Impact of cytokine gene polymorphisms on risk and treatment outcomes of aplastic anemia

Clonal evolution in aplastic anemia: failed tumor surveillance or maladaptive recovery?

Clonal evolution to secondary paroxysmal nocturnal hemoglobinuria (PNH) or myeloid neoplasia (MN) represents one of the long-term complications of patients with aplastic anemia (AA). The recent evidence in the field of immunology and the application of next-generation sequencing have shed light on the molecular underpinnings of these clonal complications, revealing clinical and molecular risk factors as well as potential immunological players. Particularly, whether MN evolution represents a failed tumor surveillance or a maladaptive recovery is still a matter of controversy in the field of bone marrow failure syndromes. However, recent studies have explored the precise dynamics of the immune-molecular forces governing such processes over time, generating knowledge useful for potential early therapeutic strategies. In this review, we will discuss the immune pathophysiology of AA and the emergence of clonal hematopoiesis with regard to the adaptive and maladaptive mechanisms at the basis of secondary evolution trajectories operating under the immune pressure.

The relationship between interferon-gamma (INF-γ) single nucleotide polymorphism +874(T/A) and occurrence risk of aplastic anemia: a meta-analysis

Objective: This meta-analysis was designed to investigate the association between interferon-gamma (IFN-γ) polymorphisms and occurrence risk of aplastic anemia.Methods: Literature search was conducted in PubMed, Embase and Cochrane Library up to April 2018. The pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated by R 3.12.Results: Total five studies with 304 aplastic anemia patients and 588 controls were included. The statistically significant results were found in the following models: allele genetic model (T vs A: OR = 2.1749, 95% CI = 1.6825-2.8114, P < 0.01), additive genetic model (TA vs AA: OR = 2.1071, 95% CI = 1.3962-3.1799, P < 0.01; TT vs AA: OR = 4.5788, 95% CI = 2.6606-7.8797, P < 0.01), recessive genetic model (TT vs AA + TA: OR = 2.5579, 95% = 1.6680-3.9226, P < 0.01), dominant genetic model (TT + TA vs AA: OR = 2.5599, 95% = 1.7424-3.7611, P < 0.01), the results suggested that the increased occurrence risk of aplastic anemia is significantly associated with the IFN-γ polymorphism.Conclusions: Patients with IFN-γ genotype carrying allele T have higher occurrence risk of aplastic anemia.

Single-Nucleotide Polymorphisms of FAS and FASL Genes and Risk of Idiopathic Aplastic Anemia

FAS/FASL signaling system plays a vital role in the regulation of apoptosis, envisaged as a death process required for immune surveillance to prevent autoimmunity and tumorigenesis along with several other biological activities. Several single-nucleotide polymorphisms (SNPs) of FAS/FASL system can result in aberrant apoptosis, which can cause different cancers and autoimmune diseases. Aplastic anemia (AA) is an autoimmune dysfunction characterized by peripheral blood pancytopenia associated with hypoplasia of bone marrow. The aim of this study was to screen Pakistani AA patients and controls for two Fas SNPs rs2234767 and rs1800682 and two FASLG SNPs rs763110 and rs5030772. Genotyping of 392 DNA samples was done by Tetra-ARMS polymerase chain reaction. Genotypic frequencies of Fas rs1800682 and FASLG rs5030772 showed significance difference in their distribution in both controls and patients, while Fas rs2234767 and FASLG rs763110 SNPs had no such difference. Carriers of rs1800682 AG+GG had a very odd ratio of 4.63, with 95% confidence interval (CI) of 3.01-7.11, while individuals with FASLG rs5030772 AG+GG were more common in controls than patients with OR 0.53 and 95% CI of 0.34-0.83. Cumulative effects of these SNPs were analyzed, and they showed almost similar trends; however, Fas rs2234767 and FASLG rs763110 genotypes in combination with Fas rs1800682 and FASLG rs5030772 demonstrated significant association. This study provided information that endorsed the involvement of FAS/FASL system SNPs in the pathogenesis of AA; further studies should be designed to understand the exact role of SNPs that can help in early diagnosis and treatment.

