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IT-901 mediates anti-lymphoma activity in a xenograft model of EBV-induced lymphoma.

IT-901 inhibits growth of human DLBCL cell lines.

c-Rel is constitutively active in a wide range of human lymphoma types.

Analysis of the biochemical efficacy of IT-901 by electrophoretic mobility shift assay (EMSA) and NF-κB DNA binding ELISA.

ROS/RNS induction by IT-­901 treatement in normal tissues.

c-Rel inhibitor treatment is associated with partial recovery of lost body weight during severe acute GVHD.

NF-κB plays a variety of roles in oncogenesis and immunity that may be beneficial for therapeutic targeting, but strategies to selectively inhibit NF-κB to exert antitumor activity have been elusive. Here, we describe IT-901, a bioactive naphthalenethiobarbiturate derivative that potently inhibits the NF-κB subunit c-Rel. IT-901 suppressed graft-versus-host disease while preserving graft-versus-lymphoma activity during allogeneic transplantation. Further preclinical assessment of IT-901 for the treatment of human B-cell lymphoma revealed antitumor properties in vitro and in vivo without restriction to NF-κB–dependent lymphoma. This nondiscriminatory, antilymphoma effect was attributed to modulation of the redox homeostasis in lymphoma cells resulting in oxidative stress. Moreover, NF-κB inhibition by IT-901 resulted in reduced stimulation of the oxidative stress response gene heme oxygenase-1, and we demonstrated that NF-κB inhibition exacerbated oxidative stress induction to inhibit growth of lymphoma cells. Notably, IT-901 did not elicit increased levels of reactive oxygen species in normal leukocytes, illustrating its cancer selective properties. Taken together, our results provide mechanistic insight and preclinical proof of concept for IT-901 as a novel therapeutic agent to treat human lymphoid tumors and ameliorate graft-versus-host disease. Cancer Res; 76(2); 377–89. ©2016 AACR.

IT-901 is a more potent c-Rel inhibitor than IT-603.

Effects of IT-901 on lymphocyte subsets in the spleen.

IT-901 has a superior pharmacokinetic profile.

IT-901 is a more potent NF-κB inhibitor than IT-603.

IT-901 has no significant adverse effects on major organ functions and blood cell counts.

Treatment with IT-901 for 14 days does not alter lymphocyte numbers.

Several NF-κB subunits are constitutively active in activated B-like DLBCL cell lines.

Objectives To determine whether catheterization rates after intradetrusor onabotulinumtoxinA injection for nonneurogenic overactive bladder and urgency incontinence differ between women with urgency urinary incontinence only and women with urgency-predominant mixed urinary incontinence. Methods This was a retrospective cohort study of patients that underwent intradetrusor onabotulinumtoxinA injection of 100 U for nonneurogenic urgency urinary incontinence. The primary outcome was the difference in catheterization rates between women with urgency urinary incontinence alone compared with women with urgency-predominant mixed urinary incontinence. Descriptive statistics and multivariate logistic regression analysis were performed. Results Of the 177 women included in the final analysis, 105 had urgency urinary incontinence and 72 had urgency-predominant mixed urinary incontinence. The overall catheterization rate after onabotulinumtoxinA injection was 11.3%, with significantly fewer women with mixed urinary incontinence requiring catheterization when compared with women with urgency urinary incontinence alone (4.2% vs 16.2%; P = 0.03), despite an older population (P = 0.02). Patient-reported improvement (P = 0.37) and decision to continue onabotulinumtoxinA treatments (P = 0.89) were similar between groups. Multivariate logistic regression analysis revealed that women with mixed urinary incontinence had significantly lower odds of requiring catheterization after onabotulinumtoxinA injections than women with urgency urinary incontinence alone (odds ratio, 0.16; 95% confidence interval, 0.04-0.67; P = 0.01). Conclusions Findings suggest that the presence of symptomatic stress urinary incontinence is associated with lower rates of catheterization after intradetrusor onabotulinumtoxinA, but does not compromise efficacy of treatment for urgency-predominant mixed urinary incontinence.

