Autologous Cytotoxicity Research Articles

Abstract 28: A CRISPR/Cas9 screening platform ImmuT Finder® enables in vivo T cell functional screening and identification of potent immunoregulatory targets for next-generation T cell therapy

Abstract Insufficient tumor infiltration and the presence of various immunosuppressive mechanisms in tumor microenvironment (TME) are two major challenges compromising the anti-tumor efficacy of T cell therapy post infusion. PD-1/PD-L1 blockade has been proven to benefit a portion of late-stage solid tumor patients, however KO of PD-1 may impact the long-term persistence of CAR-T cells, indicating target selection strategies for gene editing of cell therapy products may differ from antibody drugs. To discover potent and/or novel immunoregulatory targets that could maximize the function of T cell therapy, we established an in vivo CRISPR/Cas9 screening platform, ImmuT Finder®, to identify functional gene targets in primary mouse T cells. Notably, T cells carrying sgRNA library have been collected at different harvest time points post transfer based on different screening purposes; library size has been rationally designed to ensure good coverage of the whole library in harvest samples. We selected top targets from in vivo screening and quickly validated their function in primary human T cells in a 96-well array. Then, the top targets that showed significant enhancement in proliferation and function of human T cells were further selected, and their combinational effects on human peripheral T cells and TIL were tested both in vitro and in vivo. Finally, GT307 stands out as the most potent KO combination, which significantly improves serial tumor killing of TCR-T and CAR-T as well as autologous tumor cytotoxicity of TIL in vitro. Furthermore, GT307 KO TCR-T and TIL demonstrated significantly improved tumor control in mouse models than their unedited counterparts and promoted long-term persistence with low support of IL-2. In summary, these data demonstrated that our ImmuT Finder® platform enables discovery of potent and/or novel targets for the development of T cell product and supports the clinical assessment of GT307 as a next-generation T cell therapy. Citation Format: Jingwei Sun, Jiahui Jin, Jingman Wang, Yao Sheng, Fei Li, Lingyun Chen, Yongchao Tan, Zhao Xu, Yanbin Liu, Ke Liu, Yarong Liu. A CRISPR/Cas9 screening platform ImmuT Finder® enables in vivo T cell functional screening and identification of potent immunoregulatory targets for next-generation T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 28.

Vactosertib, a Novel TGFb Type I Receptor Kinase Inhibitor, Improves T-Cell Fitness:a Single-Arm, Phase 1b Trial in Relapsed/Refractory Multiple Myeloma

The prognosis for Multiple Myeloma (MM) patients (pts) has improved substantially over the past two decades with the success of immunomodulatory drugs (IMiDs), monoclonal antibodies, chimeric antigen receptor (CAR) T-cells and bispecific T-cell engagers (BiTEs) that broke the circulus vitiosus of tumor-induced immunosuppression to reengage the immune system. Functional blockade of the transforming growth factor-beta (TGF) signaling pathway improves the efficacy of cytotoxic and immune therapies, therefore we investigator the impact of TGF-inhibition in an steroid free regimn. Methods: We conducted a phase 1b study to determine the safety, efficacy, and maximal tolerated dose (200 mg po bid) of the potent, orally-available TGF type I receptor kinase inhibitor vactosertib in relapsed and/or refractory multiple myeloma (RRMM) pts who had received -2 lines of chemoimmunotherapy in combination with standard dosage of Pomalidomide without any corticosteroids. Results: Twenty one pts were enrolled in the phase 1b dose escalation cohort and received vactosertib plus pomalidomide as indicated (Fig. 1A). Pts' characteristics are described in Table 1The summary of grade 1-4 adverse events is shown (Table 2). A single grade 4 elevated bilirubin (5%) and a single grade 4 elevated lipase (5%) were observed as well as four grade 4 events of decreased neutrophils (19%). Four pts demonstrated a PR, two had a MR, nine had SD and four had disease progression (Fig. 1B). The median time to response for all pts and the responders eight weeks and median duration of response was ~12 weeks. The best overall response for individual pts to treatment is shown (Fig. 1C). Clinical activity was observed across all four dose levels (Table 3). To probe the tumor intrinsic anti-myeloma activity of vactosertib, we first determined the relative effect of vactosertib compared to the IMiDs pomalidomide and lenalidomide (Fig. 2A, B). The effect of vactosertib was greater than that observed with either lenalidomide or pomalidomide. MMCLs and patient CD138 + cells were then treated with vactosertib in combination with pomalidomide, and importantly, vactosertib with pomalidomide synergistically reduced myeloma viability (Fig. 3A). We next probed the systemic, tumor extrinsic effects of vactosertib by analyzing cytokines immune and tumor cells present within patient BM samples. (Fig. 4A). (Fig. 4B). Therefore, we explored the immunophenotype of CD8 + T-cells isolated from patient BM prior to and at the EOT. The relative percentage of T-cells that expressed the immunosuppressive markers programmed cell death-1 (PD-1), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3), B and T lymphocyte attenuator (BTLA), and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) was reduced following treatment relative to their expression prior to treatment (Fig. 4C). Results indicated that vactosertib and pomalidomide treatment in vivo reduced PD-1, TIM3, BTLA and CTLA-4 expression on patient CD8 + T-cells. Next, CD8 + T-cells were isolated from patient peripheral blood and cultured in the presence of TGF-1, vactosertib, pomalidomide, or vactosertib plus pomalidomide (Fig. 5B). Treatment of patient CD8 + T-cells with vactosertib decreased PD-1 expression up to 40% and decreased TIM3 expression up to 65%. Pomalidomide alone did not significantly reduce PD-1, TIM3, BTLA, or LAG-3 on patient CD8 + T-cells. Vactosertib and pomalidomide also reduced TIM3 levels on CD8 + T-cells from most pts. (Fig. 5C, D). (Fig. 5 G, H). Results indicated that vactosertib or pomalidomide did not increase CD138 + cell death (Fig. 5I). Conclusion: Vactosertib combined with pomalidomide was well-tolerated at all doses, had a manageable adverse event profile and induced durable responses with 80% progression-free survival (PFS-6) at 6 months, Vactosertib reduced TGF- in patient bone marrow and suppressed PD-1 expression on CD8 + T-cells and lead to reduction of PD-L1/PD-L2 expression on CD138 + cells and enhanced autologous T-cell cytotoxicity. Taken together, our results support the safety and efficacy of vactosertib to treat RRMM and revealed that vactosertib modulates the T-cell immunophenotype and reinvigorates T-cell fitness.

