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Serum levels of an interleukin-1 receptor family member called suppressor of tumorigenicity 2 (ST2) predict response to therapy for graft-versus-host disease (GVHD) and improve on clinical grading in assessing the risk of death without relapse after allogeneic transplantation. Although mortality related to graft-versus-host disease (GVHD) after allogeneic hematopoietic stem-cell transplantation has been reduced, 1 , 2 acute GVHD remains a major complication of allogeneic transplantation, occurring in approximately half the transplant recipients. 3 , 4 High-dose systemic glucocorticoids remain the first-line therapy for GVHD, 5 – 9 although just half of patients have complete resolution of GVHD by day 28 after therapy initiation. 6 Patients who do not have a response to GVHD therapy are at high risk for death without relapse of the primary disease for which the transplantation was performed within 6 months after therapy initiation. 10 – 13 We previously reported that a model . . .

Haemopoietic-cell transplantation (HCT) is an intensive therapy used to treat high-risk haematological malignant disorders and other life-threatening haematological and genetic diseases. The main complication of HCT is graft-versus-host disease (GVHD), an immunological disorder that affects many organ systems, including the gastrointestinal tract, liver, skin, and lungs. The number of patients with this complication continues to grow, and many return home from transplant centres after HCT requiring continued treatment with immunosuppressive drugs that increases their risks for serious infections and other complications. In this Seminar, we review our understanding of the risk factors and causes of GHVD, the cellular and cytokine networks implicated in its pathophysiology, and current strategies to prevent and treat the disease. We also summarise supportive-care measures that are essential for management of this medically fragile population.

Microbiome-derived metabolites influence intestinal homeostasis and regulate graft-versus-host disease (GVHD), but the molecular mechanisms remain unknown. Here we show the metabolite sensor G-protein-coupled receptor 43 (GPR43) is important for attenuation of gastrointestinal GVHD in multiple clinically relevant murine models. GPR43 is critical for the protective effects of short-chain fatty acids (SCFAs), butyrate and propionate. Increased severity of GVHD in the absence of GPR43 is not due to baseline differences in the endogenous microbiota of the hosts. We confirm the ability of microbiome-derived metabolites to reduce GVHD by several methods, including co-housing, antibiotic treatment, and administration of exogenous SCFAs. The GVHD protective effect of SCFAs requires GPR43-mediated ERK phosphorylation and activation of the NLRP3 inflammasome in non-hematopoietic target tissues of the host. These data provide insight into mechanisms of microbial metabolite-mediated protection of target tissues from the damage caused allogeneic T cells. The microbial metabolite sensor GPR43 has been previously shown to be a crucial modulator of immune responses. Here the authors show GPR43 is required for controlling disease pathology severity in the context of experimental models of GVHD.

The pathophysiology of acute graft-versus-host disease (GVHD) is a complex process that can be conceptualized in three phases. In the first phase, high-dose chemoradiotherapy causes damage to host tissues, including a self-limited burst of inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin 1. These cytokines activate host antigen-presenting cells (APCs). In the second phase, donor T-cells recognize alloantigens on host APCs. These activated T-cells then proliferate, differentiate into effector cells, and secrete cytokines, particularly interferon (IFN)-gamma. In the third phase, target cells undergo apoptosis mediated by cellular effectors (eg, donor cytotoxic T-lymphocytes) and inflammatory cytokines such as TNF-alpha. TNF-alpha secretion is amplified by stimuli such as endotoxin that leaks across damaged gastrointestinal mucosa injured by the chemoradiotherapy in the first phase. TNF-alpha and IFN-gamma cause further injury to gastrointestinal epithelium, causing more endotoxin leakage and establishing a positive inflammatory feedback loop. These events are examined in detail in the following review.

