Increased apoptosis is linked to severe acute GVHD in patients with Fanconi anemia

Graft-versus-host disease and other cutaneous manifestations in pediatric patients transplanted for Fanconi anemia

OBJECTIVE

The aim of this study was to elaborate a specific protocol for the assessment and early identification of skin lesions in pediatric patients with Fanconi anemia undergoing hematopoietic stem cell transplantation.

METHODS

This is a longitudinal, retrospective, and descriptive study. The medical records of 136 pediatric patients with Fanconi anemia who underwent hematopoietic stem cell transplantation between 2008 and 2018 at the Clinical Hospital of the Federal University of Paraná were reviewed. A specific protocol was created for data collection, which included age, sex, skin color, age at diagnosis of Fanconi anemia, transplantation data, family history of consanguinity, and pre- and post-transplant complications. In addition, the data included the presence of graft-versus-host disease of the skin and other organs, its classification, type of lesion, location, and also skin lesions not related to graft-versus-host disease.

RESULTS

Among the skin manifestations in pre-transplant period, café-au-lait spots stood out (32.4%). At least one organ was affected by graft-versus-host disease in 55.1% of patients; the most common involvement being the mouth, followed by the skin. Rash and erythema were the most frequently observed cutaneous manifestations of graft-versus-host disease.

CONCLUSION

A high prevalence of cutaneous manifestations of the disease was observed, as well as cutaneous manifestations of graft-versus-host disease. The protocol developed gathers relevant and standardized information for the follow-up of patients with Fanconi anemia undergoing hematopoietic stem cell transplantation, ensuring greater reliability of the information, and its implementation will allow the prospective evaluation of patients.

The Upregulation of Regenerative Activity for Extracellular Vesicles with Melatonin Modulation in Chemically Defined Media

Extracellular vesicles (EVs) derived from human mesenchymal stem cells (hMSCs) have been widely known to have therapeutic effects by representing characteristics of the origin cells as an alternative for cell-based therapeutics. Major limitations of EVs for clinical applications include low production yields, unknown effects from serum impurities, and relatively low bioactivities against dose. In this study, we proposed a cell modulation method with melatonin for human umbilical cord MSCs (hUCMSCs) cultured in serum-free chemically defined media (CDM) to eliminate the effects of serum-derived impurities and promote regeneration-related activities. miRNAs highly associated with regeneration were selected and the expression levels of them were comparatively analyzed among various types of EVs depending on culture conditions. The EVs derived from melatonin-stimulated hUCMSCs in CDM (CDM mEVs) showed the highest expression levels of regeneration-related miRNAs, and 7 times more hsa-let-7b-5p, 5.6 times more hsa-miR-23a-3p, and 5.7 times more hsa-miR-100-5p than others, respectively. In addition, the upregulation of various functionalities, such as wound healing, angiogenesis, anti-inflammation, ROS scavenging, and anti-apoptosis, were proven using in vitro assays by simulating the characteristics of EVs with bioinformatics analysis. The present results suggest that the highly regenerative properties of hUCMSC-derived EVs were accomplished with melatonin stimulation in CDM and provided the potential for clinical uses of EVs.

Irradiation-free, T-cell replete haploidentical transplant for Fanconi anaemia, weighing the benefits

The optimal haploidentical haematopoietic cell transplant approach for Fanconi anaemia (FA) patients is not well established, given the rarity of the disease, the increased sensitivity to DNA-damaging agents and the high risk of severe graft-versus-host disease (GVHD). The report by Xu et al. suggests that excellent engraftment and short-term survival can be achieved in FA patients without irradiation, but their retrospective cohort was plagued by a high rate of severe GVHD. Our commentary explores the outcomes in T-cell replete haploidentical haematopoietic cell transplant and ponders whether elimination of total body irradiation in FA patients is the best method if it limits the ability to safely administer post-transplant cyclophosphamide.

