PURPOSE There are problems with dose management in X-ray computed tomography (CT) because the protocol used for any examination is not always in the same scan range. The purpose of this study was to investigate the usefulness of setting the CT protocol based on the scan range. METHODS We evaluated the examination data of patients who underwent plain CT based on a scan range of chest to pelvis and abdomen to pelvis. The previous protocol [Chest-Abdomen Routine] was changed to the current protocols [Chest_Abdomen] and [Chest_Pelvis], and the previous protocol of [Abdomen Routine] was changed to the current protocols [Abdomen] and [Abdomen_Pelvis]. Examination data of height, scan length, volume CT dose index (CTDIvol), and dose length product (DLP) were obtained from digital imaging and communications in medicine, and radiation dose structured report using Radimetrics. The relationship between patient height and scan range, and CTDIvol and DLP was indicated in a scatter plot. Standard deviation (SD) of scan length and DLP were compared between current and previous protocols. Outliers were defined as the data exceeding average ±2SD. RESULT The SD of scan length decreased by 77.1% on abdomen to pelvis, and the SD of DLP decreased by 65.2% on abdomen to pelvis. The causes of the outliers were CT scan range, scan parameter, arm position, metal implants, and body thickness of patients. CONCLUSION Setting CT protocols based on the scan range reduced SD of scan length and DLP. It was helpful for reducing the number of scan range outliers and analyzing the cause of outliers.

The purpose of this study was to measure the scatter radiation intensity during transforaminal lumbar interbody fusion using a mobile C-arm system (Arcadis Orbic 3D; Siemens) and minimize radiation exposure. Dosimetry was performed with anterior-posterior and lateral continuous fluoroscopy, and cone beam computed tomography (CT). A scaffold tower (L: 300 cm×W: 200 cm×H: 150 cm) was built with radiation-resistant paper cylinders at intervals of 50 cm and plastic joints over the bed, and 100 optically stimulated luminescence dosimeters (nanoDot; Nagase Landauer) were placed on each joint. A human torso phantom from head to pelvis (Kyoto Kagaku) was positioned on the bed in a prone position. The scatter radiation dose in a lateral view was highest on the X-ray tube side at the height of 100 cm (170.5 μGy/min). The scatter radiation dose increased significantly on the X-ray tube side during lateral continuous fluoroscopy. Continuous change of surgeons' standing positions is important to minimize radiation exposure received by a specific surgeon.

We herein report the results of the New TARGET study 2nd-line, which collected data on patients with chronic-phase (CP) chronic myeloid leukemia (CML) who received a 2nd-line tyrosine kinase inhibitor (TKI) because of resistance and/or to a 1st-line TKI. A total of 98 patients were enrolled intolerance between April 2010 and March 2013, and 82 patients were analyzed. The median age was 54 years (range 22–88 years). Seventy-six patients (93%) received imatinib as the 1st-line TKI. Forty-five (55%) and 37 (45%) patients began nilotinib and dasatinib treatments at entry, respectively. First-line TKI treatment achieved complete hematological response in 79 patients (96%) and complete cytogenetic response (CCyR) in 49 patients (60%), respectively. Nine patients (11%) had BCR-ABL1 kinase domain point mutations at enrollment. The estimated 3-year progression-free-survival rate after enrollment was 98.7% (95% CI 91.1–99.8%). Overall, the probabilities of achieving CCyR and a major molecular response were 89.3% (95% CI 81.4–94.8%) and 87.2% (95% CI 78.1–93.8%), respectively. There were no new safety issues. This study demonstrated that CML-CP patients in Japan who are resistant and/or intolerant to a 1st-line TKI can achieve an extremely good outcome by 2nd-line TKI treatment.

This retrospective, multicenter observational study investigated the prognostic value of pretreatment serum soluble interleukin-2 receptor (sIL-2R) level for outcomes of newly diagnosed follicular lymphoma (FL) grade 1-3a who required treatment at diagnosis. A total of 628 patients were recorded, and 502 of these were eligible for analysis. Patients were divided into four quartiles, based on their serum sIL-2R levels as follows: Q1 (sIL-2R < 520 IU/mL), Q2 (520 <= sIL-2R < 1030 IU/mL), Q3 (1030 <= sIL-2R < 2530 IU/mL) and Q4 (sIL-2R >= 2530 IU/mL). Using a multivariable Cox proportional-hazards model, we showed the adjusted probability of overall survival (OS) decreased with increasing serum sIL-2R levels (p for trend = .007). Similar trends were observed for disease-specific survival (DSS) and progression-free survival (PFS). In conclusion, pretreatment serum sIL-2R levels significantly and dose-dependently associate with worse outcomes (OS, DSS and PFS) of patients with newly diagnosed FL.

