Seiichiro Katagiri

Increased natural killer cells and decreased CD3(+)CD8(+)CD62L(+) T cells in CML patients who sustained complete molecular remission after discontinuation of imatinib.

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Human herpesvirus 6 reactivation on the 30th day after allogeneic hematopoietic stem cell transplantation can predict grade 2–4 acute graft‐versus‐host disease

Viral infections and their occult reactivation occasionally cause not only organ damage, but also exacerbation of acute graft‐versus‐host disease (aGVHD), which may increase transplantation‐related mortality synergistically. To determine correlations between viral reactivation and transplantation‐related complications, we performed various viral screening tests on the 30th day after allogeneic hematopoietic stem cell transplantation (HSCT), and assessed the clinical implications.

Sustained upregulation of effector natural killer cells in chronic myeloid leukemia after discontinuation of imatinib

A number of CML patients who achieve a sustained complete molecular response (CMR) for at least 2 years during imatinib (IM) therapy can discontinue IM without relapse. With the long‐term goal of developing immunological criteria for managing IM therapy in CML patients, we compared the immunophenotypic profiles of three groups of CML patients: those who received IM and had a CMR for more than two consecutive years (CMR group); patients who received IM and did not have a sustained CMR but maintained a major molecular response for more than 2 years (fluctuating CMR group); and patients with a sustained CMR for more than 6 months after IM discontinuation (STOP‐IM group), together with healthy controls. The percentages of effector populations of natural killer (NK) cells, such as interferon (IFN)‐γ+CD3−CD56+ cells, were significantly higher in the STOP‐IM and CMR groups than in the fluctuating CMR and control groups. The elevated levels of these effector NK cells were sustained for more than 3 years after IM discontinuation. In contrast, the percentages of effector memory CD8+ T cells, such as IFN‐γ+ CCR7−CD45RO+CD8+ cells, were significantly higher in the STOP‐IM and control groups than in the CMR and fluctuating CMR groups, possibly owing to IM intake. These results suggest that the immunological activation status of NK cells contributes to CMR maintenance. Higher activation levels of effector NK cells in CML patients being treated with IM might reflect minimization of BCR‐ABL1 transcript levels and therefore could be additive information for determining whether to stop IM.

The BCL2L11 (BIM) deletion polymorphism is a possible criterion for discontinuation of imatinib in chronic myeloid leukaemia patients.

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Effects of the Hedgehog Inhibitor GDC-0449, Alone or in Combination with Dasatinib, on BCR-ABL-Positive Leukemia Cells

Hedgehog (Hh)-glioma-associated oncogene homolog (Gli) signaling is implicated in a large number of human cancers such as leukemia. In this study, we investigated the effects of the potent Hh antagonist GDC-0449 on the BCR-ABL-positive cell line OM9;22 and primary samples when leukemia cells were protected by a feeder cell line (S9 cells). The numbers of OM9;22 cells significantly increased with S9 cells. Treatment of OM9;22 cells with GDC-0449 caused cell growth inhibition and induced apoptosis. Moreover, GDC-0449 inhibited the colony growth of Philadelphia chromosome (Ph)-positive primary samples. We next investigated the effects of a combination of GDC-0449 and dasatinib on these cell lines. The growth inhibition typically promoted by dasatinib was significantly reduced in the presence of S9 cells. Treatment of Ph-positive leukemia cells with GDC-0449 and dasatinib in the presence of S9 caused significantly more cytotoxicity than that caused by each drug alone. Inhibition of Gli1 or Gli2 by siRNA transfection reduced the growth of the Ph-positive cell line K562 and increased cytotoxicity of dasatinib. Moreover, colony formations of Gli1 or Gli2 knockdown cells were also reduced. Data from this study suggest that administration of the Hh inhibitor GDC-0449 inhibits BCR-ABL-positive cell growth and enhances the cytotoxic effects of dasatinib in the presence of feeder cells.

Combination of the ABL kinase inhibitor imatinib with the Janus kinase 2 inhibitor TG101348 for targeting residual BCR-ABL-positive cells

BackgroundThe ABL kinase inhibitor imatinib is highly effective in treating most, but not all, patients with chronic myeloid leukemia (CML). This is because residual CML cells are generally present in the bone marrow microenvironment and are refractory to imatinib. Hematopoietic cytokine receptor signaling is mediated by Janus kinases (JAKs) and their downstream transcription factor, signal transducer and activator of transcription (STAT). TG101348 (SAR302503) is an oral inhibitor of JAK2.MethodsWe investigated the efficacy of imatinib and TG101348 using the break point cluster region-c-Abelson (BCR-ABL)-positive cell line and primary CML samples wherein leukemia cells were protected by a feeder cell line (HS-5).ResultsImatinib treatment resulted in partial inhibition of cell growth in HS-5-conditioned medium. Furthermore, combined treatment with imatinib and TG101348 abrogated the protective effects of HS-5-conditioned medium on K562 cells. Phosphorylation of Crk-L, a BCR-ABL substrate, decreased considerably, while apoptosis increased. In addition, the combined treatment of CD34-positive primary samples resulted in considerably increased cytotoxicity, decreased Crk-L phosphorylation, and increased apoptosis. We also investigated TG101348 activity against feeder cells and observed that STAT5 phosphorylation, granulocyte macrophage colony-stimulating factor, and interleukin 6 levels decreased, indicating reduced cytokine production in HS-5 cells treated with TG101348.ConclusionsThese results showed that JAK inhibitors may enhance the cytotoxic effect of imatinib against residual CML cells and that a combined approach may be a powerful strategy against the stroma-associated drug resistance of Philadelphia chromosome-positive cells.

