Phase 2 clinical trial evaluating abatacept in patients with steroid-refractory chronic graft-versus-host disease.

Steroid-refractory chronic graft-versus-host disease (cGVHD) after allogeneic transplant remains a significant cause of morbidity and mortality. Abatacept is a selective costimulation modulator, used for the treatment of rheumatologic diseases, and was recently the first drug to be approved by the US Food and Drug Administration for the prophylaxis of acute graft-versus-host disease. We conducted a phase 2 study to evaluate the efficacy of abatacept in steroid-refractory cGVHD. The overall response rate was 58%, seen in 21 out of 36 patients, with all responders achieving a partial response. Abatacept was well tolerated with few serious infectious complications. Immune correlative studies showed a decrease in interleukin -1α (IL-1α), IL-21, and tumor necrosis factor α as well as decreased programmed cell death protein 1 expression by CD4+ T cells in all patients after treatment with abatacept, demonstrating the effect of this drug on the immune microenvironment. The results demonstrate that abatacept is a promising therapeutic strategy for the treatment of cGVHD. This trial was registered at www.clinicaltrials.gov as #NCT01954979.

Cd39 and P2rx7-Wnt signaling enhance blast pathogenicity in an experimental model of acute myeloid leukemia.

Not available.

Personalized tumor vaccine for pancreatic cancer.

BACKGROUND: Pancreatic cancer is a highly lethal malignancy often presenting with advanced disease and characterized by resistance to standard chemotherapy. Immune-based therapies such checkpoint inhibition have been largely ineffective such that pancreatic cancer is categorized as an immunologically "cold tumor". In the present study, we examine the therapeutic efficacy of a personalized cancer vaccine in which tumor cells are fused with dendritic cells (DC) resulting in the broad induction of antitumor immunity. RESULTS: In the KPC spontaneous pancreatic cancer murine model, we demonstrated that vaccination with DC/KPC fusions led to expansion of pancreatic cancer specific lymphocytes with an activated phenotype. Remarkably, vaccination led to a reduction in tumor bulk and near doubling of median survival in this highly aggressive model. In a second murine pancreatic model (Panc02), vaccination with DC/tumor fusions similarly led to expansion of tumor antigen specific lymphocytes and their infiltration to the tumor site. Having shown efficacy in immunocompetent murine models, we subsequently demonstrated that DC/tumor fusions generated from primary human pancreatic cancer and autologous DCs potently stimulate tumor specific cytotoxic lymphocyte responses. CONCLUSIONS: DC/tumor fusions induce the activation and expansion of tumor reactive lymphocytes with the capacity to infiltrate into the pancreatic cancer tumor bed.

Leukemia vaccine overcomes limitations of checkpoint blockade by evoking clonal T cell responses in a murine acute myeloid leukemia model.

We have developed a personalized vaccine whereby patient derived leukemia cells are fused to autologous dendritic cells, evoking a polyclonal T cell response against shared and neo-antigens. We postulated that the dendritic cell (DC)/AML fusion vaccine would demonstrate synergy with checkpoint blockade by expanding tumor antigen specific lymphocytes that would provide a critical substrate for checkpoint blockade mediated activation. Using an immunocompetent murine leukemia model, we examined the immunologic response and therapeutic efficacy of vaccination in conjunction with checkpoint blockade with respect to leukemia engraftment, disease burden, survival and the induction of tumor specific immunity. Mice treated with checkpoint blockade alone had rapid leukemia progression and demonstrated only a modest extension of survival. Vaccination with DC/AML fusions resulted in the expansion of tumor specific lymphocytes and disease eradication in a subset of animals, while the combination of vaccination and checkpoint blockade induced a fully protective tumor specific immune response in all treated animals. Vaccination followed by checkpoint blockade resulted in upregulation of genes regulating activation and proliferation in memory and effector T cells. Long term survivors exhibited increased T cell clonal diversity and were resistant to subsequent tumor challenge. The combined DC/AML fusion vaccine and checkpoint blockade treatment offers unique synergy inducing the durable activation of leukemia specific immunity, protection from lethal tumor challenge and the selective expansion of tumor reactive clones.

