Search

Angioimmunoblastic T-cell lymphoma (AITL) is an intractable type of T-cell lymphoma. We and others have identified that the p.Gly17Val RHOA mutation is specifically identified in AITL. We herein report a patient whose condition deteriorated, resulting from massive pericardial effusion one month after undergoing autologous transplantation for AITL. He was diagnosed with cardiac tamponade caused by AITL recurrence in the presence of the p.Gly17Val RHOA mutation as well as T-lineage cells with an aberrant immune-phenotype in the pericardial effusion. This case suggests that a precision medicine approach by detecting the presence of a p.Gly17Val RHOA mutation is useful for the management of AITL.

Objective Graft failure (GF) is a life-threatening complication of hematopoietic stem cell transplantation (HSCT). A standardized conditioning regimen and an appropriate graft source of salvage HSCT for GF have not yet been established. Some case series have shown good hematopoietic recoveries after salvage HSCT using a short-term reduced-intensity preparative regimen consisting of fludarabine (30-90 mg/m2), cyclophosphamide (2 g/m2), and total-body irradiation (2 Gy). However, the dose of fludarabine has varied in these reports based on the clinical condition of the patients, resulting in very limited experiences with each dose of fludarabine. Methods We retrospectively analyzed 10 patients who developed GF after allogeneic HSCT and underwent salvage cord blood transplantation (CBT) using the above-mentioned conditioning regimen with a fixed dose (90 mg/m2) of fludarabine. Results Eight patients (80.0%) achieved neutrophil engraftment within 30 days from salvage HSCT with a median of 21 (range, 17-23) days. The 1-year overall survival (OS) rate after the salvage HSCT was 50.0%, and the median OS was 281 (range, 23-1,638) days. Cumulative incidences of non-relapse mortality and relapse at 1 year were 50.0% and 10.0%, respectively. Conclusion CBT using this short-term reduced-intensity conditioning regimen may be a promising salvage therapy for GF.

Angioimmunoblastic 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.

Activating mutations in the Vav guanine nucleotide exchange factor 1 (VAV1) gene are reported in various subtypes of mature T-cell neoplasms (TCN). However, oncogenic activities associated with VAV1 mutations in TCN remain unclear. To define them, we established transgenic mice expressing VAV1 mutants cloned from human TCN. Although we observed no tumors in these mice for up to a year, tumors did develop in comparably-aged mice on a p53-null background (p53-/- VAV1-Tg), and p53-/- VAV1-Tg mice died with shorter latencies than did p53-null (p53-/-) mice. Notably, various TCN with tendency of maturation developed in p53-/- VAV1-Tg mice, while p53-/- mice exhibited only immature TCN. Mature TCN in p53-/- VAV1-Tg mice mimicked human peripheral T-cell lymphoma (PTCL)-GATA3 and exhibited features of type2 T helper (TH2) cells. Phenotypes seen following transplantation of either p53-/- VAV1 or p53-/- tumor cells into nude mice were comparable, indicating cell-autonomous tumor-initiating capacity. Whole transcriptome analysis (WTA) showed enrichment of multiple Myc-related pathways in TCN from p53-/- VAV1-Tg mice relative to p53-/- or wild-type T cells. Remarkably, amplification of Myc locus were found recurrently in TCN of p53-/- VAV1-Tg mice. Finally, treatment of nude mice transplanted with p53-/- VAV1-Tg tumor cells with JQ1, a bromodomain inhibitor, which targets the Myc pathway, prolonged survival of mice. We conclude that VAV1 mutations function in malignant transformation of T cells in vivo and that VAV1-mutant expressing mice could provide an efficient tool for screening new therapeutic targets in TCN harboring these mutations. We conclude that VAV1 mutations function in malignant transformation of T cells in vivo and that VAV1-mutant expressing mice could provide an efficient tool for screening new therapeutic targets in TCN harboring these mutations.

