore, a summary of ongoing clinical trials related to PTCL is presented, with the aim of aiding clinicians in making informed treatment decisions.

Pathobiology of nodal peripheral T-cell lymphomas: current understanding and future directions

Predominantly nodal is the most common clinical presentation of peripheral T- (and NK-) cell lymphomas (PTCL), which comprise three main groups of diseases: (i) systemic anaplastic large cell lymphomas (ALCL), whether positive or negative for anaplastic lymphoma kinase (ALK); (ii) follicular helper T-cell lymphomas (TFHL); and (iii) PTCL, not otherwise specified (NOS). Recent advances in the genomic and molecular characterization of PTCL, with enhanced understanding of pathobiology, have translated into significant updates in the latest 2022 classifications of lymphomas. ALK-negative ALCL is now recognized to be genetically heterogeneous, with identification of DUSP22 rearrangements in approximately 20-30% of cases, correlated with distinctive pathological and biological features. The notion of cell-of-origin as an important determinant of the classification of nodal PTCL is best exemplified by TFHL, considered as one disease or a group of related entities, sharing oncogenic pathways with frequent recurrent epigenetic mutations as well as a relationship to clonal hematopoiesis. Data are emerging to support that a similar cell-of-origin concept might be relevant to characterize meaningful subgroups within PTCL, NOS, based on cytotoxic and/or Th1 versus Th2 signatures. The small group of primary nodal Epstein-Barr virus-positive lymphomas of T- or NK-cell derivation, formerly considered PTCL, NOS, is now classified separately, due to distinctive features, and notably an aggressive course. This review summarizes current knowledge of the pathology and biology of nodal-based PTCL entities, with an emphasis on recent findings and underlying oncogenic mechanisms.

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.

Updates in the Classification of T-cell Lymphomas and Lymphoproliferative Disorders

PURPOSE OF REVIEW

Mature T/NK-cell neoplasms comprise a heterogeneous group of diseases with diverse clinical, histopathologic, immunophenotypic, and molecular features. A clinically relevant, comprehensive, and reproducible classification system for T/NK-cell neoplasms is essential for optimal management, risk stratification, and advancing understanding of these diseases. Two classification systems for lymphoid neoplasms were recently introduced: the 5th edition of World Health Organization classification (WHO-HAEM5) and the 2022 International Consensus Classification (ICC). In this review, we summarize the basic framework and updates in the classification of mature T/NK-cell neoplasms.

RECENT FINDINGS

WHO-HAEM5 and ICC share basic concepts in classification of T/NK-cell neoplasms, emphasizing integration of clinical presentation, pathology, immunophenotype, and genetics. Major updates in both classifications include unifying nodal T-follicular helper-cell lymphomas into a single entity and establishing EBV-positive nodal T/NK-cell lymphoma as a distinct entity. However, some differences exist in taxonomy, terminology, and disease definitions. The recent classifications of mature T/NK-cell neoplasms are largely similar and provide new insights into taxonomy based on integrated clinicopathologic features.

Angioimmunoblastic T-cell lymphoma: Novel recurrent mutations and prognostic biomarkers by cell-free DNA profiling

Molecular and clinical stratification of patients with angioimmunoblastic T-cell lymphoma (AITL) is unsatisfactory, which hinders the development of personalized therapies. This study aimed to identify molecular biomarkers for AITL based on peripheral cell-free DNA (cfDNA) that could be used to predict prognosis and guide treatment non-invasively. A customized panel containing 46 genes was used to study pretreatment cfDNA and paired tumour tissues in 64 Chinese AITL patients from three clinical centres, and gene mutations in cfDNA and tumour tissue were assessed for concordance (34 paired samples). Then, the association of gene mutations and prognosis was analysed, and a functional enrichment analysis was performed. The sequencing results showed good consistency between cfDNA samples and paired tissue samples. KDM5A, STAT1, FANCM, ERBB4, PIK3R5 and NSD1 were identified as novel recurrent mutations. Mutations in FANCM or combinations of RHOA, KDM5A and FAT1 were associated with poor prognosis. Additionally, functional analysis revealed that RHOAG17 might serve as a predictive biomarker of PD-1 blockade respondence. Our findings confirmed the role of cfDNA as a liquid biopsy in AITL, and revealed novel molecular determinants that can stratify patients and guide treatment options.