Purpose: To assess the usefulness of effective diameter (D-eff) for CT dose management of adult patients with unknown body weight. Methods: A total of 642 adult patients whose height and weight had been measured before CT examination (chest CT using Aquilion Prime SP, 428 patients; chest CT using Biograph mCT, 100 patients; and abdominal CT using Aquilion Prime SP, 114 patients) were retrospectively examined between April 2018 and September 2019. The D-eff was automatically calculated from the lateral diameter on a CT localizer radiograph by a dose management software (Radimetrics). In order to determine the correlation between body weight and D-eff, we compared volume CT dose index and dose length product between patients with body weight between 50 and 70 kg and those with D-eff equivalent to body weight between 50 and 70 kg. Correlation analysis was performed by Pearson's product-moment correlation, and statistical analyses were performed by using t-test. Results: The correlation coefficient values between body weight and D-eff were 0.920 for chest CT using Aquilion Prime SP, 0.929 for chest CT using Biograph mCT, and 0.805 for abdominal CT using Aquilion Prime SP. In both chest and abdominal CT scans, there were no significant differences in volume CT dose index and dose length product between patients with body weight between 50 and 70 kg and those with D-eff equivalent to body weight between 50 and 70 kg. Conclusions: The D-eff may be useful as a somatometric parameter for CT dose management of adult patients with unknown body weight.

Introduction: Serum soluble interleukin-2 receptor (sIL-2R) is recognized as a tumor-related biomarker of malignant lymphomas, including follicular lymphoma (FL). The objective of this study is to assess the prognostic significance of pretreatment serum sIL-2R level for disease-specific overall survival (DSS) in patients with FL. Methods: We retrospectively analyzed medical records of our 10 individual institutions to identify all patients (pts) ≥ 18 years old with newly diagnosed FL between 01/01/2008 and 12/31/2018. Only pts with FL grade 1-3b, confirmed at pathological review, were included. Pts with histological transformation at diagnosis were excluded. Serum sIL-2R was determined by sandwich enzyme-linked immunosorbent assay. Clinical characteristics, therapies, response, relapse patterns and follow up status were collected and analyzed in the cohort. DSS was defined from the time of initial diagnosis to death due to lymphoma or last follow up. DSS was analyzed according to Kaplan Meier method and differences between subgroups were compared with log-rank test. Multivariate cox regression analysis was used to investigate associations of sIL-2R, FL International Prognostic Index (FLIPI) and progression or relapse within 24 months after diagnosis (POD24) with DSS. Serum levels of sIL-2R was measured before initiation of treatment and the data on the nearest date of the diagnostic biopsy within six months was adopted. Results: We recorded 565 pts and 535 pts of them with pretreatment serum sIL-2R levels available were included in the analysis with median age 64 years (range: 30-90) and 305 females (57%). Clinical characteristics are summarized in Table 1. The median of the serum sIL-2R level was 896 IU/mL (range: 145 - 23800). We decided an optimal cutoff value of 1800 IU/mL by using receiver operating characteristic (ROC) analysis, which showed it was 1830 IU/mL (AUC : 0.76, 95%CI : 0.67 - 0.84). Various poor prognostic indicators, such as bulky mass, increased LDH, ≥5 nodal lesions, poor performance status (PS), bone marrow invasion, FLIPI and FLIPI-2 high-risk, decreased Hb, advanced disease, high tumor burden, increased β2MG and existence of B symptoms, were strongly associated with high serum sIL-2R level (≥1800 IU/mL), and high sIL-2R level correlated with POD24 (P<0.001, Chi-squared test). The estimated 10-year DSS rate was 87.2% with a median follow up duration of 4.4 years. In pts with POD24 (96 pts, 18%), DSS was significantly worse than those with non-POD24; 64.3% vs 93.0% (P<0.001) and rituximab maintenance did not improve DSS in both groups (P=0.85 and 0.98, respectively). In patients with sIL-2R level of ≥1800 (high sIL-2R, 378 pts, 71%), DSS was significantly worse than those with sIL-2R level of <1800 IU/mL (low sIL-2R, 157 pts, 29%); 68.2% vs 96.0% (P<0.001), respectively (Figure 1). Multivariate analyses employing sex, PS, sIL-2R, FLIPI and POD24 demonstrated that high sIL-2R was an independent prognostic factor for DSS (HR : 2.88, 95% CI : 1.15-7.21, P<0.05). Regardless of POD24 status, pts with high sIL-2R had significantly worse DSS than those with low sIL-2R; 44.6% vs 91.5% in pts with POD24 (P<0.05) and 82.6% vs 96.8% in pts without POD24 (P<0.001), respectively. Among pts treated with rituximab plus anthracycline-containing chemotherapy as the 1st line regimen (222 pts, 41%), pts with high sIL-2R had significantly worse DSS than those with low sIL-2R; 68.1% vs 97.2% (P<0.001). Among pts treated with rituximab-bendamustine as the 1st line regimen (48 pts, 9%), there was no significant difference between high and low sIL-2R populations (P=0.2), however, among pts treated with bendamustine-containing regimen at least once in their life time (180 pts, 34%), there was significant difference between them; 63.1% vs 87.8% (P<0.05). Even in pts achieving complete metabolic response after 1st line treatment (178 pts, 33%), high pretreatment sIL-2R level was a significant factor affecting poor DSS; 75.9% vs 94.3% (P<0.05). Conclusions: High sIL-2R level ( ≥1800 IU/mL) is a significant and independent adverse prognostic factor for DSS in pts with newly diagnosed FL. This study provides us useful information to predict population with worse DSS before initiation of treatment. Disclosures Nozaki: Chugai: Honoraria; Celgene: Honoraria. Kida:Eisai Co., Ltd: Honoraria. Kosugi:Novartis Pharma Co.: Honoraria; Bristol-Myers Squibb Co.: Honoraria; Eisai Co., Ltd: Honoraria; Takeda Pharmaceutical Company Limited: Honoraria; Kyowa Kirin Co., Ltd: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; ONO PHARMACEUTICAL CO., LTD.: Honoraria; NIPPON SHINYAKU CO.,LTD.: Honoraria; Janssen Pharmaceutical K.K.: Honoraria; Celgene K.K.: Honoraria; Pfizer Inc.: Honoraria. Shibayama:Astellas, Teijin, MSD, Shionogi, Eisai, Sumitomo Dainippon, Taiho, Nippon Shinyaku: Research Funding; Celgene, Chugai, Eisai, AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Takeda, Novartis, Janssen, Chugai, Eisai, Mundi Pharma, Ono, Otsuka, Kyowa Kirin, Sumitomo Dainippon, AstraZeneca, Avvie, DaiichiSankyo, Fujimoto, Nippon Shinyaku, Sanofi, Bristol-Myers Squibb, Pfizer: Honoraria.

