RHOA G17V Mutation Research Articles

A combination of 5-azacytidine and nivolumab is a potentially effective rescue therapy in relapsed/refractory AITL.

Angioimmunoblastic T-cell lymphoma (AITL) is a peripheral T-cell lymphoma characterized by a T follicular helper cell phenotype expressing PD-1 (programmed cell death-1). AITL exhibits a poor response to conventional chemotherapy, with a median 5-year overall survival of 44% and a progression-free survival of 32%. Relapse is common, resulting in a median overall survival of 6 months. Recurrent mutations are detected in genes regulating DNA methylation, including TET2, DNMT3A, and IDH2 variants, along with the prevalent RHOA G17V mutation. In this context, patients treated with the hypomethylating agent 5-azacytidine achieved overall response and complete response rates of 75% and 41%, respectively. We hypothesized that targeted therapies combining anti-PD-1 checkpoint blockers with hypomethylating agents could be efficient in AITL patients and less toxic than standard chemotherapy. Here, we report the efficacy of a regimen combining 5-azacytidine and nivolumab in nine relapsed or refractory AITL patients. This regimen was well-tolerated, especially in elderly patients. The overall response rate was 78%, including four partial responses (44%) and three complete responses (33%). Allogeneic hematopoietic stem cell transplantation was performed in two patients who reached complete response. These preliminary favorable results may serve as a basis for further investigation in prospective studies.

Role of plasma EBV-DNA load and EBER status on newly diagnosed peripheral T-cell lymphoma.

To explore the prognostic and therapeutic role of Epstein-Barr Virus (EBV) on peripheral T-cell lymphoma (PTCL). Totally 262 newly diagnosed PTCL patients who were hospitalized from January 2014 to December 2022 were retrospectively enrolled. Molecular analysis included 31 eligible patients. EBV-encoded RNA (EBER) presence in tumor tissue and EBV DNA levels in patients at baseline (DNA1) and after 4 cycles of chemotherapy (DNA4) were assessed. Our findings revealed that the EBER-positive cohort exhibited significant differences compared to counterparts in overall survival (OS, P = 0.047) and progression-free survival (PFS, P = 0.009). Both DNA1 and DNA4 were significantly associated with inferior OS. Multivariate analysis demonstrated that DNA4 independently affected PTCL prognosis for OS (hazard ratio = 5.1617; 95% confidence interval 1.1017-24.1831; P = 0.037). Treatment with the cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) plus azacytidine regimen showed a better OS compared to CHOP or CHOP plus etoposide for patients with partially positive EBER and EBER positive statuses (P = 0.192), although the improvement was not statistically significant. This study delineated the genetic paradigm of PTCL, comparing genetic differences by EBV status and found that EBER partially positive plus positive patients were more likely to have DNMT3A (P = 0.002), RHOAG17V (P = 0.023), and TET2 mutations (P = 0.032). EBER, DNA1, and DNA4 emerged as sensitive markers for prognosis. CHOP plus azacytidine might present a preferable option for PTCL patients with DNA methylation due to EBV infection.

Clinical and histological study of follicular helper T-cell lymphomas with indolent evolution

IntroductionFollicular helper T-cell lymphomas (TFHL) have an aggressive course with a poor outcome. European and US guidelines recommend anthracycline-based chemotherapy as a first-line treatment, but the 5-year overall survival rate is still approximately 30%. We describe here the features of a cohort of TFHL patients who experienced prolonged survival despite the absence of specific treatment or the initiation of steroid-based therapy. Patients and methodsIn our study, we describe 15 adult patients who suffered from TFHL and had not received intensive chemotherapy at diagnosis for any reason. Biopsies of these cases were centrally reviewed, and the mutational pattern was determined using next-generation sequencing. ResultsThese 15 patients had the classic clinical, biological and pathological features of TFHL, angioimmunoblastic-type. TET2 mutations were found in 83% of patients; RHOA G17V, IDH2 R172 and DNMT3A mutations were found in 67%, 42% and 33% of the patients, respectively. Among the 15 patients, 8 did not receive any treatment, and 7 received steroid-based treatment. Ten patients had progression (5 in each group). Four patients died (3 of them from the progression of their lymphoma). The median follow-up in our cohort was 53 months. The 5-year OS was 66%, 100% for untreated patients and 29% for the others. In those 2 groups, the median time to treatment initiation was 22 months from diagnosis. ConclusionWe described a series of 15 well-characterized TFHL patients with an indolent outcome, suggesting that a watch-and-wait approach can be proposed in selected patients. Identifying factors predicting such evolution is warranted.

Significance of the Rhoa G17V Mutation Detected By Ddpcr in Diagnostic and Monitor of Angioimmunoblastic T-Cell Lymphoma