The graft-versus-leukemia (GVL) effect after allogeneic hematopoietic cell transplant (HCT) can prevent relapse but the risk of severe graft-versus-host disease (GVHD) leads to prolonged intensive immunosuppression and possible blunting of the GVL effect. Strategies to reduce immunosuppression in order to prevent relapse have been offset by increases in severe GVHD and nonrelapse mortality (NRM). We recently validated the MAGIC algorithm probability (MAP) that predicts the risk for severe GVHD and NRM in asymptomatic patients using serum biomarkers. In this study we tested whether the MAP could identify patients whose risk for relapse is higher than their risk for severe GVHD and NRM. The multicenter study population (n = 1604) was divided into two cohorts: historical (2006–2015, n = 702) and current (2015–2017, n = 902) with similar NRM, relapse, and survival. On day 28 post-HCT, patients who had not developed GVHD (75% of the population) and who possessed a low MAP were at much higher risk for relapse (24%) than severe GVHD and NRM (16 and 9%); this difference was even more pronounced in patients with a high disease risk index (relapse 33%, NRM 9%). Such patients are good candidates to test relapse prevention strategies that might enhance GVL.

Acute graft-versus-host disease (GVHD) remains a barrier to more widespread application of allogeneic haemopoietic stem-cell transplantation. Vorinostat is an inhibitor of histone deacetylases and was shown to attenuate GVHD in preclinical models. We aimed to study the safety and activity of vorinostat, in combination with standard immunoprophylaxis, for prevention of GVHD in patients undergoing related-donor reduced-intensity conditioning haemopoietic stem-cell transplantation. Between March 31, 2009, and Feb 8, 2013, we did a prospective, single-arm, phase 1/2 study at two centres in the USA. We recruited adults (aged ≥18 years) with high-risk haematological malignant diseases who were candidates for reduced-intensity conditioning haemopoietic stem-cell transplantation and had an available 8/8 or 7/8 HLA-matched related donor. All patients received a conditioning regimen of fludarabine (40 mg/m2 daily for 4 days) and busulfan (3·2 mg/kg daily for 2 days) and GVHD immunoprophylaxis of mycophenolate mofetil (1 g three times a day, days 0–28) and tacrolimus (0·03 mg/kg a day, titrated to a goal level of 8–12 ng/mL, starting day −3 until day 180). Vorinostat (either 100 mg or 200 mg, twice a day) was initiated 10 days before haemopoietic stem-cell transplantation until day 100. The primary endpoint was the cumulative incidence of grade 2–4 acute GVHD by day 100. This trial is registered with ClinicalTrials.gov, number NCT00810602. 50 patients were assessable for both toxic effects and response; eight additional patients were included in the analysis of toxic effects. All patients engrafted neutrophils and platelets at expected times after haemopoietic stem-cell transplantation. The cumulative incidence of grade 2–4 acute GVHD by day 100 was 22% (95% CI 13–36). The most common non-haematological adverse events included electrolyte disturbances (n=15), hyperglycaemia (11), infections (six), mucositis (four), and increased activity of liver enzymes (three). Non-symptomatic thrombocytopenia after engraftment was the most common haematological grade 3–4 adverse event (nine) but was transient and all cases resolved swiftly. Administration of vorinostat in combination with standard GVHD prophylaxis after related-donor reduced-intensity conditioning haemopoietic stem-cell transplantation is safe and is associated with a lower than expected incidence of severe acute GVHD. Future studies are needed to assess the effect of vorinostat for prevention of GVHD in broader settings of haemopoietic stem-cell transplantation. Merck, Leukemia and Lymphoma Society, National Institutes of Health, St Baldrick's Foundation, Michigan Institute for Clinical and Health Research.

