Chemically defined cytokine-free expansion of human haematopoietic stem cells.

Haematopoietic stem cells (HSCs) are a rare cell type that reconstitute the entire blood and immune systems after transplantation and can be used as a curative cell therapy for a variety of haematological diseases1,2. However, the low number of HSCs in the body makes both biological analyses and clinical application difficult, and the limited extent to which human HSCs can be expanded ex vivo remains a substantial barrier to the wider and safer therapeutic use of HSC transplantation3. Although various reagents have been tested in attempts to stimulate the expansion of human HSCs, cytokines have long been thought to be essential for supporting HSCs ex vivo4. Here we report the establishment of a culture system that allows the long-term ex vivo expansion of human HSCs, achieved through the complete replacement of exogenous cytokines and albumin with chemical agonists and a caprolactam-based polymer. A phosphoinositide 3-kinase activator, in combination with a thrombopoietin-receptor agonist and the pyrimidoindole derivative UM171, were sufficient to stimulate the expansion of umbilical cord blood HSCs that are capable of serial engraftment in xenotransplantation assays. Ex vivo HSC expansion was further supported by split-clone transplantation assays and single-cell RNA-sequencing analysis. Our chemically defined expansion culture system will help to advance clinical HSC therapies.

Impact of CD34 positive cell dose in donor graft on the outcomes after haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide - A retrospective single-center study with a Japanese cohort.

BACKGROUND: Haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with post-transplant cyclophosphamide (PTCy) is an important therapeutic option for patients lacking an HLA-matched donor. However, the significance of CD34+ cell dose in grafts has not been fully elucidated. OBJECTIVE: We aimed to explore the impact of CD34+ cell dose on outcomes after haplo-PBSCT with PTCy. STUDY DESIGN: We retrospectively investigated 111 consecutive patients who underwent haplo-PBSCT with PTCy or HLA-matched PBSCT from related donors. RESULTS: There were no statistically significant differences in 3-year overall survival (p = 0.559) or progression-free survival (p = 0.974) between haplo-PBSCT and matched PBSCT. Delayed neutrophil engraftment and a lower incidence of graft-versus-host disease were observed in haplo-PBSCT. The median dose of CD34+ cells was 4.9 × 106 /kg in 57 haplo-PBSCT and 4.5 × 106 /kg in 54 matched PBSCTs. Importantly, patients who underwent haplo-PBSCT with the administration of CD34+ cell at a dose of ≥4.0 × 106 /kg significantly had improved OS (p = 0.015) and decreased incidence of disease relapse (p = 0.001) without increasing incidence of GVHD. CONCLUSION: Our data suggest that a higher dose of CD34+ cells in haplo-PBSCT with PTCy positively impacts the outcomes without an increase of GVHD.

[Durable remission of T-cell prolymphocytic leukemia with CLEC16A::IL2 after allogeneic hematopoietic stem cell transplantation].

A 64-year-old woman presented with fine motor impairment in both hands. MRI revealed a contrast-enhanced lesion in the medulla oblongata. Lymphoid cells with abnormal blebs were observed and a CD4+/CD8+ double positive (DP) T cell population was detected by flow cytometry (FCM) in the bone marrow (BM) and the peripheral blood (PB). CLEC16A::IL2 fusion gene was identified by whole exome sequencing with DNA prepared from DP T cells. Clonal rearrangement of the T-cell receptor gene and expression of TCL1A protein were detected. This led to a diagnosis of T-cell prolymphocytic leukemia (T-PLL) with central nervous system (CNS) infiltration. Abnormal cells in BM and PB became undetectable on microscopy and FCM, and the CNS lesion disappeared on MRI after second-line therapy with alemtuzumab. Meanwhile, the CLEC16A::IL2 fusion mRNA remained detectable in PB. Allogeneic hematopoietic stem-cell transplantation was performed, and the fusion mRNA has now been undetectable for more than 5 years since transplantation. This is the first report of a T-PLL case with a CLEC16A::IL2 fusion gene.

Risk factors for CAR-T cell manufacturing failure among DLBCL patients: A nationwide survey in Japan.

