Kentaro Fukushima

AML1/RUNX1 Works as a Negative Regulator of c-Mpl in Hematopoietic Stem Cells

In this study, we analyzed the roles for AML1/RUNX1 in the regulation of the c-mpl promoter. Wild-type AML1 activated the c-mpl promoter through the proximal AML-binding site in luciferase assays using 293T and HeLa cells. In accord with this result, electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that AML1 bound to this site. Next, we analyzed the function of AML1 using a mutant of AML1 lacking the C terminus (AML1dC), which was originally found in a patient with myelodysplastic syndromes. AML1dC dominant-negatively suppressed transcriptional activity of wild-type AML1. However, unexpectedly, AML1dC-transduced murine c-Kit+Sca1+Lineage- cells expressed c-mpl mRNA and c-Mpl protein more abundantly than mock-transduced cells, which led to the enhanced thrombopoietin-mediated proliferation. Moreover, when AML1dC was induced to express during the development of hematopoietic cells from embryonic stem (ES) cells, AML1dC augmented the c-Mpl expression on hematopoietic stem/progenitor cells. Furthermore, we found that early hematopoietic cells that derived from AML1+/- ES cells expressed c-Mpl more intensely than those that developed from wild-type ES cells. In contrast, AML1dC hardly affected c-Mpl expression and maturation of megakaryocytes. As for the mechanism of the different roles of AML1 in the regulation of the c-mpl promoter, we found that AML1 forms a complex with a transcription repressor mSin3A on the c-mpl promoter in hematopoietic stem/progenitor cells, although it forms a complex with a transcription activator p300 on the same promoter in megakaryocytic cells. Together, these data indicate that AML1 can regulate the c-mpl promoter both positively and negatively by changing the binding partner according to cell types.

FIP1L1-PDGFRα Imposes Eosinophil Lineage Commitment on Hematopoietic Stem/Progenitor Cells

Although leukemogenic tyrosine kinases (LTKs) activate a common set of downstream molecules, the phenotypes of leukemia caused by LTKs are rather distinct. Here we report the molecular mechanism underlying the development of hypereosinophilic syndrome/chronic eosinophilic leukemia by FIP1L1-PDGFRα. When introduced into c-KithighSca-1+Lineage- cells, FIP1L1-PDGFRα conferred cytokine-independent growth on these cells and enhanced their self-renewal, whereas it did not immortalize common myeloid progenitors in in vitro replating assays and transplantation assays. Importantly, FIP1L1-PDGFRα but not TEL-PDGFRβ enhanced the development of Gr-1+IL-5Rα+ eosinophil progenitors from c-KithighSca-1+Lineage- cells. FIP1L1-PDGFRα also promoted eosinophil development from common myeloid progenitors. Furthermore, when expressed in megakaryocyte/erythrocyte progenitors and common lymphoid progenitors, FIP1L1-PDGFRα not only inhibited differentiation toward erythroid cells, megakaryocytes, and B-lymphocytes but aberrantly developed eosinophil progenitors from megakaryocyte/erythrocyte progenitors and common lymphoid progenitors. As for the mechanism of FIP1L1-PDGFRα-induced eosinophil development, FIP1L1-PDGFRα was found to more intensely activate MEK1/2 and p38MAPK than TEL-PDGFRβ. In addition, a MEK1/2 inhibitor and a p38MAPK inhibitor suppressed FIP1L1-PDGFRα-promoted eosinophil development. Also, reverse transcription-PCR analysis revealed that FIP1L1-PDGFRα augmented the expression of C/EBPα, GATA-1, and GATA-2, whereas it hardly affected PU.1 expression. In addition, short hairpin RNAs against C/EBPα and GATA-2 and GATA-3KRR, which can act as a dominant-negative form over all GATA members, inhibited FIP1L1-PDGFRα-induced eosinophil development. Furthermore, FIP1L1-PDGFRα and its downstream Ras inhibited PU.1 activity in luciferase assays. Together, these results indicate that FIP1L1-PDGFRα enhances eosinophil development by modifying the expression and activity of lineage-specific transcription factors through Ras/MEK and p38MAPK cascades.