Noncoding RNAs in diagnosis and prognosis of graft-versus-host disease (GVHD)

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a functional therapy for a plethora of hematologic malignancies and immune disorders. Graft-versus-host disease (GVHD), on the other hand, is one of the major complications ahead of a successful HSCT, contributing to transplant-associated morbidity and mortality. Notably, little is known about the underlying mechanism of this event; therefore, exploring precise biomarkers and uncovering the molecular pathogenesis of GVHD is valuable for early diagnosis and treatment optimization. Thanks to the advances in sequencing techniques, the noncoding sequences of the human genome-formerly considered "junk"-are now identified as functional molecules. Noncoding RNAs (ncRNA) control cellular responses by regulating gene expression, and previous studies have shown that these tiny molecules, especially microRNAs (miRNAs), can affect allogeneic T cell responses in both animal models and clinical experiments. The present study gives an overview of the functions of various miRNAs in regulating T cell responses in GVHD. We also provide an outlook on miRNAs and long noncoding RNAs (lncRNAs) potential role in GVHD with the hope of providing a future research direction for expanding their application as the sensitive and noninvasive diagnostic or prognostic biomarkers and also the promising therapeutic targets for improving outcomes after allogeneic HSCT.

Circulating miR-455-3p, miR-5787, and miR-548a-3p as potential noninvasive biomarkers in the diagnosis of acute graft-versus-host disease: a validation study

Currently, acute graft-versus-host disease (aGVHD) diagnosis is based on clinical features and pathological findings. Until now, there is no non-invasive diagnostic test for aGVHD. MicroRNAs may act as promising predictive, diagnostic, or prognostic biomarkers for aGVHD. The purpose of the current study was to validate circulating microRNAs as diagnostic biomarkers to assist clinicians in promptly diagnosing aGVHD, so that treatment can be initiated earlier. In the present study, we evaluated six microRNAs (miR-455-3p, miR-5787, miR-6729-5p, miR-6776-5p, miR-548a-3p, and miR-6732-5p) selected from miRNA array data in 40 aGVHD patients compared to 40 non-GVHD patients with RT-qPCR. Target genes of differentially expressed microRNAs (DEMs) were predicted using Targetscan, miRanda, miRDB, miRWalk, PICTAR5, miRmap, DIANA, and miRTarBase algorithms, and their functions were analyzed using EnrichNet, Metascape, and DIANA-miRPath databases. The expressions of plasma miR-455-3p and miR-5787 were significantly downregulated, whereas miR-548a-3p was significantly upregulated in aGVHD patients compared to non-GVHD patients. Moreover, DEMs showed potentially high diagnostic accuracy for aGVHD. In silico analysis of DEMs provided valuable information on the role of DEMs in GVHD, immune regulation, and inflammatory response. Our study suggested that miR-455-3p, miR-5787, and miR-548a-3p could be used as potential noninvasive biomarkers in the diagnosis of aGVHD in addition to possible therapeutic targets in aGVHD.

Posterior Reversible Encephalopathy Syndrome after Allogeneic Stem Cell Transplantation in Pediatric Patients with Fanconi Anemia, a Prospective Study

Posterior reversible encephalopathy syndrome (PRES) is one of the most common neurologic complications following hematopoietic stem cell transplantation (HSCT). We aimed to evaluate the incidence, clinical, and imaging features of PRES in pediatric patients with Fanconi anemia (FA) following HSCT. This prospective study included all post-HSCT patients with underlying FA disease between 2014 and 2017. Brain computed tomography scan and magnetic resonance imaging (MRI) were performed in all individuals who developed neurologic symptoms. PRES was diagnosed based on clinic-radiological evidence. Follow-up MRI was performed in all patients with PRES within two months. Forty-one patients with FA (28 males; mean age, 8.19 ± 3.25 years) were enrolled. Out of 15 patients with acute neurologic symptoms, PRES was diagnosed in 9 individuals (21.95% of the total cohort). The occurrence of PRES was significantly higher in patients who had a donor with a 1-locus mismatch (P= .02). Donor relation, stem cell source, and graft-versus-host disease grade did not have any significant association with the development of PRES. MRI showed asymmetric vasogenic edema in 5 patients, an overt infarct in 1 patient, and foci of microhemorrhages in 3 patients, 1 of whom developed a hemorrhagic infarct. This patient died shortly, and persistent microhemorrhages were noted in the other 2 patients. Our findings demonstrate a greater risk of developing PRES after HSCT in patients with FA compared with those with other diseases (21.95% versus 1% to 10%), and in contrast to its term, it might be irreversible and has adverse effects on HSCT outcomes. The increased vascular and endothelial fragility in FA may contribute to the higher frequency of PRES in these individuals.

