IL-12 immunotherapy of murine leukaemia: comparison of systemic versus gene modified cell therapy

Fate control engagement augments NK cell responses in LV/hu-IL-12 transduced sarcoma

INTRODUCTION

NK cells are an untapped resource for cancer therapy. Sarcomas transduced with lentiviruses to express human IL-12 are only cleared in mice bearing mature human NK cells. However, systemic inflammation limits IL-12 utilization. Fate control a.k.a. "suicide mechanisms" regulate unchecked systemic inflammation caused by cellular immunotherapies. Despite increasing utilization, there remains limited data on immune consequences or tumor-directed effects of fate control.

OBJECTIVES

We sought to engage the mutant thymidylate kinase (mTMPK) metabolic fate control system to regulate systemic inflammation and assess the impact on NK cell effector functions.

METHODS

Primary human sarcoma short-passage samples and cell lines were transduced with LV/hu-IL-12_mTMPK engineering expression of IL-12 and an AZT-associated fate control enzyme. We assessed transduced sarcoma responses to AZT engagement and subsequent modulation of NK cell functions as measured by inflammatory cytokine production and cytotoxicity.

RESULTS

AZT administration to transduced (LV/hu-IL-12_mTMPK) short-passage primary human sarcomas and human Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma cell lines, abrogated the robust expression of human IL-12. Fate control activation elicited a specific dose-dependent cytotoxic effect measured by metabolic activity (WST-1) and cell death (Incucyte). NK effector functions of IFN-γ and cytotoxic granule release were significantly augmented despite IL-12 abrogation. This correlated with preferentially induced expression of NK cell activation ligands.

CONCLUSIONS

mTMPK fate control engagement terminates transduced sarcoma IL-12 production and triggers cell death, but also augments an NK cell-mediated response coinciding with metabolic stress activating surface ligand induction. Fate control engagement could offer a novel immune activation method for NK cell-mediated cancer clearance.

Engineered murine IL-21-secreting leukemia cells induce granzyme B+ T cells and CD4+CD44+CD62L- effector memory cells while suppressing regulatory T cells, leading to long-term survival

We have explored the use of an IL-21 cell-based anti-leukemia treatment in a mouse model of acute lymphoblastic leukemia. 70Z/3 leukemia cells, engineered to secrete IL-21 and injected into the peritoneum of syngeneic mice, induced a strong anti-leukemia response resulting in 100% survival. Mice that mounted an IL-21-induced anti-leukemia immune response were immune to the parent cell line (no IL-21) when rechallenged.Above a certain threshold, IL-21 secretion correlated with improved survival compared to mice injected with parent 70Z/3 cells. IL-21 was detected in serum with peak levels on day 7, correlating with the maximum expansion of IL-21-secreting 70Z/3 cells which subsequently were eliminated. Mice injected with IL-21-secreting leukemia cells had elevated numbers of granzyme B⁺ CD4⁺ and CD8⁺ T cells in the peritoneum, compared to mice injected with the parent cell line. Regulatory T cells, which increased greatly in 70Z/3-injected mice, failed to do so in mice injected with IL-21-secreting cells. Upon rechallenge, IL-21-primed mice went through a secondary immune response, primarily requiring CD4⁺ T cells, triggering a significant increase of CD4⁺CD44⁺CD62L^- effector memory T cells. Adoptive transfer of T cells from IL21-primed/rechallenged hosts into naïve mice was successful, indicating that IL-21-primed antigen-experienced T cells convey immunity to naïve mice.Our study shows that delivery of IL-21 in a cell-based anti-leukemia protocol has the potential to induce a potent immune response leading to cancer elimination and long-term immunity-properties which make IL-21 an attractive candidate for cancer immunotherapy. Protecting against tumor antigens as well as improving cancer immunity is justified, as current strategies are limited.