BTK inhibitors, irrespective of ITK inhibition, increase efficacy of a CD19/CD3-bispecific antibody in CLL

AbstractBruton tyrosine kinase inhibitors (BTKis) are a preferred treatment of patients with chronic lymphocytic leukemia (CLL). Indefinite therapy with BTKis, although effective, presents clinical challenges. Combination therapy can deepen responses, shorten treatment duration, and possibly prevent or overcome drug resistance. We previously reported on a CD19/CD3-bispecific antibody (bsAb) that recruits autologous T-cell cytotoxicity against CLL cells in vitro. Compared with observations with samples from treatment-naïve patients, T cells from patients being treated with ibrutinib expanded more rapidly and exerted superior cytotoxic activity in response to the bsAb. In addition to BTK, ibrutinib also inhibits interleukin-2 inducible T-cell kinase (ITK). In contrast, acalabrutinib, does not inhibit ITK. Whether ITK inhibition contributes to the observed immune effects is unknown. To better understand how BTKis modulate T-cell function and cytotoxic activity, we cultured peripheral blood mononuclear cells (PBMCs) from BTKi-naive and ibrutinib- or acalabrutinib-treated CLL patients with CD19/CD3 bsAb in vitro. T-cell expansion, activation, differentiation, and cytotoxicity were increased in PBMCs from patients on treatment with either BTKi compared with that observed for BKTi-naïve patients. BTKi therapy transcriptionally downregulated immunosuppressive effectors expressed by CLL cells, including cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and CD200. CTLA-4 blockade with ipilimumab in vitro increased the cytotoxic activity of the bsAb in BTKi-naïve but not BTKi-treated PBMCS. Taken together, BTKis enhance bsAb-induced cytotoxicity by relieving T cells of immunosuppressive restraints imposed by CLL cells. The benefit of combining bsAb immunotherapy with BTKis needs to be confirmed in clinical trials.

Neddylation Pathway Regulates Treg Differentiation and T Cell Function in Chronic Lymphocytic Leukemia (CLL) Ex Vivo and Murine In Vivo Studies

Introduction: Inhibitors of B-cell receptor associated kinases (e.g., Bruton tyrosine kinase and phoshpoinotiside-3 kinase) have led to significant improvement in outcomes of patients with CLL. Furthermore, such therapies have immunomodulatory effects. This is particularly relevant given that T cells from patients with CLL are functionally compromised and demonstrate impaired immune synapse formation, adhesion, migration and cytotoxicity. It is critical to improve understanding of the immunomodulatory properties of the novel agents as this will help understand their effect on the immune system in CLL, mitigate toxicities as well as inform future drug development. Pevonedistat, (MLN4924) forms an irreversible covalent adduct with NEDD8, a ubiquitin-like modifier, thereby inhibiting the NEDD8-activating enzyme (NAE). This leads to decreased neddylation and reduced activity of cullin-RING E3 ubiquitin ligases (CRLs). Ultimately, a decrease in CRL activity leads to reduced ubiquitination and proteasomal degradation of CRL substrates, extending the half-life of these proteins, including inhibitor of NFκB (IκB). We have shown that pevonedistat abrogates NFκB activation in CLL cells. Importantly, NFκB activation is indispensable in T-cell activation. However, there is paucity of data regarding the immune effects of targeting neddylation. Here we address this knowledge gap and demonstrate that NAE inhibition may have favorable immunomodulatory effects in CLL. Methods: Peripheral blood mononuclear cells were isolated from patients with CLL and T cells were purified using Dynabeads. Pevonedistat was provided by Millennium Pharmaceuticals, Inc. (Cambridge, MA). For gene expression analysis, FACS-sorted naïve CD4+ T cells were pre-treated with pevonedistat for 1 hour prior to T-cell receptor (TCR; αCD3/CD28) stimulation; RNA was harvested 3 or 24 hours after stimulation and analyzed on a Clariom S microarray chip. For polarization assays, FACS-sorted naïve CD4+ T cells were TCR-activated for 7 days under Th1/2/17/Treg-differentiation conditions. BALB/c mice were administered 60 mg/kg pevonedistat SC twice weekly for 3 weeks and T cell populations were analyzed by flow cytometry. Results: In vitro treatment of T cells with pevonedistat led to rapid reduction in neddylated cullins and stabilization of pIκBα. NAE inhibition did not impede proximal TCR signaling following TCR stimulation (pZAP70, pERK). GSEA demonstrated downmodulation of NFκB and IL-2 signaling pathways in pevonedistat-treated cells by 3 h. Despite this, CD4/CD8+ T cells exhibited normal induction of early activation markers (CD40L, CD69). By contrast, we observed reduced expression of CD38, HLA-DR and PD-1 and diminished CD25 following continuous treatment with pevonedistat for 72 h. This was accompanied by dose-dependent decrease in IL-2 secretion and reduced proliferation of the CD4/CD8+ T cell subsets (CFSE), but no apoptosis. Sorted naive T cells treated with pevonedistat in Th/Treg polarizing conditions exhibited an increase in IFNγ secretion and a decrease in IL-4, suggesting a shift toward Th1 phenotype. Furthermore, we observed a robust decrease of the inducible Treg (iTreg) FoxP3+ population. Loss of iTregs was accompanied by ablated IL-2/STAT5 signaling. Concurrently, we observed a modest increase in Th17 subpopulation following NAE inhibition. We found increased expression of HIF-1α, a CRL target, in pevonedistat-treated T cells, which may have contributed to this phenomenon. To mimic the clinical pharmacokinetics of pevonedistat, we performed 2 h pulse treatment with pevonedistat prior to TCR stimulation. Under these conditions NFκB activity fully recovered by 24 h. Importantly, allogeneic (OCI-LY19 cells) and autologous (CD40L-stimulated CLL cells) T-cell cytotoxicity, perforin and granzyme B production were not disrupted by NAE inhibition. In vivo administration of pevonedistat in immunocompetent BALB/c mice resulted in a decrease of Treg population, confirming in vitro data. Conclusions: Our data suggest that targeting neddylation may help rebalance T cells towards healthy immune subsets in CLL via the reduction of the Treg/Th2 phenotypes. Combined with our earlier reports that targeting NAE kills CLL cells under lymph node-mimicking conditions, these data provide a strong rationale for continued investigation of pevonedistat in CLL and lymphoid malignancies. Disclosures Berger: Millennium Pharmaceuticals, Inc., Cambridge, MA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Danilov:TG Therapeutics: Consultancy; Takeda Oncology: Research Funding; MEI: Research Funding; Verastem Oncology: Consultancy, Other: Travel Reimbursement , Research Funding; AstraZeneca: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Seattle Genetics: Consultancy; Gilead Sciences: Consultancy, Research Funding; Bristol-Meyers Squibb: Research Funding; Aptose Biosciences: Research Funding; Bayer Oncology: Consultancy, Research Funding; Celgene: Consultancy; Curis: Consultancy; Abbvie: Consultancy; Pharmacyclics: Consultancy; Janssen: Consultancy.

