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1.
Low rate of nonrelapse mortality in under 4-year-olds with ALL given chemo-conditioning for HSCT: Phase III FORUM study
Bader, P., Poetschger, U., Dalle, J. H., Moser, L. M., Balduzzi, A. C., Ansari, M., Buechner, J., Güngör, T., Ifversen, M., Kriván, G., et al
Blood advances. 2023
Abstract
Allogeneic hematopoietic stem cell transplantation (HSCT) is highly effective for treating pediatric high-risk or relapsed acute lymphoblastic leukemia (ALL). In young children, total body irradiation (TBI) is associated with severe late sequelae. In the FORUM study (NCT01949129), we assessed safety, event-free survival (EFS), and overall survival (OS) of two TBI-free conditioning regimens in children with ALL <4 years old. Patients received fludarabine (Flu), thiotepa (Thio), and either busulfan (Bu) or treosulfan (Treo) before HSCT. From 2013 to 2021, 191 children were transplanted and observed for ≥6 months (median follow-up: 3 years). 3-year OS was 0.63 (95% confidence interval [95% CI]: 0.52-0.72) and 0.76 (95% CI: 0.64-0.84) for Flu/Thio/Bu and Flu/Thio/Treo (p = 0.075), respectively. 3-year EFS was 0.52 (95% CI: 0.41-0.61) and 0.51 (95% CI: 0.39-0.62), respectively (p = 0.794). Cumulative incidence of non-relapse mortality (NRM) and relapse at 3 years were 0.06 (95% CI: 0.02-0.12) versus 0.03 (95% CI: <0.01-0.09) (p = 0.406) and 0.42 (95% CI: 0.31-0.52) versus 0.45 (95% CI: 0.34-0.56) (p = 0.920), respectively. Grade >1 acute graft-versus-host disease (GvHD) occurred in 29% of patients receiving Flu/Thio/Bu and 17% receiving Flu/Thio/Treo (p = 0.049), while grade 3-4 occurred in 10% and 9% (p = 0.813). 3-year incidence of chronic GvHD was 0.07 (95% CI: 0.03-0.13) versus 0.05 (95% CI: 0.02-0.11), respectively (p = 0.518). In conclusion, both chemo-conditioning regimens were well tolerated and NRM was low. However, relapse was the major cause of treatment failure.
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2.
A novel integrative multi-omics approach to unravel the genetic determinants of rare diseases with application in sinusoidal obstruction syndrome
Waespe, N., Mlakar, S. J., Dupanloup, I., Rezgui, M. A., Bittencourt, H., Krajinovic, M., Kuehni, C. E., Nava, T., Ansari, M.
PloS one. 2023;18(4):e0281892
Abstract
BACKGROUND Genotype-phenotype analyses of rare diseases often suffer from a lack of power, due to small sample size, which makes identifying significant associations difficult. Sinusoidal obstruction syndrome (SOS) of the liver is a rare but life-threatening complication of hematopoietic stem cell transplantation (HSCT). The alkylating agent busulfan is commonly used in HSCT and known to trigger SOS. We developed a novel pipeline to identify genetic determinants in rare diseases by combining in vitro information with clinical whole-exome sequencing (WES) data and applied it in SOS patients and controls. METHODS First, we analysed differential gene expression in six lymphoblastoid cell lines (LCLs) before and after incubation with busulfan. Second, we used WES data from 87 HSCT patients and estimated the association with SOS at the SNP and the gene levels. We then combined the results of the expression and the association analyses into an association statistic at the gene level. We used an over-representation analysis to functionally characterize the genes that were associated with a significant combined test statistic. RESULTS After treatment of LCLs with busulfan, 1708 genes were significantly up-, and 1385 down-regulated. The combination of the expression experiment and the association analysis of WES data into a single test statistic revealed 35 genes associated with the outcome. These genes are involved in various biological functions and processes, such as "Cell growth and death", "Signalling molecules and interaction", "Cancer", and "Infectious disease". CONCLUSIONS This novel data analysis pipeline integrates two independent omics datasets and increases statistical power for identifying genotype-phenotype associations. The analysis of the transcriptomics profile of cell lines treated with busulfan and WES data from HSCT patients allowed us to identify potential genetic contributors to SOS. Our pipeline could be useful for identifying genetic contributors to other rare diseases where limited power renders genome-wide analyses unpromising. TRIAL REGISTRATION For the clinical dataset: Clinicaltrials.gov: NCT01257854. https://clinicaltrials.gov/ct2/history/NCT01257854.