Current challenges in the manufacture of clinical-grade autologous whole cell vaccines for hematological malignancies

Autologous whole cell vaccines use a patient's own tumor cells as a source of antigen to elicit an anti-tumor immune response in vivo. Recently, the authors conducted a systematic review of clinical trials employing these products in hematological cancers that showed a favorable safety profile and trend toward efficacy. However, it was noted that manufacturing challenges limit both the efficacy and clinical implementation of these vaccine products. In the current literature review, the authors sought to define the issues surrounding the manufacture of autologous whole cell products for hematological cancers. The authors describe key factors, including the acquisition, culture, cryopreservation and transduction of malignant cells, that require optimization for further advancement of the field. Furthermore, the authors provide a summary of pre-clinical work that informs how the identified challenges may be overcome. The authors also highlight areas in which future basic research would be of benefit to the field. The goal of this review is to provide a roadmap for investigators seeking to advance the field of autologous cell vaccines as it applies to hematological malignancies.

Sarcoma IL-12 overexpression facilitates NK cell immunomodulation

Interleukin-12 (IL-12) is an inflammatory cytokine that has demonstrated efficacy for cancer immunotherapy, but systemic administration has detrimental toxicities. Lentiviral transduction eliciting IL-12-producing human sarcoma for autologous reintroduction provides localized delivery for both innate and adaptive immune response augmentation. Sarcoma cell lines and primary human sarcoma samples were transduced with recombinant lentivirus engineering expression of human IL-12 (hu-IL-12). IL-12 expressing sarcomas were assessed in vitro and in vivo following implantation into humanized NSG and transgenic human IL-15 expressing (NSG.Tg(Hu-IL-15)) murine models. Lentiviral transduction (LV/hu-IL-12) of human osteosarcoma, Ewing sarcoma and rhabdomyosarcoma cell lines, as well as low-passage primary human sarcomas, engendered high-level expression of hu-IL-12. Hu-IL-12 demonstrated functional viability, eliciting specific NK cell-mediated interferon-γ (IFN-γ) release and cytotoxic growth restriction of spheroids in vitro. In orthotopic xenograft murine models, the LV/hu-IL-12 transduced human sarcoma produced detectable IL-12 and elicited an IFN-γ inflammatory immune response specific to mature human NK reconstitution in the NSG.Tg(Hu-IL-15) model while restricting tumor growth. We conclude that LV/hu-IL-12 transduction of sarcoma elicits a specific immune reaction and the humanized NSG.Tg(Hu-IL-15) xenograft, with mature human NK cells, can define in vivo anti-tumor effects and systemic toxicities. IL-12 immunomodulation through autologous tumor transduction and reintroduction merits exploration for sarcoma treatment.

Interleukin-15 in cancer immunotherapy: IL-15 receptor complex versus soluble IL-15 in a cancer cell-delivered murine leukemia model

Cytokines of the common γ-chain receptor family such as IL-15 are vital with respect to activating immune cells, sustaining healthy immune functions, and augmenting the anti-tumor activity of effector cells, making them ideal candidates for cancer immunotherapy. IL-15, either in its soluble form (IL-15sol) or complexed with IL-15Rα (IL-15Rc), has been shown to exhibit potent anti-tumor activities in various experimental cancer studies. Here we describe the impact of intraperitoneal IL-15 in a cancer cell-delivered IL-15 immunotherapy approach using the 70Z/3-L leukemia mouse model. Whereas both forms of IL-15 led to significantly improved survival rates compared to the parent cell line, there were striking differences in the extent of the improved survival: mice receiving cancer cells secreting IL-15sol showed significantly longer survival and protective long-term immunity compared to those producing IL-15Rc. Interestingly, injection of leukemia cells secreting IL-15sol lead to heightened expansion of CD4⁺ and CD8⁺ T-cell populations in the peritoneum compared to IL-15Rc. Cell-secreted IL-15Rc resulted in an influx and/or expansion of NK1.1⁺ cells in the peritoneum which was much less pronounced in the IL-15sol model. Furthermore, IL-15Rc but not IL-15sol lead to T-cell exhaustion and disease progression. To our knowledge, this is the first study detailing a significantly different biological effect of cell-delivered IL-15sol versus IL-15Rc in a mouse cancer immunotherapy study.

