Polymorphisms in STAT4 increase the risk of acute renal allograft rejection in the Chinese population

Analysis of 75 Candidate SNPs Associated With Acute Rejection in Kidney Transplant Recipients: Validation of rs2910164 in MicroRNA MIR146A

BACKGROUND

Identifying kidney allograft recipients who are predisposed to acute rejection (AR) could allow for optimization of clinical treatment to avoid rejection and prolong graft survival. It has been hypothesized that a part of this predisposition is caused by the inheritance of specific genetic variants. There are many publications reporting a statistically significant association between a genetic variant, usually in the form of a single-nucleotide polymorphism (SNP), and AR. However, there are additional publications reporting a lack of this association when a different cohort of recipients is analyzed for the same single-nucleotide polymorphism.

METHODS

In this report, we attempted to validate 75 common genetic variants, which have been previously reported to be associated with AR, using a large kidney allograft recipient cohort of 2390 European Americans and 482 African Americans.

RESULTS

Of those variants tested, only 1 variant, rs2910164, which alters the expression of the microRNA MIR146A, was found to exhibit a significant association within the African American cohort. Suggestive variants were found in the genes CTLA and TLR4.

CONCLUSIONS

Our results show that most variants previously reported to be associated with AR were not validated in our cohort. This shows the importance of validation when reporting the associations with complex clinical outcomes such as AR. Additional work will need to be done to understand the role of MIR146A in the risk of AR in kidney allograft recipients.

Genetics of acute rejection after kidney transplantation

Treatment of acute rejection (AR) following kidney transplantation has improved in recent years, but there are still limitations to successful outcomes. This review article covers literature in regard to recipient and donor genetics of AR kidney and secondarily of liver allografts. Many candidate gene and some genome-wide association studies (GWASs) have been conducted for AR in kidney transplantation. Genetic associations with AR in kidney and liver are mostly weak, and in most cases, the associations have not been reproducible. A limitation in the study of AR is the lack of sufficiently large populations that account for population stratification to study the AR phenotype which in this era occurs in <10% of transplants. Furthermore, the AR phenotype has been difficult to define and the definitions of classifications have evolved over time. Literature related to the pharmacogenomics of tacrolimus is robust and has been validated in many studies. Associations between gene expression and AR are emerging as markers of outcomes and AR classification. In the future, combinations of pretransplant genotype for AR risk prediction, genotype-based immune suppressant dosing, and pharmacogenomic markers to select AR maintenance or treatment and expression markers from biopsies may provide valuable clinical tools for guiding treatment.

Effect of donor STAT4 polymorphism rs7574865 on clinical outcomes of pediatric acute leukemia patients after hematopoietic stem cell transplant

STAT4 polymorphism, rs7574865 is linked to various autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Its T minor allele is associated with higher STAT4 mRNA and protein expression, indicating a stronger skewed immune response than the norm. Although widely studied in autoimmune disease patients and the general population, its effect on immunocompromised subjects is still unknown. Especially in situations, i.e. post-hematopoietic stem cell transplantation (post-HSCT), where control of the immune response is crucial. Hence, this study investigates if the presence of the T minor allele in donors would affect immunological response and clinical outcomes post-HSCT. Samples from 161 pediatric patients who underwent allogeneic HSCT for acute leukemia and showed complete chimerism by donor cells were obtained. Six clinical outcomes were investigated; hepatic veno-occlusive disease, acute graft-vs-host disease, chronic graft-vs-host disease, cytomegalovirus (CMV) infection, relapse and overall survival. The TT genotype was found to be significant in the occurrence of CMV infection (P=0.049), showing higher incidence of CMV infection compared to the others. Multivariate analysis confirmed that association of the TT genotype is independent from other variables in CMV infection occurrence (P=0.010). This is the first study on STAT4 polymorphism rs7574865 in allogeneic HSCT as well as immunocompromised patients. As the TT genotype is associated with autoimmune diseases, our results seem at a paradox with current evidence hinting at a different role of STAT4 in normal circumstances versus immunocompromised patients. Further investigation is needed to elicit the reason behind this and discover novel applications for better post-transplant outcomes.

STAT4 gene polymorphism in patients after renal allograft transplantation

Introduction

STAT4 (signal transducer and activator of transcription 4) is involved in the regulation of innate and adaptive immune responses. Some studies have suggested that STAT4 may be involved in the immune response after graft transplantation. Several polymorphisms in the STAT4 gene have been identified. The most commonly studied polymorphism in the STAT4 gene is rs7574865. In our study, we examined whether this polymorphism is associated with the early and late functions of renal allografts.

Material and methods

A total of 270 recipients of first renal transplants were included in the study. Single nucleotide polymorphisms (SNPs) within the STAT4 gene were genotyped using TaqMan genotyping assays.

Results

There were no statistically significant associations between the STAT4 gene rs7574865 polymorphism and delayed graft function, acute rejection, chronic allograft dysfunction, post-transplant diabetes mellitus, or creatinine serum concentrations after transplantation.

Conclusions

Our results suggest a lack of association between the STAT4 rs7574865 SNP and kidney allograft function in the Polish population.

Genetic variants of STAT-4 affect the development of graft fibrosis after liver transplantation for HCV-induced liver disease

BACKGROUND

Hepatitis C virus (HCV) reinfection after liver transplantation may lead to recirrhosis and seems to be influenced by genetic factors. The aim of our study was to evaluate the role of STAT-4-polymorphisms in the development of HCV-related graft disease based on protocol biopsies.

METHODS

One hundred sixty transplant patients with HCV recurrence were genotyped for STAT-4 (rs7574865) by polymerase chain reaction. Fibrosis stages were determined based on Desmet and Scheuer classification. SPSS was used for the statistical analysis of genotype distribution and of time to the development of advanced fibrosis among the genotypes.

RESULTS

During a comparable observation period of 86.2 months (P=0.654), 65 patients (46.5%) developed advanced fibrosis. Advanced fibrosis was observed significantly more frequent in patients (n=34) with at least one T-allele (53.1 vs. 32.3%; P=0.013) compared with homozygotes for G-allele (n=31). Significant differences in the duration of advanced fibrosis development were detected between patients with at least one T-allele compared with G-allele (34.4 vs. 49.0 months; P=0.022). No impact was observed regarding the outcome of interferon-based antiviral treatment (P=0.297) and the occurrence of acute cellular rejection (P=0.365).

CONCLUSION

Present results indicate a possible impact of genetic confounders in the recipient on graft fibrogenesis, thus explaining significantly different graft behavior observed after transplantation for HCV-associated liver disease. STAT-4-T-allele is identified as fibrogenic factor and seems to have a negative impact on HCV-induced fibrosis development.