Introduction Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma (PTCL) that originates from T follicular helper cells (TFH). RHOA G17V mutation is the most common hotspot locus which could be detected in 50%-70% of cases, showing its potential value for the diagnosis and clinical monitor of this disease. Methods RHOA G17V mutation were detected by Droplet digital PCR (ddPCR) in available samples from PTCL patients, at baseline and before every cycle. Response assessments were done by PET/CT and evaluated according to Lugano criteria after 3 cycles and end of first line chemotherapy(EOT), or at suspicious of disease progression. All data analyses were performed using SPSS 20.0 software (SPSS, Inc.) and GraphPad Prism 9.0 software (GraphPad software). p-Value < 0.05 was considered statistically significant. Results 30 patients with PTCL were included in our center from 2021-01-01 to 2023-07-01,21 were confirmed as AITL and 9 were PTCL-NOS by pathologist review. In whole cohort, RHOA G17V mutation could be detected in 46.7%(14/30) of all patients, also was positive in 61.9%(13/21) and negative in 38.1% (9/21) of patients with AITL. The sensitivity and specificity of RHOA G17V mutation in AITL by ddPCR is 61.9% and 88.9%, with a positive predictive value of 92.9%, and a negative predictive value of 50%. Hyperglobulinemia, positive direct Coombs test, elevated LDH, elevated β2-MG were founded in 76.9%(10/13),61.5%(8/13) ,61.5%(8/13) and 76.9% (10/13) of AITL patients with RHOA G17V mutation, which were significantly higher than those without RHOA G17V mutation(P=0.002,0.019,0.019,0.026). Furthermore, all of the of RHOA G17V mutated AITL patients were in clinical stage III or IV(100%, 13/13), 76.9%(10/13) of them with detectable whole-blood EBV-DNA(≥500 copies/mL) and all have three or more TFH markers(100%,13/13). We next evaluated the baseline and dynamical changes in RHOA G17V VAF-positive patients with AITL. Pretreatment VAF was significantly lower for patients who achieved complete remission or partial remission at EOT compared with that of patients with progressive disease or stable disease (mean VAF, 20.75% vs. 4.31%, p = 0.0028). (Figure 1). In addition, the median PFS in AITL patients with and without RHOA G17V mutation was 9.157 months and 15.154 months respectively(P=0.32).Finally, in 10 AITL patients with dynamic results of RHOA G17V mutation (Figure 2) , a good correlation was found in between dynamic changes of VAF of RHOA G17V mutation and response assessment by PET/CT, rerise of RHOA G17V mutation VAF could be detected prior to clinical progression in two patients，showing for the its protentional value for disease monitor. Conclusions Our study first reported the diagnostic value of single hotspot detection of G17V RHOA mutation by ddPCR in PTCL. Monitoring of G17V RHOA mutation in AITL has predictive value of assess tumor burden and response, also can complement the longitudinal supervise of disease.

Role of the S1P Signaling Pathway in the Pathogenesis of Angioimmunoblastic T-Cell Lymphoma

Peripheral T cell lymphomas (PTCLs) are a group of aggressive lymphoid malignancies originating from mature T cells. Angioimmunoblastic T-cell lymphomas (AITL) represent 20% to 30% of all PTCL diagnoses and are associated with autoimmune features, poor response to chemotherapy, and dismal prognosis. Molecular profiling of AITL has identified T-follicular helper (TFH) cells as the cell of origin of AITL, while mutational analysis has identified frequent alterations in epigenetic regulators ( TET2, DNMT3A, and IDH2) and elements of the TCR pathway as drivers of AITL transformation. Our group identified the highly recurrent RHOA G17V mutation as a defining hallmark of AITL and other T-cell lymphomas of TFH-cell origin (Palomero et al., 2014). Using a novel conditional knockin mouse model, we demonstrated that expression of Rhoa G17V in CD4+ T-cells induces TFH cell specification and promotes AITL lymphomagenesis in the context of loss of Tet2 (Cortes et al., 2018). Recently, we have identified that Rhoa G17V regulates the expression of the sphingosine-1-phosphate (S1P) receptor 1 (S1PR1) one of the five members of the receptor family of S1P, which plays an essential role in immune response and lymphocyte trafficking. During thymic T-cell development, expression of Rhoa G17V in CD4+ cells inhibited S1PR1 downregulation after the double positive stage leading to altered positive selection, reduced CD4+ single positive cell numbers and premature thymic egress of autorreactive T-cells which results in the development of systemic inflammation and autoimmunity. In our Tet2 −/− RHOA G17V AITL tumor model, constitutive activation of S1P receptors supported activation of the STAT3 and NFkB pathway and enhanced migration of malignant cells to peripheral organs. Mechanistically, expression of Rhoa G17V in mature CD4+ T-cells impaired re-phosphorylation of the Ezrin-Radoxin-Moesin (ERM) complex independently of ROCK signaling and led to the activation and increased migration of CD4+ T-cells. Importantly, blockade of S1PR1 signaling by fingolimod induced anti-tumor activity in Tet2 −/− RHOA G17V lymphoma-bearing mice in vivo with significant reductions in tumor burden associated with increased apoptosis and decreased STAT3 phosphorylation. Furthermore, analysis of a panel of primary tumors from AITL patients using a multiplexed staining panel and PhenoImager platform revealed significantly higher S1PR1 expression in AITL tumor cells than normal TFH cells from benign reactive lymph nodes. Our findings highlight the role of S1P signaling pathway in the pathogenesis of RHOA G17V-driven AITLs and the potential therapeutic benefit of targeting this pathway.

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.