PURPOSE: To identify biomarkers that prospectively predict IVF cycle cancellation. METHODS: In this prospective study, sera were obtained prior to any intervention, from women about to undergo an IVF cycle. The sera were assayed by ELISA for levels of insulin-like growth factor (IGF)-1, IGF-2, IGF binding protein (BP)-1, and soluble fms-like tyrosine kinase (sFLT-1). The cancellation or progression of the IVF cycle was subsequently obtained by chart review. Associations between serum components and outcome were analyzed by the Mann-Whitney test. Receiver operator curves were constructed to evaluate the strength of the correlations between biomarkers and cycle cancellation, as assessed from the area under the curve (AUC). RESULTS: A total of 205 women were included. Twenty-seven (13.2%) cycle cancellations due to poor response were recorded. Women with a cancelled cycle had reduced anti-Mullerian hormone (AMH) values (p < 0.001) and antral follicle count (p = 0.003). There were no significant differences between the two groups with regard to age and BMI. Median concentrations of IGF-1 and sFLT-1 were elevated in sera from women whose IVF cycles were cancelled as compared to those with ongoing cycles (p = 0.015 and p < 0.001, respectively); AUC for IGF-1 and sFLT-1 were 0.67 and 0.75, respectively. Concentrations of sFLT-1 remained significantly higher in patients with cancelled cycles even after controlling for AMH levels. There were no differences in IGF-2 and IGFBP-1 levels between the two groups. CONCLUSIONS: Measurement of circulating IGF-1 and sFLT-1 levels prior to initiation of an IVF cycle has the potential to identify women whose cycles have an increased likelihood to be subsequently cancelled.

Objective The number of patients who seek health information on the internet is increasing. Rates are particularly high among lesbian, gay, bisexual, transgender and queer (LGBTQ) individuals, due to health care barriers. The aim of this study was to evaluate the quality and inclusivity of web-based information pertaining to LGBTQ family building. Methods The first 100 US-based websites pertaining to LGBTQ family building were identified through a terminology-based internet search. After eliminating 45 websites, 55 websites were found to be eligible. The 2016 Website Information Reliability Evaluation Instrument (of the Office of Disease Prevention and Health Promotion, US Department of Health and Human Services) was used to analyse the quality of information on each website. Websites were analysed for inclusivity of important topics surrounding LGBTQ family building. Results A total of 46 websites (83.6%) belonged or were related to reproductive services and served as advertisements for their respective owners; nine websites (16.4%) belonged to third parties. No website met more than four of the six major reliability criteria, and 42 websites (76.4%) met only one or two of the six major reliability criteria. When inclusivity was considered, 29 websites (52.7%) mentioned options for transgender individuals and nine websites (16.4%) mentioned adoption. Conclusions There is a lack of reliable web-based information for LGBTQ family building and a need for improvement in quality and scope. Improvements could lead to a shift in reproductive health care towards better inclusion of and catering to LGBTQ individuals.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for hematological malignancies. However, graft-versus-host disease (GVHD) and relapse after allo-HSCT remain major impediments to the success of allo-HSCT. Chimeric antigen receptors (CARs) direct tumor cell recognition of adoptively transferred T cells. CD19 is an attractive CAR target, which is expressed in most B cell malignancies, as well as in healthy B cells. Clinical trials using autologous CD19-targeted T cells have shown remarkable promise in various B cell malignancies. However, the use of allogeneic CAR T cells poses a concern in that it may increase risk of the occurrence of GVHD, although this has not been reported in selected patients infused with donor-derived CD19 CAR T cells after allo-HSCT. To understand the mechanism whereby allogeneic CD19 CAR T cells may mediate anti-lymphoma activity without causing a significant increase in the incidence of GVHD, we studied donor-derived CD19 CAR T cells in allo-HSCT and lymphoma models in mice. We demonstrate that alloreactive T cells expressing CD28-costimulated CD19 CARs experience enhanced stimulation, resulting in the progressive loss of both their effector function and proliferative potential, clonal deletion, and significantly decreased occurrence of GVHD. Concurrently, the other CAR T cells that were present in bulk donor T cell populations retained their anti-lymphoma activity in accordance with the requirement that both the T cell receptor (TCR) and CAR be engaged to accelerate T cell exhaustion. In contrast, first-generation and 4-1BB-costimulated CAR T cells increased the occurrence of GVHD. These findings could explain the reduced risk of GVHD occurring with cumulative TCR and CAR signaling.

Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a ubiquitously expressed transcription factor that is well known for its role in regulating the cellular redox pathway. Although there is mounting evidence suggesting a critical role for Nrf2 in hematopoietic stem cells and innate leukocytes, little is known about its involvement in T-cell biology. In this study, we identified a novel role for Nrf2 in regulating alloreactive T-cell function during allogeneic hematopoietic cell transplantation (allo-HCT). We observed increased expression and nuclear translocation of Nrf2 upon T-cell activation in vitro, especially in CD4+ donor T cells after allo-HCT. Allo-HCT recipients of Nrf2−/− donor T cells had significantly less acute graft-versus-host disease (GVHD)-induced mortality, morbidity, and pathology. This reduction in GVHD was associated with the persistence of Helios+ donor regulatory T cells in the allograft, as well as defective upregulation of the gut-homing receptor LPAM-1 on alloreactive CD8+ T cells. Additionally, Nrf2−/− donor CD8+ T cells demonstrated intact cytotoxicity against allogeneic target cells. Tumor-bearing allo-HCT recipients of Nrf2−/− donor T cells had overall improved survival as a result of preserved graft-versus-tumor activity and reduced GVHD activity. Our findings characterized a previously unrecognized role for Nrf2 in T-cell function, as well as revealed a novel therapeutic target to improve the outcomes of allo-HCT.

As medical students' interest in surgical fields wanes, we investigated the impact of a preclinical surgical exposure program on students' attitudes toward pursuing surgical careers.This is a prospective longitudinal study of PreOp, a preclinical rotation-based surgical exposure program for first-year medical students, from 2013 to 2017. Surveys assessed PreOp rotation quality, students' surgical interest, and students' self-reported preparedness for the surgical clerkship. Surgery clerkship grades were obtained as a measure of surgical competency and compared to class-wide peers. Match data was collected and compared to class-wide peers as well as historical norms.NewYork-Presbyterian Hospital/Weill Cornell Medicine, New York, NY; tertiary care center.Fifty-four PreOp students from 2013 to 2017.Fifty-four PreOp participants were recruited. After completing the PreOp program, 66.7% of PreOp students reported being very likely to apply into a surgical field compared to 29.4% when they started medical school. Ultimately, 71.4% of PreOp students versus 21.7% of non-PreOp class-wide peers matched into surgical fields (p0.001). From the preceding 5 match years before PreOp implementation, 21.4% of all students matched into surgical fields compared to 25.6% of all students after PreOp was started (p = 0.26). In terms of preparedness, 75% of PreOp students reported feeling more prepared for the third-year surgery clerkship than their non-PreOp peers after the second year of medical school. PreOp students were significantly more likely than non-PreOp class-wide peers to receive honors in the surgery clerkship when controlling for cumulative clerkship GPA (p = 0.012, adjusted odds ratio = 5.5 [95% confidence interval 1.5-22.1]).Hands-on preclinical surgical exposure was associated with student-reported increased surgical interest that was maintained longitudinally and reflected in significantly increased surgical matches relative to non-PreOp class-wide peers. This study uniquely demonstrates that participation in PreOp was also associated with increased self-reported surgical preparedness and significantly higher surgery clerkship grades relative to overall academic performance.

PURPOSE: Retrospective cohort studies have shown a relationship between maternal serum interleukin-1β (IL-1β) and interleukin-1 receptor antagonist (IL-1Ra) levels and in vitro fertilization (IVF) cycle outcome. The objective of this investigation was to explore the correlation between serum IL-1β and/or IL-1Ra levels obtained prospectively and IVF outcomes. METHODS: Sera from 205 women were collected just prior to initiation of their IVF cycle, at the time of human chorionic gonadotropin administration, day 24 of IVF cycle, day 28, and day 35. Sera were analyzed for IL-1β and IL-1Ra using commercially available ELISA kits. Cycle outcomes were followed prospectively. Data were analyzed using Friedman analysis of variance by ranks and chi-square analysis. RESULTS: Among women with a viable pregnancy, IL-1β serum levels increased over time for those that proceeded to deliver or had an ongoing pregnancy. There was no increase in serum levels for those with subsequent pregnancy loss. Of the women that had an embryo transfer, detectable IL-1β levels at the start of the cycle were associated with successful IVF outcome (p = 0.027). Of women with a positive pregnancy test, undetectable IL-1β at the start of the cycle were associated with subsequent pregnancy loss (p = 0.046). For all IL1-Ra serum analysis, there were no significant results. CONCLUSIONS: The increasing levels of IL-1β over time are consistent with the known role of the IL-1 cytokine family in implantation and pregnancy. Additionally, we confirm in a prospective investigation the positive relationship between detectable serum IL-1β at the start of IVF cycle and outcome.

