Whole blood gene expression within days after total-body irradiation predicts long term survival in Gottingen minipigs.

Gottingen minipigs mirror the physiological radiation response observed in humans and hence make an ideal candidate model for studying radiation biodosimetry for both limited-sized and mass casualty incidents. We examined the whole blood gene expression profiles starting one day after total-body irradiation with increasing doses of gamma-rays. The minipigs were monitored for up to 45 days or time to euthanasia necessitated by radiation effects. We successfully identified dose- and time-agnostic (over a 1-7 day period after radiation), survival-predictive gene expression signatures derived using machine-learning algorithms with high sensitivity and specificity. These survival-predictive signatures fare better than an optimally performing dose-differentiating signature or blood cellular profiles. These findings suggest that prediction of survival is a much more useful parameter for making triage, resource-utilization and treatment decisions in a resource-constrained environment compared to predictions of total dose received. It should hopefully be possible to build such classifiers for humans in the future.

Organ sparing total marrow irradiation compared to total body irradiation prior to allogeneic stem cell transplantation.

OBJECTIVES: Total body irradiation (TBI) is commonly used prior to hematopoietic stem cell transplantation (HSCT) in myeloablative conditioning regimens. However, TBI may be replaced by total marrow irradiation (TMI) at centres with access to Helical TomoTherapy, a modality that has the advantage of delivering intensity-modulated radiotherapy to long targets such as the entire bone marrow compartment. Toxicity after organ sparing TMI prior to HSCT has not previously been reported compared to TBI or with regard to engraftment data. METHODS: We conducted a prospective observational study on 37 patients that received organ sparing TMI prior to HSCT and compared this cohort to retrospective data on 33 patients that received TBI prior to HSCT. RESULTS: The 1-year graft-versus-host disease-free, relapse-free survival (GRFS) was 67.5% for all patients treated with TMI and 80.5% for patients with matched unrelated donor and treated with TMI, which was a significant difference from historical data on TBI patients with a hazard ratio of 0.45 (P = .03) and 0.24 (P < .01). Engraftment with a platelet count over 20 [K/µL] and 50 [K/µL] was significantly shorter for the TMI group, and neutrophil recovery was satisfactory in both treatment cohorts. There was generally a low occurrence of other treatment-related toxicities. CONCLUSIONS: Despite small cohorts, some significant differences were found; TMI as part of the myeloablative conditioning yields a high 1-year GRFS, fast and robust engraftment, and low occurrence of acute toxicity.

Total body irradiation models in NHPs - consideration of animal sex and provision of supportive care to advance model development.

PURPOSE: Harmonized animal models are an indispensable tool for the development of safe and effective medical countermeasures (MCMs) against radiation injury, and rhesus macaques (referred herein as NHPs) play a critical role in FDA approval of radiation medical countermeasures for acute and delayed radiation syndromes. Reliance on such models requires that they be well characterized, which consists, in part, of a reproducible dose to mortality response relationship (DRR). However, data describing the DRR for both male and female NHPs from the same study are scarce. Furthermore, the level of supportive care and the use of blood transfusions may shift the DRR, yet such information can be difficult to compare across publications. To address these knowledge gaps, the DRRs of two different NHP total body irradiation (TBI) models are compared in this paper, one which is reliant on the use of male animals provided blood transfusions, and the other which incorporates both sexes wherein animals are not provided transfusions. MATERIALS AND METHODS: Studies were conducted using NHPs (Macacca mulatta) receiving TBI, with survival reported over a 60 days. Two primary studies, incorporating both male and female animals not receiving blood transfusions as a provision of supportive care, were compared to two previously published studies, which incorporated only male animals provided blood transfusions as a part of the supportive care regimen. Criterion for euthanasia, and all other provisions of supportive care were comparable. Linear probit plots estimating the lethal dose (LD) and upper and lower limits of the 95% confidence interval (CI) for 10, 30, 50, 70 and 90% mortality, were compared between individual studies and the two models presented. RESULTS: Comparison of probit estimates reveals two important findings. (1) Females have higher mortality than males at identical radiation doses, and (2) blood transfusions increased survival of male animals at lower doses but not at high doses of radiation exposure. CONCLUSIONS: The use of single sex animal models may lead to an incomplete understanding of potential sex differences in the dose to mortality response of the TBI model. Consistent use of both sexes and type of supportive care will improve the transferability and reliability of NHP-TBI models currently in use, assist in the selection of radiation doses for single dose lethality studies, and allow investigators to determine the effectiveness of a particular MCM.