Phase 1 clinical trial evaluating abatacept in patients with steroid-refractory chronic graft-versus-host disease.

Steroid-refractory chronic graft-versus-host disease (SR-cGVHD) remains a major cause of morbidity and mortality after allogeneic stem cell transplantation. Innovative immunotherapeutic strategies are urgently needed for the treatment of SR-cGVHD. We conducted a phase 1 clinical trial to evaluate the safety, efficacy, and immune effects of abatacept, a novel immunomodulatory drug that acts as an inhibitor of T-cell activation via costimulatory blockade, in the treatment of SR-cGVHD. The study followed a 3+3 design with 2 escalating abatacept doses: 3 mg/kg and 10 mg/kg, with an expansion cohort treated at 10 mg/kg. Abatacept was well-tolerated with no dose-limiting toxicities. Of the 16 evaluable patients, 44% achieved a clinical partial response per 2005 National Institutes of Health Consensus Criteria. Importantly, abatacept resulted in a 51.3% reduction in prednisone usage in clinical responders (mean baseline, 27 vs 14 mg; P = .01). Increased PD-1 expression on circulating CD4 (P = .009) and CD8 (P = .007) T cells was observed in clinical responders. In summary, abatacept was safe and led to a marked improvement in National Institutes of Health cGVHD scores and a significant reduction in prednisone use. In this cohort of heavily pretreated patients, the results suggest abatacept may be a promising therapeutic agent for SR-cGVHD, and a phase 2 trial has been initiated. This trial was registered at www.clinicaltrials.gov as #NCT01954979.

Hypomethylating agent alters the immune microenvironment in acute myeloid leukaemia (AML) and enhances the immunogenicity of a dendritic cell/AML vaccine.

Acute myeloid leukaemia (AML) is a lethal haematological malignancy characterized by an immunosuppressive milieu in the tumour microenvironment (TME) that fosters disease growth and therapeutic resistance. Hypomethylating agents (HMAs) demonstrate clinical efficacy in AML patients and exert immunomodulatory activities. In the present study, we show that guadecitabine augments both antigen processing and presentation, resulting in increased AML susceptibility to T cell-mediated killing. Exposure to HMA results in the activation of the endogenous retroviral pathway with concomitant downstream amplification of critical mediators of inflammation. In an immunocompetent murine leukaemia model, guadecitabine negatively regulates inhibitory accessory cells in the TME by decreasing PD-1 (also termed PDCD1) expressing T cells and reducing AML-mediated expansion of myeloid-derived suppressor cells. Therapy with guadecitabine results in enhanced leukaemia-specific immunity, as manifested by increased CD4 and CD8 cells targeting syngeneic leukaemia cells. We have previously reported that vaccination with AML/dendritic cell fusions elicits the expansion of leukaemia-specific T cells and protects against disease relapse. In the present study, we demonstrate that vaccination in conjunction with HMA therapy results in enhanced anti-leukaemia immunity and survival. The combination of a novel personalized dendritic cell/AML fusion vaccine and an HMA has therapeutic potential, and a clinical trial investigating this combination is planned.

MUC1-mediated induction of myeloid-derived suppressor cells in patients with acute myeloid leukemia.

Myeloid-derived suppressor cells (MDSCs) play a critical role in promoting immune tolerance and disease growth. The mechanism by which tumor cells evoke the expansion of MDSCs in acute myeloid leukemia (AML) has not been well described. We have demonstrated that patients with AML exhibit increased presence of MDSCs in their peripheral blood, in comparison with normal controls. Cytogenetic studies demonstrated that MDSCs in patients with AML may be derived from leukemic or apparently normal progenitors. Engraftment of C57BL/6 mice with TIB-49 AML led to an expansion of CD11b+ Gr1+ MDSCs in bone marrow and spleen. Coculture of the AML cell lines MOLM-4, THP-1 or primary AML cells with donor peripheral blood mononuclear cells elicited a cell contact-dependent expansion of MDSCs. MDSCs were suppressive of autologous T-cell responses as evidenced by reduced T-cell proliferation and a switch from a Th1 to a Th2 phenotype. We hypothesized that the expansion of MDSCs in AML is accomplished by tumor-derived extracellular vesicles (EVs). Using tracking studies, we demonstrated that AML EVs are taken-up myeloid progenitor cells, resulting in the selective proliferation of MDSCs in comparison with functionally competent antigen-presenting cells. The MUC1 oncoprotein was subsequently identified as the critical driver of EV-mediated MDSC expansion. MUC1 induces increased expression of c-myc in EVs that induces proliferation in the target MDSC population via downstream effects on cell cycle proteins. Moreover, we demonstrate that the microRNA miR34a acts as the regulatory mechanism by which MUC1 drives c-myc expression in AML cells and EVs.