TNFAIP8 Deficiency Exacerbates Acute Graft Versus Host Disease in a Murine Model of Allogeneic Hematopoietic Cell Transplantation

BACKGROUND

Gastrointestinal acute graft-versus-host disease (GVHD) occurring after allogeneic hematopoietic cell transplant is an allo-reactive T cell and inflammatory cytokine driven organ injury with epithelial apoptosis as 1 of its hallmark findings and is associated with significant mortality. Tumor necrosis factor (TNF)-alpha-induced protein 8 (TNFAIP8 or TIPE) acts as a negative mediator of apoptosis via inhibition of caspase-3 activation, promotes cell proliferation and Tipe deficiency is associated with increased inflammation.

METHODS

To evaluate the role of TIPE in acute GVHD, naive C57BL/6 and Tipe C57BL/6 mice were conditioned with 1000 cGy single dose total body irradiation, followed by transplantation of 10 million bone marrow cells and 20 million splenocytes from either syngeneic C57BL/6 or allogeneic BALB/c donors.

RESULTS

Allo TIPE-deficient mice developed exacerbated gut GVHD compared with allo controls and had significantly decreased survival (6 wk overall survival: 85% versus 37%; P < 0.05), higher clinical GVHD scores, more profound weight loss, increased serum proinflammatory cytokines (interleukin-17A, TNF, interleukin-6, and interferon-γ). T-cell infiltration into the ileum was increased; epithelial proliferation was decreased along with significantly higher levels of chemokines KC and monokine induced by gamma interferon. Using bone marrow chimeric experiments, TIPE was found to have a role in both hematopoietic and nonhematopoietic cells.

CONCLUSIONS

Absence of TIPE results in excessive inflammation and tissue injury after allo-HCT, supporting that TIPE confers immune homeostasis and has tissue-protective function during the development of gut GVHD and may be a potential future target to prevent or treat this complication after allogeneic HCT.

MicroRNAs as Potential Diagnostic, Prognostic, and Predictive Biomarkers for Acute Graft-versus-Host Disease

Successful treatment of various hematologic diseases with allogeneic hematopoietic stem cell transplantation is often limited due to the occurrence of acute graft-versus-host disease (aGVHD). So far, there are no approved molecular biomarkers for the diagnosis and prediction of aGVHD at the clinical level due to our incomplete understanding of the molecular biology of the disease. Various studies have been conducted on animal models and humans to investigate the role of microRNAs in aGVHD pathogenesis to implicate them as biomarkers and therapeutic targets. Because of their high stability, tissue specificity, ease of measurement, low cost, and simplicity, they are excellent targets for biomarkers. In this review, we focused on microRNA expression profiling studies that were performed recently in both animal models and human cases of aGVHD to identify diagnostic and predictive biomarkers for this disease. The expression pattern of microRNAs can be specific to cells and tissues. Because aGVHD affects several organs, microRNA signatures in target tissues may help to understand the molecular pathology of the disease. Identification of organ-specific microRNAs in aGVHD can be promising to categorize patients for organ-specific therapies. Thus, microRNAs can be used as noninvasive diagnostic tests in clinic to improve prophylaxis, predict incidence and severity, and reduce morbidity.