Maintenance of complete remission after allogeneic stem cell transplantation in leukemia patients treated with Wilms tumor 1 peptide vaccine

The prognosis of patients after allogeneic hematopoietic stem cell transplantation (HSCT) is still not satisfactory because, while treatment-related mortalities have decreased, relapse after HSCT remains a major concern. The effectiveness of allogeneic HSCT for hematological malignancies is the result of immunologic rejection of recipient leukemia cells by donor T cells, known as the graft-versus-leukemia (GVL) effect.1 It is thus obviously important to be able to exploit the GVL effect while minimizing graft-versus-host disease (GVHD). A targeted anti-leukemic immunotherapy, such as use of a leukemia vaccine,2 is a promising strategy to boost the GVL effect. Wilms tumor1 (WT1) protein is one of the best targets for leukemia vaccines. Overexpression of the wild-type WT1 gene has been detected in all types of human leukemia.3, 4, 5 We performed a phase I clinical study of immunotherapy targeting the WT1 protein in patients with leukemia, and were able to show that WT1 vaccination was safe and could induce WT1-specific cytotoxic T lymphocyte (CTL).6 Furthermore, reduction of minimal residual disease and long-lasting complete remission (CR) was observed in some leukemia patients who were given the WT1 vaccine.7 This report presents the results of phase I clinical study of WT1 vaccination for HLA-A*2402-positivie post-HSCT patients who were at high risk of relapse (HSCT in non-CR and 2nd HSCT for post-transplant relapse) or had already relapsed. The HLA-A*2402-restricted modified 9-mer WT1 peptide (amino acids 235–243 CYTWNQMNL)8 was emulsified with Montanide ISA51 adjuvant. Patients were intradermally injected with 1.0 mg (three patients: UPNs 1, 4 and 6) or 3.0 mg (other six patients) of WT1 peptide four times weekly. When no adverse effects and no obvious disease progression were observed after the fourth injection, further WT1 vaccinations at 2-week intervals were administered. Nine patients (five with acute myeloid leukemia (AML), one each with acute lymphoblastic leukemia, chronic myelomonocytic leukemia, multiple myeloma and T-cell lymphoblastic lymphoma) were enrolled in this study (Supplementary Tables 1 and 2). Local inflammatory response was observed at the vaccine injection sites of all patients. One patient (UPN5) suffered mild hypoxia (PaO2 65 mm Hg at room air) and restrictive pulmonary dysfunction (FEV1.0 40%) 65 days after the start of WT1 vaccination (day 199 after HSCT; Figure 1a). He was diagnosed with bronchioleitis obliterans (BO), which was a symptom of chronic GVHD. The patient recovered soon after administration of inhaled steroids. While early and sudden discontinuation of prednisolone and tacrolimus (day 103 after HSCT) were considered to be the reason for development of BO, the possibility of an association between BO and WT1 vaccination cannot be entirely ruled out. In other eight patients, no severe toxicities related to WT1 vaccine were observed (Table1). Figure 1 Clinical course of patients who attained CR after the start of WT1 peptide vaccination. (a) Clinical course of UPN5 who achieved CR after administration of WT1 vaccine but stopped vaccination because of the development of bronchioleitis obliterans. ( ... Table 1 Patient outcomes Three AML patients (UPN1–3), who had undergone HSCT in non-CR, started WT1 vaccine in CR (Supplementary Tables 1 and 2). They started WT1 