Establishment and activity of the planning and acting network for low dose radiation research in Japan (PLANET): 2016-2023.

The Planning and Acting Network for Low Dose Radiation Research in Japan (PLANET) was established in 2017 in response to the need for an all-Japan network of experts. It serves as an academic platform to propose strategies and facilitate collaboration to improve quantitative estimation of health risks from ionizing radiation at low-doses and low-dose-rates. PLANET established Working Group 1 (Dose-Rate Effects in Animal Experiments) to consolidate findings from animal experiments on dose-rate effects in carcinogenesis. Considering international trends in this field as well as the situation in Japan, PLANET updated its priority research areas for Japanese low-dose radiation research in 2023 to include (i) characterization of low-dose and low-dose-rate radiation risk, (ii) factors to be considered for individualization of radiation risk, (iii) biological mechanisms of low-dose and low-dose-rate radiation effects and (iv) integration of epidemiology and biology. In this context, PLANET established Working Group 2 (Dose and Dose-Rate Mapping for Radiation Risk Studies) to identify the range of doses and dose rates at which observable effects on different endpoints have been reported; Working Group 3 (Species- and Organ-Specific Dose-Rate Effects) to consider the relevance of stem cell dynamics in radiation carcinogenesis of different species and organs; and Working Group 4 (Research Mapping for Radiation-Related Carcinogenesis) to sort out relevant studies, including those on non-mutagenic effects, and to identify priority research areas. These PLANET activities will be used to improve the risk assessment and to contribute to the revision of the next main recommendations of the International Commission on Radiological Protection.

LOW DOSE-RATE RADIATION-SPECIFIC ALTERATIONS FOUND IN A GENOME-WIDE GENE EXPRESSION ANALYSIS OF THE MOUSE LIVER.

Life span shortening and increased incidences of cancer and non-cancer diseases were observed in B6C3F1 mice irradiated with gamma-rays at a low dose-rate (LDR) of 20 mGy/d for 400 d. A genome-wide gene expression profiling of livers from mice irradiated at a LDR (20 mGy/d, 100-400 d) was performed. LDR radiation affected specific pathways such as those related to lipid metabolism, e.g. 'Cholesterol biosynthesis' and 'Adipogenesis' in females irradiated for 200 and 300 d at 20 mGy/d, with increased expression of genes encoding cholesterol biosynthesis enzymes (Cyp51, Sqle, Fdps) as age and radiation dose increased. No significant alterations in the expression of these genes were observed in male mice exposed similarly. However, the genes encoding adipogenesis regulators, Srebf1 and Pparg, increased with age and radiation dose in both sexes. Comparison between LDR-irradiated and medium dose-rate (400 mGy/d) male mice revealed quite different gene expression profiles. These results seem to be consistent with the increased incidence of fatty liver and obesity in female mice exposed to LDR radiation and suggest that metabolism is an important target of LDR radiation.

ADAPTIVE RESPONSE IN MICE CONTINUOUSLY IRRADIATED WITH LOW DOSE-RATE RADIATION.

Previous reports showed a reduction in hematopoietic death in mice exposed to a high (challenge) radiation dose if exposed two weeks prior with a relatively small (priming) radiation dose (0.3-0.5 Gy). This in vivo acquisition of radioresistance, known as "adaptive response" or the "Yonezawa effect," was shown in the experiments performed using high dose-rates (HDR) for priming. In the present study, we used low (LDR) and medium dose-rates (MDR) of radiation for priming in male C57BL mice. A total dose of 0.45-0.46 Gy (LDR, 20 mGy/day × 23 days or MDR, 18 mGy/hour × 25 hours) was used for priming, and was followed by challenge exposure 12 days later at an HDR (0.8 Gy/min) to a total dose of 6.75 Gy. Increased survival rates were observed in mice exposed to priming radiation delivered at LDR or MDR, suggesting that the adaptive responses induced are comparable with those induced at HDR.

Successful Cord Blood Transplantation in a Werner Syndrome Patient with High-risk Myelodysplastic Syndrome.

Werner syndrome (WS) confers a high risk of the development of neoplasias, including hematological malignancies, and curative treatment for these malignancies is difficult to achieve. A 44-year-old man with myelodysplastic syndrome was admitted to our hospital. He was diagnosed with mutation-proven WS. He underwent cord blood transplantation (CBT) following fludarabine, busulfan, and melphalan administration. A chimerism analysis of his marrow blood on day 62 showed a donor pattern >95%, which confirmed engraftment. The patient lived for 15 months while maintaining remission of MDS without treatment-related toxicity. Our case shows that CBT can be a treatment modality for WS patients with hematological malignancies.

