Development of Immune Cell Therapy Using T Cells Generated from Pluripotent Stem Cells.

In the field of cancer immunotherapy, the effectiveness of a method in which patient-derived T cells are genetically modified ex vivo and administered to patients has been demonstrated. However, problems remain with this method, such as (1) time-consuming, (2) costly, and (3) difficult to guarantee the quality. To overcome these barriers, strategies to regenerate T cells using iPSC technology are being pursued by several groups in the last decade. The authors have been developing a method by which specific TCR genes are introduced into iPSCs and T cells are generated from those iPSCs (TCR-iPSC method). At present, our group is preparing this approach for clinical trial, where iPSCs provided from the iPSC project are transduced with WT1 antigen-specific TCR that had been already clinically tested, and killer T cells are generated from such TCR-iPSCs, to be administered to acute myeloid leukemia patients. While the adoptive T cell therapies have been mainly directed to be used in cancer immunotherapy, it is possible to apply these approaches to viral infections. Strategies by other groups to regenerate various types of T cells from iPSCs will also be introduced.

Phase 2 study of glucarpidase in patients with delayed methotrexate elimination after high-dose methotrexate therapy.

PURPOSE: High-dose methotrexate therapy (HD-MTX) is a standard treatment for various malignant tumors, but approximately 1-10% of patients experience delayed MTX elimination (DME) that can induce organ damage. Glucarpidase can hydrolyze MTX and thereby lower the level of active MTX in the blood. A multicenter, open-label, phase II investigator-initiated trial (CPG2-PII study) was conducted to evaluate glucarpidase rescue therapy in Japanese patients who showed DME after HD-MTX treatment. To confirm the robustness of this therapy, further corporate-sponsored clinical trial (OP-07-001 study) was conducted. METHODS: The primary endpoint in the CPG2-PII study was to evaluate the proportion of patients of the percentage clinical important reduction (CIR) as an indicator of MTX concentration, which can be managed with leucovorin and supportive care. The primary endpoint of the OP-07-001 study was to evaluate the decreasing rate of plasma MTX concentration at 20 min after glucarpidase administration from the baseline for four patients. Glucarpidase was administered at a dose of 50 U/kg for 15 and 4 patients, respectively in the two studies, and safety was analyzed for each of them. RESULTS: The rate of CIR was 76.9% (95% confidence interval, 46.2-95.0%) in the CPG2-PII study. The median reduction rate of plasma MTX was 98.83% in the OP-07-001 study. Hypersensitivity, blood bilirubin increased, and headache for each patient were the only study drug-related events. CONCLUSION: Glucarpidase showed an effect of reducing plasma MTX concentration in Japanese patients with DME as that observed in a previous US study, confirming its favorable safety and tolerability.

Trends in cell medicine: from autologous cells to allogeneic universal-use cells for adoptive T-cell therapies.

In currently ongoing adoptive T-cell therapies, T cells collected from patients are given back to them after ex vivo activation and expansion. In some cases, T cells are transduced with chimeric antigen receptor (CAR) or T-cell receptor (TCR) genes during the ex vivo culture period in order to endow T cells with the desired antigen specificity. Although such strategies are effective in some types of cancer, there remain issues to be solved: (i) the limited number of cells, (ii) it is time-consuming, (iii) it is costly, and (iv) the quality can be unstable. Points (ii) and (iv) can be solved by preparing allogeneic T cells and cryopreserving them in advance and methods are being developed using healthy donor-derived T cells or pluripotent stem cells as materials. Whereas it is difficult to solve (i) and (iii) in the former case, all the issues can be cleared in the latter case. However, in either case, a new problem arises: rejection by the patient's immune system. Deletion of human leukocyte antigen (HLA) avoids rejection by recipient T cells, but causes rejection by NK cells, which can recognize loss of HLA class I. Various countermeasures have been developed, but no definitive solution is yet available. Therefore, further research and development are necessary.

Regulation of lymphoid-myeloid lineage bias through regnase-1/3-mediated control of Nfkbiz.

