Doctor of Philosophy, Keio University (2016)
Hematology fellowship, Keio University (2012)
Doctor of Medicine, Keio University (2008)
Persistence of leukemic stem cells (LSCs) results in the recurrence of chronic myeloid leukemia (CML) after the administration of tyrosine kinase inhibitors (TKIs). Thus, the detection of minimal residual disease (MRD) with LSC potential can improve prognosis. Here, we analyzed 115 CML patients and found that CD25 was preferentially expressed on the phenotypic stem and progenitor cells (SPCs), and TKI therapy decreased the number of CD25-positive cells in the SPC fraction. To detect MRD harboring BCR-ABL1 fusion DNA, we developed a highly-sensitive method using patient-specific primers and next-generation sequencing. By using this method, we identified that in patients who achieved molecular remission, almost all residual CD25-positive SPCs were BCR-ABL1-negative. Moreover, in some patients BCR-ABL1 was detectable in peripheral B cells but not in SPCs. We conclude that CD25 marks LSCs at diagnosis but does not mark MRD following TKI treatment and that analysis of peripheral B cells can allow sensitive detection of MRD.
View details for DOI 10.1080/10428194.2020.1837366
View details for PubMedID 33106061
Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have promising potential for opening new avenues in regenerative medicine. However, since the tumorigenic potential of undifferentiated pluripotent stem cells (PSCs) is a major safety concern for clinical transplantation, inducible Caspase-9 (iC9) is under consideration for use as a fail-safe system. Here, we used targeted gene editing to introduce the iC9 system into human iPSCs, and then interrogated the efficiency of inducible apoptosis with normal iPSCs as well as diseased iPSCs derived from patients with acute myeloid leukemia (AML-iPSCs). The iC9 system induced quick and efficient apoptosis to iPSCs in vitro. More importantly, complete eradication of malignant cells without AML recurrence was shown in disease mouse models by using AML-iPSCs. In parallel, it shed light on several limitations of the iC9 system usage. Our results suggest that careful use of the iC9 system will serve as an important countermeasure against posttransplantation adverse events in stem cell transplantation therapies.
View details for DOI 10.1038/s41434-020-0179-z
View details for PubMedID 32704085
We encountered a case of a 73-year-old man with acute myeloid leukemia who developed Trichosporon asahii systemic infection while on itraconazole prophylaxis during severe neutropenia. Cryptococcal antigen was useful for diagnosis. Although itraconazole was ineffective in protecting against trichosporonosis, treatment was successful with voriconazole following liposomal amphotericin B.
View details for DOI 10.1016/j.mmcr.2017.11.006
View details for PubMedID 29264110
View details for PubMedCentralID PMC5726745
Hematopoietic stem cells (HSCs) exhibit multilineage differentiation and self-renewal activities that maintain the entire hematopoietic system during an organism's lifetime. These abilities are sustained by intrinsic transcriptional programs and extrinsic cues from the microenvironment or niche. Recent studies using metabolomics technologies reveal that metabolic regulation plays an essential role in HSC maintenance. Metabolic pathways provide energy and building blocks for other factors functioning at steady state and in stress. Here we review recent advances in our understanding of metabolic regulation in HSCs relevant to cell cycle quiescence, symmetric/asymmetric division, and proliferation following stress and lineage commitment, and discuss the therapeutic potential of targeting metabolic factors or pathways to treat hematological malignancies.