Screening of biomarkers for liver adenoma in low-dose-rate γ-ray-irradiated mice.

PURPOSE: Chronic low-dose-rate (20 mGy/day) γ-irradiation increases the incidence of hepatocellular adenomas (HCA) in female B6C3F1 mice. The purpose of this study is to identify potential serum biomarkers for these HCAs by a new approach. MATERIAL AND METHODS: Microarray analysis were performed to compare the gene expression profiles of HCAs from mice exposed to low-dose-rate γ-rays with those of normal livers from non-irradiated mice. From the differentially expressed genes, those for possibly secretory proteins were selected. Then, the levels of the proteins in sera were analysed by ELISA. RESULTS: Microarray analysis identified 4181 genes differentially expressed in HCAs (>2.0-fold). From these genes, those for α-fetoprotein (Afp), α-1B-glycoprotein (A1bg) and serine peptidase inhibitor Kazal type-3 (Spink3) were selected as the genes for candidate proteins. ELISA revealed that the levels of Afp and A1bg proteins in sera significantly increased and decreased, respectively, in low-dose-rate irradiated mice with HCAs and also same tendency was observed in human patients with hepatocellular carcinomas. CONCLUSION: These results indicate that A1bg could be a new serum biomarker for liver tumor. This new approach of using microarray to select genes for secretory proteins is useful for prediction of novel tumor markers in sera.

Efficacy of prophylactic irradiation to the contralateral testis for patients with advanced-stage primary testicular lymphoma: an analysis of outcomes at a single institution.

BACKGROUND: Primary testicular lymphoma (PTL) is a rare, extranodal lymphoma that often relapses in the contralateral testis. We evaluated outcomes in patients with any stage of PTL who had received CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone) with rituximab chemotherapy and prophylactic radiotherapy to the contralateral testis. METHODS: We retrospectively identified 15 patients (median age 66 years; range 39-81) diagnosed with diffuse large B-cell PTL in the period 2000-2014. Characteristics and outcomes of these cases were evaluated. RESULTS: All patients received initial orchiectomy followed by CHOP with or without rituximab. Thirteen patients received prophylactic irradiation to the contralateral testis. During follow-up (median 67 months; range 8-190), one patient died of PTL, three died of other disease, and nine were free from relapse. For stage I-II disease, 5-year progression-free and overall survival rates were 80 and 100%, respectively. For stage III-IV PTL, 5-year progression-free and overall survival rates were 50 and 72%, respectively. Notably, no patient developed contralateral testicular involvement after prophylactic irradiation. CONCLUSIONS: The observed outcomes suggest that the combination of (i) CHOP plus rituximab and (ii) radiotherapy for local recurrence prophylaxis is promising for both stage I-II and stage III-IV PTL.

Low neutrophil alkaline phosphatase score is a new aspect of calreticulin-mutated myeloproliferative neoplasms.

Calreticulin (CALR) and JAK2-V617F gene mutations, which are major genetic mutations in patients with primary myelofibrosis (PMF) and essential thrombocythemia (ET), exert different effects on the clinical features and outcomes of these diseases. We analyzed 88 and 9 patients with ET and PMF, respectively, and determined the differences in the clinical characteristics of ET patients with JAK2-V617F compared with CALR mutations. The frequency of the JAK2-V617F and CALR mutations were 64 and 22 %, respectively. Patients with CALR mutations were younger, had a lower white blood cell count, and had a lower rate of thrombotic events than patients with the JAK2 mutation. The neutrophil alkaline phosphatase (NAP) score of 16 patients with CALR mutations was significantly lower than the normal controls, which was mainly due to the high proportion of NAP-negative neutrophils. This is the first report to show an association between CALR mutations in patients with myeloproliferative neoplasms (MPN) and the NAP score. Although the mechanism is unclear, the NAP score could be a useful and reliable biochemical marker to discriminate the mutational status of MPN patients. Further investigation is warranted to determine whether these characteristics contribute to the pathogenesis of MPN and the NAP score.

Sphingosine-1-phosphate receptor 1 as a prognostic biomarker and therapeutic target for patients with primary testicular diffuse large B-cell lymphoma.