Toll-Like Receptor Stimulation by MicroRNAs in Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (aGVHD) is a frequent complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT), accounting for substantial morbidity and mortality associated with this treatment modality. The pathogenesis of aGVHD involves a complex cascade of humoral and cellular interactions in which donor T cells target HLA mismatched host tissues, causing tissue injury through secretion of pro-inflammatory cytokines and induction of direct cytotoxicity. Toll-like receptors (TLRs) are key components of the innate immune system that recognize endogenous danger-associated molecular patterns (DAMPs) and exogenous pathogen-associated molecular patterns (PAMPs). Patients receiving conditioning chemotherapy and/or whole-body irradiation prior to all-HSCT are prone to gastrointestinal damage and translocation of microbiota across compromised intestinal epithelium, resulting in release of PAMPs and DAMPs. These “danger signals” play critical roles in disease pathogenesis by both initiating and propagating aGVHD through dendritic cell maturation and alloreactive T cell responses. There are 10–15 TLRs identified in mammalian species, a subset of which recognize single-stranded RNA (ssRNA) and serve as a key component of viral immunity. Recently, ssRNAs other than those of viral origin have been investigated as potential ligands of TLRs. MicroRNAs (miRs) are short (19–24 nt) non-coding RNAs that play critical roles in a variety of diseases. While traditionally miRs post-translationally modulate gene expression, non-canonical functions such as regulating TLR stimulation by acting as TLR ligands have been described. Here, we review the role of TLRs in aGVHD pathogenesis, the function of miRs in TLR stimulation, and the recent literature describing miRs as TLR ligands in aGVHD.

Differential MicroRNA Expression Levels in Cutaneous Acute Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation is a curative treatment for numerous hematological malignancies. However, acute graft-versus-host disease (aGvHD) is a major complication affecting 40-70% of all transplant patients, whereby the earliest and most frequent presentation is in the skin. MicroRNAs play a role in varied biological process and have been reported as potential biomarkers for aGvHD. More recently, microRNAs have received added attention as circulatory biomarkers that can be detected in biofluids. In this study, we performed global microRNA expression profiling using a discovery cohort of diagnostic cutaneous aGvHD biopsies (n = 5, stages 1-3) and healthy volunteers (n = 4), in order to identify a signature list of microRNAs that could be used as diagnostic biomarkers for cutaneous aGvHD. Candidate microRNAs (n = 8) were then further investigated in a validation cohort of post-HSCT skin biopsies (n = 17), pre-HSCT skin biopsies (n = 6) and normal controls (n = 6) for their association with aGvHD. Expression of let-7c (p = 0.014), miR-503-5p (p = 0.003), miR-365a-3p (p = 0.02), miR-34a-5p (p < 0.001) and miR-34a-3p (p = 0.006) were significantly differentially expressed between groups and significantly associated with survival outcome in post-HSCT patients (miR-503-5p ROC AUC = 0.83 p = 0.021, Log Rank p = 0.003; miR-34a-3p ROC AUC = 0.93, p = 0.003, Log Rank p = 0.004). There was no association with relapse. A statistical interaction between miR-34a-3p and miR-503-5p (p = 0.016) was diagnostic for aGvHD. Expression levels of the miR-34a-5p protein target p53 were assessed in the epidermis of the skin, and an inverse correlation was identified (r² = 0.44, p = 0.039). Expression of the validated candidate microRNAs was also assessed at day 28 post-HSCT in the sera of transplant recipients, in order to investigate their potential as circulatory microRNA biomarkers. Expression of miR-503-5p (p = 0.001), miR-34a-5p (p = 0.005), and miR-34a-3p (p = 0.004) was significantly elevated in the sera of patients who developed aGvHD versus no-aGvHD (n = 30) and miR-503-5p was associated with overall survival (OS) (ROC AUC = 0.80, p = 0.04, Log Rank p = 0.041). In conclusion, this investigation reports that microRNA expression levels in clinical skin biopsies, obtained at the time of cutaneous aGvHD onset, show potential as diagnostic biomarkers for aGvHD and as predictive biomarkers for OS. In addition, the same microRNAs can be detected in the circulation and show predictive association with post-HSCT outcomes.

