Role of non-HLA gene polymorphisms in graft-versus-host disease

Genetic Predisposition to Persistent Human Papillomavirus-Infection and Virus-Induced Cancers

Human papillomaviruses (HPVs) are the most common sexually transmitted pathogens worldwide and among the more than 200 identified HPV types, approximately 15 high risk (HR-HPV) types are oncogenic, being strongly associated with the development of cervical cancer, anogenital cancers and an increasing fraction of head and neck squamous cell carcinomas (HNSCC). HPV-associated cervix cancer accounts for 83% of HPV-attributable cancers, and more than two-thirds of those cases occur in developing countries. Despite the high frequency of HPV infections, in most cases, the virus is cleared by the host immune response and only a small proportion of infected individuals develop persistent infections that can result in malignant transformation, indicating that other elements, including biological, genetic and environmental factors may influence the individual susceptibility to HPV-associated cancers. Previous studies have quantified that heritability, in the form of genetic variants, common in the general population, is implicated in nearly 30% of cervical cancers and a large number of studies conducted across various populations have identified genetic variants that appear to be associated with genes that predispose or protect the host to HPV infections thereby affecting individual susceptibility to HPV-associated cancers. In this article, we provide an overview of gene association studies on HPV-associated cancers with emphasis on genome-wide association study (GWAS) that have identified novel genetic factors linked to HPV infection or HPV-associated cancers.

Donor Heme Oxygenase-1 Promoter Gene Polymorphism Predicts Survival after Unrelated Bone Marrow Transplantation for High-Risk Patients

Heme oxygenase-1 (HO-1), an intracellular enzyme that catalyzes the degradation of heme into biliverdin, free iron, and carbon monoxide, exerts anti-inflammatory and cytoprotective effects against endothelial cell injury. The HO-1 promoter gene has one important single-nucleotide polymorphism (SNP) rs2071746 (-413A>T) that is functional, and the A allele has been reported to be associated with higher HO-1 expression levels than the T allele. We investigated the influence of the HO-1 rs2071746 SNP on the transplant outcomes in 593 patients with hematological malignancies undergoing unrelated, human leukocyte antigen (HLA)-matched, T-cell-replete bone marrow transplantation (BMT) through the Japan Donor Marrow Program. In patients with high-risk diseases, the donor A/A or A/T genotype was associated with better 5 year overall survival (35% vs. 25%; p = 0.03) and 5 year disease-free survival (35% vs. 22%; p = 0.0072), compared to the donor T/T genotype. These effects were not observed in patients with low-risk diseases. The current findings therefore indicate that HO-1 rs2071746 genotyping could be useful for selecting donors and tailoring transplant strategies for patients with high-risk hematologic malignancies.

NFKB1 gene single-nucleotide polymorphisms: implications for graft-versus-host disease in allogeneic hematopoietic stem cell transplantation

Graft-versus-host disease (GVHD) represents a significant cause of mortality after allogeneic hematopoietic stem cell transplantation (HSCT). NF-kB system is a master regulator of innate immunity responses. It controls the expression of various cytokines and chemokines many of which are involved in GVHD pathogenesis. Chemo(radio) therapy administered during conditioning induces DNA damage and activates DNA damage response (DDR) signaling resulting in irreversible cell cycle arrest - cellular senescence which has been described to be associated with robust pro-inflammatory secretion mostly controlled by NF-kB. The NFKB1 gene encodes the DNA-binding subunit of the NF-kB complex. Using the candidate gene approach, we analyzed possible association of two single-nucleotide polymorphisms (SNPs) rs3774937 C/T and rs3774959 A/G of the NFKB1 gene with GVHD and transplant-related mortality (TRM) occurrence in 109 recipients allografted from HLA-identical donor. Both SNPs in recipients were found to be strongly associated with acute GVHD. Nevertheless, no significant association with chronic GVHD and TRM was found. Presented pilot results contribute to pre-clinical observations and suggest that NF-kB may be an important regulator of HSCT-related inflammatory reactions such as acute GVHD. Novel pathogenic mechanisms of GVHD may arise from perspectives of DDR and cellular senescence where NF-kB plays an essential role.