MUC1-C drives myeloid leukaemogenesis and resistance to treatment by a survivin-mediated mechanism.

Acute myeloid leukaemia (AML) is an aggressive haematological malignancy with an unmet need for improved therapies. Responses to standard cytotoxic therapy in AML are often transient because of the emergence of chemotherapy-resistant disease. The MUC1-C oncoprotein governs critical pathways of tumorigenesis, including self-renewal and survival, and is aberrantly expressed in AML blasts and leukaemia stem cells (LSCs). However, a role for MUC1-C in linking leukaemogenesis and resistance to treatment has not been described. In this study, we demonstrate that MUC1-C overexpression is associated with increased leukaemia initiating capacity in an NSG mouse model. In concert with those results, MUC1-C silencing in multiple AML cell lines significantly reduced the establishment of AML in vivo. In addition, targeting MUC1-C with silencing or pharmacologic inhibition with GO-203 led to a decrease in active ß-catenin levels and, in-turn, down-regulation of survivin, a critical mediator of leukaemia cell survival. Targeting MUC1-C was also associated with increased sensitivity of AML cells to Cytarabine (Ara-C) treatment by a survivin-dependent mechanism. Notably, low MUC1 and survivin gene expression were associated with better clinical outcomes in patients with AML. These findings emphasize the importance of MUC1-C to myeloid leukaemogenesis and resistance to treatment by driving survivin expression. Our findings also highlight the potential translational relevance of combining GO-203 with Ara-C for the treatment of patients with AML.

A phase I study of lenalidomide plus chemotherapy with mitoxantrone, etoposide, and cytarabine for the reinduction of patients with acute myeloid leukemia.

Patients with relapsed AML have a poor prognosis and limited responses to standard chemotherapy. Lenalidomide is an immunomodulatory drug that may modulate anti-tumor immunity. We performed a study to evaluate the safety and tolerability of lenalidomide with mitoxantrone, etoposide and cytarabine (MEC) in relapsed/refractory AML. Adult patients with relapsed/refractory AML were eligible for this phase I dose-escalation study. We enrolled 35 patients using a "3 + 3" design, with a 10 patient expansion cohort at the maximum tolerated dose (MTD). Lenalidomide was initially given days 1-14 and MEC days 4-8; due to delayed count recovery, the protocol was amended to administer lenalidomide days 1-10. The dose of lenalidomide was then escalated starting at 5 mg/d (5-10-25-50). The primary objective was tolerability and MTD determination, with secondary outcomes including overall survival (OS). The MTD of lenalidomide combined with MEC was 50 mg/d days 1-10. Among the 35 enrolled patients, 12 achieved complete remission (CR) (34%, 90%CI 21-50%); 30-day mortality was 6% and 60-day mortality 13%. The median OS for all patients was 11.5 months. Among 17 patients treated at the MTD, 7 attained CR (41%); the median OS was not reached while 12-month OS was 61%. Following therapy with MEC and lenalidomide, patient CD4+ and CD8+ T-cells demonstrated increased inflammatory responses to autologous tumor lysate. The combination of MEC and lenalidomide is tolerable with an RP2D of lenalidomide 50 mg/d days 1-10, yielding encouraging response rates. Further studies are planned to explore the potential immunomodulatory effect of lenalidomide and MEC.

Bone marrow stroma protects myeloma cells from cytotoxic damage via induction of the oncoprotein MUC1.