CLONAL ARCHITECTURE OF RELAPSED OR REFRACTORY FOLLICULAR HELPER T‐CELL LYMPHOMA: AN ANCILLARY STUDY OF THE ORACLE TRIAL, A LYSA STUDY

Follicular helper T-cell lymphoma (TFHL) results from the oncogenic transformation of a TFH cell, driven by mutations in genes involved in epigenetic regulation (TET2, DNMT3A, IDH2) and T-cell signaling (RHOA). Demonstration of TET2 and DNMT3A mutations in B cells, myeloid cells, or hematopoietic progenitor cells have suggested that TFHL can emerge from clonal hematopoiesis (CH) in a multi-step process. However, the frequency, the extension, and the relevance of such CH in TFHL oncogenesis are unclear. To describe and characterize the clonal architecture of refractory/relapsed (R/R) TFHL, we collected bone marrow samples of patients included in the ORACLE trial (NCT03593018), a phase 3 trial evaluating the oral 5-azacitidine (CC-486) compared to single-agent chemotherapy in patients with R/R TFHL. Bone marrow (BM) cells from 32 patients at inclusion were cultured in methylcellulose supplemented with standard growth factors. BFU-E, CFU-GM, and CFU-GEMM were counted and individually harvested. A total of 517 colonies derived from the 32 patients were then individually genotyped by next-generation sequencing (NGS) using a capture-based panel (limit of detection: 1%) covering 43 genes recurrently mutated in CH and/or TFHL, including TET2, DNMT3A, IDH2, and RHOA. Meanwhile, bulk BM cells from 29 patients were sequenced with the same NGS panel and then compared to the mutations found in cfDNA (31 patients) and tumor biopsies (28 patients). Overall, the frequency of CH and the phylogenetic link between the myeloid progenitors and the TFHL was evaluable in 30 TFHL patients. We successfully genotyped 471/517 (91%) colonies. CH defined by at least one somatic mutation detected in at least one myeloid colony or total BM cells was found in 29/30 (97%) patients. Among the 26/29 patients with mutated myeloid colonies, the median percentage of mutated colonies was 21% (IQR 7%–53%) and 7 had subclonal architecture with a median of 3 different clones. The 2 most frequent mutations were DNMT3A and TET2, detected in 24/30 (80%) and 18/30 (60%) patients' BM, respectively. We confirmed the absence of RHOAG17V and IDH2R172 mutations in BM cells of TFHL patients. While 17/18 patients with a detectable TET2 mutation in CH had a TET2 mutated TFHL, only 13/23 patients with a DNMT3A mutated CH had a DNMT3A mutated TFHL. We thus identified 3 groups of patients according to the distribution of mutations found in the BM and the LN lymph nodes: 16/30 (53.3%) patients had a TFHL clonally derived from CH (CH-related TFHL), 13 (43.3%) had TFHL, and clonally distinct CH (CH-unrelated TFHL), and one patient (3.3%) had undetectable CH. No significant difference in patient outcome was observed regarding the presence of CH-related or unrelated TFHL, but our results are limited by the small number of patients and treatment heterogeneity. Encore Abstract—previously submitted to EHA 2023 Keywords: aggressive T-cell non-Hodgkin lymphoma, tumor biology and heterogeneity No conflicts of interests pertinent to the abstract.

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.

Flow Cytometry Analysis Reveals a Wide Cytologic and Immunophenotypic Spectrum of Peripheral B Lymphocytes in Angioimmunoblastic T-Cell Lymphoma

Introduction: Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive T-cell lymphoma commonly associated with B-cell dysregulation. Correlations involving B-cell dysregulation and clinicopathological features remain unclear. Methods: We prospectively collected blood samples from 11 AITL patients and 17 healthy controls. The percentages of B-cell subpopulations and lymphocytes with IL-21 production were assessed using flow cytometry. Peripheral blood lymphocyte morphology was evaluated microscopically. Results: Six of 11 (54.5%) patients presented with polyclonal hypergammaglobulinemia. Three of 11 (27.3%) tumor biopsies showed monoclonal immunoglobulin gene rearrangement. The patients exhibited significantly lower levels of naive (p < 0.001) and class-switched (p < 0.001) B cells than controls. The percentages of IgD−CD27− B cells (p = 0.007) and antibody-secreting cells (ASCs) (p = 0.001) were increased. Blood smears revealed atypical lymphocytes and immature plasma cells with morphological diversity. In comparison to normal controls, IL-21 production significantly increased in CD4+ (p < 0.001) and CD8+ (p = 0.020) T cells. B-cell clonality, RHOA G17V mutation, and the presence of sheets of clear cells and immature/mature plasma cells in lymph nodes were significantly associated with percentages of class-switched B cells and ASCs. The patients with circulating EBV DNA had a lower percentage of naive B cells (p = 0.009). Conclusions: Our results demonstrated a wide spectrum of peripheral B-cell morphologies and immunophenotypes of peripheral B cells in AITL. These findings correspond to dysregulated B-cell immunity and heterogeneous clinicopathological features.

Single-Cell Transcriptome Reveals Comprehensive Immune Profiles of T Follicular Helper Cell Lymphoma