Background Angioimmunoblastic T-cell lymphoma (AITL) is proposed to be initiated by age-related clonal hematopoiesis (ACH) with TET2mutations, whereas the G17V RHOA mutation in TET2-mutated immature cells facilitates development of T follicular helper (T FH)-like tumor cells. Notably, we and others have reported that immune cells derived from ACH with TET2 mutations infiltrate AITL tissues. However, how ACH-derived immune cells function as a microenvironmental niche in AITL remains largely unknown. Objective To elucidate the role of TET2-mutated immune cells in AITL tumorigenesis. Methods The G17V RHOA transgenic mice were crossed with mice lacking Tet2 in all blood cells (Mx-Crex Tet2f/f, A) and in T cells (Cd4-Crex Tet2f/f, B), respectively. Single-cell RNA sequencing (Sc-seq) was performed on >60,000 cells from AITL in mice (AITLm, n=2) and human (AITLh, n=5), and their controls to reveal the immune profiles. We used Seurat and Monocle3 pipelines for analysis of Sc-seq. Whole genome bisulfite sequencing (WGBS) was used to analyze the methylome of germinal center B (GCB) cells in AITLm and control. Results AITLm occurred only in A, but not in B. Then, we intraperitoneally transplanted Cd4 + tumor-containing cells together with various lineages of immune cells sorted from AITLm into nude mice. AITLm developed only when B-lineage cells were cotransplanted with Cd4 + tumor-containing cells. Unsupervised clustering of the Sc-seq data identified 6 T-, 6 B- and 3 myeloid clusters in AITLm. B-cell clusters were annotated into naïve B-, memory B-, GCB-, and plasma clusters along the B-cell differentiation through Geneset variable analysis (GSVA) and trajectory analysis. We found that the aberrant GCB clusters, simultaneously exhibiting DZ-like proliferation markers (Aicda and Mki67) and LZ-like activation markers (Cd40, Cd83) were markedly expanded in AITLm. Geneset Enrichment Analysis (GSEA) revealed that MYC targets and other signaling pathways involved in cell proliferation were highly enriched in the GCB clusters in AITLm. WGBS showed that the number of hypermethylated regions (HyperDMRs) was markedly higher than that of hypomethylated regions (HypoDMRs) at all the regions; promoters, exons, introns, untranslated and intergenic regions. Among HyperDMRs, Atp13a2, Pdzd2, Rapgef4, Irf4 and Egr3 expressions were downregulated in the GCB clusters of Sc-seq in AITLm. Remarkably, the number of BCR clones in GCB of AITLm were significantly less than those in controls. In addition, in AITLm mice, the number of somatic mutations in GCB cells was significantly higher than that in T FH-like tumor cells. Remarkably, we detected unique core histone mutations in the GCB cells of AITLm, including the recurrent p.Ser87Asn Histone3 mutations. Next, In silico network analysis using Sc-seq data between GCB and T FH-like clusters identified that 11 interactions, including Cd40-Cd40lg were significantly enhanced in AITLm compared to controls. Flowcytomeric analysis revealed that cell-surface expression of Cd40 were significantly higher in the GCB cells of AITLm than those of control. Pathologically, the follicular structure was disrupted in AITLm. Consequently, Cd40lg +Cd4 +tumor cells and Cd40 +Cd19 + cells were both diffusely distributed and sometimes localized adjacent to each other. Finally, administration of an anti-Cd40lg antibody prolonged the survival of nude mice transplanted with AITLm. In AITLh with TET2 mutations, unsupervised clustering of Sc-seq identified T-, B-, and myeloid-cell clusters and a cluster characterized by proliferative markers. In B-lineage cells, 9 clusters were re-clustered and annotated to naïve or memory B-, GCB- and plasmablast clusters under the same manner of mouse data. Gene ontology analysis from differential expression genes in each cluster showed that the GCB- and CD40-related genesets were enriched not only in the GCB cluster but also in the naive to memory B clusters. Furthermore, the AITL-B-specific geneset, which referred from genes (CD40, CD83, AICDA, MKI67) highly expressed in the GCB cluster in AITLm was enriched not only in the GCB cluster, but also in the naive to memory B clusters in AITLh. Conclusion This study suggests a new concept that ACH-derived GCB cells with TET2 mutations can undergo independent clonal evolution and function as microenvironmental cells to support tumorigenesis in AITL via the CD40-CD40LG axis. Disclosures Usuki: Astellas Pharma Inc.: Research Funding, Speakers Bureau; AbbVie GK: Research Funding, Speakers Bureau; Gilead Sciences, Inc.: Research Funding; SymBio Pharmaceuticals Ltd.: Research Funding, Speakers Bureau; Daiichi Sankyo Co., Ltd.: Research Funding, Speakers Bureau; Sumitomo-Dainippon Pharma Co., Ltd.: Research Funding; Otsuka Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Novartis Pharma K.K.: Research Funding, Speakers Bureau; Ono Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Janssen Pharmaceutical K.K.: Research Funding; Celgene K.K.: Research Funding, Speakers Bureau; Takeda Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Nippon-Boehringer-Ingelheim Co., Ltd.: Research Funding; Mundipharma K.K.: Research Funding; Amgen-Astellas Biopharma K.K.: Research Funding; Nippon-Shinyaku Co., Ltd.: Research Funding, Speakers Bureau; Kyowa-Kirin Co., Ltd.: Research Funding, Speakers Bureau; Pfizer Japan Inc.: Research Funding, Speakers Bureau; Alexion Pharmaceuticals, Inc.: Research Funding, Speakers Bureau; Eisai Co., Ltd.: Speakers Bureau; MSD K.K.: Research Funding, Speakers Bureau; PharmaEssentia Japan KK: Research Funding, Speakers Bureau; Yakult Honsha Co., Ltd.: Research Funding, Speakers Bureau; Bristol-Myers-Squibb K.K.: Research Funding, Speakers Bureau; Apellis Pharmaceuticals, Inc.: Research Funding; Incyte Biosciences Japan G.K.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Research Funding, Speakers Bureau; Sanofi K.K.: Speakers Bureau; Amgen K.K.: Research Funding.