Peste des Petits Ruminants Virus Fusion and Hemagglutinin Proteins Trigger Antibody-Dependent Cell-Mediated Cytotoxicity in Infected Cells.

The adaptive immune system utilizes multiple effector mechanisms to clear viral infections. Among those antibody-dependent cell-mediated cytotoxicity (ADCC) can help recognize and clear virus-infected cells. In the present work we evaluated ADCC contribution to immunity in two economically important viral diseases that affect ruminants: bluetongue and peste des petits ruminants. Immune sera obtained from sheep experimentally infected with bluetongue virus (BTV) serotype 8 or peste des petits ruminant virus (PPRV) IC'89 were used for this study. PPRV immune sera could bind to the surface of PPRV-infected ovine B cells while BTV immune sera was unable to bind to the surface of BTV-infected sheep cells but could recognize intracellular BTV antigens. BTV and PPRV immune serum ADCC potency was established using an ovine autologous cytotoxicity assay that employed an NK cell-enriched fraction as effector cells and a virus-infected B cell-enriched fraction as target cells. In this system, immune sera triggered ADCC against PPRV-infected cells, but not against BTV-infected cells. PPRV immune sera could recognize PPRV fusion and hemagglutinin proteins on the surface of transfected cells, and enhanced lysis of these cells in ADCC assays. This indicated that these viral antigens are natural ADCC targets during PPRV infection. The present work describes a novel effector immune mechanism against PPRV in the natural host that could contribute to virus clearance highlighting the importance of studying protective immune mechanisms to improve current vaccines by invoking all effector arms of immunity.

Immunomodulatory Effects of Pevonedistat, a NEDD8-Activating Enzyme (NAE) Inhibitor, in Chronic Lymphocytic Leukemia (CLL)