Background: Angioimmunoblastic T-cell lymphoma and other nodal lymphomas of T follicular helper (TFH) cell origin (TFH lymphoma) have a poor prognosis and are associated with immune dysregulation. However, comprehensive immune profiles of TFH lymphoma have not been fully investigated. The RHOA G17V mutation (G17V) is a disease-specific mutation found in 60-70% of TFH lymphoma and considered to gain a novel function through binding to VAV1 protein. Nevertheless, the prevalence of homozygous (Homo) and heterozygous (Hetero) G17V mutations and the difference in their oncogenicity due to its zygosity have not been elucidated. Here, we performed single-cell transcriptomic analysis to characterize tumor and immune cells of TFH lymphoma. Methods: We performed single-cell RNA sequencing (scRNA-seq) and T-cell/B-cell receptor sequencing (scTCR/BCR-seq) for 9 lymph nodes (LNs) and 16 peripheral blood (PB) from 14 TFH lymphoma patients (9 at initial diagnosis [ID] and 5 at relapsed/refractory diagnosis [RR]), as well as 7 homeostatic LNs (HLNs) from patients with solid cancers (Fig. 1). Whole-exome sequencing (WES) was also performed for genetic mutation analysis using bulk DNA extracted from tumor tissues and PB of the same cohort as scRNA-seq. scRNA-seq and scTCR/BCR-seq libraries were constructed using the Chromium system (10x Genomics). Publicly available scRNA-seq data from 5 healthy donors (HDs) were also integrated as control. scRNA-seq data analysis was performed by Seurat, Scater, and Batchelor for quality control, integration, and clustering; SingleR for annotation; Immunarch for TCR/BCR repertoire analysis; gene set variation analysis (GSVA) for pathway analysis, and CellPhoneDB for cell-cell interaction analysis. Genomon2 pipeline was used for calling somatic mutations in WES data. Subsequently, VarTrix was applied to estimate mutations detected by WES in scRNA-seq data. Results: In total, 68,738 cells from LNs and 98,891 cells from PB were analyzed. Unsupervised clustering and annotation by canonical markers identified 4 major cell types: CD4/CD8+ T, natural killer (NK), B, and myeloid cells. Tumor cells were identified by the expanded TCR clonality and the TFH-like gene expression signatures. Next, using scRNA-seq data, we reanalyzed a total of 393 somatic mutations discovered by WES and identified 15 mutations in more than 5 cells of scRNA-seq data, of which only RHOA G17V was identified in multiple samples. G17V-mutated cells were detected in 4 LN and 6 PB samples, mostly restricted to tumor cells. G17V-Homo and Hetero cells were identified based on frequency of mutant reads. Differentially expression gene (DEG) analysis and GSVA in G17V-mutated tumor cells of LNs revealed that the regulatory signature was significantly activated in Homo, whereas the proliferation signature was up-regulated in Hetero. Additionally, DEG analysis identified three tumor-specific gene candidates and the expression of cell surface protein PLS3 was validated by flow cytometry and immunohistochemistry. Subsequently, we performed sub-clustering and GSVA of immune cells and found that dysfunctional CD8 T cells were significantly increased in LNs and PB of patients compared to controls and exhibited oligoclonal expansion by TCR repertoire analysis. Notably, TREG, complement component 1q positive macrophages (C1Q+ Mφ), and LAMP3+ dendritic cells (DCs) were significantly increased in LNs from patients with RR diseases than HLNs. DEG analysis and GSVA revealed high expression of PD-L1 and regulatory signatures in LAMP3+ DCs. Moreover, genes related to immune suppression were significantly upregulated in TREG of patients compared to those of controls. Finally, cell-cell interaction analysis uncovered that tumor cells and TREG of RR patients strongly interacted with C1Q+ Mφ and LAMP3+ DCs via CXCR3-CXCL9 and CCR4-CCL17 interactions, respectively, indicating that these myeloid cells not only induced TREG into tumor tissues but also actively interacted with tumor cells. Conclusion: Tumor cells of TFH lymphoma acquired the immunosuppressive signature in the clonal evolution process from the G17V Hetero to Homo. Furthermore, comprehensive immune profiling of TFH lymphoma revealed expansion of cells involved in the immune escape. These results unveiled the enrichment of immune evasive phenotypes in TFH lymphoma and suggested their contribution to treatment resistance in RR patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

RHOA G17V induces T follicular helper cell specification and involves angioimmunoblastic T-cell lymphoma via upregulating the expression of PON2 through an NF-κB-dependent mechanism

ABSTRACT Angioimmunoblastic T-cell lymphoma (AITL) is a malignant hematologic tumor arising from T follicular helper (Tfh) cells. High-throughput genomic sequencing studies have shown that AITL is characterized by a novel highly recurring somatic mutation in RHOA, encoding p.Gly17Val (RHOA G17V). However, the specific role of RHOA G17V in AITL remains unknown. Here, we demonstrated that expression of Rhoa G17V in CD4+ T cells increased cell proliferation and induces Tfh cell specification associated with Pon2 upregulation through an NF-κB-dependent mechanism. Further, loss of Pon2 attenuated oncogenic function induced by genetic lesions in Rhoa. In addition, an abnormality of RHOA G17V mutation and PON2 expression is also detected in patients with AITL. Our findings suggest that PON2 associated with RHOA G17V mutation might control the direction of the molecular agents-based AITL and provide a new therapeutic target in AITL.

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

AbstractAngioimmunoblastic T-cell lymphoma (AITL) is proposed to be initiated by age-related clonal hematopoiesis (ACH) with TET2 mutations, whereas the G17V RHOA mutation in immature cells with TET2 mutations promotes the development of T follicular helper (TFH)-like tumor cells. Here, we investigated the mechanism by which TET2-mutant immune cells enable AITL development using mouse models and human samples. Among the 2 mouse models, mice lacking Tet2 in all the blood cells (Mx-Cre × Tet2flox/flox × G17V RHOA transgenic mice) spontaneously developed AITL for approximately up to a year, while mice lacking Tet2 only in the T cells (Cd4-Cre × Tet2flox/flox × G17V RHOA transgenic mice) did not. Therefore, Tet2-deficient immune cells function as a niche for AITL development. Single-cell RNA-sequencing (scRNA-seq) of >50 000 cells from mouse and human AITL samples revealed significant expansion of aberrant B cells, exhibiting properties of activating light zone (LZ)-like and proliferative dark zone (DZ)-like germinal center B (GCB) cells. The GCB cells in AITL clonally evolved with recurrent mutations in genes related to core histones. In silico network analysis using scRNA-seq data identified Cd40–Cd40lg as a possible mediator of GCB and tumor cell cluster interactions. Treatment of AITL model mice with anti-Cd40lg inhibitory antibody prolonged survival. The genes expressed in aberrantly expanded GCB cells in murine tumors were also broadly expressed in the B-lineage cells of TET2-mutant human AITL. Therefore, ACH-derived GCB cells could undergo independent clonal evolution and support the tumorigenesis in AITL via the CD40–CD40LG axis.

