Tumor-specific dendritic cells generated by genetic redirection of Toll-like receptor signaling against the tumor-associated antigen, erbB2

Bispecific antibody-mediated redirection of NKG2D-CAR natural killer cells facilitates dual targeting and enhances antitumor activity

BACKGROUND

Natural killer group 2D (NKG2D) is an activating receptor of natural killer (NK) cells and other lymphocytes that mediates lysis of malignant cells through recognition of stress-induced ligands such as MICA and MICB. Such ligands are broadly expressed by cancer cells of various origins and serve as targets for adoptive immunotherapy with effector cells endogenously expressing NKG2D or carrying an NKG2D-based chimeric antigen receptor (CAR). However, shedding or downregulation of NKG2D ligands (NKG2DL) can prevent NKG2D activation, resulting in escape of cancer cells from NKG2D-dependent immune surveillance.

METHODS

To enable tumor-specific targeting of NKG2D-expressing effector cells independent of membrane-anchored NKG2DLs, we generated a homodimeric recombinant antibody which harbors an N-terminal single-chain fragment variable (scFv) antibody domain for binding to NKG2D, linked via a human IgG₄ Fc region to a second C-terminal scFv antibody domain for recognition of the tumor-associated antigen ErbB2 (HER2). The ability of this molecule, termed NKAB-ErbB2, to redirect NKG2D-expressing effector cells to ErbB2-positive tumor cells of different origins was investigated using peripheral blood mononuclear cells, ex vivo expanded NK cells, and NK and T cells engineered with an NKG2D-based chimeric receptor.

RESULTS

On its own, bispecific NKAB-ErbB2 increased lysis of ErbB2-positive breast carcinoma cells by peripheral blood-derived NK cells endogenously expressing NKG2D more effectively than an ErbB2-specific IgG₁ mini-antibody able to induce antibody-dependent cell-mediated cytotoxicity via activation of CD16. Furthermore, NKAB-ErbB2 synergized with NK-92 cells or primary T cells engineered to express an NKG2D-CD3ζ chimeric antigen receptor (NKAR), leading to targeted cell killing and greatly enhanced antitumor activity, which remained unaffected by soluble MICA known as an inhibitor of NKG2D-mediated natural cytotoxicity. In an immunocompetent mouse glioblastoma model mimicking low or absent NKG2DL expression, the combination of NKAR-NK-92 cells and NKAB-ErbB2 effectively suppressed outgrowth of ErbB2-positive tumors, resulting in treatment-induced endogenous antitumor immunity and cures in the majority of animals.

CONCLUSIONS

Our results demonstrate that combining an NKAB antibody with effector cells expressing an activating NKAR receptor represents a powerful and versatile approach to simultaneously enhance tumor antigen-specific as well as NKG2D-CAR and natural NKG2D-mediated cytotoxicity, which may be particularly useful to target tumors with heterogeneous target antigen expression.

Engineering cell-based therapies to interface robustly with host physiology

Engineered cell-based therapies comprise a rapidly growing clinical technology for treating disease by leveraging the natural capabilities of cells, including migration, information transduction, and biosynthesis and secretion. There now exists a substantial portfolio of intracellular and extracellular sensors that enable bioengineers to program cells to execute defined responses to specific changes in state or environmental cues. As our capability to construct more sophisticated cellular programs increases, assessing and improving the degree to which cell-based therapies perform as desired in vivo will become an increasingly important consideration and opportunity for technological advancement. In this review, we seek to describe both current capabilities and potential needs for building cell-based therapies that interface with host physiology in a manner that is robust - a phrase we use in this context to describe the achievement of therapeutic efficacy across a range of patients and implementations. We first review the portfolio of sensors and outputs currently available for use in cell-based therapies by highlighting key advancements and current gaps. Then, we propose a conceptual framework for evaluating and pursuing robust clinical performance of engineered cell-based therapies.

hIL-15 gene-modified human natural killer cells (NKL-IL15) augments the anti-human hepatocellular carcinoma effect in vivo