Multiple myeloma (MM) is a lethal haematological malignancy that arises in the context of a tumour microenvironment that promotes resistance to apoptosis and immune escape. In the present study, we demonstrate that co-culture of MM cells with stromal cells results in increased resistance to cytotoxic and biological agents as manifested by decreased rates of cell death following exposure to alkylating agents and the proteosome inhibitor, bortezomib. To identify the mechanism of increased resistance, we examined the effect of the co-culture of MM cells with stroma cells, on expression of the MUC1 oncogene, known to confer tumour cells with resistance to apoptosis and necrosis. Co-culture of stroma with MM cells resulted in increased MUC1 expression by tumour cells. The effect of stromal cell co-culture on MUC1 expression was not dependent on cell contact and was therefore thought to be due to soluble factors secreted by the stromal cells into the microenvironment. We demonstrated that MUC1 expression was mediated by interleukin-6 and subsequent up-regulation of the JAK-STAT pathway. Interestingly, the effect of stromal cell co-culture on tumour resistance was partially reversed by silencing of MUC1 in MM cells, consistent with the potential role of MUC1 in mediating resistance to cytotoxic-based therapies.

Mucin 1 is a potential therapeutic target in cutaneous T-cell lymphoma.

Cutaneous T-cell lymphoma (CTCL) is an aggressive neoplasm with limited treatments for patients with advanced disease. The mucin 1 C-terminal subunit (MUC1-C) oncoprotein plays a critical role in regulating cell proliferation, apoptosis, and protection from cytotoxic injury mediated by reactive oxygen species (ROS). Although CTCL cells exhibit resistance to ROS-induced apoptosis, the expression and functional significance of MUC1 in CTCL have not been previously investigated. Present studies demonstrate that MUC1-C is overexpressed in CTCL cell lines and primary CTCL cells but is absent in resting T cells from healthy donors and B-cell lymphoma cells. We have developed a cell-penetrating peptide that disrupts homodimerization of the MUC1-C subunit necessary for its nuclear translocation and downstream signaling. We show that treatment of CTCL cells with the MUC1-C inhibitor is associated with downregulation of the p53-inducible regulator of glycolysis and apoptosis and decreases in reduced NAD phosphate and glutathione levels. In concert with these results, targeting MUC1-C in CTCL cells increased ROS and, in turn, induced ROS-mediated late apoptosis/necrosis. Targeting MUC1-C in CTCL tumor xenograft models demonstrated significant decreases in disease burden. These findings indicate that MUC1-C maintains redox balance in CTCL cells and is thereby a novel target for the treatment of patients with CTCL.

MUC1-C oncoprotein promotes FLT3 receptor activation in acute myeloid leukemia cells.

Blasts from approximately one-third of patients with acute myeloid leukemia (AML) harbor activating mutations in the FMS-like tyrosine kinase 3 (FLT3) receptor tyrosine kinase that confer a poor prognosis. The Mucin 1-C-terminal subunit (MUC1-C) oncoprotein is aberrantly expressed in AML blasts and stem cells; however, there is no known interaction between MUC1-C and FLT3. The present studies demonstrate that MUC1-C associates with wild-type and mutant FLT3 in AML cells. Targeting MUC1-C with the cell-penetrating peptide inhibitor GO-203 disrupts MUC1-C/FLT3 complexes and downregulates FLT3 activation. GO-203 treatment of AML cells was also associated with inhibition of the FLT3 downstream effectors AKT, extracellular signal-regulated kinase, and STAT5. The results further show that AML cells with FLT3-activating mutations and resistant to the FLT3 inhibitor midostaurin/PKC412 are sensitive to GO-203-induced growth arrest and death. Moreover, GO-203 increases sensitivity of mutant FLT3 AML cells to FLT3 inhibitor treatment. These results indicate that MUC1-C contributes to FLT3 activation in AML cells and that targeting MUC1-C inhibits the FLT3 signaling pathway. Our findings support the development of MUC1-C inhibitors alone and in combination with agents that target FLT3 for the treatment of wild-type and mutant FLT3 AML.

Lenalidomide enhances anti-myeloma cellular immunity.