Integrated clinical and genomic evaluation of guadecitabine (SGI-110) in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare, heterogenous malignancy with dismal outcomes at relapse. Hypomethylating agents (HMA) have an emerging role in PTCL, supported by shared mutations with myelodysplasia (MDS). Response rates to azacitidine in PTCL of follicular helper cell origin are promising. Guadecitabine is a decitabine analogue with efficacy in MDS. In this phase II, single-arm trial, PTCL patients received guadecitabine on days 1–5 of 28-day cycles. Primary end points were overall response rate (ORR) and safety. Translational sub-studies included cell free plasma DNA sequencing and functional genomic screening using an epigenetically-targeted CRISPR/Cas9 library to identify response predictors. Among 20 predominantly relapsed/refractory patients, the ORR was 40% (10% complete responses). Most frequent grade 3-4 adverse events were neutropenia and thrombocytopenia. At 10 months median follow-up, median progression free survival (PFS) and overall survival (OS) were 2.9 and 10.4 months respectively. RHOAG17V mutations associated with improved PFS (median 5.47 vs. 1.35 months; Wilcoxon p = 0.02, Log-Rank p = 0.06). 4/7 patients with TP53 variants responded. Deletion of the histone methyltransferase SETD2 sensitised to HMA but TET2 deletion did not. Guadecitabine conveyed an acceptable ORR and toxicity profile; decitabine analogues may provide a backbone for future combinatorial regimens co-targeting histone methyltransferases.

Germinal Center B Cells Derived from TET2-Mutated Clonal Hematopoiesis Provide a Microenviromental Niche for Tumor Cells in Angioimmunoblastic T-Cell Lymphoma

Germinal Center B Cells Derived from TET2-Mutated Clonal Hematopoiesis Provide a Microenviromental Niche for Tumor Cells in Angioimmunoblastic T-Cell Lymphoma

Single-Cell and Spatial Analyses Characterize Distinct Subsets of Malignant T Cells in Angioimmunoblastic T Cell Lymphoma

IntroductionAngioimmunoblastic T-cell lymphoma (AITL) is the most frequent of nodal peripheral T-cell lymphomas. AITL results from the transformation of T follicular helper (T FH) cells and is characterized by chemo-resistance and poor survival (5-year OS around 30%). Recent data from prospective clinical trials suggest that disease outcome may be impacted by factors other than genomic features, such as the tumor microenvironment (TME) and overall intra-tumoral heterogeneity. Our understanding of AITL intra-tumoral genetic, transcriptional and functional heterogeneity is limited because most molecular data generated so far have come from bulk analyses. Single-cell RNA sequencing (scRNA-seq) enables fine characterization of cell types and functional cell states. When focused on T or B cells, 5'-end scRNA-seq also yields the TCR or BCR sequences that allow tracking clonally related cells. Here we studied the intra-tumor heterogeneity of AITL tumors using integrative scRNA-seq.MethodsWe analyzed lymph node live cell suspensions from AITL patients (n=10) using droplet-based 10x Genomics 5'-end scRNA-seq. Malignant T cells from 4 AITL samples were also analyzed by FACS index sorting and plate-based 5'-end scRNA-seq to link cell surface phenotype and gene expression profile. We identified malignant T cell clones by intersecting the gene expression and TCR sequencing data, and performed separate focused analyses of TME subsets and malignant T cells. We compared subsets of malignant T cells from all patients using marker gene-based metaclustering to identify AITL T cell states conserved across patients. We explored the genetic heterogeneity of malignant T cells by mapping RHOA G17V mutations and inferring copy number variation (CNV) subclones from scRNA-seq data. In select cases, we performed in situ analysis by immunohistochemistry (IHC) or spatial transcriptomics to characterize the spatial distribution of malignant T cell subsets identified by scRNA-seq.ResultsBased on gene expression, malignant T cells grouped in patient-specific clusters, while non-malignant T, B and myeloid TME cells from all patients clustered by cell type or cell state. Among TME cells, we identified 7 subsets of B cells (including activated B cells, plasma cells, and one patient-specific monoclonal B cell proliferation), 6 subsets of myeloid cells (including macrophages, conventional and plasmacytoid dendritic cells), and 8 subsets of non-malignant T cells (including activated cytotoxic T lymphocytes (CTL) with clonal expansions). Patient-specific malignant T cells were heterogeneous and divided into several gene-expression based clusters. Metaclustering of malignant T cell subsets identified T central memory (T CM)-like and T FH-like states in 10/10 samples. We also identified in 3/10 samples clusters of CTL-like malignant T cells expressing characteristic marker genes (including NKG7, GNLY, GZMK, PRF1). We observed an intra-sample continuum of gene expression states from quiescent T CM-like to proliferating T FH-like states. T FH-like cells were larger in size and expressed higher levels of surface PD1 and ICOS than T CM-like and CTL-like subsets. We detected the RHOA G17V mutation in malignant T cells of 4/4 mutated cases, with no evidence of subclonal heterogeneity for that mutation. We detected clonal and subclonal CNV in most AITL malignant T cells. CTL-like states were enriched in specific CNV subclones, but the T CM-like to T FH-like continuum was observed in all CNV subclones, suggesting that functional plasticity and subclonal genetic evolution may occur independently. In situ staining of markers for T FH-like (PD1, ICOS, CD200) and CTL-like (GZMK, GZMA) cells showed that T FH-like and CTL-like cells occupied distinct tissue niches within the tumor. In spatial transcriptomics analysis, T FH-like cells mapped to follicular dendritic cell (FDC)-rich areas, while T CM-like cells were associated with T-zone reticular cells.ConclusionsOur analyses recapitulate known characteristics of AITL TME, and uncover previously unrecognized heterogeneity among malignant T cells across multiple patients. The distinct gene expression programs, phenotypes, genetics, and locations of T FH-like, T CM-like and CTL-like states suggest that AITL malignant T cells undergo significant functional plasticity and genetic divergence, which could influence response to therapy and overall clinical course. [Display omitted] DisclosuresLemonnier: Institut Roche: Research Funding; Gilead: Other: travel grant. Gaulard: Gilead: Consultancy; Innate Pharma: Research Funding; Sanofi: Research Funding; Alderaan: Research Funding; Takeda: Consultancy, Honoraria. Milpied: Institut Roche: Research Funding; Innate Pharma: Research Funding; Bristol Myers Squibb: Research Funding.