Donor single nucleotide polymorphism in ACAT1 affects the incidence of graft-versus-host disease after bone marrow transplantation

Acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1) is an enzyme that converts cholesterol to cholesteryl esters. A recent in vivo study reported that inhibiting ACAT1 enzyme activity upregulates the membrane cholesterol levels of T cells, enhancing their cytotoxic function. In the present study, we investigated whether the presence of the ACAT1 single nucleotide polymorphism rs11545566 in transplant donors affected the risk of graft-versus-host disease (GVHD) in 116 adult patients who underwent bone marrow transplantation from human leukocyte antigen-identical sibling donors, and who received GVHD prophylaxis with short-term methotrexate and cyclosporine. The frequencies of the AA, AG, and GG genotypes in the donors were 31%, 45%, and 24%, respectively. The cumulative incidences of grade II-IV acute GVHD on day 100 in patients whose donors had AA vs. non-AA genotypes were 6% and 18%, respectively, and those of extensive chronic GVHD at 2 years were 7% and 32%, respectively. Multivariate analyses demonstrated that donor rs11545566 non-AA genotypes showed a trend toward a higher incidence of grade II-IV acute GVHD (P = 0.079), and were significantly associated with a higher incidence of extensive chronic GVHD (P = 0.021). These results suggest that donor ACAT1 rs11545566 genotype may be predictive of GVHD.

Infection Complications in Hematopoietic Stem Cells Transplant Recipients: Do Genetics Really Matter?

Hematopoietic stem cell transplantation (HSCT) is a highly advanced technique that offers a potential cure for an increasing number of life-threatening diseases. Enormous progress achieved in the last decade, including the refinement of donor selection and advancements in patient supportive care, had significantly improved transplant outcomes; however, invasive infections, graft-vs.-host disease (GVHD) and other serious complications still represent a major source of morbidity and mortality in HSCT recipients. The damage of anatomical barriers due to pre-transplant conditioning, a severely damaged immune function and a profound disruption in the composition of gut microbial commensals (gut microbiota) are alterations inherent to the transplant procedure that are directly implicated in the development of invasive infections and other HSCT complications. Although HLA-matching represents the most important genetic predictor of transplant outcomes, genetic variants in non-HLA genes, especially single nucleotide polymorphisms (SNPs) of genes encoding proteins associated with the immune response to tissue injury and pathogen infection have also been proposed as additional risk factors implicated in the occurrence of HSCT complications. Furthermore, although the microbiota composition is affected by several factors, recent evidence suggests that certain host genetic variants are associated with an altered composition of the gut microbiome and may, therefore, predispose some individuals to invasive infectious complications. This article summarizes the current understanding of the influence that genetic variants in non-HLA genes have on the development of infectious complications in HSCT recipients.

A pilot study of single nucleotide polymorphisms in the interleukin-6 receptor and their effects on pre- and post-transplant serum mediator level and outcome after allogeneic stem cell transplantation

