Jacopo Mariotti

Regulatory T Cells and Human Myeloid Dendritic Cells Promote Tolerance via Programmed Death Ligand-1

Human regulatory T cells inhibit graft-versus-host disease that can occur after tissue transplantation, in part through expression of programmed death ligand 1 and modulation of antigen-presenting cells.

Ex Vivo Rapamycin Generates Donor Th2 Cells That Potently Inhibit Graft-versus-Host Disease and Graft-versus-Tumor Effects via an IL-4-Dependent Mechanism

Rapamycin (sirolimus) inhibits graft-vs-host disease (GVHD) and polarizes T cells toward Th2 cytokine secretion after allogeneic bone marrow transplantation (BMT). Therefore, we reasoned that ex vivo rapamycin might enhance the generation of donor Th2 cells capable of preventing GVHD after fully MHC-disparate murine BMT. Using anti-CD3 and anti-CD28 costimulation, CD4+ Th2 cell expansion was preserved partially in high-dose rapamycin (10 μM; Th2.rapa cells). Th2.rapa cells secreted IL-4 yet had reduced IL-5, IL-10, and IL-13 secretion relative to control Th2 cells. BMT cohorts receiving wild-type (WT) Th2.rapa cells, but not Th2.rapa cells generated from IL-4-deficient (knockout) donors, had marked Th2 skewing post-BMT and greatly reduced donor anti-host T cell alloreactivity. Histologic studies demonstrated that Th2.rapa cell recipients had near complete abrogation of skin, liver, and gut GVHD. Overall survival in recipients of WT Th2.rapa cells, but not IL-4 knockout Th2.rapa cells, was constrained due to marked attenuation of an allogeneic graft-vs-tumor (GVT) effect against host-type breast cancer cells. Delay in Th2.rapa cell administration until day 4, 7, or 14 post-BMT enhanced GVT effects, moderated GVHD, and improved overall survival. Therefore, ex vivo rapamycin generates enhanced donor Th2 cells for attempts to balance GVHD and GVT effects.

Effect of Age and Previous Autologous Transplantation on Nonrelapse Mortality and Survival in Patients Treated With Reduced-Intensity Conditioning and Allografting for Advanced Hematologic Malignancies

PURPOSE Older age and a previously failed autologous stem-cell transplantation (SCT) are poor prognostic factors for patients receiving myeloablative conditioning and allogeneic SCT. Reduced-intensity conditioning (RIC) regimens achieved a significant reduction of treatment-related mortality, but the influence of previously described risk factors on the outcome of this novel transplantation strategy have not been fully analyzed yet. PATIENTS AND METHODS One hundred fifty patients with advanced hematologic malignancies received a RIC regimen containing thiotepa (10 mg/kg), fludarabine (60 mg/m2), and cyclophosphamide (60 mg/kg), followed by an allogeneic transplantation from an HLA-identical sibling donor. Patients were divided into two cohorts according to age; 90 patients were younger than 55 years, and 60 patients were 55 years old or older. The other pretransplantation characteristics were fairly balanced. RESULTS Actuarial 5-year nonrelapse mortality (NRM) rate was not statistically different between the groups (13% in the younger group and 19% in the older group). By univariate and multivariate analysis, NRM was significantly higher in older patients who previously experienced failure with an autograft. The occurrence of grade 3 to 4 acute graft-versus-host disease (GVHD) or extensive chronic GVHD was associated with a higher NRM in both age cohorts. Overall survival (OS) was not statistically different between the younger (66%) and older groups (61%). By multivariate analysis, refractory disease was associated with a worse OS irrespective of age group. CONCLUSION RIC transplantations show a rather low NRM, and age > or = 55 years per se cannot be considered a risk factor anymore. The timing of transplantation and novel strategies for the prevention of severe GVHD could further improve patient outcome.