MicroRNA-155 Modulates Acute Graft-versus-Host Disease by Impacting T Cell Expansion, Migration, and Effector Function

MicroRNA-155 (miR-155) is a small noncoding RNA critical for the regulation of inflammation as well as innate and adaptive immune responses. MiR-155 has been shown to be dysregulated in both donor and recipient immune cells during acute graft-versus-host disease (aGVHD). We previously reported that miR-155 is upregulated in donor T cells of mice and humans with aGVHD and that mice receiving miR-155-deficient (miR155^-/-) splenocytes had markedly reduced aGVHD. However, molecular mechanisms by which miR-155 modulates T cell function in aGVHD have not been fully investigated. We identify that miR-155 expression in both donor CD8⁺ T cells and conventional CD4⁺ CD25^- T cells is pivotal for aGVHD pathogenesis. Using murine aGVHD transplant experiments, we show that miR-155 strongly impacts alloreactive T cell expansion through multiple distinct mechanisms, modulating proliferation in CD8⁺ donor T cells and promoting exhaustion in donor CD4⁺ T cells in both the spleen and colon. Additionally, miR-155 drives a proinflammatory Th1 phenotype in donor T cells in these two sites, and miR-155^-/- donor T cells are polarized toward an IL-4-producing Th2 phenotype. We further demonstrate that miR-155 expression in donor T cells regulates CCR5 and CXCR4 chemokine-dependent migration. Notably, we show that miR-155 expression is crucial for donor T cell infiltration into multiple target organs. These findings provide further understanding of the role of miR-155 in modulating aGVHD through T cell expansion, effector cytokine production, and migration.

MicroRNA-17-92 is required for T-cell and B-cell pathogenicity in chronic graft-versus-host disease in mice

Chronic graft-versus-host disease (cGVHD) is characterized as autoimmune-like fibrosis and antibody production mediated by pathogenic T cells and B cells. MicroRNA-17-92 (miR-17-92) influences the survival, differentiation, and function of lymphocytes in cancer, infections, and autoimmunity. To determine whether miR-17-92 regulates T- and B-cell responses in cGVHD, we generated mice conditionally deficient for miR-17-92 in T cells, B cells, or both. Using murine models of allogeneic bone marrow transplantation, we demonstrate that expression of miR-17-92 in donor T and B cells is essential for the induction of both scleroderma and bronchiolitis obliterans in cGVHD. Mechanistically, miR-17-92 expressed in T cells not only enhances the differentiation of pathogenic T helper 1 (Th1) and Th17 cells, but also promotes the generation of follicular Th cells, germinal center (GC) B cells, and plasma cells. In B cells, miR-17-92 expression is required for autoantibody production and immunoglobulin G deposition in the skin. Furthermore, we evaluated a translational approach using antagomirs specific for either miR-17 or miR-19, key members in miR-17-92 cluster. In a lupus-like cGVHD model, systemic administration of anti-miR-17, but not anti-miR-19, alleviates clinical manifestations and proteinuria incidence in recipients through inhibiting donor lymphocyte expansion, B-cell activation, and GC responses. Blockade of miR-17 also ameliorates skin damage by reducing Th17 differentiation in a scleroderma-cGVHD model. Taken together, our work reveals that miR-17-92 is required for T-cell and B-cell differentiation and function, and thus for the development of cGVHD. Furthermore, pharmacological inhibition of miR-17 represents a potential therapeutic strategy for the prevention of cGVHD.

Genetic Association of Hematopoietic Stem Cell Transplantation Outcome beyond Histocompatibility Genes