TCR Pathway Mutations in Mature T Cell Lymphomas

Mature T cell lymphomas are heterogeneous neoplasms that are aggressive and resistant to treatment. Many of these cancers retain immunological properties of their cell of origin. They express cytokines, cytotoxic enzymes, and cell surface ligands normally induced by TCR signaling in untransformed T cells. Until recently, their molecular mechanisms were unclear. Recently, high-dimensional studies have transformed our understanding of their cellular and genetic characteristics. Somatic mutations in the TCR signaling pathway drive lymphomagenesis by disrupting autoinhibitory domains, increasing affinity to ligands, and/or inducing TCR-independent signaling. Collectively, most of these mutations augment signaling pathways downstream of the TCR. Emerging data suggest that these mutations not only drive proliferation but also determine lymphoma immunophenotypes. For example, RHOA mutations are sufficient to induce disease-relevant CD4+ T follicular helper cell phenotypes. In this review, we describe how mutations in the TCR signaling pathway elucidate lymphoma pathophysiology but also provide insights into broader T cell biology.

The Role of Epigenetic Modifier Mutations in Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are a group of diseases with a low incidence, high degree of heterogeneity, and a dismal prognosis in most cases. Because of the low incidence of these diseases, there have been few therapeutic novelties developed over time. Nevertheless, this fact is changing presently as epigenetic modifiers have been shown to be recurrently mutated in some types of PTCLs, especially in the cases of PTCLs not otherwise specified (PTCL-NOS), T follicular helper (TFH), and angioimmunoblastic T-cell lymphoma (AITL). These have brought about more insight into PTCL biology, especially in the case of PTCLs arising from TFH lymphocytes. From a biological perspective, it has been observed that ten-eleven translocators (TET2) mutated T lymphocytes tend to polarize to TFH, while Tregs lose their inhibitory properties. IDH2 R172 was shown to have inhibitory effects on TET2, mimicking the effects of TET2 mutations, as well as having effects on histone methylation. DNA methyltransferase 3A (DNMT3A) loss-of-function, although it was shown to have opposite effects to TET2 from an inflammatory perspective, was also shown to increase the number of T lymphocyte progenitors. Aside from bringing about more knowledge of PTCL biology, these mutations were shown to increase the sensitivity of PTCLs to certain epigenetic therapies, like hypomethylating agents (HMAs) and histone deacetylase inhibitors (HDACis). Thus, to answer the question from the title of this review: We found the Achilles heel, but only for one of the Achilles.

The implication of next-generation sequencing in the diagnosis and clinical management of non-Hodgkin lymphomas

Next generation sequencing (NGS) is a technology that broadens the horizon of knowledge of several somatic pathologies, especially in oncological and oncohematological pathology. In the case of NHL, the understanding of the mechanisms of tumorigenesis, tumor proliferation and the identification of genetic markers specific to different lymphoma subtypes led to more accurate classification and diagnosis. Similarly, the data obtained through NGS allowed the identification of recurrent somatic mutations that can serve as therapeutic targets that can be inhibited and thus reducing the rate of resistant cases. The article's purpose is to offer a comprehensive overview of the best ways of integrating of next-generation sequencing technologies for diagnosis, prognosis, classification, and selection of optimal therapy from the perspective of tailor-made medicine.

Frequent ZNF217 mutations lead to transcriptional deregulation of interferon signal transduction via altered chromatin accessibility in B cell lymphoma

Recent exome-wide studies discovered frequent somatic mutations in the epigenetic modifier ZNF217 in primary mediastinal B cell lymphoma (PMBCL) and related disorders. As functional consequences of ZNF217 alterations remain unknown, we comprehensively evaluated their impact in PMBCL. Targeted sequencing identified genetic lesions affecting ZNF217 in 33% of 157 PMBCL patients. Subsequent gene expression profiling (n = 120) revealed changes in cytokine and interferon signal transduction in ZNF217-aberrant PMBCL cases. In vitro, knockout of ZNF217 led to changes in chromatin accessibility interfering with binding motifs for crucial lymphoma-associated transcription factors. This led to disturbed expression of interferon-responsive and inflammation-associated genes, altered cell behavior, and aberrant differentiation. Mass spectrometry demonstrates that ZNF217 acts within a histone modifier complex containing LSD1, CoREST and HDAC and interferes with H3K4 methylation and H3K27 acetylation. Concluding, our data suggest non-catalytic activity of ZNF217, which directs histone modifier complex function and controls B cell differentiation-associated patterns of chromatin structure.