Immunosurveillance markers may predict patients who can discontinue imatinib therapy without relapse.

Tyrosine kinase inhibitors have dramatically improved the treatment of chronic myeloid leukemia. Recent evidence revealed that some patients with chronic myeloid leukemia can stop imatinib without relapse after achieving a complete molecular response. This review discusses the possible predictive markers to identify these patients who can stop imatinib without relapse.

Downregulation of Plasma miR-215 in Chronic Myeloid Leukemia Patients with Successful Discontinuation of Imatinib

Approximately 40% of chronic myeloid leukemia (CML) patients who discontinue imatinib (IM) therapy maintain undetectable minimal residual disease (UMRD) for more than one year (stopping IM (STOP-IM)). To determine a possible biomarker for STOP-IM CML, we examined plasma miRNA expression in CML patients who were able to discontinue IM. We first screened candidate miRNAs in unselected STOP-IM patients, who had sustained UMRD after discontinuing IM for more than six months, in comparison with healthy volunteers, by using a TaqMan low-density array for plasma or exosomes. Exosomal miR-215 and plasma miR-215 were downregulated in the STOP-IM group compared to the control, indicating that the biological relevance of the plasma miR-215 level is equivalent to that of the exosomal level. Next, we performed real-time quantitative RT-PCR in 20 STOP-IM patients, 32 patients with UMRD on continued IM therapy (IM group) and 28 healthy volunteers. The plasma miRNA-215 level was significantly downregulated in the STOP-IM group (p < 0.0001); we determined the cut-off level and divided the IM group patients into two groups according to whether the plasma miR-215 was downregulated or not. The IM group patients with a low plasma miR-215 level had a significantly higher total IM intake, compared to the patients with elevated miR-215 levels (p = 0.0229). Functional annotation of miR-215 target genes estimated by the Database for Annotation, Visualization and Integrated Discovery (DAVID) bioinformatic tools involved cell cycle, mitosis, DNA repair and cell cycle checkpoint. Our study suggests a possible role of miR-215 in successful IM discontinuation.

Transfusion-transmitted hepatitis E in a patient with myelodysplastic syndromes

Patients with haematological diseases occasionally exhibit liver dysfunction during treatment. This liver dysfunction can have various causes such as therapy-related drugs and hepatitis B and C infections, although the cause is unclear in some cases. It was recently reported that some patients initially diagnosed with drug-induced liver dysfunction actually had hepatitis E1. Several cases of transfusion-transmitted hepatitis E infections have also been reported1,2. In Japan, screening for hepatitis E does not appear to be performed at the initial examination of patients with acute hepatitis. This might be because hepatitis E is believed to be orally transmitted and to occur mainly in developing countries and rarely in developed countries. However, hepatitis E is a zoonotic infectious disease. Cases of regional endemic hepatitis E virus (HEV) infection have been increasing in Europe, the United States, and Japan1. Although HEV usually causes self-limited acute hepatitis, it sometimes progresses to a chronic infection. Most cases of chronic infection occur in patients undergoing solid organ or haematopoietic stem cell transplantation, in those receiving anti-cancer or immunosuppressant drugs, and in patients with human immunodeficiency virus infection, in whom the condition may progress to liver cirrhosis3. HEV RNA persisted for a long period during treatment in a patient with T-cell lymphoma4. Reactivation of HEV hepatitis was reported after an allogeneic haematopoietic stem cell transplant in a patient with Philadelphia chromosome-positive acute lymphoblastic leukaemia5. On the other hand, a low risk of HEV reactivation after haematopoietic stem cell transplantation was also reported6. More studies on the risk of HEV reactivation are, therefore, required. Here, we report the case of a patient with a myelodysplastic syndrome (MDS) who developed acute hepatitis due to transfusion-transmitted HEV infection. We also review the literature on the topic.

Downregulated microRNA-148b in circulating PBMCs in chronic myeloid leukemia patients with undetectable minimal residual disease: a possible biomarker to discontinue imatinib safely

Background A subset of patients with chronic myeloid leukemia (CML) can sustain a complete molecular response after discontinuing imatinib mesylate (IM). We focused on microRNAs (miRNAs), with the aim of finding a molecular biomarker to discriminate which patients can safely and successfully discontinue IM use. Methods To identify miRNAs that showed altered expression in patients who had discontinued IM (STOP-IM group), we first screened miRNA expression of peripheral blood mononuclear cells by using a TaqMan miRNA array on samples from five unselected patients from the STOP-IM group, seven CML patients receiving IM (IM group), and five healthy volunteers. We then performed miRNA quantification in 49 CML patients with deep molecular response. Mann–Whitney U and chi-square tests were used to determine statistical significance for comparisons between the control (healthy volunteers) and test groups (STOP-IM and IM groups). Multiple groups were compared by one-way analysis of variance. Results Downregulation of miR-148b was noted in patients in the STOP-IM group and in a subset of the IM group. We then subdivided the IM patients into two groups: one with downregulated miR-148b expression (IM-1; less than the cut-off value) and the other without downregulated miR-148b expression (IM-2; greater than the cut-off value). The number of patients who had a sustained stable molecular response was significantly lower in IM-2 group. This group also had a significantly lower percentage of natural killer cells. Conclusion Downregulated miR-148 may contribute to immune surveillance in STOP-IM patients and may therefore have potential as additive information in managing CML patients undergoing treatment with IM.