ALBERT

Description: Abstract 344 Hemorrhagic cystitis is a serious complication after hematopoietic stem cell transplantation (HSCT). The pathogenesis of hemorrhagic cystitis is not fully understood and is influenced by BK virus infection, type of transplant, conditioning regimen, stem cell source, and graft-versus-host disease. Nothing is known about human genetic factors and the development of BK virus-associated hemorrhagic cystitis in patients after HSCT. Toll-like receptors (TLR) are essential components of the innate immune system. TLR have been discovered as the most important class of pattern recognition receptors, involved in the host defense against bacteria, viruses, fungi, and protozoa. C3H/HeJ mice that lack functional TLR4 receptors did not develop cystitis after intravesical instillation of E. coli. Individuals with the Asp299Gly polymorphism of the TLR4 gene showed a diminished inflammatory responsiveness to endotoxin. Because of the requirement of TLR4 in inflammatory response we hypothesized that TLR4 Asp299Gly reduces the risk of BK virus-associated hemorrhagic cystitis after hematopoietic stem cell transplantation (HSCT). 166 children (median age, 13 years) with acute lymphoblastic leukemia (n=72), acute myeloid leukemia (n=38), myelodysplastic syndrome (n=21), chronic myeloid leukemia (n=12), genetic disease (n=12) or severe aplastic anemia (n=11) who underwent allogeneic bone marrow (n=105) or peripheral blood stem cell transplantation (n=61; T-cell depleted: n=31) in a single center and their respective donors were genotyped of TLR4 for rs4986790 (A896G, Asp299Gly) using TaqMan real-time polymerase chain reaction. The donor was HLA-matched unrelated in 57% of transplants or HLA-identical related in 33% of transplants. Conditioning regimen was myeloablative in all cases and based on total body irradiation in 48% of transplants or busulfan in 47% of transplants. Two forms of post-transplant immunosuppression predominated, cyclosporine A and methotrexate in 64% of transplants and cyclosporine A alone in 25% of transplants. The Asp299Gly variant was present in 21 of the 166 patients (12.6%) and in 24 of the 166 donors (14.4%). Interestingly, we found a significantly reduced incidence of BK virus-associated hemorrhagic cystitis in patients with the Asp299Gly variant (0% versus 22.8%, p=0.009). In addition, we observed a significantly reduced incidence of BK virus-associated hemorrhagic cystitis in patients who were transplanted from a donor with this specific variant (4.2% versus 22.5%; p=0.05). In ten of the donor-patient pairs the variant was present in both individuals and no hemorrhagic cystitis was observed. The occurrence of the TLR4 Asp299Gly variant, in either recipients or donors, had no significant impact on acute and chronic GVHD, relapse rate, bacterial and fungal infectious complications, transplant related mortality, and overall survival. In conclusion, the TLR4 Asp299Gly variant in the recipient and/or the donor confers strong protection against BK virus-associated hemorrhagic cystitis after HSCT in children. This study provides the first evidence that the innate immune system through TLR4 signaling pathway seems to play an important role in the pathogenesis of BK virus-associated hemorrhagic cystitis after HSCT. Disclosures: No relevant conflicts of interest to declare.

Description: A stepwise approach which combined genome wide expression profiling and a TaqMan realtime PCR based screening was used to identify new markers for the monitoring of minimal residual disease (MRD) in acute myeloid leukemia (AML). Leukemic cells from 52 children with AML were analyzed. Seven genes were identified which are vastly over-expressed in many patients with AML compared to healthy bone marrow: CCL23, GAGED2, MSLN, SPAG6, and ST18 as well as the previously described markers WT1 and PRAME. This set of genes was analyzed in 141 follow-up samples from 25 patients. The expression of all genes decreased to normal levels in patients who achieved a continuous complete remission. Elevated levels of MRD markers were found prior to relapse in 7 out of 10 patients who relapsed. This set of genes should allow a sensitive and specific monitoring of MRD in AML. Notably, some of these markers could also serve as therapeutic targets or might be involved in leukemogenesis. MSLN is already used as a target for immunotherapy in clinical trials in other malignancies. GAGED2 and SPAG6 belong to the family of cancer testis genes which are also studied intensively as targets for immunotherapy. ST18 is a recently discovered tumor suppressor which was not yet described in hematological malignancies. CCL23 is a chemokine that inhibits the proliferation of healthy hematological stem cells. Names, symbols, and geneID of seven MRD markers Gene Symbol Gene Name GeneID CCL23 chemokine (C–C motif) ligand 23 6368 GAGED2 G antigen, family D, 2 9503 MSLN Mesothelin 10232 SPAG6 sperm associated antigen 6 9576 ST18 suppression of tumorigenicity 18 9705 WT1 Wilms tumor 1 7490 PRAME preferentially expressed antigen in melanoma 23532