Peripheral T-cell lymphoma with a T follicular-helper phenotype: A different entity? Results of the Spanish Real-T study

Nodal peripheral T-cell lymphoma (PTCL) with a T follicular helper phenotype (PTCL-TFH) is a new type of PTCL. We aimed to define its clinical characteristics and prognosis compared to PTCL not otherwise specified (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL). This retrospective observational study included 175 patients diagnosed with PTCL between 2008 and 2013 in 13 Spanish sites. Patient diagnosis was centrally reviewed, and patients were reclassified according to the World Health Organization (WHO) 2016 criteria: 21 patients as PTCL-NOS, 55 as AITL and 23 as PTCL-TFH. Median follow-up was 56.07 months (95% CI 38.7-73.4). Progression-free survival (PFS) and overall survival (OS) were significantly higher in patients with PTCL-TFH than in those with PTCL-NOS and AITL (PFS, 24.6 months vs. 4.6 and 7.8 months, respectively, p = 0.002; OS, 52.6 months vs. 10.0 and 19.3 months, respectively, p < 0.001). Histological diagnosis maintained an independent influence on both PFS (hazard ratio [HR] 4.1 vs. PTCL-NOS, p = 0.008; HR 2.6 vs. AITL, p = 0.047) and OS (HR 5.7 vs. PTCL-NOS, p = 0.004; HR 2.6 vs. AITL, p = 0.096), regardless of the International Prognostic Index. These results suggest that PTCL-TFH could have more favourable features and prognosis than the other PTCL subtypes, although larger series are needed to corroborate these findings.

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.

Follicular helper T-cell lymphomas: disease spectrum, relationship with clonal hematopoiesis, and mimics. A report of the 2022 EA4HP/SH lymphoma workshop

Follicular helper T-cell lymphomas (TFH lymphomas) were discussed in session V of the lymphoma workshop of the European Association for Haematopathology (EA4HP)/Society for Hematopathology (SH) 2022 meeting in Florence, Italy. The session focused on the morphologic spectrum of TFH lymphoma, including its three subtypes: angioimmunoblastic-type (AITL), follicular-type, and not otherwise specified (NOS). The submitted cases encompassed classic examples of TFH lymphoma and unusual cases such as those with early or indolent presentations, associated B-cell proliferations, or Hodgkin/Reed-Sternberg-like cells. The relationship between TFH lymphoma and clonal hematopoiesis was highlighted by several cases documenting divergent evolution of myeloid neoplasm and AITL from shared clonal mutations. The distinction between TFH lymphoma and peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS), was stressed, and many challenging examples were presented. Various cases highlighted the difficulties of differentiating TFH lymphoma from other established types of lymphoma and reactive conditions. Cutaneous T-cell lymphoma expressing TFH markers, particularly when resulting in lymph node involvement, should be distinguished from TFH lymphomas. Additional immunophenotyping and next-generation sequencing studies were performed on various cases in this session, highlighting the importance of these technologies to our current understanding and classification of TFH lymphomas.

Targeted panel sequencing in the routine diagnosis of mature T- and NK-cell lymphomas: report of 128 cases from two German reference centers

Diagnosing any of the more than 30 types of T-cell lymphomas is considered a challenging task for many pathologists and currently requires morphological expertise as well as the integration of clinical data, immunophenotype, flow cytometry and clonality analyses. Even considering all available information, some margin of doubt might remain using the current diagnostic procedures. In recent times, the genetic landscape of most T-cell lymphomas has been elucidated, showing a number of diagnostically relevant mutations. In addition, recent data indicate that some of these genetic alterations might bear prognostic and predictive value. Extensive genetic analyses, such as whole exome or large panel sequencing are still expensive and time consuming, therefore limiting their application in routine diagnostic. We therefore devoted our effort to develop a lean approach for genetic analysis of T-cell lymphomas, focusing on maximum efficiency rather than exhaustively covering all possible targets. Here we report the results generated with our small amplicon-based panel that could be used routinely on paraffin-embedded and even decalcified samples, on a single sample basis in parallel with other NGS-panels used in our routine diagnostic lab, in a relatively short time and with limited costs. We tested 128 available samples from two German reference centers as part of our routine work up (among which 116 T-cell lymphomas), which is the largest routine diagnostic series reported to date. Our results showed that this assay had a very high rate of technical success (97%) and could detect mutations in the majority (79%) of tested T-cell lymphoma samples.