Introduction: T cells from patients with CLL and lymphoma show highly impaired immune synapse formation, cytotoxic function, and adhesion and migration capabilities. Recent advances in immunooncology led to the emergence of therapeutic agents that permit reversal of T-cell exhaustion in cancer. However, rational development of novel combination approaches in immunotherapy requires detailed understanding of how targeted therapies influence T-cell function.We have shown that pevonedistat (TAK-924), an investigational NAE inhibitor, abrogates NFκB activation in CLL cells. Pevonedistat forms a covalent adduct with NEDD8, a ubiquitin-like modifier, thereby disrupting its interaction with NAE. This leads to reduced activity of Cullin-RING ligases (CRLs), a group of ubiquitin ligases that require modification by NEDD8 for their function. Ultimately, a decrease in CRL activity leads to reduced ubiquitination and proteasomal degradation of CRL substrates, extending the half-life of these proteins, including inhibitor of NFκB (IκB). Moreover, NFκB is critical in T-cell function. However, limited data exist on the effects of targeting neddylation on T-cell response. Here, we demonstrate that targeting neddylation in vitro preserves T-cell functionality and may lead to favorable T-cell population shifts in CLL.Methods: Peripheral blood mononuclear cells were isolated from patients with CLL (n=50), and T cells were purified using Dynabeads. Pevonedistat was obtained from Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (Cambridge, MA).Results: In vitro T-cell receptor (TCR; CD3/CD28) stimulation induced T-cell activation and proliferation. Continuous treatment of T cells with pevonedistat led to rapid (2 hour) disruption of cullin neddylation, followed by a significant reduction in activity of NFκB and NFAT as assessed by immunoblotting and immunofluorescence. Despite this reduction, CD4 and CD8 T cells continued to respond to TCR stimulation, with relative abundance of early markers of activation (CD40L, CD69). However, we observed reduced expression of CD25 and PD-1 at 72 hours. Continuous treatment with pevonedistat led to a dose-dependent decrease in IL-2 secretion and reduced proliferation of the CD4 T-cell subset (CFSE, Ki-67) but did not induce apoptosis. Unlike CLL cells, CD4 T cells did not undergo DNA re-replication and G2/M arrest in response to pevonedistat.We further analyzed T-cell subsets following TCR stimulation. Concurrent treatment with pevonedistat led to an increase in IFNγ-secreting CD4 T cells, whereas IL-4 production decreased, suggesting a shift toward the Th1 phenotype. Furthermore, we observed a robust decrease of the iTreg population, accompanied by downregulation of FoxP3 mRNA and protein within the CD4 T-cell subset, indicating that targeting neddylation may help to reverse the immunosuppressive phenotype in CLL.To mimic the in vivo pharmacokinetics of pevonedistat, we performed drug washouts where CLL-derived T cells were exposed to 2-hour pulse treatment with 1 µM pevonedistat prior to TCR stimulation. Under these conditions, cullin neddylation and NFκB activity began to recover by 8 hours, with near complete recovery by 24 hours. Moreover, pevonedistat did not disrupt allogeneic (OCI-LY19 cells) or autologous (CD40L-stimulated CLL cells) T-cell cytotoxicity. Meanwhile, CD8 T cells continued to produce perforin and granzyme B.Conclusions: Our data suggest that pharmacologic targeting of NAE preserves T-cell cytotoxic function and may enhance anti-tumor immunity in CLL. Combined with our earlier reports that targeting NAE kills CLL cells under lymph node-mimicking conditions, these data provide a strong rationale for continued investigation of pevonedistat in CLL and lymphoid malignancies. DisclosuresSpurgeon:Bristol Myers Squibb: Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Oncternal: Research Funding; Acerta: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Pharmacyclics: Consultancy, Research Funding; MEI Pharma: Consultancy. Berger:Takeda Pharmaceuticals International Co.: Employment. Danilov:Gilead Sciences: Consultancy, Research Funding; Astra Zeneca: Consultancy; Verastem: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Aptose Biosciences: Research Funding; Takeda Oncology: Research Funding; TG Therapeutics: Consultancy; Bayer Oncology: Consultancy, Research Funding.

Abstract IA13: Novel therapeutic targets in multiple myeloma

Abstract Multiple myeloma (MM) is a model for using in vitro and in vivo models of the tumor in its bone marrow (BM) microenvironment to target tumor cells, tumor-host interactions, and the BM milieu in novel therapeutics. To date proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), histone deacetylase (HDAC) inhibitors, and monoclonal antibodies (MoAbs) have translated from the bench to the bedside and FDA approval, extending the survival of patients 3- to 4-fold. Further progress is advancing in novel strategies to target protein homeostasis, novel immune therapies, and treatments targeting genomic anomalies. PIs trigger apoptosis in MM cells, modulate adhesion molecule expression on tumor and BM cells, and regulate cytokine secretion in the BM milieu. They also promote osteoclast apoptosis and promote new bone formation. Ubiquitin proteasome receptor inhibitor and ubiquitylating agent inhibitors target the ubiquitin proteasome pathway upstream of the proteasome and can overcome PI resistance. HDAC6 selective inhibitors block aggresomal protein degradation and synergize with PIs. IMiDs bind and activate cereblon ubiquitin 3 ligase activity, with degradation of IZF1/3 in MM cells. Excitingly, prototype degronimids bind to ubiquitin ligase complexes including cereblon, VHL, or MDM2, as well as bind and selectively target substrates for degradation. Multiple immune therapies are promising in MM. IMiDs activate T, NK, and NK-T cells and target regulatory T cells, at least in part related to degradation of alios/ikaros and thereby stimulating IL-2 transcription and secretion. IMiDS also bind a novel substrate p-53 related protein kinase (PRPK) and mediate cereblon-independent MM cytotoxicity. MoAbs targeting SLAMF7 and CD38 have moved rapidly from the bench to the bedside, with enhanced activity in combination with IMiDs or PIs. B-cell maturation antigen (BCMA) is a selective plasma cell antigen currently targeted with immunotoxin and bispecific antibodies, as well as by targeting its ligands BAFF and APRIL to downregulate growth and survival signaling. Checkpoint inhibitors are expressed on MM cells, as well as immune effector cells and accessory cells (myeloid-derived suppressor cells and plasmacytoid dendritic cells), which promote MM cell growth and drug resistance. Importantly, checkpoint inhibitors can overcome the effect of these accessory cells and trigger autologous cytotoxicity of patient MM cells. Moreover, IMiDs can enhance checkpoint inhibitor-induced cytotoxicity. Vaccination of patients with smoldering MM with peptide-based vaccines can trigger autologous anti-MM immunity, which is enhanced by IMiDs and shifted to a central memory phenotype by HDAC 6 inhibitor. Finally, BCMA CART cell therapies are achieving complete responses even in MM refractory to all other therapies. Combinations of these immune approaches offer the most promise. Finally, MM is very genetically heterogeneous, with ongoing DNA damage. RAS mutations are most common, with transient responses to MEK/ERK inhibitor therapy. Patients with t(11:14) MM and overexpression of BCL-2 can respond to venetoclax. Ongoing efforts are presently delineating mechanisms underlying the extensive constitutive and ongoing DNA damage, including homologous recombination, APEX nuclease activity, pan-nuclease activity, and APOBEC activity, in order to develop selective inhibitors. Other strategies target the consequences of the genetic heterogeneity, such as targeting STK4 activity to restore p73-mediated apoptotic signaling in MM with decreased YAP1 copy number. Additionally, MM with MYC amplification has high levels of replicative stress and reactive oxygen species (ROS); ATR inhibitors to block replicative stress response in combination with agents to increase ROS trigger synergistic MM cytotoxicity. Finally, targeting fast-forward loops or regulatory loops in MM, such as KDM3A-KLF2-IRF4 axis, offers great promise to target both the tumor and its microenvironment. Citation Format: Kenneth Anderson. Novel therapeutic targets in multiple myeloma [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr IA13.