The objective of this prospective clinical trial (JALSG-STIM213, UMIN000011971) was to evaluate treatment-free remission (TFR) rates after discontinuation of imatinib in chronic myeloid leukemia (CML). CML patients who received imatinib treatment for at least 3 years and sustained deep molecular response for at least 2 years were eligible. Molecular recurrence was defined as loss of major molecular response (MMR). Of the 68 eligible patients, 38.2% were women, the median age was 55.0 years, and the median duration of imatinib treatment was 97.5 months. The 12-month TFR rate was 67.6%. Patients who lost MMR were immediately treated with imatinib again; all re-achieved MMR. Three-year treatment-free survival (TFS) was estimated as 64.6% using the Kaplan–Meier method. Undetectable molecular residual disease (UMRD) was defined as no BCR-ABL1 in > 100,000 ABL1 control genes using international scale polymerase chain reaction. UMRD at the study baseline was found to be predictive of continuation of TFR. Our findings suggest that CML patients who meet all the eligibility criteria that have commonly been used in the TFR trials are able to discontinue imatinib use safely. TFR may thus be valuable as a new goal for CML treatment in Japan.

We present an acute promyelocytic leukemia (APL) patient with two subtypes of IRF2BP2–RARA, in which the IRF2BP2 gene showed completely new breakpoints. Bone marrow examination revealed morphologic features indicative of APL. However, promyelocytic leukemia–RARA fusion was not detected. A paired‐end mRNA sequencing followed by RT‐PCR and direct sequencing revealed two types of fusion transcripts between exon 1B of IRF2BP2 and exon 3 of RARA. The patient received all‐trans retinoic acid and conventional chemotherapy, but showed resistance. This is the second report of IRF2BP2 involvement in APL, and we describe various breakpoints for the IRF2BP2–RARA fusion gene.