Pharmacological GLUT3 salvage augments the efficacy of vitamin C-induced TET2 restoration in acute myeloid leukemia

Vitamin C has been demonstrated to regulate hematopoietic stem cell frequencies and leukemogenesis by augmenting and restoring Ten-Eleven Translocation-2 (TET2) function, potentially acting as a promising adjunctive therapeutic agent for leukemia. However, glucose transporter 3 (GLUT3) deficiency in acute myeloid leukemia (AML) impedes vitamin C uptake and abolishes the clinical benefit of vitamin C. In this study, we aimed to investigate the therapeutic value of GLUT3 restoration in AML. In vitro GLUT3 restoration was conducted with the transduction of GLUT3-overexpressing lentivirus or the pharmacological salvage with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) treatment to OCI-AML3, a naturally GLUT3-deficient AML cell line. The effects of GLUT3 salvage were further confirmed in patient-derived primary AML cells. Upregulation of GLUT3 expression made AML cells successfully augment TET2 activity and enhanced the vitamin C-induced anti-leukemic effect. Pharmacological GLUT3 salvage has the potential to overcome GLUT3 deficiency in AML and improves the antileukemic effect of vitamin C treatments.

Immune infiltration and drug specificity analysis of different subtypes based on functional status in angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma (PTCL) strongly correlated with worse clinical outcomes. However, the role of characteristic pathway-related genes in patients with AITL (e.g., subtype typing and pathogenesis) remains unknown. In this study, we intended to understand the potential role and prognostic value of characteristic pathways in AITL and identified a model for subtype identification based on pathway-related functional status. Transcriptomic (RNA-seq) data were obtained from the Gene Expression Omnibus database for three sets of tumor tissues from AITL patients. AITL was divided into three clusters based on the pathway profile of patients and the best clustering k = 3, and differentially expressed genes (DEGs) in the three clusters were analyzed. The top 45 important variables associated with characteristic pathways, such as Huntington's disease, VEGF signaling pathway, nucleotide excision repair, ubiquitin-mediated proteolysis, purine metabolism, olfactory transduction, etc., were used to construct a subtype identification model. The model was experimentally validated and proved to possess good predictive efficacy. In addition, pathway-related subtype typing was significantly associated with different immune cell infiltration in AITL. Further analysis revealed that the drug IC50 values predicted also differed markedly among the different subtypes, thus further identifying some subtype-specific drugs. Our study indicates a potential role of characteristic pathways in AITL staging for the first time, provides novel insights for future research targeting AITL, and points to potential therapeutic options for patients with different subtypes of AITL.

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.

How molecular advances may improve the diagnosis and management of PTCL patients

Peripheral T-cell lymphomas (PTCL) comprised more than 30 rare heterogeneous entities, representing 10 to 15% of adult non-Hodgkin lymphomas. Although their diagnosis is still mainly based on clinical, pathological, and phenotypic features, molecular studies have allowed for a better understanding of the oncogenic mechanisms involved and the refinement of many PTCL entities in the recently updated classifications. The prognosis remains poor for most entities (5-year overall survival < 30%), with current conventional therapies based on anthracyclin-based polychemotherapy regimen, despite many years of clinical trials. The recent use of new targeted therapies appears to be promising for relapsed/refractory patients, such as demethylating agents in T-follicular helper (TFH) PTCL. However further studies are needed to evaluate the proper combination of these drugs in the setting of front-line therapy. In this review, we will summarize the oncogenic events for the main PTCL entities and report the molecular targets that have led to the development of new therapies. We will also discuss the development of innovative high throughput technologies that aid the routine workflow for the histopathological diagnosis and management of PTCL patients.