Sphingosine-1-phosphate (S1P) is a potent lipid mediator that is produced during the metabolism of sphingolipid by sphingosine kinase. S1P has been implicated in the migration and trafficking of lymphocytes and several lymphoid malignancies through S1P receptors. Moreover, the overexpression of sphingosine-1-phosphate receptor 1 (S1PR1) has been correlated with the constitutive activation of signal transducer and activator of transcription (STAT)3 and poor prognosis of diffuse large B-cell lymphoma (DLBCL). Thus, in this study, we examined the expression of S1PR1 in 198 DLBCL samples collected from nodal and various extranodal sites and sub-classified formalin-fixed paraffin-embedded tissue samples into germinal centre B-cell-like (GCB) and non-GCB subgroups using immunohistochemistry. These analyses showed S1PR1 overexpression in 15·7% of all cases with DLBCL and in 54·2% of 24 cases with primary testicular (PT)-DLBCL; S1PR1 expression correlated with S1PR1mRNA expression and STAT3 phosphorylation in fresh samples. Analyses of data from a single institution suggested that S1PR1 overexpression was an independent negative prognostic marker in 68 patients with DLBCL of clinical stages I and II. The present high prevalence of S1PR1 overexpression warrants the consideration of PT-DLBCL as a distinct disease subtype and suggests the potential of the S1P/S1PR1 axis as a therapeutic target.

PIEZO1 gene mutation in a Japanese family with hereditary high phosphatidylcholine hemolytic anemia and hemochromatosis-induced diabetes mellitus.

Hereditary xerocytosis (HX) or dehydrated hereditary stomatocytosis (DHS) [OMIM 194380], in which PIEZO1 gene mutation has recently been identified, is difficult to diagnose. We report here the discovery of a PIEZO1 gene mutation in a Japanese family (father, daughter, and son) who were previously diagnosed with hereditary high phosphatidylcholine hemolytic anemia (HPCHA). All of the affected family members had non-spherocytic hemolytic anemia associated with severe hemochromatosis-related diabetes mellitus. Although the causative correlation between HPCHA and PIEZO1-gene mutated HX/DHS remains to be clarified, our findings raise an important question as to whether any of the HPCHA cases previously diagnosed in Japan may have in fact been the form of hemolytic anemia known as HX/DHS with PIEZO1 gene mutation.

[Correlation between serum L-carnitine concentration and neutrophil engraftment in patients treated with cord blood transplantation].

In cord blood transplantation (CBT), the amount of time elapsing until hematological engraftment has effects on the transplantation results. Carnitine deficiency has been reported to cause erythropoietin refractory anemia in chronic hemodialysis patients and thrombocytopenia or leukopenia of cirrhosis, and carnitine supplementation can improve hematopoiesis in patients with hepatic or renal failure. Patients who receive CBT may suffer from carnitine deficiency, but no studies have investigated the carnitine status of such patients. Herein, we determined the concentration of free carnitine (FC) and investigated the correlation between FC and engraftment in patients who received CBT. Twenty-three patients who received CBT at our hospital during the period from April 2013 to January 2015 were enrolled in this study. One patient was excluded because of graft failure, such that 22 patients were ultimately evaluable. FC concentrations of the patients were sequentially monitored at 4 time points (before conditioning therapy, day 0, day 7, and day 14), basic laboratory data were collected, and their correlations with engraftment were analyzed. FC concentrations of the patients were generally low (before conditioning therapy: 33.1, day 0: 43.2, day 7: 38.3, and day 14: 37.8 µmol/l). Significant inverse correlations were observed between FC concentrations and the number of days required for neutrophil engraftment on day 0 and day 14 (before conditioning therapy: P=0.15, r=-0.33, day 0: P=0.04, r=-0.43, day 7: P=0.30, r=-0.23, and day 14: P=0.01, r=-0.55). These results suggest carnitine to be an important nutrient that promotes hematopoietic recovery after CBT.

Primary colorectal lymphoma comprising both components of diffuse large B-cell lymphoma and mucosa-associated lymphoid tissue lymphoma combined with cytomegalovirus colitis.

A 16-year-old girl presented to our hospital with diarrhea and abdominal pain. The macroscopic findings of colonoscopy revealed multiple submucosal tumors and multiple ulcers, which were localized in the sigmoid colon, and diffuse granular mucosa which extended to the total colon. The pathological diagnosis was malignant lymphoma comprising both components of diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma, because the large lymphoma cells were CD20+, CD10-, and CD5-. Furthermore, immunohistochemical analysis of colorectal biopsy samples from multiple ulcers revealed cytomegalovirus (CMV)-positive cells. The patient was diagnosed with primary colorectal lymphoma comprising both components of DLBCL and MALT lymphoma combined with CMV colitis. She received anti-viral medication and chemotherapy.