ABSTRACT: Regulation of lineage biases in hematopoietic stem and progenitor cells (HSPCs) is pivotal for balanced hematopoietic output. However, little is known about the mechanism behind lineage choice in HSPCs. Here, we show that messenger RNA (mRNA) decay factors regnase-1 (Reg1; Zc3h12a) and regnase-3 (Reg3; Zc3h12c) are essential for determining lymphoid fate and restricting myeloid differentiation in HSPCs. Loss of Reg1 and Reg3 resulted in severe impairment of lymphopoiesis and a mild increase in myelopoiesis in the bone marrow. Single-cell RNA sequencing analysis revealed that Reg1 and Reg3 regulate lineage directions in HSPCs via the control of a set of myeloid-related genes. Reg1- and Reg3-mediated control of mRNA encoding Nfkbiz, a transcriptional and epigenetic regulator, was essential for balancing lymphoid/myeloid lineage output in HSPCs in vivo. Furthermore, single-cell assay for transposase-accessible chromatin sequencing analysis revealed that Reg1 and Reg3 control the epigenetic landscape on myeloid-related gene loci in early stage HSPCs via Nfkbiz. Consistently, an antisense oligonucleotide designed to inhibit Reg1- and Reg3-mediated Nfkbiz mRNA degradation primed hematopoietic stem cells toward myeloid lineages by enhancing Nfkbiz expression. Collectively, the collaboration between posttranscriptional control and chromatin remodeling by the Reg1/Reg3-Nfkbiz axis governs HSPC lineage biases, ultimately dictating the fate of lymphoid vs myeloid differentiation.

Vascular Reconstruction with the Cuff Technique in Mouse Orthotopic Liver Transplantation.

Mouse orthotopic liver transplantation is an effective methodology for investigating the underlying mechanisms of liver ischemia and reperfusion injury. However, the technical challenges pose a barrier to utilizing this valuable experimental model and passing on these skills to the next generation. The most challenging aspect of this procedure is vascular reconstruction, including the portal vein (PV), infrahepatic inferior vena cava (IHIVC), and suprahepatic inferior vena cava. The use of plastic cuffs, rather than sutures, allows for smoother PV and IHIVC reconstruction. Vessels are reconstructed by attaching a cuff made from an intravenous catheter to the tip of the graft vessel and interposing the cuff into the recipient vessel. The two most crucial aspects are properly visualizing the inner lumen of the vessel and avoiding the use of excessive force. Our aim is to provide a technical overview of vascular reconstructions using the cuff technique in recipient surgery. These technical tips for the cuff technique are expected to help microsurgeons facilitate vascular reconstruction and advance their research.

Evolutionary reversion in tumorigenesis.

Cells forming malignant tumors are distinguished from those forming normal tissues based on several features: accelerated/dysregulated cell division, disruption of physiologic apoptosis, maturation/differentiation arrest, loss of polarity, and invasive potential. Among them, accelerated cell division and differentiation arrest make tumor cells similar to stem/progenitor cells, and this is why tumorigenesis is often regarded as developmental reversion. Here, in addition to developmental reversion, we propose another insight into tumorigenesis from a phylogeny viewpoint. Based on the finding that tumor cells also share some features with unicellular organisms, we propose that tumorigenesis can be regarded as "evolutionary reversion". Recent advances in sequencing technologies and the ability to identify gene homologous have made it possible to perform comprehensive cross-species transcriptome comparisons and, in our recent study, we found that leukemic cells resulting from a polycomb dysfunction transcriptionally resemble unicellular organisms. Analyzing tumorigenesis from the viewpoint of phylogeny should reveal new aspects of tumorigenesis in the near future, and contribute to overcoming malignant tumors by developing new therapies.

SETBP1 is dispensable for normal and malignant hematopoiesis.