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3.
Effect of pharmacokinetics and pharmacogenomics in adults with allogeneic hematopoietic cell transplantation conditioned with Busulfan
Seydoux, C., Uppugunduri, C. R. S., Medinger, M., Nava, T., Halter, J., Heim, D., Chalandon, Y., Schanz, U., Nair, G., Cantoni, N., et al
Bone marrow transplantation. 2023
Abstract
Busulfan (Bu) combined with cyclophosphamide (Cy) is commonly used as a myeloablative conditioning regimen for allogeneic hematopoietic cell transplantation (allo-HCT). There is inter-individual variability of Bu pharmacokinetics (PK) and hence in toxicity and efficacy. The introduction of therapeutic drug monitoring (TDM) of Bu has decreased toxicity of the regimen. Hepatic metabolism of Bu is mediated through Glutathione-S-Transferases (GSTs), mainly GSTA1. Patients with GSTA1*A variants are considered normal metabolizers and GSTA1*B corresponds to poor metabolism, defined by nucleotide changes at -52 or -69 locus in GSTA1 promoter region. The aim of the study was to explore the correlation between GSTA1 polymorphisms and Bu-PK in 60 adult patients receiving an allo-HCT in the BuCyBu clinical study (ClinicalTrials.gov I, ID NCT01779882) comparing the sequence BuCy to CyBu. DNA samples prior to conditioning were genotyped for candidate variants at -52 (rs3957356) and -69 (rs3957357) loci in the GSTA1 promoter. Thirty-three % of patients were GSTA1*A*A, 49% GSTA1*A*B and 18% GSTA1*B*B. In GSTA1*A*A patients, median Bu-AUC was 3.6 ± 0.7 mg*h/L, in GSTA1*A*B 4.5 ± 1.6 and in GSTA1*B*B 4.9 ± 1.4 (AUC 35% higher than GSTA1*A*A, p = 0.03), with a similar significant correlation with Bu-clearance (p = 0.04). The correlation between GSTA1 polymorphism and AUC remained significant in multivariate linear regression analysis. There was a trend for lower non-relapse mortality (NRM) in patients with low AUC. We could not demonstrate a correlation between GSTA1 polymorphisms and NRM, acute graft-versus-host disease (aGvHD) in this small cohort, but there is a trend of higher aGvHD incidence in GSTA1*B*B patients.
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4.
Pharmacokinetic modeling and simulation with pharmacogenetic insights support the relevance of therapeutic drug monitoring for myeloablative busulfan dosing in adult HSCT
Hassine, K. B., Seydoux, C., Khier, S., Daali, Y., Medinger, M., Halter, J., Heim, D., Chalandon, Y., Schanz, U., Nair, G., et al
Transplantation and cellular therapy. 2023
Abstract
Therapeutic drug monitoring (TDM) of busulfan (Bu) is well-established in pediatric hematopoietic stem cell transplantation (HSCT), but its use in adults is limited due to a lack of clear recommendations and scarcity of evidence regarding its utility. GSTA1 promoter variants are reported to affect Bu clearance in both adults and pediatric patients. This study aimed to evaluate the value of preemptive genotyping GSTA1 and body composition (obesity) in individualizing Bu dosing in adults, through pharmacokinetic (PK) modeling and simulations. A population pharmacokinetic (PopPK) model was developed and validated with data from 60 adults who underwent HSCT. Simulations assessed different dosing scenarios based on body size metrics and GSTA1 genotypes. Due to the limited number of obese patients in the cohort, the effect of obesity on Bu pharmacokinetics (PK) was evaluated in silico using a physiologically-based pharmacokinetic (PBPK) model and relevant virtual populations from Simcyp software. Patients with at least one GSTA1*B haplotype had 16% lower clearance on average. PopPK simulations indicated that adjusting doses based on genotype increased the probability of achieving the target exposure (3.7-5.5 mg.h/L) from 53 to 60 % in GSTA1*A homozygous patients, and from 50 to 61 % in *B carriers. Still, Approximately 40% of patients would not achieve this therapeutic window without TDM. A two-sample optimal design was validated for routine model-based Bu first dose AUC(0-∞) estimation, and the model was implemented in the Tucuxi user-friendly TDM software. PBPK simulations confirmed body surface area-based doses of 29 to 31 mg/m(2)/6h as the most appropriate, regardless of obesity status. This study emphasizes the importance of individualized Bu dosing strategies in adults to achieve therapeutic targets. Preemptive genotyping alone may not have a significant clinical impact, and routine TDM may be necessary for optimal transplantation outcomes.