The outcome of hematopoietic stem cell transplantation (HSCT) is controlled by genetic factors among which the leukocyte antigen human leukocyte antigen (HLA) matching is most important. In addition, minor histocompatibility antigens and non-HLA gene polymorphisms in genes controlling immune responses are known to contribute to the risks associated with HSCT. Besides single-nucleotide polymorphisms (SNPs) in protein coding genes, SNPs in regulatory elements such as microRNAs (miRNAs) contribute to these genetic risks. However, genetic risks require for their realization the expression of the respective gene or miRNA. Thus, gene and miRNA expression studies may help to identify genes and SNPs that indeed affect the outcome of HSCT. In this review, we summarize gene expression profiling studies that were performed in recent years in both patients and animal models to identify genes regulated during HSCT. We discuss SNP–mRNA–miRNA regulatory networks and their contribution to the risks associated with HSCT in specific examples, including forkheadbox protein 3 and regulatory T cells, the role of the miR-155 and miR-146a regulatory network for graft-versus-host disease, and the function of MICA and its receptor NKG2D for the outcome of HSCT. These examples demonstrate how SNPs affect expression or function of proteins that modulate the alloimmune response and influence the outcome of HSCT. Specific miRNAs targeting these genes and directly affecting expression of mRNAs are identified. It might be valuable in the future to determine SNPs and to analyze miRNA and mRNA expression in parallel in cohorts of HSCT patients to further elucidate genetic risks of HSCT.

Serum miR-29a Is Upregulated in Acute Graft-versus-Host Disease and Activates Dendritic Cells through TLR Binding

Acute graft-versus-host disease (aGVHD) continues to be a frequent and devastating complication of allogeneic hematopoietic stem cell transplantation (HSCT), posing as a significant barrier against the widespread use of HSCTs as a curative modality. Recent studies suggested serum/plasma microRNAs (miRs) may predict aGVHD onset. However, little is known about the functional role of circulating miRs in aGVHD. In this article, we show in two independent cohorts that miR-29a expression is significantly upregulated in the serum of allogeneic HSCT patients at aGVHD onset compared with non-aGVHD patients. Serum miR-29a is also elevated as early as 2 wk before time of diagnosis of aGVHD compared with time-matched control subjects. We demonstrate novel functional significance of serum miR-29a by showing that miR-29a binds and activates dendritic cells via TLR7 and TLR8, resulting in the activation of the NF-κB pathway and secretion of proinflammatory cytokines TNF-α and IL-6. Treatment with locked nucleic acid anti-miR-29a significantly improved survival in a mouse model of aGVHD while retaining graft-versus-leukemia effects, unveiling a novel therapeutic target in aGVHD treatment or prevention.

Tissue-Specific Expression Patterns of MicroRNA during Acute Graft-versus-Host Disease in the Rat

MicroRNAs (miRNA) have emerged as central regulators of diverse biological processes and contribute to driving pathology in several diseases. Acute graft-versus-host disease (aGvHD) represents a major complication after allogeneic hematopoietic stem cell transplantation, caused by alloreactive donor T cells attacking host tissues leading to inflammation and tissue destruction. Changes in miRNA expression patterns occur during aGvHD, and we hypothesized that we could identify miRNA signatures in target tissues of aGvHD that may potentially help understand the underlying molecular pathology of the disease. We utilized a rat model of aGvHD with transplantation of fully MHC-mismatched T cell depleted bone marrow, followed by infusion of donor T cells. The expression pattern of 423 rat miRNAs was investigated in skin, gut, and lung tissues and intestinal T cells with the NanoString hybridization platform, in combination with validation by quantitative PCR. MHC-matched transplanted rats were included as controls. In the skin, upregulation of miR-34b and downregulation of miR-326 was observed, while in the intestines, we detected downregulation of miR-743b and a trend toward downregulation of miR-345-5p. Thus, tissue-specific expression patterns of miRNAs were observed. Neither miR-326 nor miR-743b has previously been associated with aGvHD. Moreover, we identified upregulation of miR-146a and miR-155 in skin tissue of rats suffering from aGvHD. Analysis of intestinal T cells indicated 23 miRNAs differentially regulated between aGvHD and controls. Two of these miRNAs were differentially expressed either in skin (miR-326) or in intestinal (miR-345-5p) tissue. Comparison of intestinal and peripheral blood T cells indicated common dysregulated expression of miR-99a, miR-223, miR-326, and miR-345-5p. Analysis of predicted gene targets for these miRNAs indicated potential targeting of an inflammatory network both in skin and in the intestines that may further regulate inflammatory cytokine production. In conclusion, comprehensive miRNA profiling in rats suffering from aGvHD demonstrate tissue-specific differences in the expression patterns of miRNA that may not be detected by profiling of peripheral blood T cells alone. These tissue-specific miRNAs may contribute to distinct pathologic mechanisms and could represent potential targets for therapy.