Quantitative polymerase chain reaction (PCR) with patient-specific, allele-specific oligonucleotide (ASO) primers for individual immunoglobulin H VDJ region (ASO-PCR) amplification was performed using several sources of clinical material, including mRNA from peripheral blood cells (PBMNCs), whole bone marrow cells (BMMNCs), and the CD20(+)CD38(-) B-cell population in bone marrow, as well as cell-free DNA from the sera of patients with multiple myeloma (MM). We designed the ASO primers and produced sufficient PCR fragments to evaluate tumor burden in 20 of 30 bone marrow samples at diagnosis. Polymerase chain reaction amplification efficiency depended on primer sequences because the production of ASO-PCR fragments did not correlate with serum M-protein levels. However, the ASO-PCR levels in BMMNCs showed statistically significant correlations with those in PBMNCs and CD20(+)CD38(-) B-cells. The good association between the BMMNC and PBMNC data indicated that PBMNCs could be a suitable source for monitoring minimal residual disease (MRD). In the case of cell-free DNA, ASO-PCR levels showed a unique pattern and remained high even after treatment. Because the sequence information for each ASO-PCR product was identical to the original, the cell-free DNA might also be useful for evaluating MRD. Moreover, the ASO-PCR products were clearly detected in 17 of 22 mRNA samples from CD20(+)CD38(-) populations, suggesting that MM clones might exist in relatively earlier stages of B cells than in plasma cells. Thus, ASO-PCR analysis using various clinical materials is useful for detecting MRD in MM patients as well as for clarifying MM pathogenesis. Copyright (C) 2015 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc.

Introduction ; The PCR with patient-specific, allele-specific oligonucleotide primers for individual IgH VDJ regions (ASO-PCR) is considered the most sensitive method to detect minimal residual disease (MRD) levels in patients with multiple myeloma (MM). In this study, we quantified the ASO-PCR products by using peripheral blood mononuclear cells (PBMNCs) as well as bone marrow mononuclear cells (BMMNCs). We also quantified the ASO-PCR products in mRNAs from CD20 + 38 - B-cells in BM to examine whether there are clonogenic cells in relatively earlier B-cell fraction as well as cell-free DNAs from the sera to examine whether there are DNA fragments from MM cells in PB. Materials and methods ; We have analyzed 30 MM cases. After an informed consent, patient-oriented PCR primers were designed from sequence information of immunoglobulin heavy chain (IgH) variable regions of myeloma cells of each patient. Results ; The median age in this cohort was 64.5 years (36-83); the ratio of men to women was 16:14; and the numbers of IgG-, IgA-, and Bence Jones protein (BJP)- type patients were 18, 7, and 5, respectively. The patient-specific ASO primers could be designed in 25 cases, but not in 3 BJP-type cases or 2 IgG-type cases. We could quantify the ASO-PCR products in 20 of 30 BMMNCs samples at diagnosis. The ASO-PCR levels (IgH/β−actin levels)in BMMNCs correlated with those in PBMNCs, but not to the percent of plasma cells in BM or the values for M-protein. However, the ASO-PCR levels were decreased after the treatment and reflected tumor burden well individually. The ASO-PCR levels in PBMNCs showed a statistically significant correlation with those in BMMNCs at diagnosis (Spearman’s ρ= 0.98, P 0.001), 6 months (Spearman’s ρ= 0.83, P = 0.020) and 12 months (Spearman’s ρ= 1.90, P = 0.001). Therefore, ASO-PCR using PBMNCs as well as BMMNCs is suitable for MRD evaluation. We could detect the patient-specific IgH DNA sequences in cell-free DNA extracted from the sera and quantify the ASO-PCR products. The sequences of the ASO-PCR product were identical to the originally designed sequence, suggesting that detection of the ASO-PCR products in cell-free DNA could reflect the persistence of myeloma cells somewhere in body. The ASO-PCR products for CD20 + CD38 - B-cells in BM were relatively low but were clearly detected in 17 cases at diagnosis. The ASO-PCR levels in CD20 + CD38 - B-cells in BM showed good correlation with both values of ASO-PCR in BMMNCs (Spearman’s ρ= 1.35, P P + CD38 - B-cell population in BM. Discussion ; Our findings that we could quantify the ASO-PCR products in PBMNCs, BM CD20 + CD38 - B-cells, cell-free DNA as well as BMMNCs strongly suggest wide sources of clinical materials to analyze. There were statistically significant correlations in values of the ASO-PCR products between BMMNCs and PBMNCs, therefore suggesting the possibility that clonogenic plasma cells or myeloma precursor cells might circulate in peripheral blood. We expect the possibility that PBMNCs will be a good source to monitor MRD. We could also detect and quantify the ASO-PCR products in cell-free DNA from the sera. To the best of our knowledge, this is the first report that IgH DNA fragments from MM cells circulate in the sera. Furthermore, we could detect and quantify the ASO-PCR products in CD20 + CD38 - B-cells in BM at diagnosis. These results indicated that clonogenic MM cells could exist not only in the CD20 - CD38 high plasma cell fraction but also in the CD20 + CD38 - B-cell fraction, which might include myeloma stem or initiating cells. Thus, we could consider the treatment strategies to include anti-CD20 antibodies against the clonogenic CD20 + CD38 - B-cell population. In conclusion, our ASO-PCR using various clinical materials is supposed to be useful for detecting MRD in the patients with MM as well as for clarifying the pathogenesis of MM. Disclosures Sata: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Shibayama: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Habuchi: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Fukushima: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Fujita: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Ezoe: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Tadokoro: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Maeda: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Mizuki: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Oritani: Celgen: Research Funding; Takeda: Research Funding; Janssen: Research Funding. Kanakura: Janssen: Research Funding; Takeda: Research Funding; Celgen: Research Funding.