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Hematopoietic cell transplantation and cellular therapies in Switzerland. Evolution over 25 years. A report from the stem cell transplantation and cellular therapies working groups of the SBST 1997-2021
Passweg, J. R., Baldomero, H., Ansari, M., Arber, C., Chalandon, Y., Daskalakis, M., Diepold, M., Diesch-Furlanetto, T., Duchosal, M. A., Gerull, S., et al
Hematological oncology. 2023
Abstract
The Swiss Blood Stem Cell Transplantation and Cellular Therapy Group (SBST) leads a mandatory national registry for all hematopoietic stem cell transplants (HCT) and cellular therapies. After 25 years, information was available for 11,226 patients receiving an HCT (4031 allogeneic and 7195 autologous), including 925 pediatric patients. We compared patient characteristics and outcome by quinquennia 1997-2001, 2002-2006, 2007-2011, 2012-2016, and 2017-2021. There were numerous changes over time. Allogeneic transplant recipients became older (median age 33.7 vs. 54.3) and had more frequently unrelated donors and reduced intensity conditioning in later quinquennia. Similarly, age increased for recipients of autologous HCT (median 48.3 vs. 59.9). We did not see a significant drop in transplant activity during the SARS-CoV-2 pandemic. Analysis of outcome showed overall survival (relative risk (RR) of death 0.664 (0.529-0.832) and progression free survival (RR 0.708 (0.577-0.870) being improved over time comparing the latest to the first quinquennium adjusting for risk factors. Non-relapse mortality decreased in recipients of allogeneic HCT (RR: 0.371 (0.270-0.509)) over time but relapse risks did not. Outcome of autologous HCT improved as well across quinquennia, this improvement was mainly due to decreased relapse risks (RR 0.681 (0.597-0.777)), possibly related to maintenance treatment or rescue treatment for relapse mainly in myeloma patients. Cellular therapies other than allogeneic or autologous HCT, particularly chimeric antigen receptor T-cells (CAR-T) treatment have started to increase after 2019, year of approval of the first commercial CAR-T product in Switzerland. Data on chimeric antigen receptor T-cell treatment are too early for comparative analyses. Detailed analyses of changes over time are presented. This study includes all HCTs, and cellular therapies, data useful for quality assurance programs, health care cost estimation and benchmarking. Between 50% and 60% of patients are long-term survivors after both types of HCT, indicating growing populations of surviving patients requiring long-term care.
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6.
Association Between the Magnitude of Intravenous Busulfan Exposure and Development of Hepatic Veno-Occlusive Disease in Children and Young Adults Undergoing Myeloablative Allogeneic Hematopoietic Cell Transplantation
Bognàr, T., Bartelink, I. H., Egberts, T. C. G., Rademaker, C. M. A., Versluys, A. B., Slatter, M. A., Kletzel, M., Nath, C. E., Cuvelier, G. D. E., Savic, R. M., et al
Transplantation and cellular therapy. 2022;28(4):196-202
Abstract
Intravenous busulfan is widely used as part of myeloablative conditioning regimens in children and young adults undergoing allogeneic hematopoietic cell transplantation (HCT). Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a serious clinical problem observed with busulfan-based conditioning HCT. The development of VOD/SOS may be associated with busulfan exposure. Getting more insight into the association between busulfan exposure and the development of VOD/SOS enables further optimization of dosing and treatment strategies. The objective of this study was to assess the association between the magnitude of busulfan exposure and the occurrence of VOD/SOS in children and young adults undergoing myeloablative conditioning with a busulfan-containing regimen before allogeneic HCT. In this observational study we included all patients who underwent allogeneic HCT with intravenous busulfan as part of the conditioning regimen at 15 pediatric transplantation centers between 2000 and 2015. The endpoint was the development of VOD/SOS. The magnitude of busulfan exposure was estimated using nonlinear mixed effect modeling and expressed as the maximal concentration (Cmax; day 1 and day 1 to 4 Cmax), cumulative area under the curve (AUC; day 1, highest 1-day AUC in 4 days, and 4-day cumulative AUC), cumulative time above a concentration of 300 µg/L, and clearance on day 1. A total of 88 out of 697 patients (12.6%) developed VOD/SOS. The number of alkylators in the conditioning regimen was a strong effect modifier; therefore we stratified the regression analysis for the number of alkylators. For patients receiving only busulfan as one alkylator (36.3%, n = 253), cumulative busulfan exposure (>78 mg × h/L) was associated with increased VOD/SOS risk (12.6% versus 4.7%; odds ratio [OR] = 2.95, 95% confidence interval [CI] 1.13 to 7.66). For individuals receiving busulfan with one or two additional alkylators (63.7%, n = 444), cumulative busulfan exposure (≤78 and >78 mg × h/L) did not further increase the risk of VOD/SOS (15.4% versus 15.2%; OR = 1.03, 95% CI 0.61 to 1.75). The effect of the magnitude of busulfan exposure on VOD/SOS risk in children and young adults undergoing HCT is dependent on the number of alkylators. In patients receiving busulfan as the only alkylator, higher cumulative busulfan exposure increased the risk of VOD/SOS, whereas in those receiving multiple alkylators, the magnitude of busulfan exposure did not further increase this risk.