Interleukin (IL)-6 is an important regulator of immunity and inflammation in many diseases. Single nucleotide polymorphisms (SNPs) in the IL-6 gene influence outcome after allogeneic stem cell transplantation (ASCT), but the possible importance of SNPs in the IL-6 receptor has not been examined. We therefore investigated whether SNPs in the IL-6R gene influenced biochemical characteristics and clinical outcomes after ASCT. We examined the IL-6 promoter variant rs1800975 and the IL-6R SNPs rs4453032, rs2228145, rs4129267, rs4845374, rs4329505, rs4845617, rs12083537, rs4845618, rs6698040 and rs4379670 in a 101 population-based cohort of allotransplant recipients and their family donors. Patients being homozygous for the major alleles of the IL-6R SNPs rs2228145 and rs4845618 showed high pretransplant CRP serum levels together with decreased sIL-6R levels; the decreased IL-6R levels persisted 6 months post-transplant. In contrast, patients being homozygous for the minor allele of the IL-6R SNP rs4379670 showed decreased pretransplant CRP levels. Furthermore, the IL-6R rs4845618 donor genotype showed an association with severe acute graft-versus-host disease (GVHD), whereas the donor genotype of the IL-6 SNP rs1800795 was associated with decreased survival 100 days post-transplant. Finally, the recipient genotype of the IL-6R SNP rs4329505 showed a strong association with 2-years non-relapse mortality, and this effect was also highly significant in multivariate analysis. IL-6 and IL-6R SNPs influence the clinical outcome after allogeneic stem cell transplantation.

Graft versus Host Disease: From Basic Pathogenic Principles to DNA Damage Response and Cellular Senescence

Graft versus host disease (GVHD), a severe immunogenic complication of allogeneic hematopoietic stem cell transplantation (HSCT), represents the most frequent cause of transplant-related mortality (TRM). Despite a huge progress in HSCT techniques and posttransplant care, GVHD remains a significant obstacle in successful HSCT outcome. This review presents a complex summary of GVHD pathogenesis with focus on references considering basic biological processes such as DNA damage response and cellular senescence.

Hematopoietic stem cell transplantation for acute myeloid leukemia

Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) yields a high rate of curability for acute myeloid leukemia (AML), it is also associated with transplant-related morbidity and mortality (TRM). The risk and severity of TRM increase with the use of an alternative donor graft in the absence of an HLA-matched sibling donor (MSD). With the declining birthrate and aging of the population, the numbers of patients with an MSD are decreasing, and alternative donor transplants, including the post-transplant cyclophosphamide method using haplo-identical donors, are increasing. Autologous (auto)-HSCT, which enables the intensification of chemotherapy, has the advantage of high availability of a transplant graft, and is associated with a lower TRM, but these benefits may be offset by a higher rate of relapse due to the lack of a graft-versus-leukemia (GVL) effect. Although allo-HSCT remains the first-line treatment for poor and very-poor-risk patients, auto-HSCT is again gaining increased attention. It has also recently been suggested that cord blood grafts may induce a stronger GVL effect than other grafts; as such, the positioning of cord blood transplantation should also be reconsidered for AML patients.

Recipient and donor JAK2 46/1 haplotypes are associated with acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation

Several genetic polymorphisms have been implicated to affect the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The role of cytokines in acute graft-versus-host disease (aGvHD) is well established and many of the involved cytokines signal through the Janus kinase (JAK) pathways. In this study, we assessed the association of recipient and donor JAK2 46/1 haplotypes and allo-HSCT outcome in a cohort of 124 acute myeloid leukemia patients. Both, recipient and donor 46/1 haplotypes significantly affected aGvHD grades II-IV development (p = 0.006 and p = 0.031, respectively), furthermore the influence of the haplotypes seemed to be additive. In multivariate analyses the recipient haplotype remained independently related (p = 0.012) to aGvHD, while the donor not (p = 0.08). We observed significantly less relapses among haplotype carriers (p = 0.004), but overall survival did not differ (p = 0.732). Our findings suggest that recipient and donor JAK2 46/1 haplotypes might be involved in the regulation of aGvHD.