Chronic active Epstein-Barr virus infection (CAEBV) is critical owing to lethal complications such as hemophagocytic lymphohistiocytosis (HLH), multiple organ failure, and malignant lymphoma. Here we present two cases of CAEBV who developed rapid and life-threatening disease progression after cytotoxic chemotherapy. Case 1: In a 34-year-old male, CAEBV recurred after 4-month remission obtained by initial therapy with etoposide, cyclosporine, and prednisolone. Accordingly, cord blood transplantation was planned. A day after administering high-dose melphalan as the conditioning, he developed respiratory failure, pancytopenia, and hyperferritinemia. He died 3 days later. Case 2: A 53-year-old female attained remission after initial therapy for CAEBV. After 1 month, she relapsed, and high-dose cytarabine (HDAC) was administered. A day after HDAC administration, she suddenly developed respiratory failure, which was followed by multiple organ failure. She died 3 days later. Thus, planned strategy for prompt allogeneic hematopoietic stem cell transplantation is necessary to prevent disease progression and control cytokinemia before cytotoxic chemotherapy for CAEBV.

A 78-year-old man was referred to Tsukuba University Hospital for right hydronephrosis. He had undergone ureteroscopy and ureteral stenting in another hospital, but no tumor was revealed in renal pelvis and ureter. The urinary cytology was negative. Computed tomography (CT) revealed remarkable thickening of right renal pelvis and ureter wall. CT also showed para-aortic, iliac, supraclavicular and mediastinal lymph node (LN) swelling. 18F-fluoro-2-deoxy-D-glucose positron emission tomography (PET) revealed high uptake at thickened right renal pelvis and ureter wall and enlarged LNs. The soluble interleukin-2 receptor was elevated to 1,110 U/ml (normal range: 613 U/ml). Those findings suggested that the malignant lymphoma originated from the renal pelvis and ureter rather than urothelial cancer. Therefore we performed open biopsy of iliac LN and periureteral tissue. The pathological diagnosis was mucosa associated lymphoid tissue (MALT) lymphoma. The patient was trasferred to the department of hematology, and treated with rituximab and bendamustine. After 6 courses of chemotherapy, swelling of renal pelvis, ureter and LN was markedly reduced. The ureteral sent could be removed. MALT lymphoma of the upper urinary tract is extremely rare and pretreatment diagnosis is difficult. In 8 of 11 reported cases, the diagnosis was made by nephroureterectomy. In our cases, open biopsy could avoid nephroureterectomy.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare subtype of myeloid neoplasm. Clonal evolution in the development of BPDCN remains to be elucidated. In the present study, we examined clonal evolution in a case of BPDCN by analyzing the distribution of gene mutations in tumor cells and non-tumor blood cells. The p.D1129fs and p.K1005fs TET2 mutations, p.P95H SRSF2 mutation, and p.L287fs NPM1 mutation were identified in a skin tumor at diagnosis and peripheral blood mononuclear cells at relapse. Notably, the p.D1129fs TET2 and p.L287fs NPM1 mutations were observed only in tumor cells, while the p.K1005fs TET2 and p.P95H SRSF2 mutations were found in both tumor cells and non-tumor blood cells. Recent genetic studies have suggested that some blood cancers may originate from clonal hematopoiesis, harboring somatic mutations. In the present case, the data suggest that BPDCN originated from clonal hematopoiesis with the p.K1005fs TET2 and p.P95H SRSF2 mutations via acquisition of the additional p.D1129fs TET2 and p.L287fs NPM1 mutations.