Analysis of Hereditary Elliptocytosis with Decreased Binding of Eosin-5-maleimide to Red Blood Cells.

Flow cytometric test for analyzing the eosin-5-maleimide (EMA) binding to red blood cells has been believed to be a specific method for diagnosing hereditary spherocytosis (HS). However, it has been reported that diseases other than HS, such as hereditary pyropoikilocytosis (HPP) and Southeast Asian ovalocytosis (SAO), which are forms in the category of hereditary elliptocytosis (HE), show decreased EMA binding to red blood cells. We analyzed EMA binding to red blood cells in 101 healthy control subjects and 42 HS patients and obtained a mean channel fluorescence (MCF) cut-off value of 36.4 (sensitivity 0.97, specificity 0.95). Using this method, we also analyzed 12 HE patients. Among them, four HE patients showed the MCF at or below the cut-off value. It indicates that some HE patients have decreased EMA binding to red blood cells. Two of these four HE patients were classified as common HE, and two were spherocytic HE with reduced spectrin. This study demonstrates that, in addition to patients with HPP or SAO, some HE patients have decreased EMA binding to red blood cells.

[Hereditary red cell membrane disorders in Japan: comparison with other countries].

Red cell membrane disorders are the most common type of inherited hemolytic disorders in the Japanese population. In hereditary spherocytosis (HS), the primary presentation is a loss of membrane surface area, leading to reduced deformability because of defects in the membrane proteins ankyrin, band 3, ß-spectrin, α spectrin, or protein 4.2 (P4.2). Complete P4.2 deficiencies, which are inherited in an autosomal recessive manner, comprise a unique HS subgroup and are common in Japanese, but rare in other populations. In contrast, the principle presentation in hereditary elliptocytosis (HE) is mechanical weakness of the erythrocyte membrane skeleton due to defects in α-spectrin, ß-spectrin, or protein 4.1. Although α-spectrin mutations are the most frequent cause of HE in Caucasian, African, and Mediterranean populations, these mutations are rare in the Japanese population, in which P4.1 deficiencies are instead most common. Furthermore, hereditary stomatocytoses (HSt) are disorders of monovalent cation permeability in the red cell membrane.

[Band 3 deficiency as a cause of hereditary spherocytosis].

Band 3 protein accounts for the largest percentage of whole erythrocyte membrane proteins. Abnormalities in this protein are closely associated with pathologies including hereditary spherocytosis (HS), Southeast Asian ovalocytosis and distant renal tubular acidosis. Currently, EMA binding capacity measurement in erythrocytes is the most useful screening test for diagnosing HS. We have also demonstrated reduced EMA binding capacity in patients with HS who have deficiencies of membrane proteins such as ankyrin not directly binding to EMA and who have as yet undetectable abnormalities of membrane proteins. However, even patients with hereditary elliptocytosis, who have a partial spectrin deficiency, were found to show reduced EMA binding capacity. Six of 7 had spherocytic elliptocytosis. Therefore, it is necessary to meticulously diagnose HS by ruling out all other possibilities.

[Performance Assessment of a Newly Developed Rapid Diagnostic Reagent for Human Immunodeficiency Virus].

Extremely early diagnosis of human immunodeficiency virus (HIV) infection has been considered highly important for its treatment. We conducted a performance assessment of a newly developed rapid diagnostic reagent for HIV by using a fourth-generation immunochromatographic assay (Alere HIV Combo). We used whole-blood, plasma, and serum samples obtained from 250 Japanese adults who visited the Kawasaki Medical School Hospital and underwent HIV screening tests. We also used 12 types of commercial HIV-1 sero- conversion panels and World Health Organization standard antigens. This method, which has a detection sensitivity of 100% and a specificity of 99.3%, was as accurate as the chemiluminescent immunoassay (CLIA) method. In a sensitivity test using seroconversion panels in the early phase of infection, the mean duration until positive conversion was 19.3 days. With this method having a high detection sensitivity for HIV-1p24 antigen, the results from whole-blood samples were the same as those from plasma and serum samples. Therefore, it can be considered as a useful rapid measurement method for general practice.

WRN protein as a novel erythroblast immunohistochemical marker with applications for the diagnosis of Werner syndrome.