The RHOA Mutation G17V Does Not Lead to Increased Migration of Human Malignant T Cells but Is Associated with Matrix Remodelling

Nodal T-follicular helper cell lymphoma, angioimmunoblastic-type (AITL), is characterized by constitutional symptoms, advanced-stage disease, and generalized lymphadenopathy. A genetic hallmark of this lymphoma is the frequent occurrence of the RHOA mutation G17V in neoplastic cells, which is observed in around 60% of patients. Because RHOA is involved in both T-cell receptor downstream signalling and cell migration, we hypothesized that the characteristic presentation of AITL could be the result of enhanced tumor cell migration. Therefore, this study aimed to elucidate the impact of the RHOA variant G17V on the migration of neoplastic T cells. We transfected the T-cell lymphoma cell lines HH and HuT78 to stably express the RHOA-G17V variant. RHOA-G17V-expressing T cells did not exhibit enhanced motility compared to empty-vector-transfected cells in microchannels, a 3D collagen gel, or primary human lymphatic tissue. Cells of the HH cell line expressing RHOA-G17V had an increased number of cells with cleaved collagen compared with the empty-vector-transfected cells. Therefore, we hypothesized that the early spread of AITL tumor cells may be related to remodelling of the extracellular matrix. Accordingly, we observed a significant negative correlation between the relative area of collagen in histological sections from 18 primary AITL and the allele frequency of the RHOA-G17V mutation. In conclusion, our results suggest that the characteristic presentation of AITL with early, widespread dissemination of lymphoma cells is not the result of an enhanced migration capacity due to the RHOA-G17V mutation; instead, this feature may rather be related to extracellular matrix remodelling.

Guanine nucleotide exchange factors for Rho GTPases (RhoGEFs) as oncogenic effectors and strategic therapeutic targets in metastatic cancer

Metastatic cancer cells dynamically adjust their shape to adhere, invade, migrate, and expand to generate secondary tumors. Inherent to these processes is the constant assembly and disassembly of cytoskeletal supramolecular structures. The subcellular places where cytoskeletal polymers are built and reorganized are defined by the activation of Rho GTPases. These molecular switches directly respond to signaling cascades integrated by Rho guanine nucleotide exchange factors (RhoGEFs), which are sophisticated multidomain proteins that control morphological behavior of cancer and stromal cells in response to cell-cell interactions, tumor-secreted factors and actions of oncogenic proteins within the tumor microenvironment. Stromal cells, including fibroblasts, immune and endothelial cells, and even projections of neuronal cells, adjust their shapes and move into growing tumoral masses, building tumor-induced structures that eventually serve as metastatic routes. Here we review the role of RhoGEFs in metastatic cancer. They are highly diverse proteins with common catalytic modules that select among a variety of homologous Rho GTPases enabling them to load GTP, acquiring an active conformation that stimulates effectors controlling actin cytoskeleton remodeling. Therefore, due to their strategic position in oncogenic signaling cascades, and their structural diversity flanking common catalytic modules, RhoGEFs possess unique characteristics that make them conceptual targets of antimetastatic precision therapies. Preclinical proof of concept, demonstrating the antimetastatic effect of inhibiting either expression or activity of βPix (ARHGEF7), P-Rex1, Vav1, ARHGEF17, and Dock1, among others, is emerging.

Epigenetic targets in B- and T-cell lymphomas: latest developments

Non-Hodgkin's lymphomas (NHLs) comprise a diverse group of diseases, either of mature B-cell or of T-cell derivation, characterized by heterogeneous molecular features and clinical manifestations. While most of the patients are responsive to standard chemotherapy, immunotherapy, radiation and/or stem cell transplantation, relapsed and/or refractory cases still have a dismal outcome. Deep sequencing analysis have pointed out that epigenetic dysregulations, including mutations in epigenetic enzymes, such as chromatin modifiers and DNA methyltransferases (DNMTs), are prevalent in both B- cell and T-cell lymphomas. Accordingly, over the past decade, a large number of epigenetic-modifying agents have been developed and introduced into the clinical management of these entities, and a few specific inhibitors have already been approved for clinical use. Here we summarize the main epigenetic alterations described in B- and T-NHL, that further supported the clinical development of a selected set of epidrugs in determined diseases, including inhibitors of DNMTs, histone deacetylases (HDACs), and extra-terminal domain proteins (bromodomain and extra-terminal motif; BETs). Finally, we highlight the most promising future directions of research in this area, explaining how bioinformatics approaches can help to identify new epigenetic targets in B- and T-cell lymphoid neoplasms.