vaccination on post-HSCT days 141, 76 and 93 and have remained in CR for 1038, 973 and 662 days, respectively (as of 8 April 2013; Table1), suggesting the potential of WT1 vaccination as a maintenance therapy after HSCT. Six patients started WT1 vaccination in non-CR and two of them became CR after WT1 vaccination. One B-ALL patient (UPN4) with MLL-AF4 underwent bone marrow transplantation from an HLA-matched unrelated donor during the first CR. On post-HSCT day 111, MLL-AF4 and WT1 mRNA in peripheral blood (PB) had increased to 16 000 and 15 000 copies/μg RNA, indicating that the disease had relapsed. Tacrolimus and prednisolone doses were tapered off to induce GVL effects. The expression levels of MLL-AF4 and WT1 mRNA in PB had decreased to 2700 and 190 copies/μg RNA by day 132, and WT1 vaccination was started on day 133. MLL-AF4 mRNA had become undetectable by day 146, and had never appeared until post-HSCT day 1312 (day 1179 after the start of WT1 vaccination as of 8 April 2013; Figure 1b). Skin tumors appeared in UPN5 (AML-M5) on post-HSCT day 103 and was diagnosed by biopsy as leukemia relapse. Tacrolimus was discontinued on day103, and WT1 vaccination was started on day 130. Cutaneous tumors had regressed 2 weeks after the start of WT1 vaccination, but vaccination was terminated after the second injection because of the development of BO as described earlier (Figure 1a). This patient has been remained in CR until post-HSCT day 972 (day 842 after the start of WT1 vaccination at 8 April 2013). While the exact contribution of the vaccination effect to the disease remission in addition to the GVL effect was unclear, the fact that both of these two patients still have remained in CR until now is encouraging to continue this trial. In the following phase II trials, the enumeration of WT1-specific CTLs should be performed more frequently after the start of vaccination to clarify the relationship between the effect of WT1 peptide vaccination and leukemia regression. WT1 (a natural 9-mer WT1 peptide) HLA-A*2402 tetramer assays could be performed with peripheral blood mononuclear cell in seven of the nine patients to determine whether WT1235 peptide-specific CD8+ T cells had increased after WT1 vaccination. The gates for WT1 tetramer+ cells were drawn as <0.1% of CD8+ T cells were included in the tetramer-positive gate in multiple healthy individuals (Supplementary Figure 1A). WT1235 tetramer+ cells increased after the start of vaccination in three (UPNs1, 2 and 4) of the four patients who have remained in CR (Figure 1b and Supplementary Figure 1B). In the cases with progressive disease, continuous increase in the frequencies of WT1235 tetramer+ cells was not observed (Supplementary Figure 1B). Our results suggest that WT1 vaccination should be started when the leukemia burden is minimal. The timing of the start of WT1 vaccination may be also important. For the cases with good outcomes, WT1 vaccination was started 76–140 days after transplantation (UPNs1–5), and at later times (days 299–1815) for PD cases (UPNs 6–9). A lymphopenic environment a few months after transplantation may be favorable for rapid and extensive expansion of tumor antigen-specific CTLs. In summary, this report suggests that WT1 vaccine can be safely administrated for post-HSCT patients with hematological malignancies and has potential as a maintenance therapy. Clinical benefit of WT1 vaccination for post-HSCT patients will be evaluated in the subsequent phase II trials.