Total Body Irradiation or Chemotherapy Conditioning in Childhood ALL: A Multinational, Randomized, Noninferiority Phase III Study.

PURPOSE: Total body irradiation (TBI) before allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients with acute lymphoblastic leukemia (ALL) is efficacious, but long-term side effects are concerning. We investigated whether preparative combination chemotherapy could replace TBI in such patients. PATIENTS AND METHODS: FORUM is a randomized, controlled, open-label, international, multicenter, phase III, noninferiority study. Patients ≤ 18 years at diagnosis, 4-21 years at HSCT, in complete remission pre-HSCT, and with an HLA-compatible related or unrelated donor were randomly assigned to myeloablative conditioning with fractionated 12 Gy TBI and etoposide versus fludarabine, thiotepa, and either busulfan or treosulfan. The noninferiority margin was 8%. With 1,000 patients randomly assigned in 5 years, 2-year minimum follow-up, and one-sided alpha of 5%, 80% power was calculated. A futility stopping rule would halt random assignment if chemoconditioning was significantly inferior to TBI (EudraCT: 2012-003032-22; ClinicalTrials.gov: NCT01949129). RESULTS: Between April 2013 and December 2018, 543 patients were screened, 417 were randomly assigned, 212 received TBI, and 201 received chemoconditioning. The stopping rule was applied on March 31, 2019. The median follow-up was 2.1 years. In the intention-to-treat population, 2-year overall survival (OS) was significantly higher following TBI (0.91; 95% CI, 0.86 to 0.95; P < .0001) versus chemoconditioning (0.75; 95% CI, 0.67 to 0.81). Two-year cumulative incidence of relapse and treatment-related mortality were 0.12 (95% CI, 0.08 to 0.17; P < .0001) and 0.02 (95% CI, < 0.01 to 0.05; P = .0269) following TBI and 0.33 (95% CI, 0.25 to 0.40) and 0.09 (95% CI, 0.05 to 0.14) following chemoconditioning, respectively. CONCLUSION: Improved OS and lower relapse risk were observed following TBI plus etoposide compared with chemoconditioning. We therefore recommend TBI plus etoposide for patients > 4 years old with high-risk ALL undergoing allogeneic HSCT.

Exploratory analysis of intensified conditioning as first line treatment for patients with high risk multiple myeloma.

Multiple myeloma has extremely heterogeneous outcomes. Among prognostic factors, t(4;14) and del(17p) are rare oncogenic events associated with very poor prognosis. In an exploratory case-control study, we compared the combination of Busulfan-Melphalan or TBI-Melphalan with high dose Melphalan as a conditioning regimen in a series of 48 patients with del(17p) or t(4;14). These regimens were preceded by a Bortezomib-containing induction. Progression-free survival (PFS) was the primary endpoint whereas overall survival (OS) and complete response (CR) rate were the secondary endpoints. Twenty consecutive cases of high-risk myeloma received a reinforced conditioning regimen of Busulfan 0.8 mg/kg x4/j IV from day-6 to day-3 pre- graft (BuMel) or total body irradiation (TBI) 12 Gy (TbiMel), having received Melphalan 140 mg/m2 at day-2 pre-graft. These cases were matched to 28 controls treated with Melphalan 200 mg/m2 at day-2 (Mel200). After intensification ± consolidation, with a median follow-up of 6.3 years, the CR rate was higher in the BuMel/TbiMel group (65% vs 50%, P = .006). No differences were observed between both groups in terms of PFS and OS (P = .96). PFS in patients with a del(17p) mutation tended to be superior in the BuMel/TbiMel group. Our exploratory study shows that reinforcing the intensification regimen with Busulfan or TBI does not seem to improve the prognosis associated to t(4;14) and del(17p) abnormalities.