Letter to the Editor

Background: VAV1 is known as an important mediator of T-cell receptor (TCR) signaling through its guanine exchange factor (GEF)-dependent and independent functions. Recent studies identified activating VAV1 mutations in several types of T-cell malignancies including peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), ALK-negative anaplastic large cell lymphoma (ALCL), and adult T-cell lymphoma/leukemia (ATLL). However, the functions of VAV1 mutations in T-cell malignancies have not been clarified. Objective: We aim to identify the oncogenic signaling of VAV1 mutations in T cells using genetically engineered mice. Methods: Human VAV1 mutant (p.165_174del) (VAV1-Del) and VAV1-STAP2 fusion cDNAs, identified in our PTCL cohort (Fujisawa, Leukemia 2018) were cloned into a VA vector under the CD2 promoter. The vectors were injected into eggs to generate VAV1-Del and VAV1-STAP2 transgenic mice. The mice were further crossed with p53-/- mice to generate p53-/- x VAV1-Del or p53-/- x VAV1-STAP2 mice. Cell surface markers of tumor cells were analyzed by flowcytometry. Cell suspension of tumors were cultured, and were intraperitoneally injected into BALBc/nu mice to examine the cell-autonomous proliferative activity in vitro and tumor-initiating capacity in vivo, respectively. RNA sequencing was performed to clarify the downstream signaling of VAV1 mutations. Results: The p53-/- mice expressing VAV1 mutants showed significantly poorer overall survival (OS) compared to p53-/- mice (p53-/- x VAV1-Del, median 16.6 weeks; p53-/- x VAV1-STAP2, median 18.6 weeks; vs p53-/-, median 33.7 weeks: p50 weeks). p53-/- x VAV1-Del and p53-/- x VAV1-STAP2 mice developed either T-cell lymphoblastic leukemias (LBL) infiltrating into thymus, lung, spleen, and liver, or mature T-cell lymphomas (Lym) into lymph nodes, spleen, and liver. In contrast, p53-/- mice developed only T-LBL at thymus. Flow cytometric analysis showed that most of T-LBL cells developed in p53-/- mice with VAV1 mutants were CD8+ single positive (SP), while those in p53-/- mice were either CD4+CD8+ (double positive, DP) or CD8+ SP. Lym cells in p53-/- mice with VAV1 mutants were either CD4+ SP or CD4-CD8- (double negative, DN) (in p53-/- x VAV1-Del mice, 5/9 CD8+ SP T-LBL, 1/9 DP T-LBL , 2/9 CD4+ SP Lym , and 1/9 DN Lym; in p53-/- x VAV1-STAP2 mice, 9/13 CD8+ SP T-LBL, 1/13 CD4+ SP Lym , and 3/13 DN Lym; p53-/- mice, 3/7 CD8+ SP T-LBL and 4/7 DP T-LBL). T-LBL with or without VAV1 mutants were immortalized in vitro over 4 weeks without any cytokines, while Lym with VAV1 mutations could not be maintained in vitro. The BALBc/nu mice transplanted with cell suspension of either T-LBL or Lym with VAV1 mutants were succumbed to death around 10 or 15 weeks, respectively. All the tumor cells developed in transplanted mice showed the similar immunophenotype to those of donor cells. Gene set enrichment analysis (GSEA) following RNA sequencing showed that G2M check point, E2F targets, mitotic spindle, PI3K/Akt/mTOR signaling, and hedgehog signaling were enriched in CD8+ SP T-LBL with VAV1 mutants compared with DP T-LBL in p53-/- mice, while E2F targets, MYC targets, G2M checkpoint, Oxidative phosphorylation, and MTORC1 signaling were upregulated in CD4+ SP Lym with VAV1 mutants in comparison with WT CD4+ spleen cells. We previously reported that TCR and Tfh pathways were enriched in TET2-/-/RHOA G17V mice through activation of VAV1 (Tran, ASH 2018). Curiously, neither of them were enriched in CD4+ SP Lym with VAV1 mutants, while TCR pathway was enriched in T-LBL with VAV1 mutants. Cell viability assay using panels over 1400 drugs showed that PI3K/Akt/mTOR pathway inhibitors and cell-cycle inhibitors effectively suppressed the cell growth of T-LBL with VAV1 mutants in vitro. Conclusions: Expression of VAV1 mutants promoted the development of T-cell malignancies in mice. Our mouse models may provide the efficient tools to screen new therapeutic targets in T-cell malignancies with VAV1 mutations. Disclosures Ohshima: NEC Corp.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Honoraria, Research Funding; Kyowa Kirin Co., Ltd.: Honoraria, Research Funding; Celgene Corp.: Honoraria, Research Funding; SRL, Inc.: Consultancy. Ogawa:Dainippon-Sumitomo Pharmaceutical, Inc.: Research Funding; RegCell Corporation: Equity Ownership; Asahi Genomics: Equity Ownership; Qiagen Corporation: Patents & Royalties; Kan Research Laboratory, Inc.: Consultancy; ChordiaTherapeutics, Inc.: Consultancy, Equity Ownership.