BCR-ABL but Not JAK2 V617F Inhibits Erythropoiesis through the Ras Signal by Inducing p21CIP1/WAF1

BCR-ABL is a causative tyrosine kinase (TK) of chronic myelogenous leukemia (CML). In CML patients, although myeloid cells are remarkably proliferating, erythroid cells are rather decreased and anemia is commonly observed. This phenotype is quite different from that observed in polycythemia vera (PV) caused by JAK2 V617F, whereas both oncogenic TKs activate common downstream molecules at the level of hematopoietic stem cells (HSCs). To clarify this mechanism, we investigated the effects of BCR-ABL and JAK2 V617F on erythropoiesis. Enforced expression of BCR-ABL but not of JAK2 V617F in murine LSK (Lineage−Sca-1hiCD117hi) cells inhibited the development of erythroid cells. Among several signaling molecules downstream of BCR-ABL, an active mutant of N-Ras (N-RasE12) but not of STAT5 or phosphatidylinositol 3-kinase (PI3-K) inhibited erythropoiesis, while N-RasE12 enhanced the development of myeloid cells. BCR-ABL activated Ras signal more intensely than JAK2 V617F, and inhibition of Ras by manumycin A, a farnesyltransferase inhibitor, ameliorated erythroid colony formation of CML cells. As for the mechanisms of Ras-induced suppression of erythropoiesis, we found that GATA-1, an erythroid-specific transcription factor, blocked Ras-mediated mitogenic signaling at the level of MEK through the direct interaction. Furthermore, enforced expression of N-RasE12 in LSK cells derived from p53-, p16INK4a/p19ARF-, and p21CIP1/WAF1-null/wild-type mice revealed that suppressed erythroid cell growth by N-RasE12 was restored only by p21CIP1/WAF1 deficiency, indicating that a cyclin-dependent kinase (CDK) inhibitor, p21CIP1/WAF1, plays crucial roles in Ras-induced suppression of erythropoiesis. These data would, at least partly, explain why respective oncogenic TKs cause different disease phenotypes.

Mycophenolate mofetil use after unrelated hematopoietic stem cell transplantation for prophylaxis and treatment of graft-vs.-host disease in adult patients in Japan.

Our previous study of 301 patients who received hematopoietic stem cell transplantation (HSCT) from related donors demonstrated the efficacy of mycophenolate mofetil (MMF) for prophylaxis and treatment of graft‐vs.‐host disease (GVHD). In this study, we investigated the safety and efficacy of MMF in 716 adult patients who received unrelated HSCT. The incidences of Grade II–IV and III–IV acute GVHD in the prophylactic administration group were 38.3% and 14.3%, respectively. These rates were not statistically significant when evaluating the MMF dosage and graft source. The incidences of limited and extensive chronic GVHD were 16.6% and 11.1%, respectively. In the therapeutic administration group, 69.1% of the subjective symptoms for both acute and chronic GVHD improved. With respect to the adverse events, 75 infections and 50 cases of diarrhea were observed, and the frequency of these events increased with increasing MMF dose. The overall survival rate was 36.4% after a median follow‐up period of three yr. This study shows that MMF is safe and effective for the prevention and treatment of GVHD in patients who have received HSCT from unrelated donors.

Myeloid neoplasm-related gene abnormalities differentially affect dendritic cell differentiation from murine hematopoietic stem/progenitor cells.

Dendritic cells (DCs) play important roles in tumor immunology. Leukemic cells in patients with myeloid neoplasms can differentiate into DCs in vivo (referred to as in vivo leukemic DCs), which are postulated to affect anti-leukemia immune responses. We established a reproducible culture system of in vitro FLT3 ligand-mediated DC (FL-DC) differentiation from murine lineage(-) Sca-1(+) c-Kit(high) cells (LSKs), which made it possible to analyse the effects of target genes on steady-state DC differentiation from hematopoietic stem/progenitor cells. Using this system, we analysed the effects of various myeloid neoplasm-related gene abnormalities, termed class I and class II mutations, on FL-DC differentiation from LSKs. All class II mutations uniformly impaired FL-DC differentiation maintaining a plasmacytoid DC (pDC)/conventional DC (cDC) ratio comparable to the control cells. In contrast, class I mutations differentially affected FL-DC differentiation from LSKs. FLT3-ITD and a constitutively active form of Ras (CA-N-Ras) yielded more FL-DCs than the control, whereas the other class I mutations tested yielded less FL-DCs. Both FLT3-ITD and FLT3-tyrosine kinase domain (TKD) mutation showed a comparable pDC/cDC ratio as the control. CA-N-Ras, c-Kit-TKD, TEL/PDGFRβ, and FIP1L1/PDGFRα showed a severe decrease in the pDC/cDC ratio. CA-STAT5 and CA-MEK1 severely inhibited pDC differentiation. FLT3-ITD, CA-N-Ras, and TEL/PDGFRβ aberrantly induced programmed death ligand-1 (PD-L1)-expressing DCs. In conclusion, we have established a simple, efficient, and reproducible in vitro FL-DC differentiation system from LSKs. This system could uncover novel findings on how myeloid neoplasm-related gene abnormalities differentially affect FL-DC differentiation from murine hematopoietic stem/progenitor cells in a gene-specific manner.