Evidence for Increased Response to Induced Endoplasmic Reticulum Stress in Myeloid Cells in Acquired Aplastic Anemia

Autoimmune response targeting the hematopoietic stem cells highlights the current understanding of acquired aplastic anemia (AAA) pathogenesis. Upregulation of the unfolded protein response is the cell's rejoinder to a variety of stresses, which either result in restoring homeostasis or cell death by increased expression of the transcription factor C/EBP homologous protein. We hypothesized that there is an inherent increased sensitivity to various cellular stressors, including the ones that target endoplasmic reticulum (ER) in AAA leading to a decreased proliferation and potentially contributing to susceptibility to autologous cytotoxicity. Using archived bone marrow aspirate samples, we demonstrate that the culture-expanded AAA myeloid cells have an increased response to ER stress induced by tunicamycin leading to decreased cell proliferation. Within the AAA myeloid samples, we show that the disease status, active versus response to therapy at the time of sampling does not alter the ER stress response. This is the first report, which provides evidence for an inherent defective stress control in the myeloid cells as a possible mechanism of evolution of the disease process in AAA.

Immune checkpoint inhibitors enhance cytotoxicity of cytokine-induced killer cells against human myeloid leukaemic blasts.

We studied whether blockade of inhibitory receptors on cytokine-induced killer (CIK) cells by immune checkpoint inhibitors could increase its anti-tumour potency against haematological malignancies. CIK cultures were generated from seven normal donors and nine patients with acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL) or multiple myeloma (MM). The inhibitory receptors B and T lymphocyte attenuator, CD200 receptor, lymphocyte activation gene-3 (LAG-3) and T cell immunoglobulin and mucin-domain-containing-3 (TIM-3) were present at variable percentages in most CIK cultures, while cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed death-1 (PD-1) and killer cell immunoglobulin-like receptors (KIR2DL1/2/3) were expressed at low level in most cultures. Without blockade, myeloid leukaemia cells were susceptible to autologous and allogeneic CIK-mediated cytotoxicity. Blockade of KIR, LAG-3, PD-1 and TIM-3 but not CTLA-4 resulted in remarkable increase in killing against these targets, even in those with poor baseline cytotoxicity. ALL and MM targets were resistant to CIK-mediated cytotoxicity, and blockade of receptors did not increase cytotoxicity to a meaningful extent. Combination of inhibitors against two receptors did not further increase cytotoxicity. Interestingly, potentiation of CIK killing by blocking antibodies was not predicted by expression of receptors on CIK and their respective ligands on the targets. Compared to un-activated T and NK cells, blockade potentiated the cytotoxicity of CIK cells to a greater degree and at a lower E:T ratio, but without significant increase in cytotoxicity against normal white cell. Our findings provide the basis for clinical trial combining autologous CIK cells with checkpoint inhibitors for patients with AML.

Optimal effector functions in human natural killer cells rely upon autocrine bone morphogenetic protein signaling.

Natural killer (NK) cells are critical for innate tumor immunity due to their specialized ability to recognize and kill neoplastically transformed cells. However, NK cells require a specific set of cytokine-mediated signals to achieve optimal effector function. Th1-associated cytokines promote effector functions that are inhibited by the prototypic Th2 cytokine IL4 and the TGFβ superfamily members TGFβ1 and activin-A. Interestingly, the largest subgroup of the TGFβ superfamily are the bone morphogenetic proteins (BMP), but the effects of BMP signaling on NK cell effector functions have not been evaluated. Here, we demonstrate that blood-circulating NK cells express type I and II BMP receptors, BMP-2 and BMP-6 ligands, and phosphorylated isoforms of Smad-1/-5/-8, which mediate BMP family member signaling. In opposition to the inhibitory effects of TGFβ1 or activin-A, autocrine BMP signaling was supportive to NK cell function. Mechanistic investigations in cytokine and TLR-L-activated NK cells revealed that BMP signaling optimized IFNγ and global cytokine and chemokine production, phenotypic activation and proliferation, and autologous dendritic cell activation and target cytotoxicity. Collectively, our findings identify a novel auto-activatory pathway that is essential for optimal NK cell effector function, one that might be therapeutically manipulated to help eradicate tumors. Cancer Res; 74(18); 5019-31. ©2014 AACR.

A Phase Ii Study (Nct01883323) Evaluating the Infusion of Autologous Tumor-Infiltrating Lymphocytes (Til) and Low-Dose Interleukin-2 (Il-2) Therapy Following Non-Myeloablative Lymphodepletion Using Cyclophosphamide and Fludarabine in Patients with Metastatic Melanoma