A central role for Foxp3+ regulatory T cells in K-Ras-driven lung tumorigenesis

Background K-Ras mutations are characteristic of human lung adenocarcinomas and occur almost exclusively in smokers. In preclinical models, K-Ras mutations are necessary for tobacco carcinogen-driven lung tumorigenesis and are sufficient to cause lung adenocarcinomas in transgenic mice. Because these mutations confer resistance to commonly used cytotoxic chemotherapies and targeted agents, effective therapies that target K-Ras are needed. Inhibitors of mTOR such as rapamycin can prevent K-Ras-driven lung tumorigenesis and alter the proportion of cytotoxic and Foxp3+ regulatory T cells, suggesting that lung-associated T cells might be important for tumorigenesis. Methods Lung tumorigenesis was studied in three murine models that depend on mutant K-Ras; a tobacco carcinogen-driven model, a syngeneic inoculation model, and a transgenic model. Splenic and lung-associated T cells were studied using flow cytometry and immunohistochemistry. Foxp3+ cells were depleted using rapamycin, an antibody, or genetic ablation. Results Exposure of A/J mice to a tobacco carcinogen tripled lung-associated Foxp3+ cells prior to tumor development. At clinically relevant concentrations, rapamycin prevented this induction and reduced lung tumors by 90%. In A/J mice inoculated with lung adenocarcinoma cells resistant to rapamycin, antibody-mediated depletion of Foxp3+ cells reduced lung tumorigenesis by 80%. Likewise, mutant K-Ras transgenic mice lacking Foxp3+ cells developed 75% fewer lung tumors than littermates with Foxp3+ cells. Conclusions Foxp3+ regulatory T cells are required for K-Ras-mediated lung tumorigenesis in mice. These studies support clinical testing of rapamycin or other agents that target Treg in K-Ras driven human lung cancer.

Th2 cell therapy of established acute graft-versus-host disease requires IL-4 and IL-10 and is abrogated by IL-2 or host-type antigen-presenting cells.

Delayed donor Th2 cell infusion permits a graft-versus-tumor (GVT) effect to occur with subsequent amelioration of established graft-versus-host disease (GVHD). Relative to GVHD controls (B6-into-BALB/c model), recipients of delayed Th2 cells (day 14 post-BMT) had increased survival (3/3 experiments [exp]; each exp P < .0001) and reduced GVHD by histology analysis 5 days post-Th2 infusion without increased tumor burden (3 of 3 exp; each exp P < or = .02). Th2 cell-mediated amelioration of GVHD was associated with greatly reduced allospecific IFN-gamma secretion, in vivo augmentation of allospecific IL-4 and IL-10 secretion, and reduction in donor CD8(+) T cell number post-BMT (3 of 3 exp; each comparison, P < or = .003). To better understand the molecular mechanism of this GVHD therapy, Th2 cells were generated from wild-type (WT), IL-4 deficient (KO), or IL-10 KO donors: remarkably, recipients of IL-4 or IL-10 KO Th2 cells had no survival advantage, no improvement in GVHD by histology, no reduction in CD8(+) T cell expansion post-BMT, and no in vivo shift toward type II cytokines. We reasoned that IL-2 and alloantigen availability may be limiting factors for Th2 cell therapy, and as such, evaluated whether coadministration of IL-2 or coinfusion of host-type antigen-presenting cells (APC) might intensify the anti-GVHD effect. However, contrary to these hypotheses, concomitant IL-2 therapy or APC administration fully abrogated the Th2 cell-mediated survival advantage and histology-defined GVHD reduction, reduced Th2 cell expansion in vivo while promoting CD8(+) T cell expansion from cells originating from the initial allograft, and impaired type II polarization in vivo. In conclusion, Th2 cell therapy can rapidly ameliorate severe GVHD via IL-4 and IL-10 mediated mechanisms, and potentially, via IL-2 consumption and APC modulation mechanisms.

Graft rejection as a Th1-type process amenable to regulation by donor Th2-type cells through an interleukin-4/STAT6 pathway.