SETBP1 is a potential epigenetic regulator whose hotspot mutations preventing proteasomal degradation are recurrently detected in myeloid malignancies with poor prognosis. It is believed that the mutant SETBP1 exerts amplified effects of wild-type SETBP1 rather than neomorphic functions. This indicates that dysregulated quantitative control of SETBP1 would result in the transformation of hematopoietic cells. However, little is known about the roles of endogenous SETBP1 in malignant and normal hematopoiesis. Thus, we integrated the analyses of primary AML and healthy samples, cancer cell lines, and a newly generated murine model, Vav1-iCre;Setbp1fl/fl. Despite the expression in long-term hematopoietic stem cells, SETBP1 depletion in normal hematopoiesis minimally alters self-renewal, differentiation, or reconstitution in vivo. Indeed, its loss does not profoundly alter transcription or chromatin accessibilities. Furthermore, although AML with high SETBP1 mRNA is associated with genetic and clinical characteristics for dismal outcomes, SETBP1 is dispensable for the development or maintenance of AML. Contrary to the evidence that SETBP1 mutations are restricted to myeloid malignancies, dependency on SETBP1 mRNA expression is not observed in AML. These unexpected results shed light on the unrecognized idea that a physiologically nonessential gene can act as an oncogene when the machinery of protein degradation is damaged.

[Development of "Off the Shelf" T Cells for Cancer Immunotherapy].

In the area of cancer immunotherapy, the efficacy of strategies in which patient derived T cells are genetically modified ex vivo and administered to patients has been demonstrated. However, some issues have remained to be addressed; the method using autologous T cells is costly and time consuming, and their quality is unstable. The time consuming problem can be solved by preparing allogeneic T cells in advance. Peripheral blood is being considered as a source of allogeneic T cells, and methods are being explored to avoid the risk of rejection or GVHD, but even so the issues of cost and quality stability still remain. On the other hand, use of pluripotent stem cells such as iPS cells or ES cells as material of T cells may solve the cost issue and achieve homogeneity of products. The authors group has been developing a method to generate T cells from iPS cells transduced with a certain T cell receptor gene, and is currently preparing for clinical trials. We believe that, when this strategy is realized, it becomes possible to deliver a universal and homogeneous T cell preparation immediately when needed.

Characteristic differences in the abundance of tumor-infiltrating lymphocytes and intratumoral developing T cells in thymoma, with special reference to PD-1 expression.

PURPOSE: Though programmed cell death-1 (PD-1) inhibitors mainly target tumor-infiltrating lymphocytes (TILs) expressing PD-1, developing T cells in thymus also express PD-1 in their process of maturation. To predict the therapeutic effect of PD-1 inhibitors for thymoma, it is necessary to clarify the proportions of TILs and intratumoral developing T cells. METHODS: The expressions of CD4, CD8, and PD-1 on T cells were analyzed by flow cytometry in 31 thymomas. The amount of T cell receptor excision circles (TRECs), which can be detected in newly formed naïve T cells in the thymus, was evaluated using sorted lymphocytes from thymomas by quantitative PCR. The expressions of granzyme B (GZMB) and lymphocyte activation gene-3 (LAG-3) in PD-1 + CD8 T cells were analyzed by image cytometry using multiplex immunohistochemistry. RESULTS: The PD-1 + rate in both CD4 and CD8 T cells was significantly higher in type AB/B1/B2 than in type A/B3 thymomas. The amounts of TRECs in CD4 and CD8 T cells were significantly higher in type AB/B1/B2 than in type A/B3 thymomas and comparable to normal thymus. PD-1 expression at each stage of T cell development of type AB/B1/B2 thymomas was comparable to that of normal thymus. Both the percentages and cell densities of PD-1 + CD8 T cells expressing GZMB or LAG-3, which are known to contain tumor-reactive T cells, were significantly lower in type AB/B1/B2 thymomas. CONCLUSION: Most PD-1 + T cells in type AB/B1/B2 thymomas are intratumoral developing T cells and are not TILs.

Pharmacokinetics and Pharmacodynamics of Glucarpidase Rescue Treatment After High-dose Methotrexate Therapy Based on Modeling and Simulation.