Quantitative polymerase chain reaction analysis with allele-specific oligonucleotide primers for individual IgH VDJ regions to evaluate tumor burden in myeloma patients

Quantitative polymerase chain reaction (PCR) with patient-specific, allele-specific oligonucleotide (ASO) primers for individual immunoglobulin H VDJ region (ASO-PCR) amplification was performed using several sources of clinical material, including mRNA from peripheral blood cells (PBMNCs), whole bone marrow cells (BMMNCs), and the CD20+ CD38- B-cell population in bone marrow, as well as cell-free DNA from the sera of patients with multiple myeloma (MM). We designed the ASO primers and produced sufficient PCR fragments to evaluate tumor burden in 20 of 30 bone marrow samples at diagnosis. Polymerase chain reaction amplification efficiency depended on primer sequences because the production of ASO-PCR fragments did not correlate with serum M-protein levels. However, the ASO-PCR levels in BMMNCs showed statistically significant correlations with those in PBMNCs and CD20+ CD38- B-cells. The good association between the BMMNC and PBMNC data indicated that PBMNCs could be a suitable source for monitoring minimal residual disease (MRD). In the case of cell-free DNA, ASO-PCR levels showed a unique pattern and remained high even after treatment. Because the sequence information for each ASO-PCR product was identical to the original, the cell-free DNA might also be useful for evaluating MRD. Moreover, the ASO-PCR products were clearly detected in 17 of 22 mRNA samples from CD20+ CD38- populations, suggesting that MM clones might exist in relatively earlier stages of B cells than in plasma cells. Thus, ASO-PCR analysis using various clinical materials is useful for detecting MRD in MM patients as well as for clarifying MM pathogenesis.

Estrogen-inducible sFRP5 inhibits early B-lymphopoiesis in vivo, but not during pregnancy.

Mammals have evolved to protect their offspring during early fetal development. Elaborated mechanisms induce tolerance in the maternal immune system for the fetus. Female hormones, mainly estrogen, play a role in suppressing maternal lymphopoiesis. However, the molecular mechanisms involved in the maternal immune tolerance are largely unknown. Here, we show that estrogen‐induced soluble Frizzled‐related proteins (sFRPs), and particularly sFRP5, suppress B‐lymphopoiesis in vivo in transgenic mice. Mice overexpressing sFRP5 had fewer B‐lymphocytes in the peripheral blood and spleen. High levels of sFRP5 inhibited early B‐cell differentiation in the bone marrow (BM), resulting in the accumulation of cells with a common lymphoid progenitor (CLP) phenotype. Conversely, sFRP5 deficiency reduced the number of hematopoietic stem cells (HSCs) and primitive lymphoid progenitors in the BM, particularly when estrogen was administered. Furthermore, a significant reduction in CLPs and B‐lineage‐committed progenitors was observed in the BM of sfrp5‐null pregnant females. We concluded that, although high sFRP5 expression inhibits B‐lymphopoiesis in vivo, physiologically, it contributes to the preservation of very primitive lymphopoietic progenitors, including HSCs, under high estrogen levels. Thus, sFRP5 regulates early lympho‐hematopoiesis in the maternal BM, but the maternal–fetal immune tolerance still involves other molecular mechanisms that remain to be uncovered.