Targeting small GTPases: emerging grasps on previously untamable targets, pioneered by KRAS

Small GTPases including Ras, Rho, Rab, Arf, and Ran are omnipresent molecular switches in regulating key cellular functions. Their dysregulation is a therapeutic target for tumors, neurodegeneration, cardiomyopathies, and infection. However, small GTPases have been historically recognized as "undruggable". Targeting KRAS, one of the most frequently mutated oncogenes, has only come into reality in the last decade due to the development of breakthrough strategies such as fragment-based screening, covalent ligands, macromolecule inhibitors, and PROTACs. Two KRAS^G12C covalent inhibitors have obtained accelerated approval for treating KRAS^G12C mutant lung cancer, and allele-specific hotspot mutations on G12D/S/R have been demonstrated as viable targets. New methods of targeting KRAS are quickly evolving, including transcription, immunogenic neoepitopes, and combinatory targeting with immunotherapy. Nevertheless, the vast majority of small GTPases and hotspot mutations remain elusive, and clinical resistance to G12C inhibitors poses new challenges. In this article, we summarize diversified biological functions, shared structural properties, and complex regulatory mechanisms of small GTPases and their relationships with human diseases. Furthermore, we review the status of drug discovery for targeting small GTPases and the most recent strategic progress focused on targeting KRAS. The discovery of new regulatory mechanisms and development of targeting approaches will together promote drug discovery for small GTPases.

Advances in the development of Rho GTPase inhibitors

Rho guanosine triphosphatases (Rho GTPases), as members of the Ras superfamily, are GDP/GTP binding proteins that behave as molecular switches for the transduction of signals from external stimuli. Rho GTPases play essential roles in a number of cellular processes including cell cycle, cell polarity as well as cell migration. The dysregulations of Rho GTPases are related with various diseases, especially with cancers. Accumulating evidence supports that Rho GTPases play important roles in cancer development and progression. Rho GTPases become potential therapeutic targets for cancer therapy. And a number of inhibitors targeting Rho GTPases have been developed. In this review, we discuss their structural features, summarize their roles in cancer, and focus on the recent progress of their inhibitors, which are beneficial for the drug discovery targeting Rho GTPases.

Potential of Synthetic and Natural Compounds as Novel Histone Deacetylase Inhibitors for the Treatment of Hematological Malignancies

Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are enzymes that remove or add acetyl groups to lysine residues of histones, respectively. Histone deacetylation causes DNA to more snugly encircle histones and decreases gene expression, whereas acetylation has the opposite effect. Through these small alterations in chemical structure, HATs and HDACs regulate DNA expression. Recent research indicates histone deacetylase inhibitors (HDACis) may be used to treat malignancies, including leukemia, B-cell lymphoma, virus-associated tumors, and multiple myeloma. These data suggest that HDACis may boost the production of immune-related molecules, resulting in the growth of CD8-positive T-cells and the recognition of nonreactive tumor cells by the immune system, thereby diminishing tumor immunity. The argument for employing epigenetic drugs in the treatment of acute myeloid leukemia (AML) patients is supported by evidence that both epigenetic changes and mutations in the epigenetic machinery contribute to AML etiology. Although hypomethylating drugs have been licensed for use in AML, additional epigenetic inhibitors, such as HDACis, are now being tested in humans. Preclinical studies evaluating the efficacy of HDACis against AML have shown the ability of specific agents, such as anobinostat, vorinostat, and tricostatin A, to induce growth arrest, apoptosis, autophagy and cell death. However, these inhibitors do not seem to be successful as monotherapies, but instead achieve results when used in conjunction with other medications. In this article, we discuss the mounting evidence that HDACis promote extensive histone acetylation, as well as substantial increases in reactive oxygen species and DNA damage in hematological malignant cells. We also evaluate the potential of various natural product-based HDACis as therapeutic agents to combat hematological malignancies.

