Analysis of Relationships between Immune Checkpoint and Methylase Gene Polymorphisms and Outcomes after Unrelated Bone Marrow Transplantation

Unrelated bone marrow transplantation (uBMT) is performed to treat blood disorders, and it uses bone marrow from an unrelated donor as the transplant source. Although the importance of HLA matching in uBMT has been established, that of other genetic factors, such as single-nucleotide polymorphisms (SNPs), remains unclear. The application of immunoinhibitory receptors as anticancer drugs has recently been attracting attention. This prompted us to examine the importance of immunoinhibitory receptor SNPs in uBMT. We retrospectively genotyped five single-nucleotide polymorphisms (SNPs) in the immune checkpoint genes, BTLA, PD-1, LAG3, and CTLA4, and two SNPs in the methylase genes, DNMT1 and EZH2, in 999 uBMT donor–recipient pairs coordinated through the Japan Marrow Donor Program matched at least at HLA-A, -B, and -DRB1. No correlations were observed between these SNPs and post-uBMT outcomes (p > 0.005). This result questions the usefulness of these immune checkpoint gene polymorphisms for predicting post-BMT outcomes. However, the recipient EZH2 histone methyltransferase gene SNP, which encodes the D185H substitution, exhibited a low p-value in regression analysis of grade 2–4 acute graft-versus-host disease (p = 0.010). Due to a low minor allele frequency, this SNP warrants further investigation in a larger-scale study.

Outcomes of Unrelated Bone Marrow Transplantation in Patients with Thalassemia

Introduction. Bone marrow transplantation from an HLA-matched related or unrelated donor remains the only curative treatment for patients with thalassemia. Although one third of patients with thalassemia can find a matched unrelated donor (MUD) few patients were treated by MUD transplantation. Early experience with the use of MUD transplant in class 3 patients with thalassemia resulted in high rates of graft rejection and transplant-related mortality with thalassemia-free (TFS) survival of 53% (La Nasa G et al. Blood 2002). Significant improvements in MUD transplantation in recent years have prompted us to consider it also for high risk patients with thalassemia. Methods . All patient-donor pairs were typed at high resolution for HLA-A, -B, -C, -DRB1, -DQA1, -DQB1, and DPB1. Fourteen consecutive patients with a median age of 5 years (range, 2-17.2) received unrelated bone marrow transplantation for thalassemia. Four patients were in class 1, 2 were in class 2 and 8 were in class 3 of risk. All patients were treated with the conditioning regimen consisting of weight-based IV Bu, thiotepa (10 mg/kg/d), CY (200 mg/kg) and thymoglobulin (10 mg/kg) preceded by preconditioning with hydroxyurea (30 mg/kg/d), azathioprine (3 mg/kg/d) from D −45, and fludarabine (30 mg/m2/d) from D −16 through D −12. Patients received CSA, methylprednisolone and a short course of MTX as GVHD prophylaxis. Results. Between May 2009 and December 2017 un unrelated donor search was performed for 47 patients at our Institute. Forty one patients were Caucasian and 6 patients black African origin. Among Caucasians 16/41 (39%) found a 10/10 and 5/41 (12%) a 9/10 HLA allele-matched unrelated donor, while 1 of 6 black African patients (16.6%) found a 10/10 HLA-matched donor. Among 22 patients with a suitable donor (10/10 or 9/10 HLA allele-matched) 14 received transplantation, 2 patients withdrew consent, 1 patient's donor refused donation, and the remaining 5 patients are awaiting transplant. Twelve patients received 10/10 and 2 patients 9/10 HLA allele-matched grafts. Eight patients had permissive DPB1 mismatches while 2 patients had non-permissive mismatches in the HvG direction and 4 patients in the GvH direction. Median TNC/kg and CD34+/kg infused were 7.2x108 (range, 3.95-12.5) and 7.75x106 (range, 3.47-16.4), respectively. Sustained engraftment occurred in all patients. The median time to neutrophil and platelet recovery was 20 days (range, 15-27) and 19 days (range, 15-28), respectively. All but one patient showed 100% donor chimerism. The patient with stable mixed chimerism (48% donor DNA) has remained transfusion independent for over 3 years with hemoglobin levels >13.5-14 g/dL. Grade 2 and 3-4 acute GVHD occurred in 3 (21%) and 2 (14%) patients, respectively. Two patients developed mild (skin) or severe (skin, gut and liver) chronic GVHD. There was no association between non permissive DPB1 mismatches in the GvH direction and GVHD. All but one patient are alive and are off immunosuppressive therapy. One patient died due to chronic GVHD-related complications. The median follow-up among surviving patients was 2.8 years (range, 0.8-8.6). The 5-year OS and TFS probabilities were 90% (95% CI 47 to 99%) (Figure 1). Patients showed suboptimal CD4+ recovery within the first year: absolute (mean±SEM) cells/ul of CD4+ at 6 months was 223±48. At 12 and 24 months recovery of CD4+, CD8+, CD19+ and CD56+ were 597±122, 1077±228, 331±75, 229±64 and 812±284, 1067±405, 218±82, 112±22, respectively. One patient developed mild to moderate hepatic sinusoidal obstruction syndrome which resolved with supportive care. CMV reactivation occurred in 9 patients and none developed CMV disease. One patient developed adenovirus gastroenteritis. EBV reactivation occurred in 4 patients; one developed posttransplant lymphoproliferative disorder that was successfully treated with Rituximab. Bacterial infections were common: 5 (38%) patients developed gram negative or gram positive sepsis and 4 (29%) patients pneumonia. Probable invasive fungal infections occurred in 2 (14%) patients. Conclusions. This study showed that unrelated donor BMT can successfully cure a proportion of patients with thalassemia. Remarkably, despite 57% of patients were in class 3 of risk the 5-year OS and TFS rates were 90%. We conclude that class 3 patients with thalassemia who have a suitably matched unrelated donor should not be denied the option of transplantation. Disclosures No relevant conflicts of interest to declare.