Description: The proof for the prenatal origin of childhood acute lymphoblastic leukemia (ALL) comes from the detection of concordant leukemia in monozygotic twins and the identification of translocation breakpoint genomic sequences at birth in a limited number of ALL patients with t(4;11) or t(12;21) chromosomal translocation. However, most patients with childhood ALL lack leukemia-specific fusion gene sequences. Therefore, we have used the rearranged immunoglobulin heavy chain (IgH) genes as a marker for the detection of preleukemic clones at birth. Guthrie card blood spots of 32 children with B-lineage ALL treated at our institution were available for this retrospective study. The ALL patients had a median age of 5 years (range, 15 months to 14 years) and had median presenting white blood cell (WBC) counts of 10150/μl (range, 800 to 103800/μl). In all patients a monoclonal IgH gene rearrangement was obtained from diagnostic bone marrow and sequenced. Clone-specific primers were designed using the specific D-N-J and N-D-N sequences. A two-stage polymerase chain reaction (PCR) using a semi-nested approach was developed to improve sensitivity and specificity of amplification. In all 32 patients, one leukemic cell could be detected in a background of 105 normal blood mononuclear cells. Nineteen of the 32 patients (59%) had detectable IgH gene rearrangements at birth using the sensitive semi-nested PCR. Sequencing of the PCR products obtained from Guthrie card blood spots revealed the identical sequences identified from diagnostic leukemic cells. The fetal characteristics of the leukemic cells were indicated by the small numbers of nucleotides inserted into the N region and the shortened D germ line segments. Interestingly, five of the six children (83%) with hyperdiploid ALL had detectable preleukemic clones at birth. Four of the five children (80%) with pro-B ALL, 13 of the 21 children (62%) with cALL and only two of the six children (33%) with pre-B ALL had preleukemic clones on their cards. We did not observe any differences in age at diagnosis or presenting WBC count between the 19 patients with preleukemic clones at birth and the 13 patients whose Guthrie cards were tested negative. Our results suggest that the majority of children with B-lineage ALL has preleukemic clones already at birth indicating a prenatal origin of leukemia. In addition, postnatal factors are important in leukemogenesis as well because of the long latency periods until clinical diagnosis of leukemia.

Description: The clinical relevance of both minimal residual disease (MRD) and chimerism after hematopoietic stem cell transplantation (HSCT) for the detection of impending relapse has not yet been extensively studied. We investigated MRD in 119 consecutive children (median age, 12 years) with ALL (n=56), AML (n=36), MDS (n=20), or CML (n=7) who underwent bone marrow (n=80) or peripheral blood stem cell (n=39; T-cell depleted: n=18) transplantation in a single center. Thirteen patients received autologous HSCT and 106 patients underwent allogeneic HSCT. The donor was HLA-matched unrelated in 58 patients and HLA-identical related in 48 patients. The Wilms’ tumor gene (WT1) expression was used for the detection of MRD because WT1 gene is overexpressed in the vast majority of patients with leukemia. In contrast, WT1 gene is not expressed in normal peripheral blood mononuclear cells (PBMCs) and only weakly expressed in normal bone marrow (BM) cells. We performed a quantitative reverse transcriptase-polymerase chain reaction (PCR) to examine the level of WT1 gene expression. For the present study, we followed up MRD in both BM and PB after HSCT. In the 119 patients, a median of 11 analyses (range, 3–27 analyses) covering a median period of 708 days (range, 29–3101 days) was performed. Analysis of 25 paired BM and PB samples revealed that the level of MRD in BM was on average 9 times higher and paralleled that in PB. All 85 patients with continuous normal WT1 expression levels in BM and continuous undetectable WT1 expression levels in PB remained in complete remission without relapse at a median of 1884 days (range, 58–5905 days) after HSCT. In contrast, all 32 patients who suffered from hematological relapse after a median of 152 days (range, 28–1104 days) presented with high levels of WT1 gene expression in BM and PB (P 〈 .001). In 19 patients, we observed a gradual or rapid increase of WT1 expression levels at a median of 31 days (range, 12–119 days) before hematological relapse. In 14 of these 19 patients, DNA was available at the time of increase of WT1 expression level to perform analysis of hematopoietic chimerism using a semi-quantitative short-tandem-repeat PCR. Interestingly, 10 of the 14 patients (71%) revealed a complete donor chimerism, whereas only 4 of the 14 patients (29%) showed a mixed chimerism. In two patients, we diagnosed a molecular relapse using WT1 gene expression at 161 and 360 days after transplantation. At the time of molecular relapse, both children revealed a complete donor chimerism. In both patients, molecular remission was achieved by withdrawal of cyclosporin A and by donor lymphocyte transfusion, respectively. Both children are alive and well without relapse at 10 and 9 years after transplantation. In conclusion, quantitative analysis of WT1 gene expression is a valuable tool for monitoring of MRD in patients with ALL, AML, CML, and MDS after HSCT. Increasing levels of WT1 gene expression strongly predict hematological relapse. Therefore, this approach is very useful for early diagnosis and treatment of molecular relapse after HSCT. MRD measurement using WT1 gene expression is more sensitive for the detection of impending relapse than the analysis of hematopoietic chimerism.