Lenalidomide is an effective therapeutic agent for multiple myeloma that exhibits immunomodulatory properties including the activation of T and NK cells. The use of lenalidomide to reverse tumor-mediated immune suppression and amplify myeloma-specific immunity is currently being explored. In the present study, we examined the effect of lenalidomide on T-cell activation and its ability to amplify responses to a dendritic cell-based myeloma vaccine. We demonstrate that exposure to lenalidomide in the context of T-cell expansion with direct ligation of CD3/CD28 complex results in polarization toward a Th1 phenotype characterized by increased IFN-γ, but not IL-10 expression. In vitro exposure to lenalidomide resulted in decreased levels of regulatory T cells and a decrease in T-cell expression of the inhibitory marker, PD-1. Lenalidomide also enhanced T-cell proliferative responses to allogeneic DCs. Most significantly, lenalidomide treatment potentiated responses to the dendritic cell/myeloma fusion vaccine, which were characterized by increased production of inflammatory cytokines and increased cytotoxic lymphocyte-mediated lysis of autologous myeloma targets. These findings indicate that lenalidomide enhances the immunologic milieu in patients with myeloma by promoting T-cell proliferation and suppressing inhibitory factors, and thereby augmenting responses to a myeloma-specific tumor vaccine.

Randomized Phase II Trial of Dendritic Cell/Myeloma Fusion Vaccine with Lenalidomide Maintenance after Upfront Autologous Hematopoietic Cell Transplantation for Multiple Myeloma: BMT CTN 1401.

PURPOSE: Vaccination with dendritic cell (DC)/multiple myeloma (MM) fusions has been shown to induce the expansion of circulating multiple myeloma-reactive lymphocytes and consolidation of clinical response following autologous hematopoietic cell transplant (auto-HCT). PATIENTS AND METHODS: In this randomized phase II trial (NCT02728102), we assessed the effect of DC/MM fusion vaccination, GM-CSF, and lenalidomide maintenance as compared with control arms of GM-CSF and lenalidomide or lenalidomide maintenance alone on clinical response rates and induction of multiple myeloma-specific immunity at 1-year posttransplant. RESULTS: The study enrolled 203 patients, with 140 randomized posttransplantation. Vaccine production was successful in 63 of 68 patients. At 1 year, rates of CR were 52.9% (vaccine) and 50% (control; P = 0.37, 80% CI 44.5%, 61.3%, and 41.6%, 58.4%, respectively), and rates of VGPR or better were 85.3% (vaccine) and 77.8% (control; P = 0.2). Conversion to CR at 1 year was 34.8% (vaccine) and 27.3% (control; P = 0.4). Vaccination induced a statistically significant expansion of multiple myeloma-reactive T cells at 1 year compared with before vaccination (P = 0.024) and in contrast to the nonvaccine arm (P = 0.026). Single-cell transcriptomics revealed clonotypic expansion of activated CD8 cells and shared dominant clonotypes between patients at 1-year posttransplant. CONCLUSIONS: DC/MM fusion vaccination with lenalidomide did not result in a statistically significant increase in CR rates at 1 year posttransplant but was associated with a significant increase in circulating multiple myeloma-reactive lymphocytes indicative of tumor-specific immunity. Site-specific production of a personalized cell therapy with centralized product characterization was effectively accomplished in the context of a multicenter cooperative group study. See related commentary by Qazilbash and Kwak, p. 4703.

Rituximab-induced direct inhibition of T-cell activation.

BACKGROUND: Rituximab, an anti-CD20 monoclonal antibody, is reported to increase the T-cell-dependent infection risk. The current study was designed to investigate whether rituximab interferes with T-cell activation. PATIENTS AND METHODS: Patients with non-Hodgkin lymphoma receiving 4-6 courses of 375 mg/m(2) rituximab underwent detailed assessment of T-cell activation pre- and post-rituximab. A similar analysis assessed the in vitro effect of rituximab on T-cell activation in response to allogeneic dendritic cells (allo-DCs) and other stimuli. RESULTS: Patients receiving rituximab exhibited a significant decline in IL-2 and IFN-γ levels in peripheral blood, most prominent after repeated rituximab courses. Evaluation at 3 months after rituximab therapy showed restoration of inflammatory cytokine production. Similarly, in vitro stimulation of peripheral blood mononuclear cells in the presence of rituximab resulted in a significant decrease in T-cell activation markers, inflammatory cytokine production and proliferative capacity. These effects were also observed using B-cell-depleted T cells (CD3(+)CD25(-)CD19(-)) and were accompanied with disappearance of CD3(+)CD20(dim) T-cell population. CONCLUSION: Rituximab administration results in transient, dose-dependent T-cell inactivation. This effect is obtained even in B-cell absence and may increase the infection risk.

