TGFB1 Functional Polymorphisms in Sibling HSCT. "Tto be or Not Tto be"

Allogeneic hematopoietic stem cell transplantation (HSCT) using sibling donors is a life-saving intervention for patients with hematological malignancies. It is recognized that numerous genetic factors in both patient and donor play a role in the outcome of the procedure. TGF beta 1 is a member of a highly pleiotrophic family of growth factors involved in the regulation of numerous immunomodulatory processes. Several functional polymorphisms have been identified in TGF-B1 gene, such as a single nucleotide polymorphism (SNP) at codon 10 of exon 1. We have previously published significant impact of this SNP on unrelated donor (UD) transplant outcome, predominantly on Non Relapse Mortality (NRM) and acute Graft-vs.-Host-Disease (aGVHD). To date there are no published data in large sibling donor HSCT cohorts looking at survival outcomes. We have hypothesized that TGF-B1 SNP may influence the outcome of sibling donor HSCT similarly to UD. Preliminary data were presented at ASH meeting 2014. Two hundred and seventeen patient/donor pairs who underwent a sibling donor HSCT in our centers were genotyped for the presence of a SNP at codon 10 (rs1982073) by an allele-specific PCR. Transplants took place between January 2000 and January 2015 and the median follow up time was 4.4 years. Median age was 33 years and 58% were male. The prevalent diagnoses were acute myeloid leukemia 64 (29%), acute lymphoid leukemia 49 (23%), lymphoproliferative disorders 28 (13%), myelodysplastic syndrome 26 (12%) and myeloproliferative neoplasm 20 (9%). Early stage of the disease was determined in 42%.  Myeloablative conditioning regimens were used in 58% of transplants; the source was PBSC in 90% of the patients. The patients' observed SNP frequencies were TT 23%, TC 55% and CC 22%, and for the donors were 26%, 53% and 21% respectively. No significant impacts were observed in the full cohort analysis. When we analyzed the myeloablative cohort, significant differences were founded. Similarly to what we observed in UD, codon 10 CC patients had a significant increase in 1 year treatment related mortality (32% vs. 9%, p=0.01) and Non Relapse Mortality (NRM) (1-3 years CC 31-31% vs. TC/TT 8-13%, Gray's test p=0.04) (figure 1). A very interesting finding was in donor's genotype. Codon 10 TT donor's receptors experienced a significant increase in aGVHD (72% vs. 49%, p=0.03), with 56% of this grades 2-4. Interestingly this group had no protection in terms of relapse, but the opposite, although not significant (1-3 years TT 36-40% vs. TC 17-34% vs. CC 9-13%, Gray's test p=0.1). Finally TT donors had a significant decrease in Overall Survival (OS) compared to other genotypes (1-3 years TT 69-50% vs. TC/CC 77-69%, log-rank p=0.04) (figure 2). No differences were observed in donor genotype in terms of NRM. Besides confirming that as in UD, patient codon 10 CC had an increase in NRM, we conclude that in sibling donor-myeloablative HSCT codon 10 TT donors might be associated with an increase in aGVHD with no protection in relapse and a significant decrease in OS. These results should be confirmed in larger series. Identification of these SNPs pre-transplant will allow for transplant conditioning and immunosuppression regimens to be tailored to the individual patient, as well as assisting in the most appropriate choice of donor.