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7.
Unrelated cord blood transplantation in children, adolescents, and young adults with acute leukemia or myelodysplastic syndrome: a retrospective comparative study from the French Society for Bone Marrow Transplantation and Cellular Therapy (SFGM-TC) between Real-World Data and previously reported results of a Randomized Clinical Trial
Teyssier, A. C., Michel, G., Jubert, C., Rialland, F., Visentin, S., Ouachée, M., Bilger, K., Gandemer, V., Beguin, Y., Marie-Cardine, A., et al
Transplantation and cellular therapy. 2022
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Editor's Choice
Abstract
BACKGROUND We previously reported results of a French randomized clinical trial (RCT) comparing the risk of transplantation failure (including transplant-related mortality (TRM), engraftment failure, and autologous recovery) in single and double unrelated cord blood (UCB) transplantation in children and young adults with hematologic malignancies. We concluded that single-UCB transplantation with an adequate cell dose is the standard of care, leading to a 70% two-year overall survival (OS). It remains unclear, however, whether RCT participants have better outcomes than comparable patients not treated in the setting of a clinical trial. We previously reported results of a French randomized clinical trial (RCT) comparing the risk of transplantation failure (including transplant-related mortality (TRM), engraftment failure, and autologous recovery) in single and double unrelated cord blood (UCB) transplantation in children and young adults with hematologic malignancies. We concluded that single-UCB transplantation with an adequate cell dose is the standard of care, leading to a 70% two-year overall survival (OS). It remains unclear, however, whether RCT participants have better outcomes than comparable patients not treated in the setting of a clinical trial. We compared the characteristics and outcomes of RCT participants (n = 137) to a Francophone population-based registry of patients (real-world (RW) group) fulfilling the eligibility criteria used in our RCT and transplanted with one or two UCB units after a myeloablative conditioning (MAC) regimen between March 2015 (end of inclusion in the RCT) and February 2019 (n = 141). The primary endpoint was the two-year cumulative incidence (CI) of transplantation strategy failure as defined in our RCT. The two groups were comparable in terms of age, disease distribution, hematologic status at transplantation, follow-up, and HLA compatibility. Patients in the RW group were more likely to be transplanted with a single-unit UCB (87.9% versus 49.6%, p < 0.001) and to receive a radiation-free regimen (39.0% vs. 60.6%, p < 0.001). The two-year CI of transplantation strategy failure, TRM, and the two-year probability of OS were similar between the two groups, although the relapse risk was higher in the RW group (31.2% ± 7.7% vs. 20.4% ± 6.8%, p = 0.01), resulting in a significantly lower DFS (59.2% ± 8.4% vs. 69.3% ± 8.0%, p = 0.047). This difference remained statistically significant only in the group of patients with acute lymphoid leukemia (ALL) who did not receive the conditioning regimen recommended by the RCT (fludarabine 75 mg/m2, total body irradiation 12 Gy, cyclophosphamide 120 mg/kg). The results of our RCT appear to be reproducible in real-world conditions, provided that the same cord blood selection criteria and conditioning regimen are used. OBJECTIVES AND STUDY DESIGN We compared the characteristics and outcomes of RCT participants (n = 137) to a Francophone population-based registry of patients (real-world (RW) group) fulfilling the eligibility criteria used in our RCT and transplanted with one or two UCB units after a myeloablative conditioning (MAC) regimen between March 2015 (end of inclusion in the RCT) and February 2019 (n = 141). The primary endpoint was the two-year cumulative incidence (CI) of transplantation strategy failure as defined in our RCT. RESULTS The two groups were comparable in terms of age, disease distribution, hematologic status at transplantation, follow-up, and HLA compatibility. Patients in the RW group were more likely to be transplanted with a single-unit UCB (87.9% versus 49.6%, p < 0.001) and to receive a radiation-free regimen (39.0% vs. 60.6%, p < 0.001). The two-year CI of transplantation strategy failure, TRM, and the two-year probability of OS were similar between the two groups, although the relapse risk was higher in the RW group (31.2% ± 7.7% vs. 20.4% ± 6.8%, p = 0.01), resulting in a significantly lower DFS (59.2% ± 8.4% vs. 69.3% ± 8.0%, p = 0.047). This difference remained statistically significant only in the group of patients with acute lymphoid leukemia (ALL) who did not receive the conditioning regimen recommended by the RCT (fludarabine 75 mg/m2, total body irradiation 12 Gy, cyclophosphamide 120 mg/kg). CONCLUSION The results of our RCT appear to be reproducible in real-world conditions, provided that the same cord blood selection criteria and conditioning regimen are used.