Rhoa Mutation Is a Potential Biomarker Associated with Adverse Prognosis and High- Tumor Burden in Patients with Nodal Peripheral Lymphomas with T-Helper Follicular Phenotype (nPTCL-Thf): Data from a Brazilian Retrospective Cohort of Nodal PTCL

Introduction: Nodal PTCL constitute a rare group of aggressive malignancies with heterogeneous clinical-biological presentation and outcomes. In the last decade, its pathophysiological knowledge has been improved, with descriptions of gene mutations associated with epigenetic phenomena (IDH2, TET2 and DNMT3A) and of the RHOA G17V mutation playing a fundamental role in the lymphomagenesis. However, the prognostic impact of these alterations is still controversial, and particularly, in the case of the RHOA mutation, it has never been previously accessed in the literature. Our group has described and validated biomarkers with potential prognostic impact in nPTCL patients, including overexpression of the genes CCNA2, GATA3 and monocytosis in peripheral blood [1,2,3]. The identification of new potential molecular biomarkers can refine the prognostic stratification of these tumors and allow identification of targets for future specific therapies. The aim of this study was to evaluate the frequency and prognostic impact of mutations in the IDH2, TET2, DNMT3 and RHOA genes in Brazilian patients with nPTCL.Methods: In this observational, retrospective and unicentric study, we analyzed the clinical-epidemiological characteristics, outcomes and mutational profile of 59 Brazilian patients with nPTCL treated at the HC-FMUSP, from January 2000 to December 2017. All cases were submitted to centralized histopathological review and were classified according to the criteria proposed by WHO-2008. Cases initially categorized as PTCL/NOS were later reclassified according to WHO-2016 criteria. FFPE-tumor samples from patients with PTCL/NOS, AITL, ALK+/ALCL and ALK-/ALCL were submitted to DNA extraction using QIAmp DNA FFPE kit. For amplification of specific products of target-genes primers flanking the hot spots regions were designed. After this step, the PCR products were submitted to first generation sequencing in 3500 Genetic Analyzer. Absolute and relative frequencies of mutations were accessed for the total cohort and its pathological subtypes. OS and PFS curves were constructed using the Kaplan-Meier method. Log-rank test was used to estimate the prognostic impact of mutations.Results: The clinical-epidemiological characteristics of the 59 Brazilian-patients with nPTCL are summarized in Table 1. With a median follow-up of 3.70 years (0.90-12.4 years), the estimated 2-years OS and PFS were 59.1% and 47.2%, respectively. ORR was 55.9% (33/59), with early relapse rate (< 12 months) of 14.3% (5/59) and global death rate of 52.5% (31/59). In the total cohort, we found a mutation frequency of 3.4% (2/59) for the IDH2 gene, 62.7% (37/59) for DNMT3A, 23.7% (14/59) for RHOA and 50.8% (30/59) for TET2. There was no statistically significant difference in the frequency distribution of IDH2, DNMT3A and TET2 mutations between the different histological subtypes of nPTCL. However, there was a statistical trend towards a higher occurrence of the RHOA mutation in the AITL and PTCL/NOS subtypes (3/9-33.3% and 7/16-43.7%, respectively; p=0.07). Among 7 cases with RHOA mutation classified as PTCL/NOS according WHO-2008 criteria, 6/7 (85.7%) expressed the PD-1 marker in immunohistochemistry, being reclassified as nPTCL with THf phenotype according to WHO-2016 criteria. So, the mutation RHOA was predominantly found in THf cell-derived neoplasms in our cohort. The mutational status of DNMT3A, RHOA and TET2 genes had no prognostic impact on OS, with p=0.85, p=0.13 and p=0.95, respectively. The same was observed in relation to PFS for the DNMT3A (p=0.70) and TET2 (p=0.52) mutations. However, the presence of the RHOA mutation was associated with the unfavorable PFS in our cohort (HR:1.98, p=0.05). We observed 2-year PFS of 28.6% (95% CI: 8.8-52.4%) for mutated-RHOA cases versus 52.9% (95% CI: 37.3-66.3%) for wild-type-RHOA patients (p=0.05) [Figure 1]. We also demonstrated that RHOA mutation was a predictor of lower ORR to first-line therapy (p=0.01) and was associated with high tumor burden (p=0.03) [Figure 2].Conclusion: In this study, for the first time was demonstrated the unfavorable prognostic impact of the RHOA mutation in patients with nPTCL-Thf (AITL and nPTCL-THf), making it a potential molecular biomarker predictor of poor-PFS, associated with resistance to primary therapy and with high tumor burden. Such results are preliminary and will need to be validated in series with a larger number of cases. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Peripheral T-cell lymphoma: molecular profiling recognizes subclasses and identifies prognostic markers