BACKGROUND: Model-informed approaches are important in drug development, including for dose optimization and the collection of evidence in support of efficacy. MATERIALS AND METHODS: We developed a modified Michaelis-Menten pharmacokinetics/pharmacodynamics model and used it to conduct simulations of glucarpidase at doses between 10 and 80 U/kg rescue treatment after high-dose methotrexate therapy. We carried out a dose-finding modeling and simulation study before a phase II study of glucarpidase. Monte-Carlo simulations were conducted using the deSolve package of R software (version 4.1.2). The proportion of samples in which the plasma methotrexate concentration was less than 0.1 and 1.0 µmol/l at 70 and 120 h after methotrexate treatment was evaluated for each dosage of glucarpidase. RESULTS: The proportion of samples in which the plasma methotrexate concentration was less than 0.1 µmol/l at 70 h after methotrexate treatment was 71.8% and 89.6% at 20 and 50 U/kg of glucarpidase, respectively. The proportion of samples in which the plasma methotrexate concentration was less than 0.1 µmol/l at 120 h after methotrexate treatment was 46.4% and 59.0% at 20 and 50 U/kg of glucarpidase, respectively. CONCLUSION: We determined a recommended glucarpidase dose of 50 U/kg to be ethically acceptable. A rebound in the serum concentration of methotrexate may be observed in many patients after the administration of glucarpidase, and long-term monitoring (over 144 h) of the serum methotrexate concentration may be needed after the administration of glucarpidase. Its validity was confirmed in the phase II study and glucarpidase was approved for manufacturing in Japan.

Development of a population pharmacokinetics and pharmacodynamics model of glucarpidase rescue treatment after high-dose methotrexate therapy.

Introduction: Glucarpidase (CPG2) reduces the lethal toxicity of methotrexate (MTX) by rapid degradation. Methods: In this study, a CPG2 population pharmacokinetics (popPK) analysis in healthy volunteers (phase 1 study) and a popPK-pharmacodynamics (popPK-PD) analysis in patients (phase 2 study, n = 15) who received 50 U/kg of CPG2 rescue for delayed MTX excretion were conducted. In the phase 2 study, the first CPG2 treatment at a dose of 50 U/kg was intravenously administered for 5 min within 12 h after the first confirmation of delayed MTX excretion. The second dose of CPG2, with a plasma MTX concentration >1 µmol/L, was administered to the patient more than 46 h after the start of CPG2 administration. Results: The population mean PK parameters (95% CI) of MTX, obtained from the final model post hoc, were estimated as follows: CLrMTX = 2.424 L/h (95% CI: 1.755-3.093), VcMTX = 12.6 L (95% CI: 10.8-14.3), VpMTX = 2.15 L (95% CI: 1.60-2.70), and α = 8.131 x 105 (4.864 x 105-11.398 x 105). The final model, including covariates, was CLrMTX (L/h): 3.248 x Body Weight/Serum creatinine/60 (CV 33.5%), VcMTX (L): 0.386 x Body Weight/body surface area (CV 29.1%), VpMTX (L):3.052 x Body Weight/60 (CV 90.6%), and α (L/h): 6.545 x 105 (CV 79.8%). Discussion: These results suggest that the pre-CPG2 dose and 24 h after CPG2 dosing were the most important sampling points in the Bayesian estimation of plasma MTX concentration prediction at 48 h. These CPG2-MTX popPK analysis and Bayesian estimation of rebound in plasma MTX concentrations are clinically important to estimate >1.0 µmol/L 48 h after the first CPG2 dosing. Clinical trial registration: https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRS06/JMACTRS06.aspx?seqno=2363, identifier JMA-IIA00078 and https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRS06/JMACTRS06.aspx?seqno=2782, identifier JMA-IIA00097.

Murine breast cancers disorganize the liver transcriptome in a zonated manner.