ABSTRACT Background: The Immune Therapy Program at the Princess Margaret Cancer Centre, Toronto, is the first adoptive cell therapy (ACT) program in Canada. Current TIL protocols aim to achieve anti-tumor responses by using minimally cultured TIL, pretreating with high dose lymphodepleting chemotherapy and IV administration of high dose IL-2, a T cell growth factor. High dose IL-2 can result in significant treatment-limiting toxicity and suitable patients must be highly selected. Our group has modified this approach to expand TIL using a rapid expansion protocol (REP) in moderate dose IL-2 (Nguyen 2010), thus enabling moderate dose IL-2 administration post TIL infusion. Trial design: A single arm phase II trial in metastatic melanoma was designed to assess safety and response of our modified TIL protocol. TIL in vitro expansion and function is assessed by flow cytometry for CD3, CD4, and CD8 phenotype, and, in response to autologous tumor, cytotoxicity and IFN-γ production. TIL are then prepared for autologous infusion using a REP. Eligible patients must have measureable stage IV melanoma or unresectable stage III disease with a lesion suitable for TIL production, a life expectancy of > 3 months, ECOG ≤1 and stable brain metastases for ≥3 months from time of definitive treatment. Patients are admitted on day -5 for preconditioning with cyclophosphamide (60mg/kg for 2 days) and fludarabine (25mg/m2 for 5 days). TIL infusion (1x10^10–1.6x10^11 cells) occurs on day 0 and moderate dose daily IL-2 (125,000 IU/kg subcutaneous injection) commences three hours after TIL infusion, for 10 days with 2 days rest after 5 days; toxicity allowing. The first radiological assessment of response is at 4 weeks post TIL infusion and q3 monthly thereafter. Ex vivo immune monitoring is ongoing to assess persistence and function of infused T cells. This study has opened, and patients are actively undergoing treatment. The trial follows a two-stage Simon design that allows for early stopping for futility. A response rate of 5% or lower is considered too low to be of interest (p0 = 0.05), while if the treatment has a response rate of 30% or more it will be considered to be effective (pA = 0.3). If there is ≥1 responder documented in the first 5 subjects treated, the study will continue to a target of 12 patients (type I error rate of 0.084). Disclosure: All authors have declared no conflicts of interest.

The natural killer–activating receptor, NKG2D, on CD3+CD8+ T cells plays a critical role in identifying and killing autologous myeloma cells

The NKG2D receptor, one of the natural killer (NK) cell-activating receptors, is expressed on the surface of CD3+CD8+ T cells, γδ+ T cells, NK cells, NKT cells, and a few CD4+ T cells. We show, for the first time, a critical role for the NKG2D receptor on CD3+CD8+ T cells isolated from myeloma patients, in identifying and killing autologous myeloma cells isolated from the same patients' marrow. We also show that blocking NKG2D using anti-NKG2D reverses the cytotoxicity while blocking HLA-I using antibodies does not have the same effect, showing that the autologous cytotoxicity is NKG2D dependent and major histocompatibility complex (MHC)-I independent. We further confirmed the NKG2D specificity by small interfering RNA (siRNA) down regulation of NKG2D receptor. Using ex vivo expansion methods that enrich for NKG2D+CD3+CD8+ T cells, we investigated whether these ex vivo expanded NKG2D+CD3+CD8+ T cells would recognize and lyse autologous and allogeneic myeloma cells, independent of T-cell receptor or MHC-I expression. Myeloma cell lysis by the NKG2D+CD3+CD8+ T cells correlated with the amount of NKG2D ligand expression. With receptor-ligand interaction, interferon-γ and tumor necrosis factor-α were released. Blocking the NKG2D receptor by using either monoclonal antibodies or siRNAs inhibited the receptor's function and prevented myeloma cell lysis. Clinical trials are ongoing to determine a correlation with the number and function of NKG2D+CD3+CD8+ T cells and clinical outcomes in transplanted myeloma patients, including lymphocyte recovery following transplant and overall survival.

Ex-vivo expanded human NK cells express activating receptors that mediate cytotoxicity of allogeneic and autologous cancer cell lines by direct recognition and antibody directed cellular cytotoxicity

BackgroundThe possibility that autologous NK cells could serve as an effective treatment modality for solid tumors has long been considered. However, implementation is hampered by (i) the small number of NK cells in peripheral blood, (ii) the difficulties associated with large-scale production of GMP compliant cytolytic NK cells, (iii) the need to activate the NK cells in order to induce NK cell mediated killing and (iv) the constraints imposed by autologous inhibitory receptor-ligand interactions. To address these issues, we determined (i) if large numbers of NK cells could be expanded from PBMC and GMP compliant cell fractions derived by elutriation, (ii) their ability to kill allogeneic and autologous tumor targets by direct cytotoxitiy and by antibody-mediated cellular cytotoxicity and (iii) defined NK cell specific receptor-ligand interactions that mediate tumor target cell killing.MethodsHuman NK cells were expanded during 14 days. Expansion efficiency, NK receptor repertoire before and after expansion, expression of NK specific ligands, cytolytic activity against allogeneic and autologous tumor targets, with and without the addition of chimeric EGFR monoclonal antibody, were investigated.ResultsCell expansion shifted the NK cell receptor repertoire towards activation and resulted in cytotoxicity against various allogeneic tumor cell lines and autologous gastric cancer cells, while sparing normal PBMC. Blocking studies confirmed that autologous cytotoxicity is established through multiple activating receptor-ligand interactions. Importantly, expanded NK cells also mediated ADCC in an autologous and allogeneic setting by antibodies that are currently being used to treat patients with select solid tumors.ConclusionThese data demonstrate that large numbers of cytolytic NK cells can be generated from PBMC and lymphocyte-enriched fractions obtained by GMP compliant counter current elutriation from PBMC, establishing the preclinical evidence necessary to support clinical trials utilizing autologous expanded NK cells, both directly and in combination with monoclonal antibodies in future cell-based immunotherapy in select solid tumors.

