A 40-year-old man was diagnosed with Langerhans cell histiocytosis (LCH) in October 2010. His LCH was refractory to conventional chemotherapy, and thus worsened to Langerhans cell sarcoma (LCS) in May 2011. Although we repeated combination chemotherapies, new infiltration of the liver and bone marrow, as well as primary lesions of the bone, lymph nodes, and skin, appeared. These intensive chemotherapies caused candida liver abscesses, invasive aspergillosis, disseminated varicella zoster virus infection and bacterial sepsis. We administered bendamustine for chemotherapy, which resulted in a partial response (PR) with no severe adverse events. Because of pancytopenia caused by secondary myelodysplastic syndrome, we stopped the bendamustine chemotherapy after two courses. PR was maintained for 4 months. We plan to perform allogeneic hematopoietic stem cell transplantation from a sibling donor after a conditioning regimen. Optimal therapy for adult LCH, which is a rare and treatment-resistant disease, has yet to be established. Bendamustine is a potential chemotherapeutic agent for standard treatment of LCS.
Significance Aminoacyl-tRNA synthetases (aaRSs) catalyze aminoacylation of tRNAs in the first step of protein synthesis in the cytoplasm. However, in higher eukaryotes, they acquired additional functions beyond translation. In the present study, we show that an activated form of tyrosyl-tRNA synthetase (YRS ACT ) functions to enhance megakaryopoiesis and platelet production in vitro and in vivo. These findings were confirmed with human megakaryocytes differentiated from peripheral blood CD34 + hematopoietic stem cells and with human induced pluripotent stem (iPS) cells. The activity of YRS ACT is independent of thrombopoietin (TPO), as evidenced by expansion of the megakaryocytes from iPS cell-derived hematopoietic stem cells from a patient deficient in TPO signaling. These findings demonstrate a previously unrecognized function of an aaRS which may have implications for therapeutic interventions.
Recombinant matrices have enabled feeder cell-free maintenance cultures of human pluripotent stem cells (hPSCs), with laminin 511-E8 fragment (LM511-E8) being widely used. However, we herein report that hPSCs maintained on LM511-E8 resist differentiating to multipotent hematopoietic progenitor cells (HPCs), unlike hPSCs maintained on LM421-E8 or LM121-E8. The latter two LM-E8s bound weakly to hPSCs compared with LM511-E8 and activated the canonical Wnt/β-catenin signaling pathway. Moreover, the extracellular LM-E8-dependent preferential hematopoiesis was associated with a higher expression of integrin β1 (ITGB1) and downstream integrin-linked protein kinase (ILK), β-catenin and phosphorylated JUN. Accordingly, the lower coating concentration of LM511-E8 or addition of a Wnt/β-catenin signaling activator, CHIR99021, facilitated higher HPC yield. In contrast, the inhibition of ILK, Wnt or JNK by inhibitors or mRNA knockdown suppressed the HPC yield. These findings suggest that extracellular laminin scaffolds modulate the hematopoietic differentiation potential of hPSCs by activating the ITGB1-ILK-β-catenin-JUN axis at the undifferentiated stage. Finally, the combination of low-concentrated LM511-E8 and a revised hPSC-sac method, which adds bFGF, SB431542 and heparin to the conventional method, enabled a higher yield of HPCs and higher rate for definitive hematopoiesis, suggesting a useful protocol for obtaining differentiated hematopoietic cells from hPSCs in general.
Sunitinib is an orally administered multi-targeted tyrosine kinase inhibitor and has been approved for the treatment of advanced renal cell carcinoma (RCC). It is well known that sunitinib induces hematologic adverse events, such as neutropenia, anemia, and thrombocytopenia, primarily through myelosuppression. Here, we report that the first case of immune-thrombocytopenia occurred in a patient receiving sunitinib for the treatment of metastatic RCC. The thrombocytopenia was refractory to repeated platelet transfusion. The bone marrow aspiration study revealed an increased number of megakaryocytes. No thrombotic microangiopathy was seen. The thrombocytopenia was successfully treated with high-dose corticosteroid, although intravenous immunoglobulin administration was not effective. These findings suggest that an immune-mediated mechanism was responsible for the thrombocytopenia in this patient, which developed during sunitinib administration.
Abstract We recently achieved the first-in-human transfusion of induced pluripotent stem cell-derived platelets (iPSC-PLTs) as an alternative to standard transfusions, which are dependent on donors and therefore variable in supply. However, heterogeneity characterized by thrombopoiesis-biased or immune-biased megakaryocytes (MKs) continues to pose a bottleneck against the standardization of iPSC-PLT manufacturing. To address this problem, here we employ microRNA (miRNA) switch biotechnology to distinguish subpopulations of imMKCLs, the MK cell lines producing iPSC-PLTs. Upon miRNA switch-based screening, we find imMKCLs with lower let-7 activity exhibit an immune-skewed transcriptional signature. Notably, the low activity of let-7a-5p results in the upregulation of RAS like proto-oncogene B ( RALB ) expression, which is crucial for the lineage determination of immune-biased imMKCL subpopulations and leads to the activation of interferon-dependent signaling. The dysregulation of immune properties/subpopulations, along with the secretion of inflammatory cytokines, contributes to a decline in the quality of the whole imMKCL population.