Intratumoral expression using a NFkB-based promoter enhances IL12 antitumor efficacy

Interleukin 12 is a promising anti-cancer agent; however, IL12 systemic administration is hampered by side-effects. Although intratumoral administration of IL12 is giving promising results in clinical trials, only a small percentage of patients show a complete therapeutic response. This outcome could be improved by controlling the IL12 expression window. In this work we have tested the efficacy of a self-processing P2A and codon optimized murine IL12 (mIL12Pop) using inflammation-regulated lentivectors in a syngeneic tumor model. Our results show that implantation of cells expressing mIL12Pop employing either the strong constitutive SFFV promoter or a NFkB-based promoter reduced tumor growth, caused CD8⁺ T cell activation and increased IFNγ production. Importantly, the use of NFkBp-mIL12Pop increased the number of CD8⁺ TILs and improved the remission rate without increasing IL12-serum concentration. Further experiments suggest that there is a threshold intratumoral IL12 concentration that must be reached to trigger an efficient antitumor response and a limit that once surpassed causes detrimental systemic side effects. Altogether, these results demonstrate that using NFKBp-mIL12Pop significantly increases the overall survival of the mice. In summary, this new inflammation-regulated expression system might be useful for the development of new IL12 delivery systems with improved anti-tumor activity and limited toxicity.

Neuraminidase 1 activates insulin receptor and reverses insulin resistance in obese mice

OBJECTIVES

Neuraminidase 1 (NEU1) cleaves terminal sialic acids of glycoconjugates during lysosomal catabolism. It also modulates the structure and activity of cellular surface receptors affecting diverse pathways. Previously we demonstrated that NEU1 activates the insulin receptor (IR) and that NEU1-deficient CathAS190A-Neo mice (hypomorph of the NEU1 activator protein, cathepsin A/CathA) on a high-fat diet (HFD) develop hyperglycaemia and insulin resistance faster than wild-type animals. The major objective of the current work was to reveal the molecular mechanism by which NEU1 desialylation activates the IR and to test if increase of NEU1 activity in insulin target tissues reverses insulin resistance and glucose intolerance.

METHODS

To test if desialylation causes a conformational change in the IR dimer we measured interaction between the receptor subunits by Bioluminescence Resonance Energy Transfer in the HEK293T cells either overexpressing NEU1 or treated with the NEU1 inhibitor. The influence of NEU1 overexpression on insulin resistance was studied in vitro in palmitate-treated HepG2 cells transduced with NEU1-expressing lentivirus and in vivo in C57Bl6 mice treated with HFD and either pharmacological inducer of NEU1, Ambroxol or NEU1-expressing adenovirus. NEU1-deficient CathAS190A-Neo mice were used as a control.

RESULTS

By desialylation of IR, NEU1 induced formation of its active dimer leading to insulin signaling. Overexpression of NEU1 in palmitate-treated HepG2 cells restored insulin signaling, suggesting that increased NEU1 levels may reverse insulin resistance. Five-day treatment of glycemic C57Bl6 mice receiving HFD with the activator of the lysosomal gene network, Ambroxol, increased NEU1 expression and activity in muscle tissue, normalized fasting glucose levels, and improved physiological and molecular responses to glucose and insulin. Ambroxol did not improve insulin sensitivity in obese insulin-resistant CathAS190A-Neo mice indicating that the Ambroxol effect is mediated through NEU1 induction. Sustained increase of liver NEU1 activity through adenovirus-based gene transfer failed to attenuate insulin resistance most probably due to negative feedback regulation of IR expression.

CONCLUSION

Together our results demonstrate that increase of NEU1 activity in insulin target tissues reverses insulin resistance and glucose intolerance suggesting that a pharmacological modulation of NEU1 activity may be potentially explored for restoring insulin sensitivity and resolving hyperglycemia associated with T2DM.