Cobomarsen, an Oligonucleotide Inhibitor of miR-155, Slows DLBCL Tumor Cell Growth In Vitro and In Vivo.

PURPOSE: miRNA-155 is an oncogenic miRNA highly expressed in B-cell malignancies, particularly in the non-germinal center B-cell or activated B-cell subtype of diffuse large B-cell lymphoma (ABC-DLBCL), where it is considered a potential diagnostic and prognostic biomarker. Thus, miR-155 inhibition represents an important therapeutic strategy for B-cell lymphomas. In this study, we tested the efficacy and pharmacodynamic activity of an oligonucleotide inhibitor of miR-155, cobomarsen, in ABC-DLBCL cell lines and in corresponding xenograft mouse models. In addition, we assessed the therapeutic efficacy and safety of cobomarsen in a patient diagnosed with aggressive ABC-DLBCL. EXPERIMENTAL DESIGN: Preclinical studies included the delivery of cobomarsen to highly miR-155-expressing ABC-DLBCL cell lines to assess any phenotypic changes, as well as intravenous injections of cobomarsen in NSG mice carrying ABC-DLBCL xenografts, to study tumor growth and pharmacodynamics of the compound over time. To begin to test its safety and therapeutic efficacy, a patient was recruited who underwent five cycles of cobomarsen treatment. RESULTS: Cobomarsen decreased cell proliferation and induced apoptosis in ABC-DLBCL cell lines. Intravenous administration of cobomarsen in a xenograft NSG mouse model of ABC-DLBCL reduced tumor volume, triggered apoptosis, and derepressed direct miR-155 target genes. Finally, the compound reduced and stabilized tumor growth without any toxic effects for the patient. CONCLUSIONS: Our findings support the potential therapeutic application of cobomarsen in ABC-DLBCL and other types of lymphoma with elevated miR-155 expression.

Combining a CAR and a chimeric costimulatory receptor enhances T cell sensitivity to low antigen density and promotes persistence.

Despite the high remission rates achieved using T cells bearing a chimeric antigen receptor (CAR) against hematogical malignancies, there is still a considerable proportion of patients who eventually experience tumor relapse. Clinical studies have established that mechanisms of treatment failure include the down-regulation of target antigen expression and the limited persistence of effective CAR T cells. We hypothesized that dual targeting mediated by a CAR and a chimeric costimulatory receptor (CCR) could simultaneously enhance T cell cytotoxicity and improve durability. Concomitant high-affinity engagement of a CD38-binding CCR enhanced the cytotoxicity of BCMA-CAR and CD19-CAR T cells by increasing their functional binding avidity. In comparison to second-generation BCMA-CAR or CD19-CAR T cells, double-targeted CAR + CD38-CCR T cells exhibited increased sensitivity to recognize and lyse tumor variants of multiple myeloma and acute lymphoblastic leukemia with low antigen density in vitro. In addition, complimentary costimulation by 4-1BB and CD28 endodomains provided by the CAR and CCR combination conferred increased cytokine secretion and expansion and improved persistence in vivo. The cumulatively improved properties of CAR + CCR T cells enabled the in vivo eradication of antigen-low tumor clones, which were otherwise resistant to treatment with conventional CAR T cells. Therefore, multiplexing targeting and costimulation through the combination of a CAR and a CCR is a powerful strategy to improve the clinical outcomes of CAR T cells by enhancing cytotoxic efficacy and persistence, thus preventing relapses of tumor clones with low target antigen density.

Allogeneic induced human FOXP3(+)IFN-gamma(+) T cells exhibit selective suppressive capacity.