Graft rejection has been defined as the mirror image of graft-versus-host disease, which is biologically characterized primarily as a Th1-type process. As such, we reasoned that graft rejection would represent a Th1 response amenable to Th2 modulation. Indeed, adoptive transfer of host Th1-type cells mediated rejection of fully MHC-disparate murine bone marrow allografts more effectively than host Th2-type cells. Furthermore, STAT1-deficient host T cells did not differentiate into Th1-type cells in vivo and failed to mediate rejection. We next hypothesized that donor Th2 cell allograft augmentation would prevent rejection by modulation of the host Th1/Th2 balance. In the setting of donor Th2 cell therapy, host-anti-donor allospecific T cells acquired Th2 polarity, persisted posttransplantation, and did not mediate rejection. Abrogation of rejection required donor Th2 cell IL-4 secretion and host T-cell STAT6 signaling. In conclusion, T cell-mediated marrow graft rejection primarily resembles a Th1-type process that can be abrogated by donor Th2 cell therapy that promotes engraftment through a novel mechanism whereby cytokine polarization is transferred to host T cells.

Pharmacologic Inhibition of JAK1/JAK2 Signaling Reduces Experimental Murine Acute GVHD While Preserving GVT Effects

Purpose: Immune-mediated graft-versus-tumor (GVT) effects can occur after allogeneic hematopoietic stem cell transplantation (HSCT), but GVT is tightly linked to its main complication, graft-versus-host disease (GVHD). Strategies aimed at modulating GVHD, while maintaining the GVT effect, are needed to improve the cure rate of transplant. Given the emerging role of Janus-activated kinase (JAK) signaling in lymphoproliferative and myeloproliferative diseases and its established function at dictating T-cell differentiation, we postulated that JAKs might be potential therapeutic targets through a pharmacologic approach. Experimental Design: We examined the effect of JAK1/JAK2 modulation by ruxolitinib in a mouse model of fully MHC mismatched bone marrow transplant comprising in vivo tumor inoculation. Results: JAK1/JAK2 inhibition by ruxolitinib improved both overall survival (P = 0.03) and acute GVHD pathologic score at target organs (P ≤ 0.001) of treated mice. In addition, treatment with ruxolitinib was associated with a preserved GVT effect, as evidenced by reduction of tumor burden (P = 0.001) and increase of survival time (P = 0.01). JAK1/JAK2 inhibition did not impair the in vivo acquisition of donor T-cell alloreactivity; this observation may account, at least in part, to the preserved GVT effect. Rather, JAK1/JAK2 inhibition of GVHD was associated with the modulation of chemokine receptor expression, which may have been one factor in the reduced infiltration of donor T cells in GVHD target organs. Conclusions: These data provide further evidence that JAK inhibition represents a new and potentially clinically relevant approach to GVHD prevention. Clin Cancer Res; 21(16); 3740–9. ©2015 AACR.

Ex Vivo Rapamycin Generates Apoptosis-Resistant Donor Th2 Cells That Persist In Vivo and Prevent Hemopoietic Stem Cell Graft Rejection

Because ex vivo rapamycin generates murine Th2 cells that prevent Graft-versus-host disease more potently than control Th2 cells, we hypothesized that rapamycin would generate Th2/Tc2 cells (Th2/Tc2.R cells) that abrogate fully MHC-disparate hemopoietic stem cell rejection more effectively than control Th2/Tc2 cells. In a B6-into-BALB/c graft rejection model, donor Th2/Tc2.R cells were indeed enriched in their capacity to prevent rejection; importantly, highly purified CD4+ Th2.R cells were also highly efficacious for preventing rejection. Rapamycin-generated Th2/Tc2 cells were less likely to die after adoptive transfer, accumulated in vivo at advanced proliferative cycles, and were present in 10-fold higher numbers than control Th2/Tc2 cells. Th2.R cells had a multifaceted, apoptosis-resistant phenotype, including: 1) reduced apoptosis after staurosporine addition, serum starvation, or CD3/CD28 costimulation; 2) reduced activation of caspases 3 and 9; and 3) increased anti-apoptotic Bcl-xL expression and reduced proapoptotic Bim and Bid expression. Using host-versus-graft reactivity as an immune correlate of graft rejection, we found that the in vivo efficacy of Th2/Tc2.R cells 1) did not require Th2/Tc2.R cell expression of IL-4, IL-10, perforin, or Fas ligand; 2) could not be reversed by IL-2, IL-7, or IL-15 posttransplant therapy; and 3) was intact after therapy with Th2.R cells relatively devoid of Foxp3 expression. We conclude that ex vivo rapamycin generates Th2 cells that are resistant to apoptosis, persist in vivo, and effectively prevent rejection by a mechanism that may be distinct from previously described graft-facilitating T cells.