Polymorphisms of the TGF-β1 gene and the risk of acquired aplastic anemia in a Chinese population

Acquired aplastic anemia (AA) is a hematological disease characterized by failure of bone marrow hematopoiesis resulting in pancytopenia. While immune-mediated destruction of hematopoietic stem/progenitor cells (HSPCs) plays a central role in the pathophysiology of acquired AA, the transforming growth factor-β1 (TGF-β1) is crucial in adjusting the immune system. The aim of our study was to investigate the role of TGF-β1 gene polymorphisms rs1800469 and rs2317130 in susceptibility to acquired AA. Via the approach of SNaPshot, we genotyped rs1800469 and rs2317130 in 101 patients with acquired AA and 165 controls. It derived us to the conclusion that the genotype TT of rs1800469 (C/T) was significantly associated with decreased risk of acquired AA (adjusted OR = 0.39, 95% CI = 0.18-0.83, P = 0.014). Furthermore, this decreased risk was more pronounced among male patients (adjusted OR = 0.35, 95% CI = 0.13-0.95, P = 0.038) and SAA/vSAA (severe AA/very severe AA) patients (adjusted OR = 0.31, 95% CI = 0.12-0.77, P = 0.02) compared with controls in subgroup analysis. However, a significant increased risk was observed in the genotype distributions of rs2317130 for TT genotype (adjusted OR = 2.52, 95% CI = 1.03-6.19, P = 0.04) compared with the CC genotype among the SAA/vSAA patients and controls in the severity stratification analysis. Our results indicated that TGF-β1 gene polymorphisms might be involved in the munity of acquired AA in a Chinese population. This initial analysis provides valuable clues for further study of TGF-β1 pathway genes in acquired AA.

Association of aplastic anemia and FoxP3 gene polymorphisms in Koreans

OBJECTIVES

Aplastic anemia (AA) is characterized by pancytopenia and bone marrow failure, and most acquired AA is an immune-mediated disorder. Regulatory T cells (T_regs) suppressing autoreactive T cells were decreased in AA patients. FoxP3 is a major regulator for the development and function of T_regs. Polymorphism in FoxP3 was shown to be associated with various autoimmune diseases, however, has not yet been studied in AA. In this study, we examined the association between FoxP3 polymorphisms and AA in Korean patients.

METHODS

The study population consisted of 94 patients diagnosed by bone marrow examination in Seoul National University Hospital (SNUH) during 1997-2012 and 195 healthy controls. FoxP3 polymorphisms (rs5902434 del/ATT, rs3761548 C/A, rs3761549 C/T, rs2232365 A/G) were analyzed by PCR-sequencing method. We analyzed differences of genotype and allele frequencies between patients and controls. We also compared differences of genotype and allele frequencies between responder and non-responder in patients treated with immunosuppressive therapy (IST). For the statistical analysis, the chi-square test and Fisher's exact test were used and P < 0.05 was regarded as statistically significant.

RESULTS

There was no significant difference in the genotype frequencies of FoxP3 polymorphisms between patients and controls. With regards to the allele frequencies, rs3761548 C allele was significantly higher in AA patients than in controls (87.4% vs. 79.7%, P = 0.047). In patients treated with IST, rs3761549 C allele was significantly higher in non-responder patients than in responders (89.6% vs. 66.7%, P = 0.036) and female rs3761549 C/C genotype carriers were associated with greater risk for non-response to IST (84.2% vs. 16.7%, P = 0.006).

CONCLUSION

Polymorphisms in rs3761548 and rs3761549 of FoxP3 in our population were associated with disease susceptibility and response for IST, respectively. This study suggests an association between FoxP3 polymorphisms and AA in Korean patients and will be useful in further understanding the genetic basis of disease susceptibility and response to IST in AA patients.

The association of cytokine genes polymorphisms and susceptibility to aplastic anemia in Egyptian patients

BACKGROUND AND OBJECTIVE

Aplastic anemia (AA) remains a rare disease, with very interesting pathophysiology that is being investigated for years now. The present study aimed to determine the association between cytokine gene polymorphisms (TGF-β1 -509 C/T, TNF-α -308 G/A, IFN-γ +874 A/T) and susceptibility to AA in Egyptian patients.

METHODS

The study included 80 participants subjected to determination of gene polymorphisms on genomic DNA using polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS

It was found that IFN-γ +874 A/T gene polymorphism is associated with three-fold increased risk of development of AA (odds ratio (OR) 3.116, P = 0.019), while TNF-α -308 G/A gene polymorphism is associated with decreased risk (OR 0.318, P = 0.026). TGF-β1 -509 C/T gene polymorphism showed comparable risk between patients and controls (P = 0.263).