Acute Radiation-induced GI-ARS and H-ARS in a Canine Model of Mixed Neutron/Gamma Relative to Reference Co-60 Gamma Radiation: A Retrospective Study.

Studies performed decades ago in the canine and nonhuman primate established the dose response relationships for the hematopoietic acute radiation syndrome in response to mixed neutron/gamma, x-radiation, and Co gamma radiation. There were no published studies that determined the dose response relationships for the gastrointestinal acute radiation syndrome in response to either noted radiation quality. This analysis of a retrospective, unpublished study provided the dose response relationships in a canine model for the acute gastrointestinal syndrome relative to the acute hematopoietic syndrome due to mixed neutron/gamma radiation. Canines were exposed to total-body, steady state, bilateral, 0.40 Gy min, mixed neutron/gamma (5.4:1) radiation from a TRIGA reactor. The average neutron/gamma energy (MeV) was 0.85/0.9, and exposure was reported as midline tissue dose. Medical management was not administered. The mixed neutron/gamma exposure resulted in an estimated LD50/6 of 2.83 Gy [2.76, 2.94] and LD50/30 of 2.16 Gy [2.01, 2.24] for the GI- and H-ARS respectively. The mean survival times for decedents after mixed neutron/gamma exposure approximate to the LD50/6 were 8.5 d, 10.5 d, and 4 d for 2.75 Gy, 2.80 Gy, 3.00, and 3.12 Gy exposures, respectively. The mean survival times for decedents for mixed neutron/gamma exposure approximate to the LD50/30 were 21.3 d and 15.6 d for 2.00 Gy and 2.25 Gy, respectively. Furthermore, the dose response relationships for the acute hematopoietic syndrome due to mixed neutron/gamma exposure (0.85/0.9 MeV; 5.4:1) resulted in an estimated relative biological effectiveness of 1.2 as compared with reference Co gamma radiation.

The impact of total body irradiation-based regimens on outcomes in children and young adults with acute lymphoblastic leukemia undergoing allogeneic hematopoietic stem cell transplantation.

INTRODUCTION: Total body irradiation (TBI)-based conditioning is the standard of care in the treatment of acute lymphoblastic leukemia (ALL) that requires allogeneic hematopoietic stem cell transplantation (HSCT). However, TBI is known to be associated with an increased risk of late effects, and therefore, non-TBI regimens have also been utilized successfully. A recent study showed that patients that were next-generation sequencing-minimal residual disease (NGS-MRD) negative prior to allogeneic HSCT had a very low risk of relapse, and perhaps could avoid exposure to TBI without compromising disease control. We examined outcomes at our institution in patients that received a TBI or non-TBI regimen, as well as explored the impact of NGS-MRD status in predicting risk of relapse post transplant. PROCEDURES: This retrospective analysis included 57 children and young adults with ALL that received their first myeloablative allogeneic HSCT from 2012 to 2017 at the University of California San Francisco. Our primary endpoint was the cumulative incidence of relapse at 3 years post transplant. RESULTS: We demonstrated similar cumulative incidence of relapse for patients treated with either a TBI or non-TBI conditioning regimen, while NGS-MRD positivity prior to transplant was highly predictive of relapse. The presence of acute graft-versus-host disease was associated with decreased relapse rates, particularly among patients that received a TBI conditioning regimen and patients that were NGS-MRD positive prior to HSCT. CONCLUSIONS: Our data suggest that the decision to use either a TBI or non-TBI regimens in ALL should depend on NGS-MRD status, with conditioning regimens based on TBI reserved for patients that cannot achieve NGS-MRD negativity prior to allogeneic HSCT.