High response rate and manageable toxicity with an intensive, short-term chemotherapy programme for Burkitt's lymphoma in adults

A very short, intensive paediatric chemotherapy programme was tested in a consecutive monoinstitutional group of 22 adult Burkitts lymphoma (BL) patients. After a 5‐week induction phase of weekly infusions consisting of vincristine, cyclophosphamide, doxorubicin, high‐dose (HD) methotrexate (MTX) plus leukovorin rescue, and intrathecal MTX or cytarabine (ARA‐C), a consolidation phase including HD ARA‐C plus cisplatin was given. Responding patients achieving less than complete response (CR) after completion of the initial induction phase, were promptly shifted to a high‐dose, stem cell supported sequential chemotherapy schema (R‐HDS). Patient characteristics: median age, 35·5 (range 18–76) years; Ann Arbor stage I–II/III–IV, 11/11; bulky disease, 15 patients; LDH ≥ 460 U/l, 11 patients. The median duration of the chemotherapy programme was 62 d (range, 43–94 d). Seventeen patients achieved a CR (77%), one patient died of progressive disease and four partial responders following induction were converted to CR following R‐HDS. Of 17 patients in CR, one died of infectious toxicity while in CR, and one relapsed at 30 months and died of progressive disease. After a median follow‐up of 28·7 months (range, 6–158 months), 16 patients (73%) were in continued CR. Overall survival and progression‐free survival were 77% [95% confidence interval (CI), 52–99%] and 68% (95% CI, 43–99%) respectively. Confirmation of these excellent efficacy and feasibility results by larger, multicentre and prospective studies is warranted.

Rapamycin generates anti-apoptotic human Th1/Tc1 cells via autophagy for induction of xenogeneic GVHD.

Murine T cells exposed to rapamycin maintain flexibility towards Th1/Tc1 differentiation, thereby indicating that rapamycin promotion of regulatory T cells (Tregs) is conditional. The degree to which rapamycin might inhibit human Th1/Tc1 differentiation has not been evaluated. In the presence of rapamycin, T cell costimulation and polarization with IL-12 or IFN-α permitted human CD4+ and CD8+ T cell differentiation towards a Th1/Tc1 phenotype; activation of STAT1 and STAT4 pathways essential for Th1/Tc1 polarity was preserved during mTOR blockade but instead abrogated by PI3 kinase inhibition. Such rapamycin-resistant human Th1/Tc1 cells: (1) were generated through autophagy (increased LC3BII expression; phenotype reversion by autophagy inhibition via 3-MA or siRNA for Beclin1); (2) expressed anti-apoptotic bcl-2 family members (reduced Bax, Bak; increased phospho-Bad); (3) maintained mitochondrial membrane potentials; and (4) displayed reduced apoptosis. In vivo, type I polarized and rapamycin-resistant human T cells caused increased xenogeneic graft-versus-host disease (x-GVHD). Murine recipients of rapamycin-resistant human Th1/Tc1 cells had: (1) persistent T cell engraftment; (2) increased T cell cytokine and cytolytic effector function; and (3) T cell infiltration of skin, gut, and liver. Rapamycin therefore does not impair human T cell capacity for type I differentiation. Rather, rapamycin yields an anti-apoptotic Th1/Tc1 effector phenotype by promoting autophagy.