Genetic modification of NK cells may provide new possibilities for developing effective cancer immunotherapy by improving NK cell function and specificity. We previously established human interleukin-15 (hIL-15) gene-modified NKL cells (NKL-IL15) and demonstrated their therapeutic efficiency against human hepatocellular carcinoma (HCC) in vitro. To further assess the applicability of NKL-IL15 cells in adoptive cellular immunotherapy, we further investigated their natural cytotoxicity against HCC in vivo in the present study. NKL-IL15 cells exhibited strong inhibition on the growth of transplanted human HCC tumors in xenograft nude mouse models. Further investigation showed that NKL-IL15 cells expressed much higher levels of cytolysis-related molecules, including NKp80, TRAIL, granzyme B, IFN-γ, and TNF-α, than parental NKL cells in response to HCC stimulation. Moreover, soluble mediators secreted by NKL-IL15 cells decreased HCC cell proliferation; in particular, NKL-IL15-derived TNF-α and IFN-γ induced higher NKG2D ligand expression on target cells and resulted in the increased susceptibility of HCCs to NKL-mediated cytolysis. These results show that hIL-15 gene-modified human NK cells can augment the anti-tumor effect of NK cells on human HCC in vivo and suggest their promising applicability as a new candidate for adoptive immunotherapy against HCCs in the future.

Assessing T-cell responses in anticancer immunotherapy: Dendritic cells or myeloid-derived suppressor cells?

Since dendritic cells operate as professional antigen-presenting cells (APCs) and hence are capable of jumpstarting the immune system, they have been exploited to develop a variety of immunotherapeutic regimens against cancer. In the few past years, myeloid-derived suppressor cells (MDSCs) have been shown to mediate robust immunosuppressive functions, thereby inhibiting tumor-targeting immune responses. Thus, we propose that the immunomodulatory activity of MDSCs should be carefully considered for the development of efficient anticancer immunotherapies.

Synergistic antitumor effect of JAWSII dendritic cells and interleukin 12 in a melanoma mouse model

One of the possible ways to augment dendritic cell (DC) efficacy in presentation of tumor antigens to effector T cells is pulsing them with tumor-cell lysates and incubation with certain immunostimulators. We present the results of an immunotherapeutic approach in a murine B78-H1 model using as a vaccine JAWSII DCs in combination with IL-12. Prior to the in vivo experiments, phenotypic characterization of JAWSII cells was performed and optimal conditions for stimulation of these cells were established. As no production of IL-12 by JAWSII cells was found, injections of this cytokine were introduced to vaccination protocols. Three vaccination schedules have been tested: i) prophylactic, ii) therapeutic-intratumoral, and iii) therapeutic-systemic. In all the protocols, vaccination with pulsed + stimulated JAWSII cells in combination with IL-12 was superior to the treatment with either agent alone and led to eradication of the tumor in several cases. The results of the study may be helpful in planning optimal DC-based therapeutic protocols in cancer patients.

Immunotherapy of malignant disease using chimeric antigen receptor engrafted T cells

Chimeric antigen receptor- (CAR-) based immunotherapy has been under development for almost 25 years, over which period it has progressed from a new but cumbersome technology to an emerging therapeutic modality for malignant disease. The approach involves the genetic engineering of fusion receptors (CARs) that couple the HLA-independent binding of cell surface target molecules to the delivery of a tailored activating signal to host immune cells. Engineered CARs are delivered most commonly to peripheral blood T cells using a range of vector systems, most commonly integrating viral vectors. Preclinical refinement of this approach has proceeded over several years to the point that clinical testing is now being undertaken at several centres, using increasingly sophisticated and therapeutically successful genetic payloads. This paper considers several aspects of the pre-clinical and clinical development of CAR-based immunotherapy and how this technology is acquiring an increasing niche in the treatment of both solid and haematological malignancies.