CONCLUSION

IFN-γ +874 A/T gene polymorphism is associated with the etiology of AA in Egyptian patients.

The complex pathophysiology of acquired aplastic anaemia

Immune-mediated destruction of haematopoietic stem/progenitor cells (HSPCs) plays a central role in the pathophysiology of acquired aplastic anaemia (aAA). Dysregulated CD8(+) cytotoxic T cells, CD4(+) T cells including T helper type 1 (Th1), Th2, regulatory T cells and Th17 cells, natural killer (NK) cells and NK T cells, along with the abnormal production of cytokines including interferon (IFN)-γ, tumour necrosis factor (TNF)-α and transforming growth factor (TGF)-β, induce apoptosis of HSPCs, constituting a consistent and defining feature of severe aAA. Alterations in the polymorphisms of TGF-β, IFN-γ and TNF-α genes, as well as certain human leucocyte antigen (HLA) alleles, may account for the propensity to immune-mediated killing of HSPCs and/or ineffective haematopoiesis. Although the inciting autoantigens remain elusive, autoantibodies are often detected in the serum. In addition, recent studies provide genetic and molecular evidence that intrinsic and/or secondary deficits in HSPCs and bone marrow mesenchymal stem cells may underlie the development of bone marrow failure.

TNF-α -308 G>A polymorphism and risk of bone marrow failure syndrome: A meta-analysis

The influence of the TNF-α -308 G>A polymorphism on bone marrow failure syndrome susceptibility is unclear. We have conducted a meta-analysis of all relevant published studies. We searched PubMed, Chinese Biomedical Literature and China National Knowledge Infrastructure databases up to February 2015. Odds ratios (ORs) with 95% confidence intervals (CIs) were applied to assess the strength of associations. Eleven case-control studies with a total sample size of 909 cases and 1803 controls were eligible to assess the association between the TNF-α -308 G>A polymorphism and susceptibility to bone marrow failure syndrome. Overall, the TNF-α -308 G>A polymorphism was significantly associated with an increased risk of bone marrow failure syndrome in any genetic model. In stratified analysis by disease type, there was a significant association between the TNF-α -308 G>A polymorphism and increased risk of aplastic anemia but no significant association with myelodysplastic syndrome (AA vs. GG: OR=2.23, 95% CI=1.23-4.05, P=0.006; recessive model: OR=3.52, 95% CI=1.30-9.53, P=0.010). In subgroup analysis by ethnicity, there were significant associations between the TNF-α -308 G>A polymorphism and increased risk of bone marrow failure syndrome for Caucasians in two models, but not in Asian populations (AA vs. GG: OR=2.66, 95% CI=1.36-5.21, P=0.003; recessive model: OR=2.68, 95% CI=1.37-5.24, P=0.002). In conclusion, our meta-analysis suggests that the TNF-α -308 G>A polymorphism may contribute to the risk of bone marrow failure syndrome, particularly among Caucasian and aplastic anemia patients. Further investigations are needed to clarify the role of the TNF-α -308 G>A polymorphism in bone marrow failure syndrome.

Genetic associations in acquired immune-mediated bone marrow failure syndromes: insights in aplastic anemia and chronic idiopathic neutropenia

Increasing interest on the field of autoimmune diseases has unveiled a plethora of genetic factors that predispose to these diseases. However, in immune-mediated bone marrow failure syndromes, such as acquired aplastic anemia and chronic idiopathic neutropenia, in which the pathophysiology results from a myelosuppressive bone marrow microenvironment mainly due to the presence of activated T lymphocytes, leading to the accelerated apoptotic death of the hematopoietic stem and progenitor cells, such genetic associations have been very limited. Various alleles and haplotypes of human leucocyte antigen (HLA) molecules have been implicated in the predisposition of developing the above diseases, as well as polymorphisms of inhibitory cytokines such as interferon-γ, tumor necrosis factor-α, and transforming growth factor-β1 along with polymorphisms on molecules of the immune system including the T-bet transcription factor and signal transducers and activators of transcription. In some cases, specific polymorphisms have been implicated in the outcome of treatment on those patients.