NK-Cell Recruitment Is Necessary for Eradication of Peritoneal Carcinomatosis with an IL12-Expressing Maraba Virus Cellular Vaccine

Despite improvements in chemotherapy and radical surgical debulking, peritoneal carcinomatosis (PC) remains among the most common causes of death from abdominal cancers. Immunotherapies have been effective for selected solid malignancies, but their potential in PC has been little explored. Here, we report that intraperitoneal injection of an infected cell vaccine (ICV), consisting of autologous tumor cells infected ex vivo with an oncolytic Maraba MG1 virus expressing IL12, promotes the migration of activated natural killer (NK) cells to the peritoneal cavity in response to the secretion of IFNγ-induced protein-10 (IP-10) from dendritic cells. The recruitment of cytotoxic, IFNγ-secreting NK cells was associated with reduced tumor burden and improved survival in a colon cancer model of PC. Even in mice with bulky PC (tumors > 8 mm), a complete radiologic response was demonstrated within 8 to14 weeks, associated with 100% long-term survival. The impact of MG1-IL12-ICV upon NK-cell recruitment and function observed in the murine system was recapitulated in human lymphocytes exposed to human tumor cell lines infected with MG1-IL12. These findings suggest that an MG1-IL12-ICV is a promising therapy that could provide benefit to the thousands of patients diagnosed with PC each year. Cancer Immunol Res; 5(3); 211-21. ©2017 AACR.

Preclinical validation: LV/IL-12 transduction of patient leukemia cells for immunotherapy of AML

Interleukin-12 (IL-12) is a potent cytokine that may be harnessed to treat cancer. To date, nearly 100 IL-12-based clinical trials have been initiated worldwide. Yet systemic administration of IL-12 is toxic. Different strategies are being developed to reduce such toxicities by restricting IL-12 distribution. Our previous studies employed lentivector-mediated expression of murine IL-12 in tumor cells and demonstrated effective protection in both mouse leukemia and solid tumor challenge models. In this study, we carried out preclinical validation studies using a novel lentivector to engineer expression of human IL-12 in acute myeloid leukemia blast cells isolated from 21 patients. Acute myeloid leukemia cells were transduced with a bicistronic lentivector that encodes the human IL-12 cDNA as a fusion, as well as a LNGFR (ΔLNGFR)/mutant thymidylate kinase cassette as a marking and cell-fate control element. A range of 20-70% functional transduction efficiencies was achieved. Transduced acute myeloid leukemia cells produced bioactive IL-12 protein and displayed dose-dependent sensitivity to the prodrug 3'-azido-3'-deoxythymidine. In vitro immortalization assays using transduced mouse hematopoietic stem cells demonstrated minimal genotoxic risk from our IL-12 vector. Scale-up transduction and cell processing was subsequently validated in a GMP facility to support our (now approved) Clinical Trial Application (CTA).

Lentiviral vectors in cancer immunotherapy

Basic science advances in cancer immunotherapy have resulted in various treatments that have recently shown success in the clinic. Many of these therapies require the insertion of genes into cells to directly kill them or to redirect the host's cells to induce potent immune responses. Other analogous therapies work by modifying effector cells for improved targeting and enhanced killing of tumor cells. Initial studies done using γ-retroviruses were promising, but safety concerns centered on the potential for insertional mutagenesis have highlighted the desire to develop other options for gene delivery. Lentiviral vectors (LVs) have been identified as potentially more effective and safer alternative delivery vehicles. LVs are now in use in clinical trials for many different types of inherited and acquired disorders, including cancer. This review will discuss current knowledge of LVs and the applications of this viral vector-based delivery vehicle to cancer immunotherapy.

