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

Germline genetic variants that predispose to myeloproliferative neoplasms and hereditary myeloproliferative phenotypes

Epidemiological evidence of familial predispositions to myeloid malignancies and myeloproliferative neoplasms (MPN) has long been recognised, but recent studies have added to knowledge of specific germline variants in multiple genes that contribute to the familial risk. These variants may be common risk alleles in the general population but have low penetrance and cause sporadic MPN, such as the JAK2 46/1 haplotype, the variant most strongly associated with MPN. Association studies are increasingly identifying other MPN susceptibility genes such as TERT, MECOM, and SH2B3, while some common variants in DDX41 and RUNX1 appear to lead to a spectrum of myeloid malignancies. RBBP6 and ATM variants have been identified in familial MPN clusters and very rare germline variants such as chromosome 14q duplication cause hereditary MPN with high penetrance. Rarely, there are hereditary non-malignant diseases with an MPN-like phenotype. Knowledge of those genes and germline genetic changes which lead to MPN or diseases that mimic MPN helps to improve accuracy of diagnosis, aids with counselling regarding familial risk, and may contribute to clinical decision-making. Large scale population exome and genome sequencing studies will improve our knowledge of both common and rare germline genetic contributions to MPN.

Study of the Janus kinase 2 (JAK2) gene haplotype 46/1 association with driver mutations of chronic Ph-negative myeloproliferative neoplasms

Introduction. Haplotype JAK2 46/1 is associated with more frequent development of Ph-negative myeloproliferative neoplasms (MPN) and with an increased detection rate of the JAK2 V617F mutation. At the same time, the molecular mechanisms of such associations remain unclear. Previously, there were no studies of regional, age and gender aspects of the predictive value of carriage of the 46/1 JAK2 haplotype, which could assess this relationship in some observations.

Aim — to analyze the degree of association between 46/1 haplotype and the V617F mutation of the JAK2 gene depending on the sex, age, and place of residence of patients examined for suspected MPN.

Methods. The study included 949 DNA samples from patients with suspected MPN. Samples of 150 volunteers and blood donors were included in the control group. Haplotype 46/1 (rs10974944), V617F mutation in the JAK2 gene, mutations in the CALR gene (type 1: c.1092_1143del; L367fs*46, COSV57116546; type 2: c.1154_1155insTTGTC; K385fs*47, COSV57116551) and in the MPL gene (W515K, W515L) were determined for all samples using real-time polymerase chain reaction (PCR-RT).

Results. The 46/1 JAK2 haplotype were shown to be associated with a clinically significant level (> 2 %) of the allelic burden of the JAK2 V617F mutation. The odds ratio of the risk of developing a V617F positive MPN when carrying this haplotype variant did not depend on the main place of residence of the patients and was found to be most pronounced in men under 50 years of age. The odds ratio of the risk did not depend on the age of the examined women.

Conclusion. The association of 46/1 haplotype with the presence of other drivers of MPN mutations in the CALR or MPL genes was also statistically significant, which confirms the hypothesis of “favorable soil” rather than “hypermutability” of the JAK2 gene.

The Contribution of JAK2 46/1 Haplotype in the Predisposition to Myeloproliferative Neoplasms

Haplotype 46/1 (GGCC) consists of a set of genetic variations distributed along chromosome 9p.24.1, which extend from the Janus Kinase 2 gene to Insulin like 4. Marked by four jointly inherited variants (rs3780367, rs10974944, rs12343867, and rs1159782), this haplotype has a strong association with the development of BCR-ABL1-negative myeloproliferative neoplasms (MPNs) because it precedes the acquisition of the JAK2V617F variant, a common genetic alteration in individuals with these hematological malignancies. It is also described as one of the factors that increases the risk of familial MPNs by more than five times, 46/1 is associated with events related to inflammatory dysregulation, splenomegaly, splanchnic vein thrombosis, Budd-Chiari syndrome, increases in RBC count, platelets, leukocytes, hematocrit, and hemoglobin, which are characteristic of MPNs, as well as other findings that are still being elucidated and which are of great interest for the etiopathological understanding of these hematological neoplasms. Considering these factors, the present review aims to describe the main findings and discussions involving the 46/1 haplotype, and highlights the molecular and immunological aspects and their relevance as a tool for clinical practice and investigation of familial cases.