For successful chimeric antigen receptor T (CAR-T) cell therapy, CAR-T cells must be manufactured without failure caused by suboptimal expansion. In order to determine risk factors for CAR-T cell manufacturing failure, we performed a nationwide cohort study in Japan and analysed patients with diffuse large B-cell lymphoma (DLBCL) who underwent tisagenlecleucel production. We compared clinical factors between 30 cases that failed (7.4%) with those that succeeded (n = 378). Among the failures, the proportion of patients previously treated with bendamustine (43.3% vs. 14.8%; p < 0.001) was significantly higher, and their platelet counts (12.0 vs. 17.0 × 104 /µL; p = 0.01) and CD4/CD8 T-cell ratio (0.30 vs. 0.56; p < 0.01) in peripheral blood at apheresis were significantly lower than in the successful group. Multivariate analysis revealed that repeated bendamustine use with short washout periods prior to apheresis (odds ratio [OR], 5.52; p = 0.013 for ≥6 cycles with washout period of 3-24 months; OR, 57.09; p = 0.005 for ≥3 cycles with washout period of <3 months), low platelet counts (OR, 0.495 per 105 /µL; p = 0.022) or low CD4/CD8 ratios (

Safety of romiplostim administered immediately after cord-blood transplantation: a phase 1 trial.

Graft failure and delayed hematopoietic recovery are the major limitations of cord-blood transplantation (CBT). Romiplostim, a thrombopoietin-receptor agonist, promotes megakaryopoiesis and multilineage hematopoiesis in aplastic anemia. The decreased number of hematopoietic stem cells in the early phase after CBT and aplastic anemia share certain characteristics. Therefore, we hypothesized that romiplostim administration immediately after CBT may promote multilineage hematopoietic recovery. We investigated the safety and preliminary efficacy of administering romiplostim a day after CBT. This phase 1 dose-escalation study included six adults with hematologic malignancies in remission. Romiplostim was administered subcutaneously within 7 days after single-unit CBT, initially at doses of 5 µg/kg or 10 µg/kg in three patients, then once a week for 14 weeks or until platelet recovery. The maximum dose was 20 µg/kg. The median number of romiplostim administrations was 6 (range, 3-15). Romiplostim-related adverse events included bone pain (3/6) and injection site reaction (1/6). Non-hematological grade ≥ 3 toxicities were observed in four patients; febrile neutropenia was the most common (4/6). All patients achieved neutrophil engraftment and the median time was 14 days (range, 12-32). Platelet counts ≥ 50 × 109 /L were recorded in all patients except for one who died on day 48; the median time was 34 days (range, 29-98). No relapse, thrombosis, or bone marrow fibrosis was observed during a median follow-up of 34 months. Romiplostim may be safely administered in the early phase of CBT. Further phase 2 trial is warranted for its efficacy evaluation. Trial registration number: UMIN000033799, August 18, 2018.

Repeated immunosuppressive rabbit antithymocyte globulin therapy for adult patients with relapsed or refractory aplastic anemia.

OBJECTIVES: Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporin A is the standard treatment for aplastic anemia (AA). However, the efficacy of repeated IST with rabbit ATG (rATG) as salvage therapy remains unclear in patients with relapsed or refractory AA. METHODS: We retrospectively evaluated the efficacy and safety of IST2 with rATG (IST2-rATG) in 19 consecutive patients with relapsed or refractory AA who received first-line IST with rATG in two centers between 2009 and 2020. RESULTS: The overall 6-month response rate of the patients was 58%. The response rates were similar between patients with relapsed and refractory AA. The presence of glycophosphatidylinositol-deficient blood cells was associated with a better response to IST2-rATG. Despite retreatment with the same rATG, serum disease and severe allergic reactions were not observed. CONCLUSION: IST2-rATG is effective and safe for the treatment of adult patients with relapsed and refractory AA after receiving first-line IST with rATG.

[Waldenström macroglobulinemia complicated by peripheral neuropathy due to neural infiltration].