We report a case of donor cell-derived chronic myeloproliferative disease with t(7;11)(p15;p15) occurring after cord blood transplantation (CBT). A 41-year-old man developed precursor B-cell acute lymphoblastic leukemia with a karyotype of 46, XY, t(9;22)(q34;q11) and inv(9)(p11;q13), for which he received CBT from a sex-mismatched donor at the first complete remission of the leukemia. Five months after CBT, gradual neutrophilia of unknown origin developed following the myeloid reconstitution after CBT. Karyotyping of bone marrow cells at 9 months after CBT showed 46,XX, t(7;11)(p15;p15) in 17/20 dividing cells, but neither Philadelphia chromosome (Ph) nor inv(9)(p11;q13) was present. This is the first report of chronic myeloproliferative disease with t(7;11)(p15;p15) that developed in donor cells after CBT. The donor was well-developed and healthy, at least at the time of follow-up, half a year after the birth.

A 59-year-old man was a potential donor for allogeneic hematopoietic stem cell transplantation and was found to be healthy but slightly polycythemic. The bone marrow was morphologically normal, but karyotyping of bone marrow cells showed t(6;10)(q27;q22) in 7 of 20 metaphases analyzed by G-banding and only the t(6;10) abnormality in 3 of 5 metaphases analyzed by the spectral karyotyping method. G-banding analysis of peripheral blood mononuclear cells cultured with phyto-hemagglutinin for 72 hours showed a normal karyotype in all 20 metaphases analyzed. These findings suggest clonal expansion with t(6;10)(q27;q22) in the bone marrow of this individual. He was determined to be ineligible for donation. A coordinated nationwide work-up for older donors is necessary to ensure high-quality standards.

We reviewed the records of 235 consecutive recipients of allogeneic bone marrow transplantation (allo-BMT) at our center between February 1983 and October 2000. Sepsis occured in 25 patients (10.6%) at a median of 10 days (range, 1–280 days) after BMT. Five of the 25 patients (20%) died of sepsis. Pathogens isolated from blood culture were gram-positive cocci in 19 patients, gram-negative rods in 7, fungi in 2, and others in 1 patient. Two pathogens were detected concomitantly in 4 patients. Univariate analysis revealed that risk factors for sepsis were selective gut decontamination using lomefloxacin hydrochloride and nystatin, an unrelated donor, HLA mismatched BMT, and stomatitis. Multivariate logistic regression analysis revealed that an unrelated donor was the only significant independent risk factor, with a relative risk of 5.432. In 12 of 25 patients with sepsis, the pathogens of sepsis were sensitive to antibiotics used for gut decontamination. Selective gut decontamination significantly increased the incidence of sepsis, especially that with gram-positive cocci, but not the mortality rate of sepsis, compared with total gut decontamination using vancomycin. We also found a significant relationship between pathogens isolated from blood culture and those isolated from surveillance cultures of stool, urine, and gargled water in the period before sepsis occurred. The present study revealed an independent risk factor for sepsis (unrelated donor), the feasibility of selective gut decontamination, and the importance of surveillance culture.