The spatially organized gene expression program within the liver specifies hepatocyte functions according to their relative distances to the bloodstream (i.e., zonation), contributing to liver homeostasis. Despite the knowledge that solid cancers remotely disrupt liver homeostasis, it remains unexplored whether solid cancers affect liver zonation. Here, using spatial transcriptomics, we thoroughly investigate the abundance and zonation of hepatic genes in cancer-bearing mice. We find that breast cancers affect liver zonation in various distinct manners depending on biological pathways. Aspartate metabolism and triglyceride catabolic processes retain relatively intact zonation patterns, but the zonation of xenobiotic catabolic process genes exhibits a strong disruption. The acute phase response is induced in zonated manners. Furthermore, we demonstrate that breast cancers activate innate immune cells in particular neutrophils in distinct zonated manners, rather than in a uniform fashion within the liver. Collectively, breast cancers disorganize hepatic transcriptomes in zonated manners, thereby disrupting zonated functions of the liver.

Remote solid cancers rewire hepatic nitrogen metabolism via host nicotinamide-N-methyltransferase.

Cancers disrupt host homeostasis in various manners but the identity of host factors underlying such disruption remains largely unknown. Here we show that nicotinamide-N-methyltransferase (NNMT) is a host factor that mediates metabolic dysfunction in the livers of cancer-bearing mice. Multiple solid cancers distantly increase expression of Nnmt and its product 1-methylnicotinamide (MNAM) in the liver. Multi-omics analyses reveal suppression of the urea cycle accompanied by accumulation of amino acids, and enhancement of uracil biogenesis in the livers of cancer-bearing mice. Importantly, genetic deletion of Nnmt leads to alleviation of these metabolic abnormalities, and buffers cancer-dependent weight loss and reduction of the voluntary wheel-running activity. Our data also demonstrate that MNAM is capable of affecting urea cycle metabolites in the liver. These results suggest that cancers up-regulate the hepatic NNMT pathway to rewire liver metabolism towards uracil biogenesis rather than nitrogen disposal via the urea cycle, thereby disrupting host homeostasis.

Aberrant EVI1 splicing contributes to EVI1-rearranged leukemia.

Detailed genomic and epigenomic analyses of MECOM (the MDS1 and EVI1 complex locus) have revealed that inversion or translocation of chromosome 3 drives inv(3)/t(3;3) myeloid leukemias via structural rearrangement of an enhancer that upregulates transcription of EVI1. Here, we identify a novel, previously unannotated oncogenic RNA-splicing derived isoform of EVI1 that is frequently present in inv(3)/t(3;3) acute myeloid leukemia (AML) and directly contributes to leukemic transformation. This EVI1 isoform is generated by oncogenic mutations in the core RNA splicing factor SF3B1, which is mutated in >30% of inv(3)/t(3;3) myeloid neoplasm patients and thereby represents the single most commonly cooccurring genomic alteration in inv(3)/t(3;3) patients. SF3B1 mutations are statistically uniquely enriched in inv(3)/t(3;3) myeloid neoplasm patients and patient-derived cell lines compared with other forms of AML and promote mis-splicing of EVI1 generating an in-frame insertion of 6 amino acids at the 3' end of the second zinc finger domain of EVI1. Expression of this EVI1 splice variant enhanced the self-renewal of hematopoietic stem cells, and introduction of mutant SF3B1 in mice bearing the humanized inv(3)(q21q26) allele resulted in generation of this novel EVI1 isoform in mice and hastened leukemogenesis in vivo. The mutant SF3B1 spliceosome depends upon an exonic splicing enhancer within EVI1 exon 13 to promote usage of a cryptic branch point and aberrant 3' splice site within intron 12 resulting in the generation of this isoform. These data provide a mechanistic basis for the frequent cooccurrence of SF3B1 mutations as well as new insights into the pathogenesis of myeloid leukemias harboring inv(3)/t(3;3).

Propionic Acid, Induced in Gut by an Inulin Diet, Suppresses Inflammation and Ameliorates Liver Ischemia and Reperfusion Injury in Mice.