The transduction pattern of IL-12-encoding lentiviral vectors shapes the immunological outcome

In situ modification of antigen-presenting cells garnered interest in cancer immunotherapy. Therefore, we developed APC-targeted lentiviral vectors (LVs). Unexpectedly, these LVs were inferior vaccines to broad tropism LVs. Since IL-12 is a potent mediator of antitumor immunity, we evaluated whether this proinflammatory cytokine could enhance antitumor immunity of an APC-targeted LV-based vaccine. Therefore, we compared subcutaneous administration of broad tropism LVs (VSV-G-LV) with APC-targeted LVs (DC2.1-LV)-encoding enhanced GFP and ovalbumin, or IL-12 and ovalbumin in mice. We show that codelivery of IL-12 by VSV-G-LVs or DC2.1-LVs augments CD4(+) or CD8(+) T-cell proliferation, respectively. Furthermore, we demonstrate that codelivery of IL-12 enhances the CD4(+) TH 1 profile irrespective of its delivery mode, while an increase in cytotoxic and therapeutic CD8(+) T cells was only induced upon VSV-G-LV injection. While codelivery of IL-12 by DC2.1-LVs did not enhance CD8(+) T-cell performance, it increased expression of inhibitory checkpoint markers Lag3, Tim3, and PD-1. Finally, the discrepancy between CD4(+) T-cell stimulation with and without functional CD8(+) T-cell stimulation by VSV-G- and DC2.1-LVs is partly explained by the observation that IL-12 relieves CD8(+) T cells from CD4(+) T-cell help, implying that a T(H)1 profile is of minor importance for antitumor immunotherapy if IL-12 is exogenously delivered.

CD4+ T cell plasticity engenders robust immunity in response to cytokine therapy

CD4⁺ T cells represent an entire arm of the immune system that has hitherto been incompletely understood, but their potential to act as both helper and effector may make them optimal protagonists in immunotherapeutic approaches to treat cancer. Cytokine therapy can activate this population in a manner that ensures maximal diversification of effector function for a robust immune response.

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.

Localized interleukin-12 delivery for immunotherapy of solid tumours

Interleukin (IL)-12 is the key cytokine in the initiation of a Th1 response and has shown promise as an anti-cancer agent; however, clinical trials involving IL-12 have been unsuccessful due to toxic side-effects. To address this issue, lentiviral vectors were used to transduce tumour cell lines that were injected as an autologous tumour cell vaccine. The focus of the current study was to test the efficacy of this approach in a solid tumour model. SCCVII cells that were transduced to produce IL-12 at different concentrations were then isolated. Subcutaneous injection of parental SCCVII cells results in tumour development, while a mixture of IL-12-producing and non-producing cells results in tumour clearance. Interestingly, when comparing mice injected a mixture of SCCVII and either high IL-12-producing tumour cells or low IL-12-producing tumour cells, we observed that mixtures containing small amounts of high producing cells lead to tumour clearance, whereas mixtures containing large amounts of low producing cells fail to elicit protection, despite the production of equal amounts of total IL-12 in both mixtures. Furthermore, immunizing mice with IL-12-producing cells leads to the establishment of both local and systemic immunity against challenge with SCCVII. Using depletion antibodies, it was shown that both CD4(+) and CD8(+) cells are crucial for therapy. Lastly, we have established cell clones of other solid tumour cell lines (RM-1, LLC1 and moto1.1) that produce IL-12. Our results show that the delivery of IL-12 by cancer cells is an effective route for immune activation.