A 51-year-old man with the chief complaint of glove- and stocking-type dysesthesia for >3 years was diagnosed with Waldenström's macroglobulinemia (WM) based on IgM-type M-proteinemia, bone marrow infiltration of plasmacytoid B cells, multiple lymphadenopathies, and splenomegaly. A nerve conduction examination suggested demyelinating neuropathy. Serum anti-myelin-associated glycoprotein antibody was negative. Sural nerve biopsy showed myelin thinning, suggesting demyelination. Axonal damage and tumor cell infiltration in the intrafascicular epineurium were also observed. After chemotherapies with rituximab and bendamustine, M-proteinemia and lymphadenopathies disappeared. However, abnormalities in the nerve conduction examination and dysesthesia were only slightly alleviated. As articles describing patients with WM with peripheral nerve infiltration are limited, we report this case with a literature review.

[Hematopoietic recovery by ASXL1-mutated clones after immune suppressive therapy in a patient with severe aplastic anemia].

Sequencing technology has identified aplastic anemia (AA) not only as an autoimmune bone marrow failure syndrome, but also as a clonal hematopoietic disease. Here, we present a case in which an ASXL1-mutated clone was predominantly expanded during the treatment of AA. A 58-year-old man with chronic glomerulonephritis on maintenance hemodialysis presented with pancytopenia. The findings of bone marrow biopsy indicated a hypoplastic bone marrow. Magnetic resonant imaging showed fatty changes in the bone marrow. The patient was eventually diagnosed with severe AA. He was treated with anti-human thymocyte globulin, cyclosporine, granulocyte colony-stimulating factor, and the thrombopoietin receptor agonist (TPO-RA) eltrombopag. After switching to another TPO-RA, romiplostim, the neutrophil, reticulocyte, and platelet counts gradually improved, and blood transfusion was not needed 1 year after treatment. Mutational analyses revealed that reconstituted hematopoietic cells originated from the ASXL1-mutated clone. Nevertheless, the patient's blood cell counts remained normal 2 years after treatment.

[Lymphoplasmacytic lymphoma accompanied by severe myelofibrosis].

A 61-year-old female was referred to our hospital because of pancytopenia and febrile neutropenia. On admission, computed tomography showed mild hepatosplenomegaly and intra-abdominal abscess formation in the right pelvic region; however, no lymphadenopathy was found. Bone marrow (BM) examination showed severe fibrosis by silver staining. Several small- to medium-sized lymphocytes with a constriction in the nuclei were observed, exhibiting CD3 (-), CD10 (-), CD20 (+), BCL-2 (+-), and CD138 (+-). Genetic testing revealed that BM cells were positive for MYD88 mutation and positive for IgH rearrangement, whereas neither JAK2 nor CALR mutation was positive. A diagnosis of BM infiltration of lymphoplasmacytic lymphoma (LPL) was made. Rituximab monotherapy was administered once a week for four times. BM examination 4 weeks after the end of treatment showed that lymphoma cells had disappeared and that myelofibrosis had been almost gone. The MYD88 mutation of BM turned out to be negative at that moment.

[Acute myeloid leukemia harboring NUP98::DDX10].

NUP98::DDX10 is a rare fusion gene associated with acute myeloid leukemia (AML), for which the prognosis and indication for allogeneic hematopoietic stem cell transplantation are unknown. A 48-year-old woman was diagnosed with AML harboring NUP98::DDX10. The results of quantitative RT-PCR of the fusion mRNA as a minimal residual disease (MRD) marker guided the treatment. In August 2019, the patient achieved hematological remission following standard remission induction therapy with idarubicin and cytarabine. After four cycles of consolidation therapies, MRD was detected, and she underwent allogeneic stem cell transplantation in May 2020. As MRD persisted in June, the immunosuppressant was stopped and three cycles of azacitidine were administered. Despite this, a hematological relapse occurred in January 2021 that was resistant to high-dose cytarabine and an investigational agent. She died as a result of the disease's progression. Thus, a second thought should be given to the timing of transplantation, the bridging, and the intervention for relapse after transplantation. The cases must be accumulated.

Early administration of cyclosporine may reduce the incidence of cytokine release syndrome after HLA-haploidentical hematopoietic stem-cell transplantation with post-transplant cyclophosphamide.