Toll-like receptor 1 variation increases the risk of transplant-related mortality in hematologic malignancies

Toll-like receptor 1 (TLR1) genetic variant (rs5743551, -7202A>G) has been reported to be associated with susceptibility to various infectious diseases. We retrospectively examined the impact of TLR1 variation on transplant outcomes in a cohort of 320 patients who underwent unrelated HLA-matched bone marrow transplantation (BMT) for hematologic malignancies. A multivariate analysis showed that the G/G genotype in the recipients and the donors was associated with a significantly lower 3-year transplant-related mortality (TRM). The recipient G/G genotype also resulted in a better 3-year progression-free survival. This study suggests that the recipient and donor TLR1 G/G genotypes are comparably associated with a reduced risk of death that was not related to relapse. Thus, TLR1 genotyping may be useful for selecting the donor, managing patients in a risk-adapted manner, and creating therapeutic strategies to prevent complications after hematopoietic stem cell transplantation.

Graft-versus-Host Disease after HLA-Matched Sibling Bone Marrow or Peripheral Blood Stem Cell Transplantation: Comparison of North American Caucasian and Japanese Populations

The risk of acute graft-versus-host disease (GVHD) after HLA-matched sibling bone marrow transplantation (BMT) is lower in Japanese than in Caucasian patients. However, race may have differential effect on GVHD dependent on the graft source. North American Caucasian and Japanese patients receiving their first allogeneic BMT or peripheral blood stem cell transplantation from an HLA-matched sibling for leukemia were eligible. BMT was performed in 13% of the Caucasian patients and in 53% of the Japanese patients. On multivariate analysis, the interaction term between race and graft source was not significant in any of the models, indicating that graft source does not affect the impact of race on outcomes. The risk of grade III or IV acute GVHD was significantly lower in the Japanese patients compared with the Caucasian patients (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.57 to 0.96), which resulted in lower risk of nonrelapse mortality in the Japanese patients (HR, 0.69; 95% CI, 0.54 to 0.89). The risk of relapse was also lower in this group. The lower risks of nonrelapse mortality and relapse resulted in lower overall mortality rates among the Japanese patients. In conclusion, our data indicate that irrespective of graft source, the risk of severe acute GVHD is lower in Japanese patients, resulting in a lower risk of nonrelapse mortality.

Cyclosporine and methotrexate-related pharmacogenomic predictors of acute graft-versus-host disease

Effective immunosuppression is mandatory to prevent graft-versus-host disease and to achieve a successful clinical outcome of hematopoietic stem cell transplantation. Here we tested whether germline single nucleotide polymorphisms in 20 candidate genes related to methotrexate and cyclosporine metabolism and activity influence the incidence of graft-versus-host disease in patients who undergo stem cell transplantation for hematologic disorders. Recipient genetic status of the adenosine triphosphate-binding cassette sub-family C1 and adenosine triphosphate-binding cassette sub-family C2 transporters, 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/ inosine monophosphate cyclohydrolase within the methotrexate pathway, and nuclear factor of activated T cells (cytoplasmic 1) loci exhibit a remarkable influence on severe acute graft-versus-host disease prevalence. Indeed, an increased risk of acute graft-versus-host disease was observed in association with single nucleotide polymorphisms located in 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (hazard ratio=3.04; P=0.002), nuclear factor of activated T cells (cytoplasmic 1) (hazard ratio=2.69; P=0.004), adenosine triphosphate-binding cassette sub-family C2 (hazard ratio=3.53; P=0.0018) and adenosine triphosphate-binding cassette sub-family C1 (hazard ratio=3.67; P=0.0005). While donor single nucleotide polymorphisms of dihydrofolate reductase and solute carrier family 19 (member 1) genes are associated with a reduced risk of acute graft-versus-host disease (hazard ratio=0.32-0.41; P=0.0009-0.008), those of nuclear factor of activated T cells (cytoplasmic 2) are found to increase such risk (hazard ratio=3.85; P=0.0004). None of the tested single nucleotide polymorphisms was associated with the occurrence of chronic graft-versus-host disease. In conclusion, by targeting drug-related biologically relevant genes, this work emphasizes the potential role of germline biomarkers in predicting acute graft-versus-host disease. Further investigations are warranted to improve our understanding of these relationships to personalize immunosuppressive therapy and optimize outcomes.