AbstractPeripheral T-cell lymphoma (PTCL) is a clinically aggressive disease, with a poor response to therapy and a low overall survival rate of approximately 30% after 5 years. We have analyzed a series of 105 cases with a diagnosis of PTCL using a customized NanoString platform (NanoString Technologies, Seattle, WA) that includes 208 genes associated with T-cell differentiation, oncogenes and tumor suppressor genes, deregulated pathways, and stromal cell subpopulations. A comparative analysis of the various histological types of PTCL (angioimmunoblastic T-cell lymphoma [AITL]; PTCL with T follicular helper [TFH] phenotype; PTCL not otherwise specified [NOS]) showed that specific sets of genes were associated with each of the diagnoses. These included TFH markers, cytotoxic markers, and genes whose expression was a surrogate for specific cellular subpopulations, including follicular dendritic cells, mast cells, and genes belonging to precise survival (NF-κB) and other pathways. Furthermore, the mutational profile was analyzed using a custom panel that targeted 62 genes in 76 cases distributed in AITL, PTCL-TFH, and PTCL-NOS. The main differences among the 3 nodal PTCL classes involved the RHOAG17V mutations (P < .0001), which were approximately twice as frequent in AITL (34.09%) as in PTCL-TFH (16.66%) cases but were not detected in PTCL-NOS. A multivariate analysis identified gene sets that allowed the series of cases to be stratified into different risk groups. This study supports and validates the current division of PTCL into these 3 categories, identifies sets of markers that can be used for a more precise diagnosis, and recognizes the expression of B-cell genes as an IPI-independent prognostic factor for AITL.

Bio-O2-08 - Mutational landscape of nodal peripheral T-cell lymphoma subtypes

<h3>Introduction:</h3> Nodal peripheral T-cell lymphoma (PTCL) subclassification (Angioimmunoblastic TCL, PTCL-with T Follicular Helper phenotype and PTCL-NOS) and therapeutic targeting is still controversial. Overall survival (OS) is only around 30% after 5 years. <h3>Methods:</h3> We performed targeted next-generation sequencing of 61 selected genes in 76 PTCL patients. Among the 76cases, 44 were classified as AITL, 18 as PTCL-TFH and 14 as PTCL-NOS. <h3>Results:</h3> Our analysis revealed a wide variety of genetic variants that possibly drive the development of AITL, PTCL-TFH and/or PTCL-NOS. We identified an average of 4 variants per patient, mainly clustered in genes regulating chromatin conformation (TET2, DNMT3A) and T-cell differentiation (RHOA, MTOR, IDH2, VAV1 and NOTCH1). More frequently mutated genes were TET2 (76,31%) and DNMT3A (27,63%). Multiple mutations were found in TET2, VAV1, RHOA, NOTCH1, MTOR, JAK1, ZEB1, ATM, DNMT3A and ARID1B. Main difference among the three Nodal PTCL classes was the higher frequency of RHOAG17V mutations (p<0.0001), present approximately 2 times more frequently in AITL cases (34,09%) than in PTCL-TFH (16,66%), and they were not detected in PTCL-NOS. All three Nodal PTCL subtypes share finding suggesting Clonal Hematopoiesis (CH) in TET2 and DNMT3A genes. Cases with higher variant allele frequencies (VAF)s in TET2 and DNMT3A genes vs. other mutated genes were attributed to CH. In our study we found this phenomenon to take place in all Nodal PTCL subtypes (AITL: 31,8%; PTCL-TFH: 50%; PTCL-NOS: 35,71%). A correlation was not found between specific mutations, mutational index, mutations attributed to CH and clinical outcome. <h3>Conclusions:</h3> There is a common molecular basis for the three Nodal PTCL with very frequent mutations in genes regulating chromatin conformation associated with mutations in genes governing T-cell differentiation. RHOA G17V mutations were highly significant enriched in AITL. Findings suggesting Clonal Hematopoiesis were found in the three types of nodal PTCL.

RHOA MUTATION IS A POTENTIAL BIOMARKER ASSOCIATED WITH ADVERSE PROGNOSIS AND HIGH- TUMOR BURDEN IN PATIENTS WITH NODAL PERIPHERAL LYMPHOMAS WITH T-HELPER FOLLICULAR PHENOTYPE (NPTCL-THF): DATA FROM A BRAZILIAN RETROSPECTIVE COHORT OF NPTCL