Human induced CD4(+)CD25(+) T cells have been shown to express FOXP3, similar to naturally occurring Treg cells (nTreg). However, the suppressive capacity of these cells is still under debate. The current study was designed to investigate functional characteristics of CD25(+)FOXP3(+) derived from CD25(-) T cells. Stimulation of CD25(-) PBMC with allogeneic PBMC resulted in production of CD4(+)CD25(high) T cells. This process was more rapid and prominent when highly mature DC were used for stimulation. The resultant CD4(+)CD25(high) population concurrently exhibited regulatory markers FOXP3, CTLA-4, GITR, and inflammatory cytokines IL-2 and IFN-gamma. These human-induced FOXP3(+)IFN-gamma(+) T cells were shown, for the first time, to markedly inhibit alloreactive T-cell expansion, similar to nTreg. However, in contrast to nTreg, the induced CD4(+)CD25(+)FOXP3(+) cells did not suppress proliferation against a third party donor stimulus or CMV. This suggested that the cell population possessed a more selective suppressive capacity targeted against the original stimulus only. The induced human CD4(+)CD25(+)FOXP3(+) subset derived from CD25(-) T cells, while expressing inflammatory cytokines, exhibits a suppressive cell contact-dependent effect, restricted against T cells responding to the original stimulus. Such unique properties suggest that these cells are potentially ideal for the use as post-transplant GVH disease prophylaxis.

Epstein-Barr virus-encoded EBNA2 alters immune checkpoint PD-L1 expression by downregulating miR-34a in B-cell lymphomas.

Cancer cells subvert host immune surveillance by altering immune checkpoint (IC) proteins. Some Epstein-Barr virus (EBV)-associated tumors have higher Programmed Cell Death Ligand, PD-L1 expression. However, it is not known how EBV alters ICs in the context of its preferred host, the B lymphocyte and in derived lymphomas. Here, we found that latency III-expressing Burkitt lymphoma (BL), diffuse large B-cell lymphomas (DLBCL) or their EBNA2-transfected derivatives express high PD-L1. In a DLBCL model, EBNA2 but not LMP1 is sufficient to induce PD-L1. Latency III-expressing DLBCL biopsies showed high levels of PD-L1. The PD-L1 targeting oncosuppressor microRNA miR-34a was downregulated in EBNA2-transfected lymphoma cells. We identified early B-cell factor 1 (EBF1) as a repressor of miR-34a transcription. Short hairpin RNA (shRNA)-mediated knockdown of EBF1 was sufficient to induce miR-34a transcription, which in turn reduced PD-L1. MiR-34a reconstitution in EBNA2-transfected DLBCL reduced PD-L1 expression and increased its immunogenicity in mixed lymphocyte reactions (MLR) and in three-dimensional biomimetic microfluidic chips. Given the importance of PD-L1 inhibition in immunotherapy and miR-34a dysregulation in cancers, our findings may have important implications for combinatorial immunotherapy, which include IC inhibiting antibodies and miR-34a, for EBV-associated cancers.

Vulnerabilities in mIDH2 AML confer sensitivity to APL-like targeted combination therapy.

Although targeted therapies have proven effective and even curative in human leukaemia, resistance often ensues. IDH enzymes are mutated in ~20% of human AML, with targeted therapies under clinical evaluation. We here characterize leukaemia evolution from mutant IDH2 (mIDH2)-dependence to independence identifying key targetable vulnerabilities of mIDH2 leukaemia that are retained during evolution and progression from early to late stages. Mechanistically, we find that mIDH2 leukaemia are metastable and vulnerable at two distinct levels. On the one hand, they are characterized by oxidative and genotoxic stress, in spite of increased 1-carbon metabolism and glutathione levels. On the other hand, mIDH2 leukaemia display inhibition of LSD1 and a resulting transcriptional signature of all-trans retinoic acid (ATRA) sensitization, in spite of a state of suppressed ATRA signalling due to increased levels of PIN1. We further identify GSH/ROS and PIN1/LSD1 as critical nodes for leukaemia maintenance and the combination of ATRA and arsenic trioxide (ATO) as a key therapeutic modality to target these vulnerabilities. Strikingly, we demonstrate that the combination of ATRA and ATO proves to be a powerfully synergistic and effective therapy in a number of mouse and human mIDH1/2 leukemic models. Thus, our findings pave the way towards the treatment of a sizable fraction of human AMLs through targeted APL-like combinatorial therapies.