MicroRNA-17-92 controls T-cell responses in graft-versus-host disease and leukemia relapse in mice

MicroRNAs (miRs) play important roles in orchestrating many aspects of the immune response. The miR-17-92 cluster, which encodes 6 miRs including 17, 18a, 19a, 20a, 19b-1, and 92-1, is among the best characterized of these miRs. The miR-17-92 cluster has been shown to regulate a variety of immune responses including infection, tumor, and autoimmunity, but the role of this cluster in T-cell response to alloantigens has not been previously explored. By using major histocompatibility complex (MHC)-matched, -mismatched, and haploidentical murine models of allogeneic bone marrow transplantation (allo-BMT), we demonstrate that the expression of miR-17-92 on donor T cells is essential for the induction of graft-versus-host disease (GVHD), but dispensable for the graft-versus-leukemia (GVL) effect. The miR-17-92 plays a major role in promoting CD4 T-cell activation, proliferation, survival, and Th1 differentiation, while inhibiting Th2 and iTreg differentiation. Alternatively, miR-17-92 may promote migration of CD8 T cells to GVHD target organs, but has minimal impact on CD8 T-cell proliferation, survival, or cytolytic function, which could contribute to the preserved GVL effect mediated by T cells deficient for miR-17-92. Furthermore, we evaluated a translational approach and found that systemic administration of antagomir to block miR-17 or miR-19b in this cluster significantly inhibited alloreactive T-cell expansion and interferon-γ (IFNγ) production, and prolonged the survival in recipients afflicted with GVHD while preserving the GVL effect. Taken together, the current work provides a strong rationale and demonstrates the feasibility to target miR-17-92 for the control of GVHD while preserving GVL activity after allo-BMT.

Fanconi Anemia: Overview of the Disease and the Role of Hematopoietic Transplantation

Fanconi anemia (FA) is an inherited bone marrow failure syndrome characterized by congenital abnormalities and chromosomal breakages with the occurrence of hematological and solid malignancies. FA is the most common type of inherited bone marrow failure and poses tremendous challenges. FA patients are uniquely hypersensitive to hematopoietic stem cell transplantation (HSCT) conditioning agents due to the underling chromosomal instability. HSCT has shown important progress in the last years, especially after the introduction of fludarabine and the reduction of cyclophosphamide in the preparative regimen. For patients with HLA-identical-related donors HSCT should be performed as first-line therapy, for patients with alternative donors HSCT remains a therapy with increased morbidity and mortality.

MicroRNAs as biomarkers for graft-versus-host disease following allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HCT) is a well-established treatment for many malignant and non-malignant hematological disorders. As frequent complication in up to 50 % of all patients, graft-versus-host disease (GVHD) is still the main cause for morbidity and non-relapse mortality. Diagnosis of GVHD is usually done clinically, even though confirmation by pathology is often used to support the clinical findings. Effective treatment requires intensified immunosuppression as early as possible. Although several promising biomarkers have been proposed for an early diagnosis, no internationally recognized consensus has yet been established. Here, microRNAs (miRs) represent an interesting tool since miRs have been recently reported to be an important regulator of various cells, including immune cells such as T cells. Therefore, we could assume that miRs play a key role in the pathogenesis of acute GVHD, and their detection might be an interesting possibility in the early diagnosis and monitoring of acute GVHD. Recent studies additionally demonstrated the implication of miRs in the pathogenesis of acute GVHD. In this review, we aim to summarize the previous reports of miRs, focusing on the pathogenesis of acute GVHD and possible implications in diagnostic approaches.