Fibronectin (FN) is supposed to play important roles in various aspects of hematopoiesis through binding to very late antigen 4 (VLA4) and VLA5. However, effects of FN on hematopoietic stem cells are largely unknown. In an effort to determine if FN had a growth-supporting activity on hematopoietic stem cells, human CD34+/VLA4bright/VLA5dullhematopoietic stem cells and a murine stem cell factor (SCF)-dependent multipotent cell line, EML-C1, were treated with or without FN in a serum and growth-factor–deprived medium, and then subjected to clonogenic assay in the presence of hematopoietic growth factors. The pretreatment of the CD34+ cells with FN gave rise to significantly increased numbers of granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst colony-forming units, and mixed erythroid-myeloid colony-forming units. In addition, the numbers of blast colony-forming units and CFU-GM that developed after culture of EML-C1 cells with SCF and the combination of SCF and interleukin-3, respectively, were augmented by the pretreatment with FN. The augmented colony formation by FN was completely abrogated by the addition of CS1 fragment, but not of GRGDSP peptide, suggesting an essential role of FN-VLA4 interaction in the FN effects. Furthermore, the effects of various FN fragments consisting of RGDS-containing cell-binding domain (CBD), heparin-binding domain (HBD), and/or CS1 portion were tested on clonogenic growth of CD34+ cells. Increased colony formation was induced by CBD-CS1 and CBD-HBD-CS1 fragments, but not with other fragments lacking CBD or CS1 domains, suggesting that both CS1 and CBD of FN were required for the augmentation of clonogenic growth of hematopoietic stem/progenitor cells in vitro. In addition to the in vitro effects, the in vivo administration of CBD-CS1 fragment into mice was found to increase the numbers of hematopoietic progenitor cells in bone marrow and spleen in a dose-dependent manner. Thus, FN may function on hematopoietic stem/progenitor cells as a growth-supporting factor in vitro and in vivo.

Transforming growth factor-β (TGF- β) has been found to block the progression of the cell-cycle by up-regulating a Cdk inhibitor, p15, only in epithelial cells; on the other hand, wild-type p53 was shown to activate transcriptionally the gene for another Cdk inhibitor, p21. The regulatory effects of TGF-β on hematopoietic tissues is poorly understood. Hence, we investigated the effect of TGF-β on hematopoietic progenitor cells in p53-deficient mice to determine whether an inhibitory signal from TGF-β is linked to p53 in hematopoietic regulation. We found that the proliferation of megakaryocyte-progenitors (CFU-Mk) in our wild-type mice was markedly inhibited by TGF-β. Contrary to an earlier report, an erythroid and a granulocyte–macrophage progenitor, stimulated by IL-3, were not significantly inhibited, whereas TGF-β also completely inhibited the growth of high-proliferative potential progenitor cells (HPP-CFC) in the marrow of mice with 5-fluorouracil (5FU), as reported. It is interesting that in the p53-deficient mice, the inhibitory action of TGF-β on the HPP-CFC was incompletely abolished. The response curve we obtained for graded doses of TGF-β suggests that there is, at least, a subpopulation of HPP-CFC which is less sensitive to the regulation by TGF-β. In contrast to HPP-CFC, the CFU-Mk, which TGF-β inhibited only in wild-type mice not treated with 5FU, remained inhibited in the p53-deficient strain. Thus, HPP-CFC might be regulated by TGF-β through their signal pathways which are linked to p53.

Hemopoietic stem cells lacking with p53 are known to be resistant to radiation apoptosis: p53-product induces, on one hand, the cells that have been injured by radiation to stop cell-cycle at G, phase, and on the other hand the cells that have not been repaired to go into apoptosis. Thus, in the p53-deficient mice, the hemopoietic stem cells after graded dose of radiation show a flatter survival curve for radiation, i.e., like a curve for radio-resistant phenotype. However, we found the radio-resistance in the stem cell was only transient, and an apoptosis in p53-deficient hemopoietic stem cells, we made concentrated analysis including the end-labeling technique to detect double strand breaks of DNA. Results clearly showed that, according to the end-labeling for spleen colonies, the p53-deficiency showed rather higher incidence of apoptosis (30-50%) as compared with the wild-control (17%). Irradiation with 200cGy for the recipient mice two months after transplantation, showed an induction of higher incidence of hemopoietic malignancies, when the heterozygous marrow was repopulated, however, none of increase was observed in the recipient mice repopulated with the homozygous bone marrow. Clear difference between the hetero- and the homozygous in inducing hemopoietic malignancies with the 200cGy-radiation may be reflected by the different degree of delayed appearance of apoptosis during the development of the spleen colonies.