Liver ischemia and reperfusion injury (IRI) is one of the obstacles in liver surgery such as liver resection and transplantation. In this study, we investigated the preventive effect on mouse liver IRI by feeding mice with inulin, which is a heterogeneous blend of indigestible fructose polymer. Mice were fed either a control ordinary diet (CD) or an inulin diet (ID) containing 5% inulin in the CD, for 14 days before the ischemia and reperfusion (IR) maneuver. IR induced-liver damages were significantly ameliorated in the ID group, compared with those in the CD group. Feeding mice with an ID, but not a CD, elevated levels of Bacteroidetes among gut microbiota, and especially increased Bacteroides acidifaciens in mouse feces, which resulted in significant elevation of short-chain fatty acids (SCFAs) in the portal vein of mice. Among SCFAs, propionic acid (PA) was most significantly increased. The microbial gene functions related to PA biosynthesis were much higher in the fecal microbiome of the ID group compared to the CD. However, the action of PA on liver IRI has not been yet clarified. Direct intraperitoneal administration of PA alone prior to the ischemia strongly suppressed liver cell damages as well as inflammatory responses caused by liver IR. Furthermore, PA suppressed the secretion of inflammatory cytokines from peritoneal macrophages stimulated in vitro through TLR-4 with high-mobility group box 1 protein (HMGB-1), known to be released from apoptotic liver cells during the IR insult. The present study shows that PA may play a key role in the inulin-induced amelioration of mouse liver IRI.

Isolation of TCR genes with tumor-killing activity from tumor-infiltrating and circulating lymphocytes in a tumor rejection cynomolgus macaque model.

To develop effective adoptive cell transfer therapy using T cell receptor (TCR)-engineered T cells, it is critical to isolate tumor-reactive TCRs that have potent anti-tumor activity. In humans, tumor-infiltrating lymphocytes (TILs) have been reported to contain CD8+PD-1+ T cells that express tumor-reactive TCRs. Characterization of tumor reactivity of TILs from non-human primate tumors could improve anti-tumor activity of TCR-engineered T cells in preclinical research. In this study, we sought to isolate TCR genes from CD8+PD-1+ T cells among TILs in a cynomolgus macaque model of tumor transplantation in which the tumors were infiltrated with CD8+ T cells and were eventually rejected. We analyzed the repertoire of TCRα and ß pairs obtained from single CD8+PD-1+ T cells in TILs and circulating lymphocytes and identified multiple TCR pairs with high frequency, suggesting that T cells expressing these recurrent TCRs were clonally expanded in response to tumor cells. We further showed that the recurrent TCRs exhibited cytotoxic activity to tumor cells in vitro and potent anti-tumor activity in mice transplanted with tumor cells. These results imply that this tumor transplantation macaque model recapitulates key features of human TILs and can serve as a platform toward preclinical studies of non-human primate tumor models.

CD153/CD30 signaling promotes age-dependent tertiary lymphoid tissue expansion and kidney injury.

Tertiary lymphoid tissues (TLTs) facilitate local T and B cell interactions in chronically inflamed organs. However, the cells and molecular pathways that govern TLT formation are poorly defined. Here, we identified TNF superfamily CD153/CD30 signaling between 2 unique age-dependent lymphocyte subpopulations, CD153+PD-1+CD4+ senescence-associated T (SAT) cells and CD30+T-bet+ age-associated B cells (ABCs), as a driver for TLT expansion. SAT cells, which produced ABC-inducing factors IL-21 and IFN-γ, and ABCs progressively accumulated within TLTs in aged kidneys after injury. Notably, in kidney injury models, CD153 or CD30 deficiency impaired functional SAT cell induction, which resulted in reduced ABC numbers and attenuated TLT formation with improved inflammation, fibrosis, and renal function. Attenuated TLT formation after transplantation of CD153-deficient bone marrow further supported the importance of CD153 in immune cells. Clonal analysis revealed that SAT cells and ABCs in the kidneys arose from both local differentiation and recruitment from the spleen. In the synovium of aged rheumatoid arthritis patients, T peripheral helper/T follicular helper cells and ABCs also expressed CD153 and CD30, respectively. Together, our data reveal a previously unappreciated function of CD153/CD30 signaling in TLT formation and propose targeting the CD153/CD30 signaling pathway as a therapeutic target for slowing kidney disease progression.

Regeneration of antigen-specific T cells by using induced pluripotent stem cell (iPSC) technology.

