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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 THP1GSTM1(non−null) and LCLsGSTM1(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.

Background: Relapse is the major cause of treatment failure in children with hematological malignancies (HMs) undergoing busulfan (BU)- based allogeneic hematopoietic stem cell transplantation (HSCT). Glutathione S-transferases (GSTs) isoforms that participate in BU detoxification and protect cells against stress and cell death may be linked to post-HSCT outcomes. 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 HMs undergoing BU- containing allogeneic HSCT and to assess the impact of these variants on BU-induced cytotoxicity on the immortalized and tumor lymphoblastoid cell lines (LCLs).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 x 10-5]). BU induced cell death preferentially in THP1GSTM1(non-null) and LCLsGSTM1(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. Trial registration: ClinicalTrials.gov identifier: NCT01257854, Registered February 2008 – retrospectively registered.

BackgroundRelapse is the major cause of treatment failure in children with hematological malignancies (HMs) undergoing busulfan (BU)- based allogeneic hematopoietic stem cell transplantation (HSCT). Glutathione S-transferases (GSTs) isoforms that participate in BU detoxification and protect cells against stress and cell death may be linked to post-HSCT outcomes. 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 HMs undergoing BU- containing allogeneic 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.MethodsGSTM1- 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. ResultsCarrying 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 x 10-5]). BU induced cell death preferentially in THP1GSTM1(non-null) and LCLsGSTM1(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. ConclusionThe 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. Trial registrationClinicalTrials.gov identifier: NCT01257854, Registered February 2008 – retrospectively registered.

Background Large sample sizes are often required to detect statistically significant associations between pharmacogenetic markers and treatment response. Meta-analysis may be performed to synthesize data from several studies, increasing sample size and, consequently, power to detect significant genetic effects. However, performing robust synthesis of data from pharmacogenetic studies is often challenging because of poor reporting of key data in study reports. There is currently no guideline for the reporting of pharmacogenetic studies that has been developed using a widely accepted robust methodology. The objective of this project was to develop the STrengthening the Reporting Of Pharmacogenetic Studies (STROPS) guideline. Methods and findings We established a preliminary checklist of reporting items to be considered for inclusion in the guideline. We invited representatives of key stakeholder groups to participate in a 2-round Delphi survey. A total of 52 individuals participated in both rounds of the survey, scoring items with regards to their importance for inclusion in the STROPS guideline. We then held a consensus meeting, at which 8 individuals considered the results of the Delphi survey and voted on whether each item ought to be included in the final guideline. The STROPS guideline consists of 54 items and is accompanied by an explanation and elaboration document. The guideline contains items that are particularly important in the field of pharmacogenetics, such as the drug regimen of interest and whether adherence to treatment was accounted for in the conducted analyses. The guideline also requires that outcomes be clearly defined and justified, because in pharmacogenetic studies, there may be a greater number of possible outcomes than in other types of study (for example, disease–gene association studies). A limitation of this project is that our consensus meeting involved a small number of individuals, the majority of whom are based in the United Kingdom. Conclusions Our aim is for the STROPS guideline to improve the transparency of reporting of pharmacogenetic studies and also to facilitate the conduct of high-quality systematic reviews and meta-analyses. We encourage authors to adhere to the STROPS guideline when publishing pharmacogenetic studies., Marty Chaplin and co-authors recount the development of a guideline for reporting pharmacogenetic studies.