Calcitonin A Genotype Is Associated with Risk of Acute Graft-Versus-Host Disease Following Allogeneic Bone Marrow Transplantation for Children with Acute Myeloid Leukemia in First Remission.

Background: Procalcitonin (PCT) is a 13 kD 116-amino acid prohormone. Elevated serum levels of procalcitonin have been noted in patients with bacterial infections such as septicemia, pneumonia and immune-mediated conditions like graft-versus-host disease (GvHD) and organ rejection. In this study, we sought to examine if a single base pair polymorphism (a T to C transition) at position −624 of the calcitonin A gene (CALCA) was associated with risk of acute GvHD.

Subjects: 113 children (median age 10 y; range 0.38 – 19.0 y) with de novo acute myeloid leukemia (AML) treated on recent Children’s Oncology Group protocols 2891, 2941 or 2961. All of these patients received matched sibling bone marrow transplant (BMT) in first clinical remission. Ablative conditioning consisted of busulfan and cyclophosphamide. All patients received methotrexate until day 100 for GvHD prophylaxis.

Methods: All clinical DNA specimens were subjected to whole genome amplification. Genotyping was performed using the 5′-nuclease (TaqMan) assay on the ABI 7700 DNA analyzer (Applied Biosystems).

Results: Observed CALCA -624 T>C genotypes in 113 patients were: TT = 52 (46%), TC = 43 (38%) and CC = 18 (16%); T allele = 73 (65%) and C allele = 40 (35%). There were no significant differences in patient characteristics (age, gender, race, study 2891/2941/2961, white blood count at diagnosis, FAB type, or cytogenetics) between the TT vs. combined TC or CC groups. Overall, acute GvHD grade I–IV (Seattle criteria) was observed in 55/113 patients (49%). Nineteen out of 52 (37%) with TT, while 21 out of 43 (49%) with TC, and 15 out of 18 (83%) with CC CALCA genotypes developed acute GvHD. Alternatively, acute GvHD was observed in 37% patients with common TT genotype and in 59% patients with variant TC or CC genotype (p=0.023). The odds ratio for developing acute GvHD (grade I – IV) for children with TC or CC genotypes was 2.5 (CI 1.17, 5.33) compared with those with TT genotype. The difference in observed acute GvHD remained significant when the analyses were limited to more uniform subgroups: 54 patients on single trial, 2961 only (p=0.028) and 42 whites only on 2961 trial (p=0.028). Severe acute GvHD (grade III – IV) was seen in 6/52 (12%) patients with TT vs. 6/61 (10%) in those with TC or CC genotypes; this difference was not statistically significant (p =0.771). There were no significant differences in day +100 transplant related deaths, engraftment, relapse rate or overall survival. Plans: Association between CALCA genotypes and infectious complications will be also analyzed when clinical data abstraction is completed. CALCA −1752 C>G and 3740 A>G genotyping is in progress and clinical correlative analyses will be repeated at genotype and haplotype levels.