NF-κB plays a variety of roles in oncogenesis and immunity that may be beneficial for therapeutic targeting, but strategies to selectively inhibit NF-κB to exert antitumor activity have been elusive. Here, we describe IT-901, a bioactive naphthalenethiobarbiturate derivative that potently inhibits the NF-κB subunit c-Rel. IT-901 suppressed graft-versus-host disease while preserving graft-versus-lymphoma activity during allogeneic transplantation. Further preclinical assessment of IT-901 for the treatment of human B-cell lymphoma revealed antitumor properties in vitro and in vivo without restriction to NF-κB–dependent lymphoma. This nondiscriminatory, antilymphoma effect was attributed to modulation of the redox homeostasis in lymphoma cells resulting in oxidative stress. Moreover, NF-κB inhibition by IT-901 resulted in reduced stimulation of the oxidative stress response gene heme oxygenase-1, and we demonstrated that NF-κB inhibition exacerbated oxidative stress induction to inhibit growth of lymphoma cells. Notably, IT-901 did not elicit increased levels of reactive oxygen species in normal leukocytes, illustrating its cancer selective properties. Taken together, our results provide mechanistic insight and preclinical proof of concept for IT-901 as a novel therapeutic agent to treat human lymphoid tumors and ameliorate graft-versus-host disease. Cancer Res; 76(2); 377–89. ©2016 AACR.

The thymus is not only extremely sensitive to damage but also has a remarkable ability to repair itself. However, the mechanisms underlying this endogenous regeneration remain poorly understood, and this capacity diminishes considerably with age. We show that thymic endothelial cells (ECs) comprise a critical pathway of regeneration via their production of bone morphogenetic protein 4 (BMP4) ECs increased their production of BMP4 after thymic damage, and abrogating BMP4 signaling or production by either pharmacologic or genetic inhibition impaired thymic repair. EC-derived BMP4 acted on thymic epithelial cells (TECs) to increase their expression of Foxn1, a key transcription factor involved in TEC development, maintenance, and regeneration, and its downstream targets such as Dll4, a key mediator of thymocyte development and regeneration. These studies demonstrate the importance of the BMP4 pathway in endogenous tissue regeneration and offer a potential clinical approach to enhance T cell immunity.

Velardi et al. show that sex steroids regulate thymopoiesis by directly modulating Notch signaling, and provide a novel clinical strategy to boost immune regeneration., Paradoxical to its importance for generating a diverse T cell repertoire, thymic function progressively declines throughout life. This process has been at least partially attributed to the effects of sex steroids, and their removal promotes enhanced thymopoiesis and recovery from immune injury. We show that one mechanism by which sex steroids influence thymopoiesis is through direct inhibition in cortical thymic epithelial cells (cTECs) of Delta-like 4 (Dll4), a Notch ligand crucial for the commitment and differentiation of T cell progenitors in a dose-dependent manner. Consistent with this, sex steroid ablation (SSA) led to increased expression of Dll4 and its downstream targets. Importantly, SSA induced by luteinizing hormone-releasing hormone (LHRH) receptor antagonism bypassed the surge in sex steroids caused by LHRH agonists, the gold standard for clinical ablation of sex steroids, thereby facilitating increased Dll4 expression and more rapid promotion of thymopoiesis. Collectively, these findings not only reveal a novel mechanism underlying improved thymic regeneration upon SSA but also offer an improved clinical strategy for successfully boosting immune function.