View details for DOI 10.1007/s12185-017-2261-x
View details for PubMedID 28540498
Although the introduction of tyrosine kinase inhibitors (TKIs) has improved overall survival of patients with chronic myeloid leukemia (CML), about half of the patients eventually relapse after cessation of TKIs. In contrast, the remainder of the patients maintain molecular remission without TKIs, indicating that the patients' immune system could control proliferation of TKI-resistant leukemic stem cells (LSCs). However, the precise mechanism of immunity against CML-LSCs is not fully understood. We have identified a novel immune target, CXorf48, expressed in LSCs of CML patients. Cytotoxic T cells (CTLs) induced by the epitope peptide derived from CXorf48 recognized CD34+CD38- cells obtained from the bone marrow of CML patients. We detected CXorf48-specific CTLs in the peripheral blood mononuclear cells from CML patients who have discontinued imatinib after maintaining complete molecular remission for more than 2 years. Significantly, the relapse rate of CXorf48-specific CTL-negative patients was 63.6%, compared to 0% in CXorf48-specific CTL-positive patients. These results indicate that CXorf48 could be a promising therapeutic target of LSCs for immunotherapy to obtain durable treatment-free remission in CML patients.
View details for DOI 10.1038/bcj.2017.84
View details for PubMedID 28862699
View details for PubMedCentralID PMC5709753
Hematopoietic stem cells (HSCs) maintain quiescence by activating specific metabolic pathways, including glycolysis. We do not yet have a clear understanding of how this metabolic activity changes during stress hematopoiesis, such as bone marrow transplantation. Here, we report a critical role for the p38MAPK family isoform p38? in initiating hematopoietic stem and progenitor cell (HSPC) proliferation during stress hematopoiesis in mice. We found that p38MAPK is immediately phosphorylated in HSPCs after a hematological stress, preceding increased HSPC cycling. Conditional deletion of p38? led to defective recovery from hematological stress and a delay in initiation of HSPC proliferation. Mechanistically, p38? signaling increases expression of inosine-5'-monophosphate dehydrogenase 2 in HSPCs, leading to altered levels of amino acids and purine-related metabolites and changes in cell-cycle progression in vitro and in vivo. Our studies have therefore uncovered a p38?-mediated pathway that alters HSPC metabolism to respond to stress and promote recovery.
View details for DOI 10.1016/j.stem.2016.05.013
View details for Web of Science ID 000381622000013
View details for PubMedID 27345838
Upon systemic bacterial infection, hematopoietic stem and progenitor cells (HSPCs) migrate to the periphery in order to supply a sufficient number of immune cells. Although pathogen-associated molecular patterns reportedly mediate HSPC activation, how HSPCs detect pathogen invasion in vivo remains elusive. Bacteria use the second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) for a variety of activities. Here, we report that c-di-GMP comprehensively regulated both HSPCs and their niche cells through an innate immune sensor, STING, thereby inducing entry into the cell cycle and mobilization of HSPCs while decreasing the number and repopulation capacity of long-term hematopoietic stem cells. Furthermore, we show that type I interferon acted as a downstream target of c-di-GMP to inhibit HSPC expansion in the spleen, while transforming growth factor-? was required for c-di-GMP-dependent splenic HSPC expansion. Our results define machinery underlying the dynamic regulation of HSPCs and their niches during bacterial infection through c-di-GMP/STING signaling.
View details for DOI 10.1016/j.celrep.2015.02.066
View details for Web of Science ID 000352279800008
View details for PubMedID 25843711
Cytomegalovirus (CMV) enteritis (or colitis) is generally diagnosed in immunocompromised patients in association with human immunodeficiency virus infection as well as in recipients of solid organ or hematopoietic stem cell transplant. CMV enteritis has been reported only sporadically in immunocompetent individuals. We encountered a 76-year-old woman who developed CMV enteritis without any previously identified immunocompromised states. An extensive literature review of 33 cases of CMV enteritis or colitis diagnosed in immunocompetent individuals, including the present case, revealed that the median age of the patients was 68, the accompanying symptoms were diarrhea (76%), abdominal pain (52%), and hematochezia or melena (27%), and that the outcome was generally favorable, including resolution without any treatment in 24% of the patients. CMV enteritis should be recognized more widely as a disease entity not only in immunocompromised patients but also in immunocompetent individuals, especially in elderly populations.
View details for DOI 10.1016/j.jiac.2013.12.004
View details for PubMedID 24751234