Description: Insulin-like growth factor (IGF) system plays an important role in regulating cellular proliferation. Alterations to the Insulin-like growth factor system have been reported for different tumors. They are of particular interest in the search for new prognostic and therapeutic approaches to cancer treatment. This study aimed to investigate the expression of IGFBP-2, IGFBP-3, IGF-I and IGF-II genes in leukemic cells from children with previously untreated acute myeloblastic leukemia (AML).The expression of IGF-I and IGF-II genes as well as IGFBP-2 and IGFBP-3 genes were measured using TaqMan real-time PCR in 50 children (mean age 10.8±4.8 years). All four genes were expressed with a great variability. RNA samples were extracted from leukemic cells enriched by Ficoll-Hypaque density gradient separation of bone marrow or peripheral blood mononuclear cells (MNC). MNC samples from peripheral blood and bone marrow of healthy children were used as controls. The median expression of IGFBP-2 was 25 times higher in AML cells than in peripheral MNC (p

Description: The IL23R gene on chromosome 1p31 encodes a subunit of the receptor for the proinflammatory cytokine interleukin-23. Recently, IL23R could be identified as a novel inflammatory bowel disease susceptibility gene. The exchange of arginine with glutamine at position 381 of IL23R causes a blockade of the IL-23 signaling pathway which is associated with a reduced risk of both Crohn’s disease and ulcerative colitis. IL-23 is a pivotal cytokine in the differentiation of T cells into inflammatory, IL-17-producing T cells. Because of the requirement for IL-23 in autoimmune disease we hypothesized that IL23R Arg381Gln reduces the risk of graft-versus host disease (GVHD) after hematopoietic stem cell transplantation (HSCT). 141 donors and 141 children (median age, 12 years) with acute lymphoblastic leukemia (n=63), acute myeloid leukemia (n=40), myelodysplastic syndrome (n=26) or chronic myeloid leukemia (n=12) who underwent allogeneic bone marrow (n=93) or peripheral blood stem cell transplantation (n=48; T-cell depleted: n=22) in a single center were genotyped of IL23R for rs11209026 (c.1142G〉A, p.Arg381Gln) using TaqMan real-time polymerase chain reaction. The donor was HLA-matched unrelated in 60% of transplants and HLA-identical related in 30% of transplants. Conditioning regimen was myeloablative in all cases. Two forms of post-transplant immunosuppression predominated, cyclosporine A and methotrexate in 65% of transplants and cyclosporine A alone in 24% of transplants. The IL23R Arg381Gln variant was present in 16 of the 141 donors (11.3%) and in 15 of the 141 patients (10.6%). Interestingly, we found a significantly reduced incidence of acute GVHD grade II–IV in patients who were transplanted from a donor with this specific variant (6.2% versus 33.6%; p=0.025). Furthermore, there was no severe acute GVHD grade III–IV if the variant occurred in the donor (0% versus 14.4%). In three of the donor-patient pairs the variant was present in both individuals and no acute GVHD was observed. The occurrence of the IL23R variant, in either donors or recipients, had no significant impact on chronic GVHD, relapse rate, treatment related mortality, and overall survival. In conclusion, IL23R Arg381Gln variant in the donor confers strong protection against acute GVHD after HSCT in children with hematological malignancies. Therefore, the IL23 signaling pathway seems to play an important role in the pathogenesis of acute GVHD. Blockade of the IL23 receptor by a monoclonal antibody could be a rational therapeutic strategy for acute GVHD.