Nodal-PTCL constitute a rare group of aggressive malignancies with heterogeneous clinical-biological presentation and outcomes. Recently its pathophysiological knowledge has been highly improved, with descriptions of gene mutations associated with epigenetic phenomena and of the RHOA G17V mutation playing a fundamental role in the lymphomagenesis. However, the prognostic impact of these alterations is still controversial, and particularly, in the case of the RHOA mutation, it has never been previously accessed in the literature. The aim of this study was to evaluate the frequency and prognostic impact of mutations in the IDH2, TET2, DNMT3 and RHOA genes in Brazilian patients with nPTCL. In this observational, retrospective and unicentric study, we analyzed the clinical-epidemiological characteristics, outcomes and mutational profile of 59 Brazilian patients with nPTCL treated at the HC-FMUSP, from January 2000 to December 2017. All cases were submitted to centralized histopathological review and were classified according to the criteria proposed by WHO-2016. FFPE tumor samples from patients with PTCL/NOS, AITL, ALK+/ALCL and ALK-/ALCL were deparaffinized and submitted to DNA extraction using QIAmp DNA FFPE kit. For amplification of specific products of target-genes primers flanking the hot spots regions were designed. After this step, the PCR products were submitted to first generation sequencing. Absolute and relative frequencies of mutations were accessed for the total cohort and its pathological subtypes. OS and PFS curves were constructed using the Kaplan-Meier method. Log-rank test was used to estimate the prognostic impact of mutations in the studied population. With a median follow-up of 3.70 years, the estimated 2-years OS and PFS were 59.1% and 47.2%, respectively. ORR was 55.9%, with early relapse rate (< 12 months) of 14.3% and global death rate of 52.5%. In the total cohort, we found a mutation frequency of 3.4% (2/59) for the IDH2 gene, 62.7% (37/59) for DNMT3A , 23.7% (14/59) for RHOA and 50.8% (30/59) for TET2 . There was no statistically significant difference in the frequency distribution of IDH2, DNMT3A and TET2 mutations between the different histological subtypes of nPTCL. However, there was a statistical trend towards a higher occurrence of the RHOA mutation in the AITL and nPTCL-Thf subtypes (3/9–33.3% and 7/16-43.7%, respectively; p = 0.07). So, the mutation RHOA was predominantly found in THf cell-derived neoplasms in our cohort. The mutational status of DNMT3A, RHOA and TET2 genes had no prognostic impact on OS, with p = 0.85, p = 0.13 and p = 0.95, respectively. The same was observed in relation to PFS for the DNMT3A (p = 0.70) and TET2 (p = 0.52) mutations. However, the presence of the RHOA mutation was associated with the unfavorable PFS in our cohort (HR:1.98, p = 0.05). We observed 2-year PFS of 28.6% (95% CI: 8.8-52.4%) for mutated- RHOA cases versus 52.9% (95% CI: 37.3-66.3%) for wild-type- RHOA patients (p = 0.05). We also demonstrated that the presence of the RHOA mutation was a predictor of lower ORR to first-line therapy (p = 0.01) and was associated with high tumor burden (p = 0.03). For the first time we demonstrated the unfavorable prognostic impact of the RHOA mutation in patients with nPTCL with THf-phenotype, making it a potential molecular biomarker predictor of poor-PFS, associated with resistance to primary therapy and with high tumor burden.

TCL-239: Clinical, Pathological, and Prognostic Implications of RHOAG17V Mutation in Peripheral T-Cell Lymphomas

Context RHOAG17V mutation has been implicated in peripheral T-cell lymphomas (PTCL), characteristically angioimmunoblastic T-cell lymphomas (AITL). However, the association of the dominant-negative control with clinicopathological profile of the neoplasm is yet not clear. Objective To study the impact of RHOAG17V on the clinicopathological presentation and prognostication of T-follicular helper (TFH) cell-derived PTCL and PTCL-NOS. Design This was an ambispective study over six years (2015–2020), including 88 patients with diagnoses of PTCL-NOS (44), AITL (37), PTCL-TFH phenotype (P-TFH; 6), and follicular T-cell lymphoma (1) from the archives of Department of Pathology (AIIMS, New Delhi). Mutational analysis was performed using allele-specific polymerase chain reaction (PCR), validated by the sequencing of cloned products, along with conventional Sanger sequencing. Detailed clinicopathological correlation was done. Main Outcome Measures The association between the presence of mutation and diagnosis, clinical factors (demographics, performance status, organomegaly, IPI/PIT score, stage, marrow involvement), histologic and immunophenotypic presentation (pattern, high endothelial venules [HEV], immunopositivity for TFH markers [CD10, ICOS, PD1, BCL6, and others], CD30, and EBER ISH), and survival (overall and progression-free survival) was analyzed. Results RHOAG17V mutation was present in association with diagnosis of AITL (51.35%) in comparison to PTCL-NOS (25%) and P-TFH (16.67%; p-value=0.027). Sanger sequencing of conventional PCR did not yield any mutations, and the results were based on allele-specific PCR. Mutant cases of AITL had an overall worse performance status at presentation (p-value=0.045), along with a diffuse pattern of nodal involvement (p-value=0.046). Two diffuse large B-cell lymphoma-transformed cases harbored the mutation. Amongst the PTCL-NOS patients, immunopositivity for ICOS (p-value=0.045), along with the presence of increased HEV (p-value=0.035), was noted. None of these factors showed any association with P-TFH. On multivariate analysis, wild-type status predicted an inferior OS (p-value=0.029) in AITL, whereas no significant difference was noted in PFS. Mutation did not confer a survival advantage in PTCL-NOS or P-TFH. Conclusions RHOAG17V mutation, though not specific, shows an association with diagnosis of AITL and has been studied as a lineage-assigning marker for the TFH phenotype, as implicated by ICOS immunopositivity and HEVs in PTCL-NOS. Low variant allelic frequency could lead to false-negative results with conventional PCR products. Mutant status can have prognostic implications with translational relevance and requires larger cohorts for validation. Funding Thanks to Science Engineering Research Board and AIIMS Research section (SERB-EEQ/2016/402, AIIMS A-653).