The effect of melphalan dose and total body irradiation as reduced-intensity conditioning for acute lymphoblastic leukemia patients undergoing allogeneic stem cell transplantation.

To evaluate the prognostic impact of melphalan dose and total body irradiation (TBI) in acute lymphoblastic leukemia (ALL) patients undergoing reduced-intensity allogeneic transplantation, we retrospectively compared the outcomes between higher-dose melphalan (120-140 mg/m2) with (HDM/TBI+, n = 118) or without 2-4 Gy TBI (HDM/TBI-, n = 152) and lower-dose melphalan (80-110 mg/m2) with TBI (LDM/TBI+, n = 237). At 3 years, the overall survival was 49.6% in the HDM/TBI+, 51.7% in the HDM/TBI-, and 47.3% in the LDM/TBI + groups (p = .67). The relapse rate and non-relapse mortality were comparable among the three groups. Multivariate analysis revealed that conditioning regimen was not associated with overall survival, relapse, and non-relapse mortality; however, central nervous system complication was less frequent with LDM/TBI + than with HDM/TBI+. Our findings suggest reduced-intensity conditioning with LDM/TBI + might be a reasonable option, especially in vulnerable ALL patients, with similar transplant outcomes to HDM with or without TBI.

Higher Reported Lung Dose Received During Total Body Irradiation for Allogeneic Hematopoietic Stem Cell Transplantation in Children With Acute Lymphoblastic Leukemia Is Associated With Inferior Survival: A Report from the Children's Oncology Group.

PURPOSE: To examine the relationship between lung radiation dose and survival outcomes in children undergoing total body irradiation (TBI)-based hematopoietic stem cell transplantation (HSCT) for acute lymphoblastic leukemia on the Children's Oncology Group trial. METHODS AND MATERIALS: TBI (1200 or 1320 cGy given twice daily in 6 or 8 fractions) was used as part of 3 HSCT preparative regimens, allowing institutional flexibility regarding TBI techniques, including lung shielding. Lung doses as reported by each participating institution were calculated for different patient setups, with and without shielding, with a variety of dose calculation techniques. The association between lung dose and transplant-related mortality, relapse-free survival, and overall survival (OS) was examined using the Cox proportional hazards regression model controlling for the following variables: TBI dose rate, TBI fields, patient position during TBI, donor type, and pre-HSCT minimal residual disease level. RESULTS: Of a total of 143 eligible patients, 127 had lung doses available for this analysis. The TBI techniques were heterogeneous. The mean lung dose was reported as 904.5 cGy (standard deviation, ±232.3). Patients treated with lateral fields were more likely to receive lung doses ≥800 cGy (P < .001). The influence of lung dose ≥800 cGy on transplant-related mortality was not significant (hazard ratio [HR], 1.78; P = .21). On univariate analysis, lung dose ≥800 cGy was associated with inferior relapse-free survival (HR, 1.76; P = .04) and OS (HR, 1.85; P = .03). In the multivariate analysis, OS maintained statistical significance (HR, 1.85; P = .04). CONCLUSIONS: The variability in TBI techniques resulted in uncertainty with reported lung doses. Lateral fields were associated with higher lung dose, and thus they should be avoided. Patients treated with lung dose <800 cGy in this study had better outcomes. This approach is currently being investigated in the Children's Oncology Group AALL1331 study. Additionally, the Imaging and Radiation Oncology Core Group is evaluating effects of TBI techniques on lung doses using a phantom.

Radioprotective effects of roxadustat (FG-4592) in haematopoietic system.