There is a substantial unmet clinical need for new strategies to protect the hematopoietic stem cell (HSC) pool and regenerate hematopoiesis after radiation injury from either cancer therapy or accidental exposure. Increasing evidence suggests that sex hormones, beyond their role in promoting sexual dimorphism, regulate HSC self-renewal, differentiation, and proliferation. We and others have previously reported that sex-steroid ablation promotes bone marrow (BM) lymphopoiesis and HSC recovery in aged and immunodepleted mice. Here we found that a luteinizing hormone (LH)-releasing hormone antagonist (LHRH-Ant), currently in wide clinical use for sex-steroid inhibition, promoted hematopoietic recovery and mouse survival when administered 24 h after an otherwise-lethal dose of total-body irradiation (L-TBI). Unexpectedly, this protective effect was independent of sex steroids and instead relied on suppression of LH levels. Human and mouse long-term self-renewing HSCs (LT-HSCs) expressed high levels of the LH/choriogonadotropin receptor (LHCGR) and expanded ex vivo when stimulated with LH. In contrast, the suppression of LH after L-TBI inhibited entry of HSCs into the cell cycle, thus promoting HSC quiescence and protecting the cells from exhaustion. These findings reveal a role of LH in regulating HSC function and offer a new therapeutic approach for hematopoietic regeneration after hematopoietic injury.

There is a substantial unmet clinical need for new strategies to protect the hematopoietic stem cell (HSC) pool and regenerate hematopoiesis after radiation injury, either from cancer therapy or accidental exposure1,2. In addition to their role in promoting sexual dimorphisms, increasing evidence suggests that sex hormones regulate HSC self-renewal, differentiation, and proliferation3–5. We and others previously reported that sex steroid ablation promotes bone marrow (BM) lymphopoiesis and HSC recovery in aged and immunodepleted mice5–7. Here we show that a luteinizing hormone-releasing hormone-antagonist (LHRH-Ant), currently used widely in the clinic for sex steroid inhibition, promoted hematopoietic recovery and mouse survival when administered 24 h after an otherwise lethal dose of total body irradiation (L-TBI). Unexpectedly, this protective effect was independent of sex steroids, but instead relied on suppression of luteinizing hormone (LH) levels. Human and mouse long-term self-renewing HSCs (LT-HSCs) expressed high levels of the luteinizing hormone/choriogonadotropin receptor (LHCGR) and expand ex vitro when stimulated with LH. In contrast, suppression of LH after L-TBI inhibited entry of HSCs into the cell cycle, thus promoting quiescence of HSCs and protecting them from exhaustion. These findings reveal a role for LH in regulating HSC function and offer a new therapeutic approach for hematopoietic regeneration after injury.

T-cell deficiency related to disease, medical treatment, or aging represents a major clinical challenge and is associated with significant morbidity and mortality in cancer and bone marrow transplantation recipients. This study describes several innovative and clinically relevant strategies to manipulate thymic function based on an interventional radiology technique for intrathymic injection of cells or drugs. We show that intrathymic injection of multipotent hematopoietic stem/progenitor cells into irradiated syngeneic or allogeneic young or aged recipients resulted in efficient and long-lasting generation of functional donor T cells. Persistence of intrathymic donor cells was associated with intrathymic presence of cells resembling long-term hematopoietic stem cells, suggesting a self-renewal capacity of the intrathymically injected cells. Furthermore, our approach enabled the induction of long-term antigen-specific T-cell–mediated antitumor immunity following intrathymic injection of progenitor cells harboring a transgenic T-cell receptor gene. The intrathymic injection of interleukin-7 prior to irradiation conferred radioprotection. In addition, thymopoiesis of aged mice improved with a single intrathymic administration of low-dose keratinocyte growth factor, an effect that was sustained even in the setting of radiation-induced injury. Taken together, we established a preclinical framework for the development of novel clinical protocols to establish lifelong antigen-specific T-cell immunity.