Frontline Management of Nodal Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) represent only 10%-15% of all non-Hodgkin lymphoma but encompass a diverse group of diseases with over 30 different subtypes. As a result of both disease heterogeneity and rarity, therapeutic progress of PTCLs has lagged behind B-cell lymphomas with very few randomized controlled studies to guide management. The most common subtypes are the so-called nodal PTCLs: PTCL-not otherwise specified (NOS), anaplastic large cell lymphoma (ALCL), and nodal T follicular helper cell lymphoma (TFHL) lymphoma, the latter of which includes angioimmunoblastic T-cell lymphoma. Anthracycline-based primary chemotherapy is still the mainstay of treatment for these common PTCL subtypes, but in recent years, we have moved into an era where more personalized therapy can be applied in some settings. Cyclophosphamide, doxorubicin, prednisone, and brentuximab vedotin CHP-BV is the first therapy in PTCL to show an overall survival benefit and represents a new standard for ALCL; however, there is less therapeutic certainty in other CD30-positive PTCLs. Recurrent mutations of epigenetic modifier genes typify TFHLs lymphomas, and collective studies demonstrate a heightened sensitivity to epigenetic therapies, leading to trials integrating these agents in the frontline setting. Molecular studies of PTCL-NOS have defined at least two subtypes, GATA3 and TBX21, the former having a poorer prognosis, but how this guides therapeutics remains unknown. Outside of ALCL, there is a growing debate as to whether trials should focus on adding a novel agent to cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or whether combination novel therapies should be explored in the frontline therapy setting. Finally, the role of consolidative autologous stem-cell transplant in first remission remains an area of active debate.

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 Interplay between T Cells and Cancer: The Basis of Immunotherapy

Over the past decade, immunotherapy has emerged as one of the most promising approaches to cancer treatment. The use of immune checkpoint inhibitors has resulted in impressive and durable clinical responses in the treatment of various cancers. Additionally, immunotherapy utilizing chimeric antigen receptor (CAR)-engineered T cells has produced robust responses in blood cancers, and T cell receptor (TCR)-engineered T cells are showing promising results in the treatment of solid cancers. Despite these noteworthy advancements in cancer immunotherapy, numerous challenges remain. Some patient populations are unresponsive to immune checkpoint inhibitor therapy, and CAR T cell therapy has yet to show efficacy against solid cancers. In this review, we first discuss the significant role that T cells play in the body's defense against cancer. We then delve into the mechanisms behind the current challenges facing immunotherapy, starting with T cell exhaustion due to immune checkpoint upregulation and changes in the transcriptional and epigenetic landscapes of dysfunctional T cells. We then discuss cancer-cell-intrinsic characteristics, including molecular alterations in cancer cells and the immunosuppressive nature of the tumor microenvironment (TME), which collectively facilitate tumor cell proliferation, survival, metastasis, and immune evasion. Finally, we examine recent advancements in cancer immunotherapy, with a specific emphasis on T-cell-based treatments.

Unraveling the Oncogenic Potential of VAV1 in Human Cancer: Lessons from Mouse Models

VAV1 is a hematopoietic signal transducer that possesses a GDP/GTP nucleotide exchange factor (GEF) that is tightly regulated by tyrosine phosphorylation, along with adapter protein domains, such as SH2 and SH3. Research on VAV1 has advanced over the years since its discovery as an in vitro activated oncogene in an NIH3T3 screen for oncogenes. Although the oncogenic form of VAV1 first identified in the screen has not been detected in human clinical tumors, its wild-type and mutant forms have been implicated in mammalian malignancies of various tissue origins, as well as those of the hematopoietic system. This review article addresses the activity of human VAV1 as an overexpressed or mutated gene and also describes the differences in the distribution of VAV1 mutations in the hematopoietic system and in other tissues. The knowledge accumulated thus far from GEMMs expressing VAV1 is described, with the conclusion that GEMMs of both wild-type VAV1 and mutant VAV1 do not form tumors, yet these will be generated when additional molecular insults, such as loss of p53 or KRAS mutation, occur.

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.

Current Concepts in Nodal Peripheral T-Cell Lymphomas

This review summarizes the current understanding of mature T-cell neoplasms predominantly involving lymph nodes, including ALK-positive and ALK-negative anaplastic large cell lymphomas, nodal T-follicular helper cell lymphoma, Epstein-Barr virus-positive nodal T/NK-cell lymphoma, and peripheral T-cell lymphoma (PTCL), not otherwise specified. These PTCLs are clinically, pathologically, and genetically heterogeneous, and the diagnosis is made by a combination of clinical information, morphology, immunophenotype, viral positivity, and genetic abnormalities. This review summarizes the pathologic features of common nodal PTCLs, highlighting updates in the fifth edition of the World Health Organization classification and the 2022 International Consensus Classification.