BACKGROUND: Ionizing radiation often causes severe injuries to radiosensitive tissues, especially haematopoietic system. Novel radioprotective drugs with low toxicity and high effectiveness are required. Prolyl hydroxylases domain (PHD) inhibitors have been reported to protect against radiation-induced gastrointestinal toxicity. In this study, we demonstrated the protective effects of a PHD inhibitor, roxadustat (FG-4592), against radiation-induced haematopoietic injuries in vitro and in vivo. METHODS: Tissue injuries were evaluated by Haematoxilin-Eosin (HE) staining assay. HSCs were determined by flow cytometry with the Lin- Sca-1+ c-Kit+ (LSK) phenotype. Cell apoptosis was determined by Annexin V/PI staining assay. Immunofluorescence was performed to measure radiation-induced DNA damage. A western blot assay was used to detect the changes of proteins related to apoptosis. RESULTS: We found that FG-4592 pretreatment increased survival rate of irradiated mice and protected bone marrow and spleen from damages. Number of bone marrow cells (BMCs) and LSK cells were also increased both in irradiated mice and recipients after bone marrow transplantation (BMT). FG-4592 also protected cells against radiation-induced apoptosis and double strand break of DNA. CONCLUSIONS: Our data showed that FG-4592 exhibited radioprotective properties in haematopoietic system both in vivo and in vitro through up-regulating HIF-1α, indicating a potential role of FG-4592 as a novel radioprotector.

Effect of dose rate on pulmonary toxicity in patients with hematolymphoid malignancies undergoing total body irradiation.

BACKGROUND: This study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI), for hematopoietic stem cell transplantation. METHODS: The incidence of pulmonary toxicity (PT) and treatment efficacy were compared between the conventional (≥ 6 cGy/min) and reduced dose rate (< 6 cGy/min). Seventy-seven patients receiving once-daily TBI between 2000 and 2016 were reviewed. We compared the cumulative rate of PT, overall survival (OS), relapse, and transplantation-related mortality (TRM) between conventional (n = 54) and reduced (n = 23) groups. Factors associated with PT were assessed in the presence of competing risks. RESULTS: The median follow-up time was 40.7 months, and PT occurred in 50 patients (64.9%). On multivariate analyses, the groups classified by the dose rate (P = 0.010), total dose (P = 0.025), and conditioning regimen (P = 0.029) were significant factors for the development of PT. OS was significantly reduced when PT occurred (P < 0.001). However, the OS, relapse, and TRM were not different between the two groups. CONCLUSIONS: In summary, about two-thirds of the patients undergoing daily TBI experienced PT, which affected OS. Therefore, reducing the dose rate (less than 6 cGy/min) of TBI can decrease the risk of PT, without compromising the treatment efficacy.

Total Body Irradiation Is Safe and Similarly Effective as Chemotherapy-Only Conditioning in Autologous Stem Cell Transplantation for Mantle Cell Lymphoma.

Autologous stem cell transplant (ASCT) consolidation has become a standard approach for patients with mantle cell lymphoma (MCL), yet there is little consensus on the role of total body irradiation (TBI) as part of high-dose transplantation conditioning. We analyzed 75 consecutive patients with MCL who underwent ASCT at our institution between 2001 and 2011 with either TBI-based (n = 43) or carmustine, etoposide, cytarabine, melphalan (BEAM; n = 32) high-dose conditioning. Most patients (97%) had chemosensitive disease and underwent transplantation in first remission (89%). On univariate analysis, TBI conditioning was associated with a trend toward improved PFS (hazard ratio [HR], .53; 95% confidence interval [CI], .28-1.00; P = .052) and similar OS (HR, .59; 95% CI, .26-1.35; P = .21), with a median follow-up of 6.3 years in the TBI group and 6.6 years in the BEAM group. The 5-year PFS was 66% in the TBI group versus 52% in the BEAM group; OS was 82% versus 68%, respectively. However, on multivariate analysis, TBI-based conditioning was not significantly associated with PFS (HR, .57; 95% CI .24-1.34; P = .20), after controlling for age, disease status at ASCT, and receipt of post-transplantation rituximab maintenance. Likewise, early toxicity, nonrelapse mortality, and secondary malignancies were similar in the 2 groups. Our data suggest that both TBI and BEAM-based conditioning regimens remain viable conditioning options for patients with MCL undergoing ASCT.