JAK2 gene knockout inhibits corneal allograft rejection in mice by regulating dendritic cell-induced T cell immune tolerance

Corneal allograft rejection can be seen in some patients after corneal transplantation. The present study intends to investigate whether JAK2 gene knockout affects corneal allograft rejection through regulation of dendritic cells (DCs)-induced T cell immune tolerance. In order to identify the target gene related to corneal allograft rejection, high-throughput mRNA sequencing and bioinformatics analysis were performed. JAK2 knockout mice were constructed and subjected to corneal allograft transplantation. The incidence of immune rejection was observed, the percentage of CD4⁺ T cells was detected, and the expression of Th1 cytokine interferon γ (IFN-γ) was determined. Flow cytometry and ELISA were performed to analyze the effects of JAK2 gene knockout on bone marrow-derived DCs (BMDCs). JAK2 was the target gene related to corneal allograft rejection. JAK2 gene knockout contributed to significantly prolonged survival time of corneal grafts in mice and inhibited corneal allograft rejection. The in vitro cell experiment further confirmed that JAK2 gene knockout contributed to the inactivation of CD4⁺ T cells and induced IFN-γ expression, accompanied by inhibition of DC immune function, development, maturation, and secretion of inflammatory cytokines. Collectively, JAK2 gene knockout inactivates CD4⁺ T cells to decrease IFN-γ expression, as well as inhibits DC development, maturation, and secretion of inflammatory cytokines, thereby reducing corneal allograft rejection.

Investigation of TGFB1 -1347C>T variant as a biomarker after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapeutic option for malignant hematopoietic diseases. Cytokines including transforming growth factor β1 (TGFβ1) play a pivotal role in immune reconstruction, and the development of graft versus host disease (GvHD) or infections. The aim of this study was to investigate the role of TGFB1 gene -1347C>T variant in the outcome of HSCT in a cohort of 409 adult recipient-donor pairs. TGFB1 variant was analysed from genomic DNA with LightCycler hybridisation probe method. In case of myeloablative conditioning, donor TGFB1 genotype correlated with overall survival (60-month OS for CC: 62.1 ± 4.8%; CT: 46.8 ± 4.8%; TT: 35.6 ± 9.3%; p = 0.032), which was independent of age, donor type and GvHD prophylaxis in multivariate analysis (HR:2.35, 95%CI:1.35-4.10, p = 0.003). The cumulative incidence of acute GvHD grade III-IV [CC:10%; CT:17%; TT:24%], and non-relapse mortality was higher in TT-carriers (24-month NRM: CC:24%; CT:26%; TT:46%, p = 0.035). We did not find any association between recipient TGFB1 -1347C>T polymorphism and HSCT outcome. Our results suggest that donor TGFB1 -1347C>T may exert an adverse influence on the outcome of myeloablative conditioning transplantation.

The JAK2 GGCC (46/1) Haplotype in Myeloproliferative Neoplasms: Causal or Random?

The germline JAK2 haplotype known as “GGCC or 46/1 haplotype” (haplotype^GGCC_46/1) consists of a combination of single nucleotide polymorphisms (SNPs) mapping in a region of about 250 kb, extending from the JAK2 intron 10 to the Insulin-like 4 (INLS4) gene. Four main SNPs (rs3780367, rs10974944, rs12343867, and rs1159782) generating a “GGCC” combination are more frequently indicated to represent the JAK2 haplotype. These SNPs are inherited together and are frequently associated with the onset of myeloproliferative neoplasms (MPN) positive for both JAK2 V617 and exon 12 mutations. The association between the JAK2 haplotype^GGCC_46/1 and mutations in other genes, such as thrombopoietin receptor (MPL) and calreticulin (CALR), or the association with triple negative MPN, is still controversial. This review provides an overview of the frequency and the role of the JAK2 haplotype^GGCC_46/1 in the pathogenesis of different myeloid neoplasms and describes the hypothetical mechanisms at the basis of the association with JAK2 gene mutations. Moreover, possible clinical implications are discussed, as different papers reported contrasting data about the correlation between the JAK2 haplotype^GGCC_46/1 and blood cell count, survival, or disease progression.

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.