Long-term protection from syngeneic acute lymphoblastic leukemia by CpG ODN-mediated stimulation of innate and adaptive immune responses

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and remains a major cause of mortality in children with recurrent disease and in adults. Despite observed graft-versus-leukemia effects after stem cell transplantation, successful immune therapies for ALL have proven elusive. We previously reported immunostimulatory oligodeoxynucleotides containing CpG motifs (CpG ODN) enhance allogeneic T(h)1 responses and reduce leukemic burden of primary human ALL xenografts. To further the development of CpG ODN as a novel ALL therapy, we investigated the antileukemia activity induced by CpG ODN in a transplantable syngeneic pre-B ALL model. CpG ODN induced early killing of leukemia by innate immune effectors both in vitro and in vivo. Mice were treated with CpG ODN starting 7 days after injection with leukemia to mimic a minimal residual disease state and achieved T cell-dependent remissions of more than 6 months. In addition, mice in remission after CpG ODN treatment were protected from leukemia rechallenge, and adoptive transfer of T cells from mice in remission conferred protection against leukemia growth. To our knowledge, this is the first demonstration that CpG ODN induce a durable remission and ongoing immune-mediated protection in ALL, suggesting this treatment may have clinical utility in patients with minimal residual disease.

Coexpression of IL-18 strongly attenuates IL-12-induced systemic toxicity through a rapid induction of IL-10 without affecting its antitumor capacity

IL-12 is an excellent candidate for the treatment of cancer due to its ability to drive strong antitumor responses. Recombinant IL-12 protein is currently used in cancer patients; however, systemic expression of rIL-12 presents disadvantages including cost and dose limitation due to its toxicity. In this study, we used hydrodynamic shear of cDNA as a tool to achieve systemic expression of IL-12. We found that sustained but toxic levels of serum IL-12 could be generated in 6- to 7-wk-old B6 mice after a single injection of the cDNA. Unexpectedly, we observed that when IL-12 cDNA is coinjected with IL-18 cDNA, IL-12 antitumor activity was maintained, but there was a significant attenuation of IL-12 toxicity, as evidenced by a greater survival index and a diminution of liver enzymes (ALT and AST). Interestingly, after IL-12 plus IL-18 cDNA administration, more rapid and higher IL-10 levels were observed than after IL-12 cDNA treatment alone. To understand the mechanism of protection, we coinjected IL-12 plus IL-10 cDNAs and observed an increase in survival that correlated with diminished serum levels of the inflammatory cytokines TNF-alpha and IFN-gamma. Confirming the protective role of early IL-10 expression, we observed a significant decrease in survival in IL-10 knockout mice or IL-10R-blocked B6 mice after IL-12 plus IL-18 treatment. Thus, our data demonstrate that the high and early IL-10 expression induced after IL-12 plus IL-18 cDNA treatment is critical to rapidly attenuate IL-12 toxicity without affecting its antitumor capacity. These data could highly contribute to the design of more efficient/less toxic protocols for the treatment of cancer.

Adoptive transfer of allogeneic tumor-specific T cells mediates effective regression of large tumors across major histocompatibility barriers

Graft-versus-tumor effects can be achieved after allogeneic bone marrow transplantation in patients with malignancies of the kidney or hematopoietic system but are often accompanied by severe graft-versus-host-disease (GVHD). We sought to maximize graft-versus-tumor while minimizing GVHD using tumor-specific allogeneic effector T cells rather than open-repertoire T cells. We transferred allogeneic CD8(+) pmel-1 or CD4(+) TRP-1 T cells specific for the melanoma-associated antigens, glycoprotein 100 (gp100) and tyrosinase-related protein-1 (TRP-1), respectively, into B16-melanoma-bearing mice. Mice receiving a preparative regimen of nonmyeloablating (5 Gy) total body irradiation experienced the rapid rejection of tumor-specific allogeneic lymphocytes with no impact on tumor growth. However, when mice were given more intense total body irradiation conditioning regimens combined with autologous bone marrow transplantation, adoptively transferred allogeneic tumor-specific T lymphocytes persisted at detectable levels for several weeks and mediated significant regression of large, vascularized tumors. We found that the risk of GVHD was low when tumor-specific T cells were transferred and significant toxicity was observed only when substantial numbers of open repertoire allogeneic naive T cells were mixed with the tumor-specific lymphocytes. Taken together, these data indicate that the use of tumor-specific allogeneic CD8(+) T cells or CD4(+) can result in significant antitumor effects in the absence of measurable GVHD.