Innate lymphoid cells (ILCs) are a newly described heterogeneous population of immune cells that can be defined by their expression of specific transcription factors (Tbet, GATA3 or RORgt) and their production of cytokines (IFNg, IL-13, or IL-22). Group 3 ILCs (which can be identified by expression of RORgt and production of IL-22) have been implicated in the maintenance and function of tissues as diverse as liver, gut, lung, spleen and lymph nodes. We have recently described a central role for intrathymic group 3 ILCs (tILC3) in a complex network of endogenous thymic regeneration (Dudakov et al. 2012 Science 336:91-95); a crucial function that allows for renewal of immune competence following infection or immune depletion caused by cytoreductive chemotherapy or radiation injury. In this model, 1) loss of thymic cellularity (and in particular the depletion of CD4+CD8+ double positive, DP, thymocytes) triggers, 2) upregulation of IL-23 by dendritic cells (DCs) which induces, 3) the production of IL-22 by tILC3. Given that IL-22 promotes the survival and proliferation of thymic epithelial cells (TECs), this cascade of events leads to regeneration of the supporting epithelial microenvironment and, ultimately, to rejuvenation of thymopoiesis. In our previous studies we had demonstrated that, unlike other lymphoid cells, tILC3 were extremely radio-resistant with little if any depletion of cells after even lethal doses of total body irradiation (TBI). Consistent with these findings, here we show that a considerable proportion of tILC3 were non-cycling in steady-state conditions and expressed high endogenous levels of the anti-apoptotic protein Bcl-2 (Fig. 1a). Perhaps unsurprising given their resistance to proliferation-targeted damage, a residual population of host-derived tILC3s could be identified for up to 12 months after syngeneic hematopoietic stem cell transplantation (HSCT). Although at this stage it is unclear if this is because they are very long-lived or if they have the capacity for self-renewal, residual host tILC3 were almost exclusively non-proliferating and expressed high levels of Bcl-2, indicating a quiescent state. Transcriptome analysis of IL-22 target cells revealed two mechanisms by which IL-22 mediates its effects on TECs; 1) by directly promoting the upregulation of proliferation-associated molecules such as E2f2; and 2) by reducing expression of negative signalling regulators such as Socs3 (an inhibitor of cytokine signalling) and Tnfrsf11b (Osteoprotegerin, a RANKL decoy receptor). This suggests a possible secondary role for IL-22 in promoting enhanced responsiveness to other regenerative factors, such as KGF, BMP4 and RANKL, all of which are increased in the thymus as part of the regenerative response after TBI (Fig. 1b). In our previous studies we found that increased production of IL-22 by tILC3 in response to immune injury was strikingly consistent across several mouse models with lesions in T cell development, including TBI, exposure to corticosteroids, and in mice with genetic mutations. However, one model where this increase in IL-22 does not occur is in the setting of graft versus host disease (GVHD), where tILC3s are profoundly depleted in the thymus (Fig. 1c), likely contributing towards reduced rejuvenation of thymic cellularity and failure to recover during GVHD. Intriguingly, although IL-22 appears to play a considerable role in the regenerative capacity of tILC3, preliminary studies suggest that depletion of tILC3 in IL-22 deficient mice leads to significantly worse recovery compared to Il22-/- mice replete with tILC3 (Fig. 1d). Consistent with this hypothesis of an alternate role in regeneration beyond IL-22 production, production of RANKL is also increased by tILC3 after thymic damage. Thus, we have identified that tILC3 are highly radio-resistant and long-lived owing largely to their quiescent nature and resistance to apoptosis. These pre-clinical studies focusing on tILC3 biology not only help to identify the mechanisms that allow this nascent cell population to mediate its regenerative effects, but also offer a tantalising glimpse into an alternate pathway mediating their regeneration in the thymus. Taken together, these studies could have the potential to result in novel clinical approaches to enhance T cell immunity in individuals with T cell deficiencies due to aging, infectious disease, chemotherapy or radiation injury. Disclosures: No relevant conflicts of interest to declare.