An update on genetic aberrations in T-cell neoplasms

T-cell neoplasms are a highly heterogeneous group of leukaemias and lymphomas that represent 10-15% of all lymphoid neoplasms. Traditionally, our understanding of T-cell leukaemias and lymphomas has lagged behind that of B-cell neoplasms, in part due to their rarity. However, recent advances in our understanding of T-cell differentiation, based on gene expression and mutation profiling and other high throughput methods, have better elucidated the pathogenetic mechanisms of T-cell leukaemias and lymphomas. In this review, we provide an overview of many of the molecular abnormalities that occur in various types of T-cell leukaemia and lymphoma. Much of this knowledge has been used to refine diagnostic criteria that has been included in the fifth edition of the World Health Organization. This knowledge is also being used to improve prognostication and identify novel therapeutic targets, and we expect this progress will continue, eventually resulting in improved outcomes for patients with T-cell leukaemias and lymphomas.

Follicular Helper T-Cell-derived Nodal Lymphomas: Study of Histomorphologic, Immunophenotypic, Clinical, and RHOA G17V Mutational Profile

The study was designed to review the demographic, clinical, and pathologic characteristics of follicular helper T cells (TFH)-derived nodal PTCL in India including angioimmunoblastic T-cell lymphoma (AITL), peripheral T-cell lymphoma (PTCL) with follicular helper T cell phenotype (P-TFH), and follicular T-cell lymphoma with additional immunohistochemistry (IHC) and RHOAG17V mutational analysis, as well as their impact on survival. This retrospective study included 88 cases of PTCL that were reclassified using IHC for TFH markers (PD1, ICOS, BCL6, and CD10) and dendritic-meshwork markers (CD21, CD23). Cases of TFH cell origin were evaluated for RHOAG17V mutation using Sanger sequencing and amplification-refractory mutation system-polymerase chain reaction (PCR) (validated using cloning and quantitative PCR) with detailed clinicopathologic correlation. Extensive re-evaluation with added IHC panel resulted in a total of 19 cases being reclassified, and the final subtypes were AITL (37 cases, 42%), PTCL-not otherwise specified (44, 50%), P-TFH (6, 7%), and follicular T-cell lymphoma (1, 1%). The presence of at least 2 TFH markers (>20% immunopositivity) determined the TFH origin. AITL patients tended to be male and showed increased presence of B-symptoms and hepatosplenomegaly. Histomorphology revealed that 92% of AITL cases had pattern 3 involvement. Sanger sequencing with conventional PCR did not yield any mutation, while RHOAG17V was detected by amplification-refractory mutation system-PCR in AITL (51%, P =0.027) and P-TFH (17%), which was validated with cloning followed by sequencing. Cases of RHOAG17V-mutant AITL had a worse Eastern Cooperative Oncology Group performance status initially but fared better in terms of overall outcome ( P =0.029). Although not specific for AITL, RHOAG17V mutation shows an association with diagnosis and requires sensitive methods for detection due to low-tumor burden. The mutant status of AITL could have prognostic implications and translational relevance.

Pathologic and molecular insights in nodal T-follicular helper cell lymphomas

T-follicular helper (TFH) cells are one of the T-cell subsets with a critical role in the regulation of germinal center (GC) reactions. TFH cells contribute to the positive selection of GC B-cells and promote plasma cell differentiation and antibody production. TFH cells express a unique phenotype characterized by PD-1^hi, ICOS^hi, CD40L^hi, CD95^hi, CTLA^hi, CCR7^lo, and CXCR5^hi . Three main subtypes of nodal TFH lymphomas have been described: 1) angioimmunoblastic-type, 2) follicular-type, and 3) not otherwise specified (NOS). The diagnosis of these neoplasms can be challenging, and it is rendered based on a combination of clinical, laboratory, histopathologic, immunophenotypic, and molecular findings. The markers most frequently used to identify a TFH immunophenotype in paraffin-embedded tissue sections include PD-1, CXCL13, CXCR5, ICOS, BCL6, and CD10. These neoplasms feature a characteristic and similar, but not identical, mutational landscape with mutations in epigenetic modifiers (TET2, DNMT3A, IDH2), RHOA, and T-cell receptor signaling genes. Here, we briefly review the biology of TFH cells and present a summary of the current pathologic, molecular, and genetic features of nodal lymphomas. We want to highlight the importance of performing a consistent panel of TFH immunostains and mutational studies in TCLs to identify TFH lymphomas.