Radioprotective and radiomitigative effects of BP-C2, a novel lignin-derived polyphenolic composition with ammonium molybdate, in two mouse strains exposed to total body irradiation.

PURPOSE: There remains an unmet medical need for radioprotective and mitigative agents. BP-C2 is a novel lignin-derived polyphenolic composition with ammonium molybdate, developed as radioprotector/radiomitigator. OBJECTIVES: The present study evaluated BP-C2 for the mitigation of acute radiation syndrome (ARS). METHODS: A total-body irradiation mouse model (TBI, 4.0-8.0 Gy) was used in the study. RESULTS: In a 30-day survival study, performed in CBA mice, BP-C2, at a dosage of 81.0 mg/kg, improved survival (dose reduction factor (DRF) = 1.1) and increased the formation of endogenous spleen colony-forming units (CFU). In C57BL/6 mice, BP-C2, when administered daily for 7 days, starting 24 hours after TBI, also improved survival. In animals irradiated with 5.0 Gy, BP-C2 increased the number of CFUs (6.7 ± 5.1) compared to the 5.0 Gy placebo group (2.3 ± 2.3, p = .0245). The number of surviving intestinal crypts was maintained in the 5.0 Gy BP-C2 group (133.7 ± 13.9), in contrast to the 5.0 Gy placebo group (124.2 ± 10.5, p < .0023). BP-C2 also increased the number of LGR5 + positive cells in intestinal crypts. CONCLUSION: BP-C2 mitigates radiation-induced damage in mid-lethal range of radiation doses. Effects are mediated by enhancement of extramedullar hematopoiesis in the spleen and a protective effect on the intestinal epithelium.

Cardiovascular effects of fission neutron or 60Co γ exposure in the B6CF1 mouse.

In this study, the B6CF1 mice from the JANUS program at the Argonne National Laboratory were analyzed for increased cardiovascular disease (CVD) mortality from 60Co γ ray or fission neutron exposures administered in either a single dose or protracted weekly doses. The data used for this study represent the last studies conducted at Argonne and have been archived for at least 15 years. CVD mortality increased in a dose-dependent manner from γ rays as well as from neutron exposures. The relative biological effectiveness (RBE) for neutrons is about 4 or 5. CVD mortality appeared to be enhanced when the dose was protracted, with a DDREF (dose and dose rate effectiveness factor) in the range of 0.4-0.45 for neutron and gamma ray exposure, respectively.

The Addition of Low-Dose Total Body Irradiation to Fludarabine and Melphalan Conditioning in Haplocord Transplantation for High-Risk Hematological Malignancies.

BACKGROUND: Preliminary evidence indicates that the addition of low-dose total body irradiation (TBI) (2-4 Gy) to reduced intensity conditioning may reduce the rate of relapse in allogeneic stem cell transplants. In very high-risk patients receiving combination haploidentical single-unit cord blood transplants, we have added 4 Gy TBI to the widely used fludarabine, melphalan conditioning regimen, in hopes of reducing relapse and decreasing graft rejection. METHODS: We retrospectively reviewed the posttransplant outcomes of patients who underwent haplocord stem cell transplant between May 2013 and March 2015 and who received fludarabine 30 mg/m day (D)-7 to -3, melphalan 140 mg/m D-2, and 2 Gy TBI D-4 and -3. RESULTS: All 25 patients achieved primary neutrophil engraftment after a median of 12 days. The median time to platelet engraftment was 27 days. The cumulative incidence of nonrelapse mortality was 16% by D+100 and 33% by 1 year. The cumulative incidence of grade III to IV acute graft-versus-host disease was 36% by D+100. The CIR was 13% by D+100 and 29% by 1 year. The estimated 1-year overall survival and progression-free survival were 40% and 37%, respectively. In a subgroup analysis, we compared the outcome of 13 acute myeloid leukemia patients receiving this conditioning regimen with age and disease risk index-matched acute myeloid leukemia patients receiving fludarabine-melphalan without TBI. The TBI group had lower incidence of relapse at 1 year (15% vs 54%, P = 0.05). CONCLUSIONS: Overall, combination fludarabine-melphalan with low-dose TBI after haplocord stem cell transplant assures good engraftment and leads to acceptable toxicity and disease control in the setting of high risk, heavily pretreated patients. These findings warrant further investigation at a larger-scale, prospective level.