Association of human papillomavirus with Fanconi anemia promotes carcinogenesis in Fanconi anemia patients

Fanconi anemia (FA) is a rare recessive disorder associated with chromosomal fragility. FA patients are at very high risk of cancers, especially head and neck squamous cell carcinomas and squamous cell carcinomas caused by infection of human papillomaviruses (HPVs). By integrating into the host genome, HPV oncogenes E6 and E7 drive the genomic instability to promote DNA damage and gene mutations necessary for carcinogenesis in FA patients. Furthermore, E6 and E7 oncoproteins not only inhibit p53 and retinoblastoma but also impair the FANC/BRCA signaling pathway to prevent DNA damage repair and alter multiple signals including cell-cycle checkpoints, telomere function, cell proliferation, and interference of the host immune system leading to cancer development in FA patients. In this review, we summarize recent advances in unraveling the molecular mechanisms of FA susceptibility to HPV-induced cancers, which facilitate rational preventive and therapeutic strategies.

Innate immune activation by tissue injury and cell death in the setting of hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) with donor lymphocyte infusion is the mainstay of treatment for many types of hematological malignancies, but the therapeutic effect and prevention of relapse is complicated by donor T-cell recognition and attack of host tissue in a process known as graft-versus-host disease (GvHD). Cytotoxic myeloablative conditioning regimens used prior to Allo-HSCT result in the release of endogenous innate immune activators that are increasingly recognized for their role in creating a pro-inflammatory milieu. This increased inflammatory state promotes allogeneic T-cell activation and the induction and perpetuation of GvHD. Here, we review the processes of cellular response to injury and cell death that are relevant following Allo-HSCT and present the current evidence for a causative role of a variety of endogenous innate immune activators in the mediation of sterile inflammation following Allo-HSCT. Finally, we discuss the potential therapeutic strategies that target the endogenous pathways of innate immune activation to decrease the incidence and severity of GvHD following Allo-HSCT.

Deletion of Fanca or Fancd2 dysregulates Treg in mice

Fanconi anemia (FA) is a genetic disorder associated with bone marrow (BM) failure and leukemia. Recent studies demonstrate variable immune defects in FA. However, the cause for FA immunodeficiency is unknown. Here we report that deletion of Fanca or Fancd2 dysregulates the suppressive activity of regulatory T cells (Tregs), shown functionally as exacerbation of graft-vs-host disease (GVHD) in mice. Recipient mice of Fanca(-/-) or Fancd2(-/-) BM chimeras exhibited severe acute GVHD after allogeneic BM transplantation (BMT). T cells from Fanca(-/-) or Fancd2(-/-) mice induced higher GVHD lethality than those from wild-type (WT) littermates. FA Tregs possessed lower proliferative suppression potential compared with WT Tregs, as demonstrated by in vitro proliferation assay and BMT. Analysis of CD25(+)Foxp3(+) Tregs indicated that loss of Fanca or Fancd2 dysregulated Foxp3 target gene expression. Additionally, CD25(+)Foxp3(+) Tregs of Fanca(-/-) or Fancd2(-/-) mice were less efficient in suppressing the production of GVHD-associated inflammatory cytokines. Consistently, aberrant NF-κB activity was observed in infiltrated T cells from FA GVHD mice. Conditional deletion of p65 in FA Tregs decreased GVHD mortality. Our study uncovers an essential role for FA proteins in maintaining Treg homeostasis, possibly explaining, at least in part, the immune deficiency reported in some FA patients.

MicroRNAs: The Missing Link in the Biology of Graft-Versus-Host Disease?

Graft-versus-host disease (GVHD) is still the major complication of allogeneic hematopoietic stem cell transplantation. Despite extensive studies in understanding the pathophysiology of GVHD, its pathogenesis remains unclear. Recently, important functions of microRNAs have been demonstrated in various autoimmune diseases and cancers such as psoriasis and lymphoma. This review highlights the need to investigate the role of microRNAs in GVHD and hypothesizes that microRNAs may be one of the missing links in our understanding of GVHD, with the potential for novel therapeutics.