Mechanisms regulating host tissue recovery from immune-mediated damage in gastrointestinal graft vs. host disease (GI GVHD) remain incompletely understood. Prophylactic strategies selectively promoting epithelial regeneration after allogeneic hematopoietic stem/progenitor cell transplantation (allo-HCT) have the potential to reduce GVHD without limiting therapeutic graft vs. leukemia/lymphoma (GVL) responses. We have previously shown that IL-22 produced by recipient-derived innate lymphoid cells (ILCs) provides a critical signal for epithelial recovery following experimental allo-HCT. IL-22-deficient recipients demonstrated increased GVHD mortality and significantly worse loss of crypt base intestinal stem cells (ISCs) during GVHD. Paradoxically, GVHD led to reduced GI IL-22 levels in wild-type (WT) recipients due to the elimination of radioresistant intestinal ILCs. We therefore sought to determine if IL-22 administration after allo-HCT could negate the effect of ILC elimination and reduce GVHD pathology without impairing GVL. We utilized a clinically modeled LP into C57BL/6 (B6) minor antigen mismatched model with T cell-depleted marrow and MACS-purified T cells transplanted into lethally irradiated mice. Recipients were treated daily with PBS or 4ug murine recombinant (r)IL-22 delivered via intraperitoneal (IP) injection starting day 7 post-HCT. This schedule was based on the results of rIL-22 pharmacokinetics tested in untransplanted mice. We found that daily IP administration with rIL-22 led to decreased GVHD pathology in recipient small intestine, large intestine, and liver three weeks post-HCT (Figure 1, p To assess the effects of IL-22 administration on the ISC compartment, we performed LP into B6 allo-HCT using Lgr5-LacZ ISC reporter mice. Recipients treated with rIL-22 demonstrated increased numbers of Lgr5+ ISC three weeks post-HCT during active GVHD with no immunosuppression (Figure 2, p Given the lack of IL-22R expression in hematopoietic cells, we hypothesized that IL-22 administration would not limit GVL. This was confirmed by monitoring luciferase+ A20 bioluminescence in B6 into BALB/c tumor challenge recipients treated with rIL-22. Finally, we have previously shown that rIL-22 administration can increase the number of double positive thymocytes post-HCT by protecting thymic epithelium from radiation injury and from GVHD. We hypothesized that this could translate into improved peripheral T cell reconstitution even during active GVHD. Indeed, FVB into BALB/c MHC-mismatched transplant with Rag2-GFP marrow and WT T cells indicated that IL-22 administration increased the development of donor marrow-derived CD4 and CD8+ thymic emigrants four weeks post-HCT (Figure 3, p In summary, we found that IL-22 administration could reduce intestinal pathology, improve ISC recovery, and promote donor marrow-derived T cell development during GVHD. Importantly, IL-22 administration did not impair GVL. These results suggest that post-transplant IL-22 administration represents a novel strategy to protect intestinal epithelium and improve immune reconstitution after allo-HCT. Disclosures: No relevant conflicts of interest to declare.

Thymopoiesis is a complex process involving crosstalk between developing thymocytes and the non-hematopoietic stromal microenvironment, which includes thymic epithelial cells (TECs), fibroblasts and endothelial cells (ECs). Despite its importance, the thymus is exquisitely sensitive to cellular insults, including cytoreductive chemo- and radiation therapy required for successful hematopoietic stem cell transplantation; therefore identification of thymic repair mechanisms will offer promising therapeutic targets for immune regeneration. Recent studies in tissues such as liver, lung and bone marrow have revealed that ECs not only passively deliver oxygen and nutrients to tissues, but also actively produce distinct paracrine factors that can orchestrate their repair. The role of thymic ECs in thymopoiesis beyond their contribution of local circulation and the importation of lymphoid progenitors has not been comprehensively studied. In order to evaluate the role of ECs in thymic regeneration, we closely examined the kinetics of thymic recovery following total body irradiation (TBI, 550cGy) in young C57BL/6 mice. Although we observed a dramatic decline in total thymic cellularity, we found no significant change in the number of thymic ECs, suggesting they are extremely radio-resistant (Fig. 1A). Interestingly, although thymic ECs appeared to be resistant to the cytoreductive effects of TBI, we revealed an increase in their proliferation as measured by expression of Ki67 shortly after injury, indicating a role in the endogenous regeneration of the thymus (Fig. 1B). Given their radioresistance and cycling after TBI, we hypothesized that thymic ECs can provide instructive signals supporting thymic regeneration. To explore potential regenerative signals stemming from ECs during thymic regeneration, we performed a transcriptome analysis of highly purified ECs of untreated mice and at days 4 and 7 following TBI. Among the 288 genes that were altered in ECs after TBI (131 upregulated and 157 downregulated), we found significant upregulation in the expression of BMP4 (which has previously been implicated in thymic regeneration) and was validated using quantitative PCR (Fig 1C). In addition, we have developed a novel light sheet fluorescence microscopy approach to visualize the thymic vasculature in 3D at high resolution (Fig. 1D). Consistent with their potential role in aiding thymic regeneration, administration of ex vivo expanded thymic ECs (ex-EC) could significantly enhance thymic regeneration when given after TBI. Intriguingly, this regenerative effect of ex-ECs was tissue specific as ex-EC derived from heart or kidney did not exhibit a similar regenerative effect (Fig. 1E). Similar to our findings in the endogenous regeneration setting, we found that thymic ex-ECs demonstrated a significantly higher BMP4 expression compared to cardiac and kidney ex-ECs (Fig. 1F). Previous reports have suggested that BMP4 signaling is capable of directly regulating the key transcription factor of TEC function, FOXN1. We found that incubation of the TEC cell line C9 with thymic ex-EC conditioned medium induced an increase in FOXN1 expression but was abrogated in the presence of Noggin, a potent BMP signaling inhibitor (Fig. 1G). These findings support the hypothesis that BMP4 mediates the regenerative effect of ECs in thymic regeneration. In summary, we found that thymic ECs are capable of mediating endogenous thymic regeneration, likely via their expression of BMP4. Adoptive transfer of ex-ECs leads to enhanced thymic regeneration after immune injury. Thus, adoptive transfer of thymic ECs represents a novel strategy to improve immune function in immunocompromised patients. Figure 1 Figure 1. Disclosures Ginsberg: Angiocrine Bioscience: Employment. Rafii:Angiocrine Biosciences: Founder Other.