PICO Summary
Population
Children, adolescents and young adults with acute leukaemia or myelodysplastic syndrome
Intervention
Participants in a randomised controlled trial (RCT) (n=137)
Comparison
Patients from a real-world cohort reported to a Francohpone regisistry, receiving onr or two cord blood units after myeloablative conditioning (RW group, n=141)
Outcome
The two groups were comparable in terms of age, disease distribution, hematologic status at transplantation, follow-up, and HLA compatibility. Patients in the RW group were more likely to be transplanted with a single-unit UCB (87.9% versus 49.6%) and to receive a radiation-free regimen (39.0% vs. 60.6%). The two-year CI of transplantation strategy failure, Transplant related mortality, and the two-year probability of overall survival were similar between the two groups, although the relapse risk was higher in the RW group (31.2% ± 7.7% vs. 20.4% ± 6.8%), resulting in a significantly lower DFS (59.2% ± 8.4% vs. 69.3% ± 8.0%). This difference remained statistically significant only in the group of patients with acute lymphoid leukemia (ALL) who did not receive the conditioning regimen recommended by the RCT (fludarabine 75 mg/m2, total body irradiation 12 Gy, cyclophosphamide 120 mg/kg).
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Defibrotide shows efficacy in the prevention of sinusoidal obstruction syndrome after allogeneic hematopoietic stem cell transplantation: A retrospective study on 237 patients
Chalandon, Y., Mamez, A. C., Giannotti, F., Beauverd, Y., Dantin, C., Mahne, E., Mappoura, M., Bernard, F., Ortiz, C. R., Stephan, C., et al
Transplantation and cellular therapy. 2022
Abstract
BACKGROUND Sinusoidal obstruction syndrome (SOS), also known as hepatic veno-occlusive disease (VOD), is a well-known complication of allogeneic hematopoietic stem cell transplantation (HSCT) associated with a mortality rate of up to 85%. Defibrotide has shown efficacy in treatment of SOS/VOD. Moreover, evidence exists supporting the efficacy of defibrotide as SOS/VOD prophylaxis. OBJECTIVES We have previously reported our single center experience on 52 HSCT recipients receiving defibrotide as SOS/VOD prophylaxis which has shown that the patients did not develop any SOS/VOD under this prophylaxis. The aim of the present study was to see if we can confirm the previous results, mainly on the decrease incidence of SOS/VOD as well as improve event-free survival (EFS) on a larger study population. STUDY DESIGN We extended our previous study in a single center retrospective analysis to include 237 consecutive patients (248 transplantations) transplanted between 1999 and 2009 for hematological diseases and receiving intravenous defibrotide as prophylaxis. This cohort was compared to 241 patients (248 transplantations) treated before 1999 or after 2009 when defibrotide prophylaxis was not routinely employed in our center. RESULTS Median follow-up for the study group was 10 (range 2-16) years and for the control group 2.7 (range 1-18) years. None of the 237 patients in the defibrotide group developed SOS/VOD. The cumulative incidence (CI) of SOS/VOD was 0% in the defibrotide group as compared to 4.8% (95%CI 2.6-8%; p=0.00046) in the control group. There was also a better one-year event-free survival (EFS) with 38% (95%CI 32%-44%) in the defibrotide group vs 28% (95%CI 22%-34%), p=0.00969 and decreased cumulative incidence of acute graft versus host disease (GVHD) in the defibrotide group 31% (95%CI 25%-37%) vs 42% (95%CI 36%-48%), p=0.026. The one-year overall survival (OS), relapse incidence (RI) and non-relapse mortality (NRM) were not statistically different. Multivariable analysis, performed taking into account clinical factors known to influence the risk of SOS/VOD, confirmed the favorable impact of defibrotide on SOS/VOD (HR 1.38e-08 [95%CI 3.28e-09-5.80e-08]; p<0.00001). Conversely, multivariable analysis failed to confirm the impact of defibrotide on 1-year EFS or acute GvHD. CONCLUSIONS This large retrospective study on SOS/VOD-prophylaxis with defibrotide suggests that this approach may be of benefit. These results need to be confirmed in a prospective randomized trial.