The inflammatory cytokine, GM-CSF, alters the developmental outcome of murine dendritic cells

Fms-like tyrosine kinase 3 ligand (Flt3L) is a major cytokine that drives development of dendritic cells (DCs) under steady state, whereas GM-CSF becomes a prominent influence on differentiation during inflammation. The influence GM-CSF exerts on Flt3L-induced DC development has not been thoroughly examined. Here, we report that GM-CSF alters Flt3L-induced DC development. When BM cells were cultured with both Flt3L and GM-CSF, few CD8⁺ equivalent DCs or plasmacytoid DCs developed compared to cultures supplemented with Flt3L alone. The disappearance of these two cell subsets in GM-CSF + Flt3L culture was not a result of simple inhibition of their development, but a diversion of the original differentiation trajectory to form a new cell population. As a consequence, both DC progeny and their functions were altered. The effect of GM-CSF on DC subset development was confirmed in vivo. First, the CD8⁺ DC numbers were increased under GM-CSF deficiency (when either GM-CSF or its receptor was ablated). Second, this population was decreased under GM-CSF hyperexpression (by transgenesis or by Listeria infection). Our finding that GM-CSF dominantly changes the regulation of DC development in vitro and in vivo has important implications for inflammatory diseases or GM-CSF therapy.

Targeting lentiviral vectors for cancer immunotherapy

Delivery of tumour-associated antigens (TAA) in a way that induces effective, specific immunity is a challenge in anti-cancer vaccine design. Circumventing tumour-induced tolerogenic mechanisms in vivo is also critical for effective immunotherapy. Effective immune responses are induced by professional antigen presenting cells, in particular dendritic cells (DC). This requires presentation of the antigen to both CD4(+) and CD8(+) T cells in the context of strong co-stimulatory signals. Lentiviral vectors have been tested as vehicles, for both ex vivo and in vivo delivery of TAA and/or activation signals to DC, and have been demonstrated to induce potent T cell mediated immune responses that can control tumour growth. This review will focus on the use of lentiviral vectors for in vivo gene delivery to DC, introducing strategies to target DC, either targeting cell entry or gene expression to improve safety of the lentiviral vaccine or targeting dendritic cell activation pathways to enhance performance of the lentiviral vaccine. In conclusion, this review highlights the potential of lentiviral vectors as a generally applicable 'off-the-shelf' anti-cancer immunotherapeutic.

Genetic modification of natural killer cells for adoptive cellular immunotherapy

Immunotherapy of cancer is a rapidly developing field; one such development is the manipulation and use of natural killer (NK) cells. These cells with 'killer instincts' are an attractive cell to utilize, as they are directly reactive toward tumor and could potentially activate the endogenous adaptive immune system. Their employment in adoptive cell transfer treatments has yielded important results and discoveries, although effective antitumor responses are limited. To address these limitations, NK cells are the target of a new generation of immunotherapy involving gene transfer. The gene modification of immune cells is a relatively recent technique and some groups have targeted NK cells for gene modification to improve their antitumor efficacy. This review will investigate studies describing the gene modification of NK cells and their encouraging antitumor effects.

Biology by design: from top to bottom and back

Synthetic biology is a nascent technical discipline that seeks to enable the design and construction of novel biological systems to meet pressing societal needs. However, engineering biology still requires much trial and error because we lack effective approaches for connecting basic “parts” into higher-order networks that behave as predicted. Developing strategies for improving the performance and sophistication of our designs is informed by two overarching perspectives: “bottom-up” and “top-down” considerations. Using this framework, we describe a conceptual model for developing novel biological systems that function and interact with existing biological components in a predictable fashion. We discuss this model in the context of three topical areas: biochemical transformations, cellular devices and therapeutics, and approaches that expand the chemistry of life. Ten years after the construction of synthetic biology's first devices, the drive to look beyond what does exist to what can exist is ushering in an era of biology by design.

