Image courtesy of the National Institute of General Medical Sciences
Genome analysis
ORLANDO, FL—Results of a genome-wide association study suggest that several genetic variants are associated with outcomes of allogeneic hematopoietic stem cell transplant (HSCT) in patients with acute lymphoblastic leukemia (ALL).
Investigators identified several single-nucleotide polymorphisms (SNPs) in ALL patients and their unrelated donors that were associated with disease-related death or progression-free survival (PFS) within 1 year of HSCT.
“We believe that these findings will lead to a better understanding of the biology of this disease,” said investigator Theresa Hahn, PhD, of Roswell Park Cancer Institute in Buffalo, New York.
“Additionally, we expect that this work will eventually help clinical teams to identify unrelated donors with genotypes that yield better survival in transplant patients and enhance the chances for successful blood and marrow transplants.”
Dr Hahn presented this work as a “Best Abstract” at the 2017 BMT Tandem Meetings (abstract 1).
For this study, she and her colleagues analyzed data on patients treated at more than 150 US transplant centers between 2000 and 2011. The investigators evaluated data on more than 3000 patients with acute leukemias or myelodysplastic syndromes, but Dr Hahn only presented findings in the ALL patients and their donors.
The patients and donors were divided into 2 cohorts. Cohort 1 included 483 ALL patients who underwent HSCT from 2000 to 2008 and 466 unrelated donors who were a 10/10 HLA match for the patients.
Cohort 2 included 94 ALL patients who received a transplant from a 10/10 HLA-matched donor between 2009 and 2011 or from an 8/8 HLA-matched donor between 2000 and 2011. There were 92 donors in this cohort.
The investigators sequenced blood samples from the recipients and donors to identify SNPs. The SNPs were then measured for association with disease-related death and PFS using Cox proportional hazards models adjusted for recipient age, disease status at HSCT (early, intermediate, or advanced), graft source (blood or marrow), and year of transplant.
SNPs in donors
The top 2 SNPs in donors that were associated with a significant increase in disease-related death were:
- rs79503405 in LRP2 on chromosome 2.
- rs77618918 in ASIC2 on chromosome 17.
Dr Hahn noted that rs79503405 is in complete linkage disequilibrium (r2=1.0) with a genotyped missense variant (rs17848149) and a synonymous coding variant (rs35114151) in LRP2.
She also pointed out that the other top SNP (rs77618918) associated with disease-related death is not in linkage disequilibrium with other SNPs of functional importance, so the significance of this SNP is unknown.
There were no SNPs in donors that were significantly associated with PFS.
SNPs in recipients
In HSCT recipients, there were 3 linked variants in NRG1 on chromosome 8 (rs79853417, rs6990973, and rs145488394) that were significantly associated with disease-related death.
Another SNP (rs60640657) on chromosome 2 (CTNNA3/LOC101928961/LRRTM3) was also significantly associated with ALL-related death.
In addition, Dr Hahn and her colleagues found that 1 region in recipient genomes contains multiple variants (rs113263921 and others) associated with PFS. The SNPs are located on chromosome 3 in MLH1 and TRANK1.
“The donor and recipient genetic variants contributed independently to death due to ALL,” Dr Hahn said in closing. “Genetic variants for PFS do not overlap with death due to ALL, and this is probably due to the inclusion of both non-fatal disease progression as well as transplant-related mortality in the definition of PFS.”
“Constitutional genetic variants in recipients and donors increase the risk of death due to ALL, and they warrant further study into the impact of these genes on disease and transplant-related biology.”