Adenovirus mediated transfer of p53, GM-CSF and B7-1 suppresses growth and enhances immunogenicity of glioma cells

Objectives: Malignant gliomas are good targets for gene therapy because they have been proven incurable with conventional treatments. However, malignant gliomas are genetically and physiologically highly heterogeneous, and current gene therapy interventions have been designed to target only a few variations of this kind of disease. Hence, we developed a combined gene therapy approach using a recombinant adenovirus carrying human wild-type p53 (WT-p53), granulocyte–macrophage colony-stimulating factor (GM-CSF) and B7-1 genes (designated BB-102) to combat the disease.Methods: Human malignant glioma cells U251 and U87 were transduced with BB-102. Expression of WT-p53, GM-CSF and B7-1 genes were determined by Western blot, enzyme linked immunosorbent assay and flow cytometric analysis, respectively. Growth rates were determined by serial cell counts. Apoptosis was detected by flow cytometric analysis. Proliferation of autologous peripheral blood lymphocytes (PBLs) and cytotoxicity against primary glioma cells were assessed by cell proliferation and cytotoxicity assay kits, respectively.Results: By the transduction of BB-102, high expression levels of the three exogenesis genes were detected in glioma cells. Cell growth was inhibited and apoptosis was induced. Significant proliferation of autologous PBLs and specific cytotoxicity against primary glioma cells were also induced by the infection of BB-102 in vitro, with the effect being more evident than that of Ad-p53.Conclusion: These results suggest that glioma cell vaccination co-transferred with p53, GM-CSF and B7-1 genes may be a feasible and effective immunotherapeutic approach in glioma treatments.

Bortezomib treatment and regulatory T-cell depletion enhance the antitumor effects of adoptively infused NK cells

AbstractLigation of inhibitory receptors renders natural killer (NK) cells inactive against autologous tumors. Recently, the proteasome inhibitor bortezomib was shown to sensitize tumors to autologous NK-cell cytotoxicity in vitro. Here, we show bortezomib augments the antitumor effects of syngeneic NK-cell infusions in tumor-bearing animals; this effect is further enhanced in regulatory T cell (Treg cell)–depleted hosts. In vitro, bortezomib-treated tumors had higher tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) and perforin/granzyme-mediated caspase-8 activity, which enhanced their susceptibility to NK-cell lysis. Bioluminescence imaging of mice with established tumors showed treatment with bortezomib and syngeneic NK cells reduced tumor growth and prolonged survival compared with controls receiving bortezomib or NK cells alone. In contrast, tumor progression was not delayed when animals received bortezomib and perforin-deficient NK cells, showing drug-induced augmentation in NK-cell cytotoxicity was mediated through perforin/granzyme. Furthermore, tumor growth was slower in bortezomib-treated recipients when host Treg cells were eradicated with anti-CD25 antibody before infusing NK cells compared with mice without Treg-cell ablation (tumor doubling time, 16.7 vs 4.9 days, respectively; P = .02). These findings suggest that depletion of Treg cells followed by bortezomib-induced tumor sensitization to autologous NK cells could be used as a novel strategy to treat cancer.

Immune mediated autologous cytotoxicity against hematopoietic precursor cells in patients with myelodysplastic syndrome

An activated immune system has been observed in patients with myelodysplastic syndrome but its exact contribution to disease development and control is not fully clarified. On the one hand an activated and skewed T-cell repertoire has been reported, but on the other hand, decreased natural killer cell function has been found. Immune activation could reflect undesired autoimmune reactions against normal hematopoietic precursor cells as well as effective immune-surveillance against dysplastic clones. We have investigated immune effector cells (lymphocyte subsets, lymphocyte activation markers, and natural killer cells) of 40 low and intermediate risk myelodysplastic syndrome patients and compared them to those of 10 age-matched healthy donors. Furthermore, we have analyzed the cytotoxic capacity of effector cells against autologous bone marrow hematopoietic precursor cells of 8 myelodysplastic syndrome patients and 2 healthy donors. In myelodysplastic syndrome patients, we have found an activated state of lymphocytes, determined by increased percentages of effector T cells with cytotoxic profile, more skewing of the T-cell receptor Vbeta (TCR-Vbeta) repertoire, and decreased frequencies of regulatory T cells, when compared to healthy donors. The percentage of natural killer cells did not differ between myelodysplastic syndrome patients and healthy donors, but natural killer cells of myelodysplastic syndrome patients expressed increased levels of granzyme B. Finally, we have demonstrated non-MHC restricted autologous cytotoxicity up to 90% against aberrant hematopoietic precursor cells, presumably mediated by natural killer cells. Our data point to a role for active immune-surveillance in myelodysplastic syndrome, as demonstrated by activated T cells and TCR-Vss skewing. Autologous cytotoxicity against hematopoietic precursor cells was natural killer cell dependent, which points to an additional role for the innate immune system in immune-surveillance of myelodysplastic syndrome patients.

Tumor‐infiltrating lymphocytes derived from human renal cell carcinoma: Clonal analysis of its characteristics

To assess the characteristics of activated tumor-infiltrating lymphocytes (TIL), we report the isolation, growth response, and functional analysis of a CD4(-) CD8(+) TIL-clone derived from human renal cell carcinoma (RCC). Bulk TILs were expanded from a human RCC and the lymphocytes were separated into a CD8(+) enriched population. Subsequently, using the limiting dilution technique, a TIL clone was established and its growth response, phenotype and cytotoxic activity were analyzed. A clone, T16-13, by day 94 numbering 1 x 10(7) cells, was harvested and characterized as a CD4(-) CD8(+) clone. On day 144, the cytotoxic activity of this clone against the autologous tumor was relatively high (2.3 +/- 0.7 LU(30)/10(6) cells). Meanwhile, against allogeneic renal tumors, there was no cytotoxic activity (-0.1 LU(30)/10(6) cells). A TIL clone possessing modest autologous tumor-specific cytotoxicity can be isolated from human RCC. The characteristics analysis of various TIL clones may provide a better understanding of an RCC tumor microenvironment and may help to establish new modalities for the treatment of patients with metastatic kidney cancer.

Activated T Cell-Mediated Immunotherapy with a Chimeric Receptor Against CD38 in B-Cell Malignancies.