Cytokine release syndrome (CRS), occurring in more than 70% of HLA-haploidentical hematopoietic stem-cell transplantations with post-transplant cyclophosphamide (PT/CY-haplo), can lead to hemodynamic instability and worsen clinical outcomes. A calcineurin inhibitor is initiated after cyclophosphamide administration in the commonly used PT/CY regimens. Here, we conducted a phase I/II, prospective, single-center trial of PT/CY-haplo to evaluate the safety and efficacy of cyclophosphamide on days 3 and 5 along with cyclosporin and mycophenolate mofetil started from day - 1. Thirty-five adults with hematologic malignancies were enrolled. Myeloablative and reduced-intensity conditioning were used in 25 and 10 patients, respectively. Graft sources were bone marrow in 11 patients and mobilized peripheral blood stem cells in 24 patients. Disease-free survival on day 100, the primary endpoint, was 86% (95% confidence interval (CI), 69-94), which was over the predefined threshold of 50%. Unexpectedly, only 20% (95% CI, 8.4-37) of patients developed fever of > 38 °C early after graft infusion, all CRS grade 1, and all of which resolved just after cyclophosphamide administration. The cumulative incidences of grades II-IV acute graft-versus-host disease (GVHD), III-IV acute GVHD, and moderate-severe chronic GVHD were 23% (95% CI, 11-38), 6% (95% CI, 1-17), and 11% (95% CI, 4-25), respectively. The 3-year overall survival rate was 49% (95% CI, 31-64). Our results suggest that administration of cyclosporine and mycophenolate mofetil prior to PT/CY can reduce the frequency and severity of CRS without increasing GVHD. UMIN Clinical Trial Registry numbers: 000006631 and 000015694.

[IgG-variant Bing-Neel syndrome diagnosed by detecting MYD88 L265P mutation in the cerebrospinal fluid cells].

Bing-Neel syndrome (BNS), which presents with a variety of neurological complications, is a rare manifestation of the lymphoplasmacytic lymphoma (LPL) and is characterized by the infiltration of LPL cells into the central nervous system. In this study, we report the case of a patient with BNS, which was confirmed by detecting MYD88 L265P mutation in the cerebrospinal fluid (CSF) cells. A 74-year-old patient was diagnosed with IgG-variant LPL. He achieved a very good partial response to the treatment with rituximab and bendamustine (RB) and was stable for over 5 years, when presenting a slowly progressive motor deficit in the lower limbs. It was difficult to confirm BNS from morphological analysis of the CSF cells. After detecting MYD88 L265P mutation in the CSF cells, he was subsequently diagnosed with BNS and treated with RB and intrathecal chemotherapy, resulting in rapid clinical improvement. With the onset of neurological manifestation during the clinical course of LPL, the detection of MYD88 L265P mutation in the CSF cells could be helpful for the diagnosis and management of BNS.

[Acquired platelet dysfunction with severe bleeding tendency in triple-negative myelofibrosis].

A 50-year-old man demonstrated markedly increased number of white blood cells, anemia, severe splenomegaly, and bleeding tendency. Bone marrow analysis revealed remarkable hypercellularity; dysplasia in multilineage cells, including megakaryocytes; and fibrosis. He was eventually diagnosed with triple-negative myelofibrosis. A massive hematoma developed at the bone marrow biopsy site. A similar episode recurred after the second bone marrow biopsy. The von Willebrand factor and other coagulation factor activities were within normal ranges. Platelet aggregation analyses demonstrated highly impaired aggregation induced by ADP, collagen, and epinephrine. Treatment with hydroxyurea and ruxolitinib, a JAK inhibitor, was ineffective, and he eventually died on day 144 after hospitalization. Acquired platelet dysfunction uncommonly occurs in patients with myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN), without precise elucidation of the frequency and underlying mechanism. The onset of bleeding tendency in the current patient suggested that platelet dysfunction may be caused by somatic genetic events. Here, we discuss the mechanisms of acquired platelet dysfunction in MDS or MPN with a literature review.

Notch Signaling in Nestin-Expressing Cells in the Bone Marrow Maintains Erythropoiesis via Macrophage Integrity.