Hematopoietic cell transplantation (HCT) is a potentially curative therapy for hematologic malignancies that relies on the graft-versus-leukemia (GVL) effect to eradicate malignant cells. GVL is tightly linked to graft-versus-host disease (GVHD) however, in which donor T cells damage healthy host tissues. Acute GVHD occurs in nearly 50% of patients receiving HCT, and damages the skin, liver, and gastrointestinal (GI) tract. The organ stages are totaled in an overall grade (I–IV), and severe (grade III/IV) GVHD has a high mortality rate (50–70%). In the past decade, serum biomarkers have emerged as an additional potential measurement of acute GVHD severity. The discovery and validation of GVHD biomarkers is a principal objective of the Mount Sinai Acute GVHD International Consortium (MAGIC), a group of 25 HCT centers conducting GVHD research. MAGIC has validated an algorithm that combines two GI biomarkers (ST2 and REG3α) into a single value that estimates the probability of 6 month nonrelapse mortality (NRM) for individual patients, known as the MAGIC algorithm probability (MAP). The MAP reflects GI crypt damage and serves as a ‘liquid biopsy’ of the lower GI tract; it also predicts response to treatment and maximum GVHD severity and is now commercially available and widely used among scores of centers in clinical practice. The MAP is the focus of this review, with consideration of the categorization of types of biomarkers as defined by the United States National Institutes of Health (NIH) and Food and Drug Administration (FDA).

Acute graft-versus-host disease (GVHD) and leukemic relapse are the two major obstacles to successful outcomes after allogeneic bone marrow transplantation (BMT), an effective therapy for hematological malignacies. Several studies have demonstrated that the dys-regulation of proinflammatory cytokines and the loss of gastrointestinal tract integrity contribute to GVHD, whereas the donor cytotoxic responses are critical for graft-versus-leukemia (GVL) preservation. Suberoylanilide hydroxamic acid (SAHA) is currently in clinical trials as an antitumor agent; it inhibits the activity of histone deacetylases and at low doses exhibits antiinflammatory effects by reducing the production of proinflammatory cytokines. Using two well characterized mouse models of BMT, we have studied the effects of SAHA on GVHD severity and GVL activity. Administration of SAHA from day +3 to day +7 after BMT reduced serum levels of the proinflammatory cytokines and decreased intestinal histopathology, clinical severity, and mortality from acute GVHD compared with vehicle-treated animals. However, SAHA had no effect on donor T cell proliferative and cytotoxic responses to host antigens in vivo or in vitro. When mice received lethal doses of tumor cells at the time of BMT, administration of SAHA did not impair GVL activity and resulted in significantly improved leukemia-free survival by using two different tumor and donor/recipient combinations. These findings reveal a critical role for histone deacetylase inhibition in the proinflammatory events contributing to GVHD and suggest that this class of pharmacologic agents may provide a strategy to reduce GVHD while preserving cytotoxic T cell responses to host antigens and maintaining beneficial GVL effects.

With improvements in breast imaging and image-guided interventions, there is interest in ablative techniques for breast cancer. Cryosurgery initiates inflammation and leaves tumor-specific antigens intact, which may induce an anti-tumor immune response. To help define the mechanisms involved in the cryoimmunologic response, we compared cryosurgery to surgery in a murine model of breast cancer. BALB/c mice with MT-901 tumors underwent cryoablation or resection. Mice successfully treated were re-challenged with MT-901 or RENCA. Serum cytokine levels were analyzed by ELISA. Tumor draining lymph nodes (TDLN) and spleens were harvested, lymphocytes were activated and assessed for a specific anti-tumor response by both an interferon-gamma (IFNgamma) release assay and ELISPOT. NK cell activity was assessed by cytotoxicity against YAC-1, an NK-susceptible cell line. After re-challenge, tumors developed in 86% of mice treated by surgical excision compared to 16% of mice treated by cryosurgery (p=0.025). Cryoablation of MT-901 had no effect on re-challenge with RENCA. Cryoablation led to significantly higher levels of interleukin (IL)-12 (383.6 pg/ml +/- 32.8 versus 251.6 +/- 16.5, p=0.025) and IFN-gamma (1564 pg/ml +/- 49 versus 1244 pg/ml +/- 101, p=0.009), but no changes in IL-4 or IL-10. Tumor-specific T-cell responses were evident after cryosurgery in lymphocytes from TDLN but not from spleen. Cryoablation also increased NK activity compared to surgery (24.5% +/- 17.3 versus 16.5% +/- 5.9, p < 0.001). Cryoablation results in the induction of both a tumor-specific T-cell response in the TDLN and increased systemic NK cell activity, which correlates with rejection of tumors upon re-challenge.