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Genetic susceptibility to acute graft versus host disease in pediatric patients undergoing HSCT
Ansari, M., Petrykey, K., Rezgui, M. A., Del Vecchio, V., Cortyl, J., Ameur, M., Nava, T., Beaulieu, P., St-Onge, P., Mlakar, S. J., et al
Bone marrow transplantation. 2021
Abstract
The most frequent complication of allogeneic hematopoietic stem cell transplantation is acute Graft versus Host Disease (aGVHD). Proliferation and differentiation of donor T cells initiate inflammatory response affecting the skin, liver, and gastrointestinal tract. Besides recipient-donor HLA disparities, disease type, and the conditioning regimen, variability in the non-HLA genotype have an impact on aGVHD onset, and genetic variability of key cytokines and chemokines was associated with increased risk of aGVHD. To get further insight into the recipient genetic component of aGVHD grades 2-4 in pediatric patients, we performed an exome-wide association study in a discovery cohort (n = 87). Nine loci sustained correction for multiple testing and were analyzed in a validation group (n = 168). Significant associations were replicated for ERC1 rs1046473, PLEK rs3816281, NOP9 rs2332320 and SPRED1 rs11634702 variants through the interaction with non-genetic factors. The ERC1 variant was significant among patients that received the transplant from HLA-matched related individuals (p = 0.03), bone marrow stem cells recipients (p = 0.007), and serotherapy-negative patients (p = 0.004). NOP9, PLEK, and SPRED1 effects were modulated by stem cell source, and serotherapy (p < 0.05). Furthermore, ERC1 and PLEK SNPs correlated with aGVHD 3-4 independently of non-genetic covariates (p = 0.02 and p = 0.003). This study provides additional insight into the genetic component of moderate to severe aGVHD.
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10.
GSTM1 and GSTT1 double null genotypes determining cell fate and proliferation as potential risk factors of relapse in children with hematological malignancies after hematopoietic stem cell transplantation
Mlakar, S. J., Satyanarayana, C. R. U., Nava, T., Mlakar, V., Golay, H., Robin, S., Waespe, N., Rezgui, M. A., Chalandon, Y., Boelens, J. J., et al
Journal of cancer research and clinical oncology. 2021
Abstract
PURPOSE This study aimed to retrospectively evaluate the genetic association of null variants of glutathione S-transferases GSTM1 and GSTT1 with relapse incidence in children with hematological malignancies (HMs) undergoing busulfan (BU)- containing allogeneic hematopoietic stem cell transplantation (HSCT) and to assess the impact of these variants on BU-induced cytotoxicity on the immortalized lymphoblastoid cell lines (LCLs) and tumor THP1 GST gene-edited cell models. METHODS GSTM1- and GSTT1-null alleles were genotyped using germline DNA from whole blood prior to a conditioning BU-based regimen. Association of GSTM1- and GSTT1-null variants with relapse incidence was analyzed using multivariable competing risk analysis. BU-induced cell death studies were conducted in GSTs- null and non-null LCLs and CRISPR-Cas9 gene-edited THP1 leukemia cell lines. RESULTS Carrying GSTM1/GSTT1 double null genotype was found to be an independent risk factor for post-HSCT relapse in 86 children (adjusted HR: 6.52 [95% Cl, 2.76-15.42; p?=?1.9?×?10(-5)]). BU-induced cell death preferentially in THP1(GSTM1(non-null)) and LCLs(GSTM1(non-null)) as shown by decreased viability, increased necrosis and levels of the oxidized form of glutathione compared to null cells, while GSTT1 non-null cells showed increased baseline proliferation. CONCLUSION The clinical association suggests that GSTM1/GSTT1 double null genotype could serve as genetic stratification biomarker for the high risk of post-HSCT relapse. Functional studies have indicated that GSTM1 status modulates BU-induced cell death. On the other hand, GSTT1 is proposed to be involved in baseline cell proliferation.