Similar outcome after allogeneic stem cell transplantation with a modified FLAMSA conditioning protocol substituting 4 Gy TBI with treosulfan in an elderly population with high-risk AML.

The fludarabine, amsacrine, and cytarabine (FLAMSA)-reduced-intensity conditioning (RIC) protocol has been described to be effective in patients with high-risk and refractory acute myeloic leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation (aSCT). To increase safety and tolerability of the conditioning, we previously reported the feasibility to substitute the TBI component by treosulfan in elderly AML patients. We now present long-term follow-up data on patients treated with FLAMSA/treosulfan compared to the original FLAMSA/4Gy TBI protocol. We retrospectively analyzed 130 consecutive patients with high-risk or relapsed AML after aSCT following FLAMSA conditioning at our center. Fifty-eight patients were treated with FLAMSA/treosulfan due to age and/or comorbidities. Seventy-two patients were treated with FLAMSA/TBI. Median age of patients treated with FLAMSA/treosulfan was 60 years compared to 46 years in those treated with FLAMSA/TBI. The cumulative incidence of a non-relapse mortality at 4 years was 28% in FLAMSA/treosulfan patients as compared to 13% in FLAMSA/TBI. Cumulative incidence of relapse was higher in patients treated with FLAMSA/TBI (46 vs. 32%). This difference was even more prominent for patients treated in blast persistence prior to transplant (relapse incidence 70% for TBI vs. 35% for treosulfan). The overall and relapse-free survival rates at 4 years were 47 and 41%, respectively, for patients treated with FLAMSA/TBI as compared to 43 and 40% in patients treated with FLAMSA/treosulfan. These data indicate an anti-leukemic activity by FLAMSA/treosulfan especially in patients with a blast persistence prior to transplant. Older age was an independent factor for a higher non-relapse mortality. Translating FLAMSA/treosulfan to younger patients, a lower non-relapse mortality, and an improved anti-leukemic activity might add up to improved overall survival. Randomized studies are required to demonstrate an improved efficacy of treosulfan- versus TBI-based FLAMSA conditioning.

An oral HemokineTM, α-methylhydrocinnamate, enhances myeloid and neutrophil recovery following irradiation in vivo.

An oral therapeutic which reduces duration of cytopenias and is active following accidental radiation exposures is an unmet need in radiation countermeasures. Alpha methylhydrocinnamate (ST7) prolongs STAT-5 phosphorylation, reduces growth-factor dependency of multi-lineage cell lines, and stimulates erythropoiesis. Here, ST7 and its isomers were studied for their effects on myeloid progenitors and hematopoietic stem cells (HSCs) following radiation, in nonhuman primates, and murine irradiation models. Addition of ST7 or ST7-S increased CFU-GM production by 1.7-fold (p<0.001), reduced neutrophil apoptosis comparable to G-CSF, and enhanced HSC survival post-radiation by 2-fold, (p=0.028). ST7 and ST7-S administered in normal baboons increased ANC and platelet counts by 50-400%. In sub-lethally-irradiated mice, ANC nadir remained >200/mm3 and neutropenia recovered in 6days with ST7 treatment and 18days in controls (p<0.05). In lethally-irradiated mice, marrow pathology at 15days was hypocellular (10% cellularity) in controls, but normal (55-75% cellularity) with complete neutrophil maturation with ST7-S treatment. Following lethal irradiation, ST7, given orally for 4days, reduced mortality, with 30% survival in ST7-animals vs 8% in controls, (p<0.05). Collectively, the studies indicate that ST7 and ST7-S enhance myeloid recovery post-radiation and merit further evaluation to accelerate hematologic recovery in conditions of radiation-related and other marrow hypoplasias.