Dendritic cells for active anti-cancer immunotherapy: targeting activation pathways through genetic modification

Tumour immunotherapy has become a treatment modality for cancer, harnessing the immune system to recognize and eradicate tumour cells specifically. It is based on the expression of tumour associated antigens (TAA) by the tumour cells and aims at the induction of TAA-specific effector T cell responses, whilst overruling various mechanisms that can hamper the anti-tumour immune response, e.g. regulatory T cells (Treg). (Re-) activation of effector T cells requires the completion of a carefully orchestrated series of specific steps. Particularly important is the provision of TAA presentation and strong stimulatory signals, delivered by co-stimulatory surface molecules and cytokines. These can only be delivered by professional antigen-presenting cells, in particular dendritic cells (DC). Therefore, DC need to be loaded with TAA and appropriately activated. It is not surprising that an extensive part of DC research has focused on the delivery of both TAA and activation signals to DC, developing a one step approach to obtain potent stimulatory DC. The simultaneous delivery of TAA and activation signals is therefore the topic of this review, emphasizing the role of DC in mediating T cell activation and how we can manipulate DC for the pill-pose of enhancing tumour immunotherapy. As we gain a better understanding of the molecular and cellular mechanisms that mediate induction of TAA-specific T cells, rational approaches for the activation of T cell responses can be developed for the treatment of cancer.

Genetic redirection of T cells for cancer therapy

Adoptive immunotherapy can induce dramatic tumor regressions in patients with melanoma or viral-induced malignancies, but extending this approach to many common cancers has been hampered by a lack of naturally occurring tumor-specific T cells. In this review, we describe recent advances in the genetic modification of T cells using genes encoding cell-surface receptors specific for tumor-associated antigen. Using genetic modification, the many functional properties of T cells, including cytokine secretion and cytolytic capacity, are redirected from their endogenous specificity toward the elimination of tumor cells. Advances in gene design, vectors, and cell production are discussed, and details of the progress in clinical application of this approach are provided.

Lentiviral vectors in gene therapy: their current status and future potential

The concept of gene therapy originated in the mid twentieth century and was perceived as a revolutionary technology with the promise to cure almost any disease of which the molecular basis was understood. Since then, several gene vectors have been developed and the feasibility of gene therapy has been shown in many animal models of human disease. However, clinical efficacy could not be demonstrated until the beginning of the new century in a small-scale clinical trial curing an otherwise fatal immunodeficiency disorder in children. This first success, achieved after retroviral therapy, was later overshadowed by the occurrence of vector-related leukemia in a significant number of the treated children, demonstrating that the future success of gene therapy depends on our understanding of vector biology. This has led to the development of later-generation vectors with improved efficiency, specificity, and safety. Amongst these are HIV-1 lentivirus-based vectors (lentivectors), which are being increasingly used in basic and applied research. Human gene therapy clinical trials are currently underway using lentivectors in a wide range of human diseases. The intention of this review is to describe the main scientific steps leading to the engineering of HIV-1 lentiviral vectors and place them in the context of current human gene therapy.

Characterization of murine dendritic cell line JAWS II and primary bone marrow-derived dendritic cells in Chlamydia muridarum antigen presentation and induction of protective immunity

Dendritic cells (DCs) appear to orchestrate much of the immunobiology of Chlamydia infection, but most studies of Chlamydia-DC interaction have been limited by the availability and heterogeneity of primary bone marrow-derived DCs (BMDCs). We therefore evaluated the immunobiology of Chlamydia muridarum infection in an immortal DC line termed JAWS II derived from BMDCs of a C57BL/6 p53-knockout mouse. JAWS II cells were permissive to the developmental cycle of Chlamydia. Infection-induced cell death was 50 to 80% less in JAWS II cells than in BMDCs. Chlamydia infected JAWS II cells and yielded infectious progeny 10-fold greater than that with primary BMDCs. JAWS II cells showed an expression pattern of cell activation markers and cytokine secretion following Chlamydia infection similar to that of primary BMDCs by up-regulating the expression of CD86, CD40, and major histocompatibility complex class II and secreting significant amounts of interleukin-12 (IL-12) but not IL-10. JAWS II cells pulsed with Chlamydia stimulated immune CD4(+) T cells to secrete gamma interferon. Adoptive transfer of ex vivo Chlamydia-pulsed JAWS II cells conferred levels of immunity on C57BL/6 mice similar to those conferred by primary BMDCs. Taken together, the data show that JAWS II cells exhibit immunobiological characteristics and functions similar to those of primary BMDCs in terms of Chlamydia antigen presentation in vitro and antigen delivery in vivo. We conclude that the JAWS II cell line can substitute for primary BMDCs in Chlamydia immunobiological studies.