CD38 is expected to be one of the most useful molecular targets on the surface of malignant B-cells. T cell-mediated immunotherapy with a chimeric receptor could provide a powerful tool for treating cancer. However, since CD38 is also expressed on effector cells such as activated T cells, NK cells, and monocytes, these cells with the chimeric receptor could be eliminated by autologous cytotoxicity through the interaction with the antigen. In this study, we developed a novel methodology for enhancing the survival and clonal expansion of T lymphocytes expressing an anti-CD38 chimeric receptor. Hut78 T cells, which express very little CD38, retrovirally transduced with the anti-CD38 chimeric receptor showed powerful cytotoxic activity against B cell lines expressing CD38, such as HT (lymphoma), RPMI8226 (myeloma), 380 (ALL-Ph1−) and OP-1 (ALL-Ph1+) cells (mean specific cytotoxicity was 97.94% ± 0.31% after four days of culture in vitro). However, in activated human T cells and Jurkat cells constitutively expressing CD38, the recovery rate of cells transduced with the chimeric receptor was extremely low, because the cells eradicated each other and/or themselves by inducing apoptosis. To block the interaction of the anti-CD38 chimeric receptor with CD38 antigen, we incubated activated T cells and Jurkat cells in medium supplemented with an anti-CD38 antibody before the transduction. The number of viable cells harvested after the transduction was dramatically increased by the antibody in a dose-dependent manner. Using this method, we prepared human peripheral T cells bearing the chimeric receptor and injected them into NOD/SCID mice, which were transplanted with HT cells labeled with luciferase. Lucuferase activity was not detectable in 13 days in five of six mice with T cells transduced with the chimeric receptor. In contrast, the activity had a rapid and steady increase in all of the mice injected with vector-transduced T cells. These results clearly showed that even though human peripheral T cells express any molecule on their surface, an antibody could protect T cells transduced with a chimeric receptor-containing vector from cytolysis, and apoptosis. These findings may provide us with a powerful tool for improving T cell-mediated targeting therapy.

T Cell Mediated Autologous Cytotoxicity Against Hematopoietic Precursor Cells in Low and Intermediate-1 Risk Myelodysplastic Syndrome.

The immune system plays a role in the pathogenesis of myelodysplastic syndrome (MDS) but its precise contribution to disease development and control is not fully clarified. T cell activation could reflect undesired autoimmune reactions against normal hematopoietic precursor cells as well as effective immune-surveillance against dysplastic clones. We have investigated lymphocyte subsets and activation markers of 42 low risk and intermediate-1 risk MDS patients and compared them to those of intermediate-2 risk, high risk MDS patients, and healthy donors. In low and intermediate-1 risk MDS patients, we have found an activated state of lymphocytes, determined by increased percentages of effector T cells with cytotoxic profile, increased number of clonal expansions, increased frequencies of Wilms' Tumor 1 (WT1) specific lymphocytes and decreased regulatory T cell activation, as compared to healthy donors. Moreover, we demonstrate autologous T cell mediated cytotoxicity against aberrant hematopoietic precursor cells. These findings provide evidence for the existence of immune-surveillance in the pathogenesis of low and intermediate-1 risk MDS patients. Our data are important for adequate evaluation of the role of immune-modulatory drugs in the future and justify the reconsideration of the role of immune-suppressing therapy for low and intermediate-1 risk MDS patients.

Phase I study of intraperitoneal MHC unrestricted adoptive cell therapy with TALL-104 cells in patients with peritoneal carcinosis

3054 Background: TALL-104 is an irradiated human leukemic T cell line (CD3+, CD4- CD8+, CD56+, CD16-) grown in IL-2- containing medium, that has the ability to kill tumor cells in preclinical models in a MHC unrestricted way. A phase I trial in metastatic breast cancer patients, has shown that multiple i.v. infusions (infs) of TALL-104 cells can be given safely. In order to optimise the tumor:effector cell ratio, we have designed a phase I study of intraperitoneal infs of γ-irradiated TALL-104 cells. Methods: Patients (pts) with peritoneal carcinosis from ovarian or gastrointestinal tumors not responding to at least 2 lines of chemotherapy were eligible for study entry. The treatment included 5 i.p. infs (day 1, 3, 5, 15, 30) and the study aimed to test three cell dose levels: 1 x 108, 5 x 108, 2.5 x 109. End points of the study were: safety, kinetic of TALL-104 cells on ascites (if present) and peripheral blood (PB) by PCR, levels of cytokines (TGF-β, GM-CSF, IL-2, IL-4, IL-10, IFN-γ, TNF-a and -β, HGF, sIL-2R, sICAM-1) on ascites and serum, and cytotoxicity of autologous PB mononuclear cells (MNC) against K562 cells. Results: So far 10 pts have been treated: 6 with GI and 4 with ovarian cancer; 7 patients had ascites. Five pts have been treated at the 1st and 5 pts at the 2nd dose level. No treatment-related adverse events were observed. TALL-104 cells were detected in ascites (100 % of the pts) and PB (43 % of the pts) up to 48 hrs after the infs. Cytotoxicity of MNC showed a mean 5-fold increase at day 3 through 7 and it was still evident at day 30 in both dose levels. Cytokine levels are available for the first 5 pts. In one pt 18-fold increase of TNF-a was observed in ascites after the first infusion with a peak of 40-fold at day 15. sIL-2R and sICAM-1 showed both a mean 1.2-fold and 1.5-fold increase in serum in ascites respectively up to day 45. TGF-β1 level increased in average 3.3-fold in serum and 1.5-fold in ascites during the same observation period. HGF showed a mean 1.2-fold increase both in serum and ascites. Conclusions: These preliminary results show that the i.p. infusion of TALL-104 is safe. Moreover, the increased autologous cell-mediated cytotoxicity and the levels of soluble cytokines after i.p. infs indicate that TALL-104 cells may elicit potential antitumor activity. No significant financial relationships to disclose.