Genetic testing for mutations in the WRN gene is critical for the diagnosis of Werner syndrome (WS); however, these tests cannot be performed in a clinical setting. Nearly all of the WRN mutations result in expression of truncated WRN proteins that are missing the C-terminal nuclear localization signal. We evaluated the use of WRN protein immunohistochemistry for diagnosing WS using paraffin-embedded bone marrow sections. Using a well-defined commercially available polyclonal antibody against the C terminus of WRN, we found that of all the cell types tested, bone marrow erythroid precursors showed the strongest nuclear expression of WRN. Immunohistochemical analysis of bone marrow samples from 120 patients with non-WS hematological disorders (age range, 7 days-90 years) revealed WRN staining of the nuclei of CD71-positive early and late erythroid precursors. Erythroblasts negative for WRN immunostaining were only observed in two patients, both of whom were diagnosed with WS: one with concomitant myelodysplastic syndrome and the other with erythroleukemia with overexpression of TP53. Western blot analysis and immunocytochemistry indicated WRN was localized in the nuclei of the four positive control cell lines from non-WS patients but not in the five cell lines from WS patients, who had three different types of WRN mutations. Thus, immunohistochemical detection of WRN in erythroblasts from bone marrow paraffin sections could be useful in screening of WS cases and worthy of further molecular confirmation.

Delayed false elevation of circulating tacrolimus concentrations after cord blood transplantation in a patient with myelodysplastic syndrome.

We herein describe the case of a 60-year-old man with a history of Behçet's disease and myelodysplastic syndrome who received cord blood transplantation (CBT). The patient was given anti-thymocyte globulin conditioning and tacrolimus to prevent graft-versus-host disease. Two months after CBT, his blood Tac concentration measured by an antibody-conjugated magnetic immunoassay (ACMIA) was found to have increased >4-fold, even after the Tac treatment was stopped. This false response was caused by the interference of endogenous heterophilic antibodies with ACMIA. Therefore, physicians must be aware of possible false ACMIA results for patients with a history of autoimmune disease and/or treated by xenogeneic antibody therapy.

Severe Colitis Associated with both Epstein-Barr Virus and Cytomegalovirus Reactivation in a Patient with Severe Aplastic Anemia.

Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are members of the herpesvirus family and common causes of viral infection in humans. CMV infection of the gastrointestinal tract occurs mainly in immunocompromised individuals, on the other hand EBV infection and reactivation involving the gastrointestinal tract is very rare. A 56-year-old man was diagnosed with severe aplastic anemia and treated with antithymocyte globulin (ATG) and cyclosporine (CSP). After 2 years of ATG/CSP therapy, he suddenly started passing bloody diarrhea and developed a high fever despite CSP treatment. Endoscopic features included severe edema and multiple superficial ulcers; the patient was initially diagnosed with severe colitis resembling inflammatory bowel disease (IBD). However, his symptoms did not resolve with steroid treatment. Immunohistochemical analysis of samples obtained from a second colonoscopy showed cells positive for CMV, and in situ hybridization revealed EBV-encoded small RNA-1-positive cells. Additionally, the patient's serum was positive for C7-HRP, and both blood and colon tissues were positive for EBV DNA, which was detected using PCR analysis. We finally diagnosed the patient with colitis associated with reactivation of both CMV and EBV. The patient remains diarrhea-free after 1.5 years with scheduled globulin treatment and after cessation of immunosuppressive drug therapy. To our knowledge, this is the first reported case of an immunodeficient patient with severe hemorrhagic colitis that was associated with reactivation of both EBV and CMV, and whose endoscopic findings mimicked IBD.

Philadelphia chromosome-positive acute lymphoblastic leukemia with extramedullary and meningeal relapse after allogeneic hematopoietic stem cell transplantation that was successfully treated with dasatinib.

Central nervous system (CNS) relapse is a critical issue while treating Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). A 58-year-old woman with Ph-positive ALL who relapsed after bone marrow transplantation for meningeal leukemia was treated with high-dose methotrexate, which resulted in remission. She underwent allogeneic cord blood transplantation followed by reduced intensity conditioning chemotherapy with imatinib; however, she experienced CNS relapse and developed an extramedullary mass on the right side of the temporal region. We treated 40 mg of dasatinib once daily, which had to be temporarily discontinued because she developed grade 2 pleural effusion and grade 2 hematemesis. After reinitiation of dasatinib, the extramedullary mass disappeared and meningeal leukemia ameliorated almost immediately. With 40 mg dasatinib administered once daily, its trough level and cerebrospinal fluid (CSF) concentration were 32 ng/mL and below the sensitivity threshold of 1 ng/mL, respectively. Treatment was continued, and the patient remained in complete remission until she died of pneumonia 7 years after the initial diagnosis of ALL. Dasatinib can be an effective treatment for Ph-positive ALL with CNS relapse. Although the concentration in the CSF seems low, it may be sufficient to exert anti-leukemic effects in the human CNS.