Notch signaling plays pivotal roles in both hematopoietic stem/progenitor and their niche cells. Myeloproliferative phenotypes are induced by disruption of Notch signaling in nonhematopoietic bone marrow (BM) cells. Nestin-expressing cells in the BM reportedly represent a component of the hematopoietic stem cell niche. We established mice in which rare Nestin-expressing cells in the BM were marked by green fluorescent protein, and Notch signaling was conditionally disrupted in these cells specifically. We observed impairment of erythropoiesis in the BM accompanying splenomegaly with BM hematopoietic programs in other lineages undisturbed. Transplantation experiments revealed that the microenvironmental rather than the hematopoietic cells were attributable to these phenotypes. We further found that the erythroid-island-forming ability of BM central macrophages was compromised along with the transcriptional upregulation of interleukin-6. Various Inflammatory conditions hamper BM erythropoiesis, which often accompanies extramedullary hematopoiesis. The mouse model demonstrated here may be of relevance to this common pathophysiologic condition. Stem Cells 2019;37:924-936.

[Haploidentical transplantation from a related donor as first-line treatment for fulminant aplastic anemia].

Immunosuppressive therapy (IST) is the first-line treatment for young patients with severe aplastic anemia (AA) when a human leucocyte antigen (HLA)-matched related donor (MRD) is unavailable. Fulminant AA (FAA) is defined as AA with a complete absence of neutrophils at presentation and no response to granulocyte-colony stimulating factor (G-CSF) treatment. Here we report a 38-year-old male FAA patient who underwent allogeneic stem cell transplantation from an HLA haplotype-mismatched donor as first-line treatment. The patient had no remarkable disease history and was referred to our hospital because of a peritonsillar abscess and severe pancytopenia. Bone marrow biopsy revealed marked hypocellularity without dysplasia. His neutrophil count remained 0.0×109/l following G-CSF administration, and he was diagnosed with FAA. His siblings were not MRDs, but his sister had haploidentical HLAs. After administering a conditioning regimen, the patient received a transplant of peripheral blood stem cells donated by his sister. Neutrophil engraftment was observed on post-transplant day 16, and he experienced acute graft-versus-host disease (grade I, skin stage 1), but no other complications were observed. Hematopoietic stem cell transplantation from an HLA haplotype-mismatched related donor may be a viable option for first-line treatment of FAA when an MRD is unavailable.

[Philadelphia chromosome-positive acute lymphoblastic leukemia complicated by bone marrow necrosis during consolidation chemotherapy].

A 46-year-old man who had previously undergone open surgery for renal cell carcinoma (RCC) developed Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-ALL). After the induction therapy, he achieved complete molecular remission. However, fever and bilateral buttock pain continued during the consolidation therapy. 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) showed FDG accumulation in both iliac bones and in the sacrum; however, no causative diseases, including relapse of Ph-ALL and RCC, were detected. Iliac bone marrow biopsy revealed bone marrow necrosis (BMN), the etiology of which was presumed to be the leukemia itself and the therapeutic response to chemotherapy. Fever resolution and buttock pain alleviation were observed over the next months. We observed diffuse fibrosis in the bone marrow at day 162 and day 364 after cord blood transplantation. Moreover, the FDG accumulation was significantly reduced on PET-CT. BMN is not widely recognized despite its potential association with hematologic malignancies. Additional cases of BMN should be reviewed to clarify BMN etiology and clinical features.

Genetic evidence implies that primary and relapsed tumors arise from common precursor cells in primary central nervous system lymphoma.

Primary central nervous system lymphoma (PCNSL) is a rare subtype of lymphoma that arises within the brain or the eyes. PCNSL recurs within the central nervous system (CNS) in most relapsed cases, whereas extra-CNS relapse is experienced in rare cases. The present study aimed at identifying the presence of common precursor cells (CPC) for primary intra- and relapsed extra-CNS tumors, and further assessing the initiating events in bone marrow (BM). Targeted deep sequencing was carried out for five paired primary intra- and relapsed extra-CNS tumors of PCNSL. Two to five mutations were shared by each pair of intra- and extra-CNS tumors. In particular, MYD88 mutations, L265P in three and P258L in one, were shared by four pairs. Unique somatic mutations were observed in all five intra-CNS tumors and in four out of five extra-CNS tumors. Remarkably, IgH clones in the intra- and the extra-CNS tumors in two pairs were distinct from each other, whereas one pair of tumors shared identical monoclonal IgH rearrangement. In a cohort of 23 PCNSL patients, L265P MYD88 mutations were examined in tumor-free BM mononuclear cells (MNC) in which the PCNSL tumors had L265P MYD88 mutations. L265P MYD88 mutations were detected by a droplet digital PCR method in nine out of 23 bone marrow mononuclear cells. These results suggest that intra- and extra-tumors are derived from CPC with MYD88 mutations in most PCNSL, arising either before or after IgH rearrangement. The initiating MYD88 mutations may occur during B-cell differentiation in BM.