In currently ongoing adoptive T-cell therapies, T cells collected from the patient are given back to the patient after ex vivo cell activation and expansion. In some cases, T cells are transduced with chimeric antigen receptor (CAR) or T-cell receptor (TCR) genes during the ex vivo culture period. Although such strategies have been shown to be effective in some types of cancer, there remain issues to be solved; these methods (i) are time-consuming, (ii) are costly and (iii) it is difficult to guarantee the quality because the products depend on patient-derived T cells. To address these issues, several groups including ours have developed methods in which cytotoxic cells are mass-produced by using induced pluripotent stem cell (iPSC) technology. For the regeneration of T cells, the basic idea is as follows: iPSCs produced from T cells inherit rearranged TCR genes, and thus all regenerated T cells should express the same TCR. Based on this idea, various types of T cells have been regenerated, including conventional cytotoxic T lymphocytes (CTLs), γδT cells, NKT cells and mucosal-associated invariant T (MAIT) cells. On the other hand, any cytotoxic cells can be used as the base cells into which CAR is introduced, and thus iPSC-derived NK cells have been developed. To apply the iPSC-based cell therapy in an allogeneic setting, the authors' group developed a method in which non-T-cell-derived iPSCs are transduced with exogenous TCR genes (TCR-iPSC method). This approach is being prepared for a clinical trial to be realized in Kyoto University Hospital, in which acute myeloid leukemia patients will be treated by the regenerated WT1 antigen-specific CTLs.

[The origin of blood cells and myeloid cells].

In human hematopoiesis, cells of various lineages exist, such as neutrophils, lymphocytes, and erythrocytes. Unveiling the pathway from stem cells to the various lineages helps us understand the blood disorders and develop therapies for them. We have studied the developmental pathway of hematopoiesis for decades and found that myeloid potential is retained just before the differentiation into each lineage of the various lineage progenitors. This uniqueness of myeloid cells might reflect the character of mixed-phenotype leukemia and provide a very important clue in determining the evolutional history of blood cells. Recent studies concerning the differentiation pathways of megakaryocytes and granulocytes as well as the findings on the hemocytes of invertebrates have strongly supported the concept of the uniqueness of myeloid cells and enabled us to propose insights into the evolutional history of blood. In this paper, we discuss the origin of blood cells in the context of developmental pathways during ontogeny and phylogeny.

Phase I study of tamibarotene monotherapy in pediatric and young adult patients with recurrent/refractory solid tumors.

PURPOSE: Tamibarotene is a synthetic retinoid that inhibits proliferation and induces differentiation of malignant cells by binding to the retinoic acid receptor α/ß. Previous in vitro studies have shown that some pediatric solid tumors with retinoic acid receptors differentiate in response to retinoic acid. We conducted a phase I dose-escalation study to determine the recommended dose of tamibarotene for further study in pediatric and young adult patients with recurrent/refractory solid tumors. METHODS: Pediatric and young adult patients with recurrent/refractory solid tumors were administered tamibarotene at 4, 6, 8, 10, and 12 mg/m2/day for 14 or 21 days of a 28 day cycle. Safety, efficacy, and pharmacokinetics of tamibarotene were evaluated. RESULTS: Twenty-two patients (median age 8 years) were enrolled in this study. No dose-limiting toxicity (DLT) was encountered, and tamibarotene was generally well tolerated. Two patients experienced severe adverse events (AEs), leading to discontinuation of the treatment. One grade 4 venous thrombosis and one grade 2 erythema multiforme were observed, which promptly resolved after tamibarotene discontinuance. The grade 4 venous thrombosis was a severe AE but not DLT because it occurred after the evaluation period. Pharmacokinetic analyses showed a dose-dependent increase in the maximum drug concentration (Cmax) and area under the concentration-time curve (AUC). None of the patients achieved a complete response or partial response. Seven patients had stable disease lasting longer than 18 weeks. CONCLUSIONS: The recommended dose for phase II study of tamibarotene in pediatric and young adult patients with refractory solid tumors is 12 mg/m2/day for 21 days in a 28 day cycle.