RB localizes to DNA double-strand breaks and promotes DNA end resection and homologous recombination through the recruitment of BRG1.

The retinoblastoma (RB) tumor suppressor is recognized as a master regulator that controls entry into the S phase of the cell cycle. Its loss leads to uncontrolled cell proliferation and is a hallmark of cancer. RB works by binding to members of the E2F family of transcription factors and recruiting chromatin modifiers to the promoters of E2F target genes. Here we show that RB also localizes to DNA double-strand breaks (DSBs) dependent on E2F1 and ATM kinase activity and promotes DSB repair through homologous recombination (HR), and its loss results in genome instability. RB is necessary for the recruitment of the BRG1 ATPase to DSBs, which stimulates DNA end resection and HR. A knock-in mutation of the ATM phosphorylation site on E2F1 (S29A) prevents the interaction between E2F1 and TopBP1 and recruitment of RB, E2F1, and BRG1 to DSBs. This knock-in mutation also impairs DNA repair, increases genomic instability, and renders mice hypersensitive to IR. Importantly, depletion of RB in osteosarcoma and breast cancer cell lines results in sensitivity to DNA-damaging drugs, which is further exacerbated by poly-ADP ribose polymerase (PARP) inhibitors. We uncovered a novel, nontranscriptional function for RB in HR, which could contribute to genome instability associated with RB loss.

Late effects in patients with Fanconi anemia following allogeneic hematopoietic stem cell transplantation from alternative donors.

Hematopoietic stem cell transplantation (HSCT) is curative for hematological manifestations of Fanconi anemia (FA). We performed a retrospective analysis of 22 patients with FA and aplastic anemia, myelodysplastic syndrome or acute myelogenous leukemia who underwent a HSCT at Memorial Sloan Kettering Cancer Center and survived at least 1 year post HSCT. Patients underwent either a TBI- (N=18) or busulfan- (N=4) based cytoreduction followed by T-cell-depleted transplants from alternative donors. Twenty patients were alive at time of the study with a 5- and 10-year overall survival of 100 and 84% and no evidence of chronic GvHD. Among the 18 patients receiving a TBI-based regimen, 11 (61%) had persistent hemochromatosis, 4 (22%) developed hypothyroidism, 7 (39%) had insulin resistance and 5 (27%) developed hypertriglyceridemia after transplant. Eleven of 16 evaluable patients (68%), receiving TBI, developed gonadal dysfunction. Two patients who received a TBI-based regimen died of squamous cell carcinoma. One patient developed hemochromatosis, hypothyroidism and gonadal dysfunction after busulfan-based cytoreduction. TBI appears to be a risk factor for malignant and endocrine late effects in the FA host. Multidisciplinary follow-up of patients with FA (including cancer screening) is essential for early detection and management of late complications, and improving long-term outcomes.

Recombinant human thrombopoietin promotes hematopoietic reconstruction after severe whole body irradiation.

Recombinant human thrombopoietin (rHuTPO) is a drug that is used clinically to promote megakaryocyte and platelet generation. Here, we report the mitigative effect of rHuTPO (administered after exposure) against severe whole body irradiation in mice. Injection of rHuTPO for 14 consecutive days following exposure significantly improved the survival rate of lethally irradiated mice. RHuTPO treatment notably increased bone marrow cell density and LSK cell numbers in the mice after sub-lethal irradiation primarily by promoting residual HSC proliferation. In lethally irradiated mice with hematopoietic cell transplantation, rHuTPO treatment increased the survival rate and enhanced hematopoietic cell engraftment compared with the placebo treatment. Our observations indicate that recombinant human TPO might have a therapeutic role in promoting hematopoietic reconstitution and HSC engraftment.