[Successful management of primary immune thrombocytopenia with romiplostim during open heart surgery in a hemodialysis patient].

A 66-year-old male undergoing maintenance hemodialysis presented with mild thrombocytopenia. He also had aortic valve stenosis and required aortic valve replacement. In addition, he required anticoagulation therapy with warfarin because of chronic subclavian artery occlusion. He was eventually diagnosed with immune thrombocytopenic purpura (ITP), although there were no bleeding tendencies. The patient was preoperatively treated with thrombopoietin receptor agonist (romiplostim®) because of the risk of bleeding complication during cardiac surgery. The platelet count rapidly increased with low-dose romiplostim, and no thrombotic complication occurred. During surgery, no significant bleeding complications were observed. This report suggests that romiplostim is a useful treatment option for the management of bleeding complication during cardiac surgery in a hemodialysis patient with ITP.

Clinical significance of disease-specific MYD88 mutations in circulating DNA in primary central nervous system lymphoma.

Recent sequencing studies demonstrated the MYD88 L265P mutation in more than 70% of primary central nervous system lymphomas (PCNSL), and the clinical significance of this mutation has been proposed as diagnostic and prognostic markers in PCNSL. In contrast, mutational analyses using cell-free DNAs have been reported in a variety of systemic lymphomas. To investigate how sensitively the MYD88 L265P mutation can be identified in cell-free DNA from PCNSL patients, we carried out droplet digital PCR (ddPCR) and targeted deep sequencing (TDS) in 14 consecutive PCNSL patients from whom paired tumor-derived DNA and cell-free DNA was available at diagnosis. The MYD88 L265P mutation was found in tumor-derived DNA from all 14 patients (14/14, 100%). In contrast, among 14 cell-free DNAs evaluated by ddPCR (14/14) and TDS (13/14), the MYD88 L265P mutation was detected in eight out of 14 (ddPCR) and in 0 out of 13 (TDS) samples, implying dependence on the detection method. After chemotherapy, the MYD88 L265P mutation in cell-free DNAs was traced in five patients; unexpectedly, the mutations disappeared after chemotherapy was given, and they remained undetectable in all patients. These observations suggest that ddPCR can sensitively detect the MYD88 L265P mutation in cell-free DNA and could be used as non-invasive diagnostics, but may not be applicable for monitoring minimal residual diseases in PCNSL.

TNF-α priming enhances CD4+FoxP3+ regulatory T-cell suppressive function in murine GVHD prevention and treatment.

CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) have been shown to effectively prevent graft-versus-host disease (GVHD) when adoptively transferred in murine models of hematopoietic cell transplantation and in phase 1/2 clinical trials. Critical limitations to Treg clinical application are the paucity of cells and limited knowledge of the mechanisms of in vivo function. We hypothesized that inflammatory conditions in GVHD modify Treg characteristics and activity. We found that peripheral blood of recipient animals during acute GVHD (aGVHD) induces Treg activation and enhances their function. The serum contains high levels of tumor necrosis factor-α (TNF-α) that selectively activates Tregs without impacting CD4(+)FoxP3(-) T cells. TNF-α priming induces Treg in vivo proliferation, whereas it limits the ability of CD4 and CD8 conventional T cells (Tcons) to proliferate and induce GVHD. TNF-α-primed Tregs prolong animal survival as compared with unprimed Tregs when used at an unfavorable Treg:Tcon ratio, demonstrating enhanced in vivo efficacy of TNF-α-primed Tregs. Because TNF-α is produced by several immune cells during inflammation, our work elucidates aspects of the physiologic mechanisms of Treg function. Furthermore, TNF-α priming of Tregs provides a new tool to optimize Treg cellular therapies for GVHD prevention and treatment.