Thymopoiesis is a complex process dependent on precise signals from the supporting thymic stromal microenvironment that orchestrates the progression of precursor T cells through well-defined maturation stages. It is well documented that the decline in thymic size and function with age is in part correlated with an increase in sex steroids. This age-related decline in function can be detrimental to the recovery of the thymus in patients receiving radio or chemo-therapy with hematopoietic stem cell transplantation (HSCT). Delayed immune reconstitution, especially in the T cell lineage, is associated with an increased risk of opportunistic infections and malignant relapses. Therefore strategies to enhance thymic reconstitution has the potential to decrease the period of T cell lymphopenia and increase overall clinical outcome. In the process of evaluating the effects of sex steroids in the decline of the thymic function, we found a decrease in the expression of the key thymopoietic factors IL-7, CCL25 and Delta-like 4 (DLL4) by thymic stromal cells after testosterone treatment (Figure 1A). We then addressed if these transcriptional changes were the result of a direct regulation by the androgen receptor (AR). Using a computational approach, and subsequently confirmed by ChIP studies, we found that AR directly bound and negatively regulated the promoter of DLL4, a critical gene involved in T cell commitment and differentiation. We and others have previously shown that sex steroid ablation (SSA) can regenerate young and aged immune system by promoting bone marrow and thymic lymphopoiesis and promoting recovery from autologous and allogeneic HSCT. However the mechanisms underlying the sex steroid-mediate thymic involution and its regeneration after SSA are poorly understood. Moreover, one of the main drawbacks to standard clinical methods of sex steroid ablation using luteinizing hormone releasing hormone (LHRH) agonists (LHRH-Ag) is the initial surge in sex steroids they cause. To address this, we employed a novel class of LHRH-antagonists (LHRH-Ant) that rapidly block the secretion of sex steroids without causing their initial surge that can be even more detrimental to thymopoiesis. Mice treated with LHRH-Ant showed a significantly faster increase in thymic cellularity compared with LHRH-Ag treated mice (Figure 1B). Given the negative regulation of DLL4 by the AR, we hypothesized that DLL4 expression would conversely increase after SSA in vivo. Indeed, we found a significant increase in DLL4 expression after SSA and also an increase in genes downstream of DLL4, such as Ptcra, Hes1 and Cd25 (Figure 1C). We next evaluated if treatment with the LHRH-Ant would provide a faster immune recovery after injury to the immune system. We found that mice treated with LHRH-Ant showed a faster thymic regeneration after total body irradiation (TBI) compared to the control irradiated mice (Figure 1D) and enhanced viral clearance (Figure 1E). Finally, we also found that LHRH-Ant enhanced thymic and peripheral reconstitution up to 3 months after allo-HSCT (Figure 1F). In conclusion, we found that down-regulation of DLL4 may represent one of the mechanisms underlying the effects of sex steroids on thymic function. We demonstrate that SSA with a novel LHRH-Ant increases DLL4 expression and enhances thymic and peripheral T cell recovery and function after immune injury. These findings suggest that the employment of a LHRH-Ant, which is already in clinical use for prostate cancer patients, represents a novel therapeutic strategy to enhance immune recovery and function in immunocompromised patients. Disclosures: No relevant conflicts of interest to declare.