Finding a place for tumor-specific T cells in targeted cancer therapy

The armed oncolytic adenovirus ZD55-IL-24 eradicates melanoma by turning the tumor cells from the self-state into the nonself-state besides direct killing

ZD55-IL-24 is similar but superior to the oncolytic adenovirus ONYX-015, yet the exact mechanism underlying the observed therapeutic effect is still not well understood. Here we sought to elucidate the underlying antitumor mechanism of ZD55-IL-24 in both immunocompetent and immunocompromised mouse model. We find that ZD55-IL-24 eradicates established melanoma in B16-bearing immunocompetent mouse model not through the classic direct killing pathway, but mainly through the indirect pathway of inducing systemic antitumor immunity. Inconsistent with the current prevailing view, our further results suggest that ZD55-IL-24 can induce antitumor immunity in B16-bearing immunocompetent mouse model in fact not due to its ability to lyse tumor cells and release the essential elements, such as tumor-associated antigens (TAAs), but due to its ability to put a “nonself” label in tumor cells and then turn the tumor cells from the “self” state into the “nonself” state without tumor cell death. The observed anti-melanoma efficacy of ZD55-IL-24 in B16-bearing immunocompetent mouse model was practically caused only by the viral vector. In addition, we also notice that ZD55-IL-24 can inhibit tumor growth in B16-bearing immunocompetent mouse model through inhibiting angiogenesis, despite it plays only a minor role. In contrast to B16-bearing immunocompetent mouse model, ZD55-IL-24 eliminates established melanoma in A375-bearing immunocompromised mouse model mainly through the classic direct killing pathway, but not through the antitumor immunity pathway and anti-angiogenesis pathway. These findings let us know ZD55-IL-24 more comprehensive and profound, and provide a sounder theoretical foundation for its future modification and drug development.

Immunotherapeutic approaches for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

With the introduction of the anti-CD20 monoclonal antibody rituximab, B-cell non-Hodgkin lymphoma was the first malignancy successfully treated with an immunotherapeutic agent. Since then, numerous advances have expanded the repertoire of immunotherapeutic agents available for the treatment of a variety of malignancies, including many lymphoma subtypes. These include the introduction of monoclonal antibodies targeting a variety of cell surface proteins, including the successful targeting of immunoregulatory checkpoint receptors present on T-cells or tumour cells. Additionally, cellular immunotherapeutic approaches utilize T- or Natural Killer-cells generated with chimeric antigen receptors against cell surface proteins or Epstein-Barr virus-associated latent membrane proteins. The following review describes the current state of immunotherapy for non-Hodgkin lymphoma including a summary of currently available data and promising agents currently in clinical development with future promise in the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma.

T cells expressing a LMP1-specific chimeric antigen receptor mediate antitumor effects against LMP1-positive nasopharyngeal carcinoma cells in vitro and in vivo

T cells modified with chimeric antigen receptor are an attractive strategy to treat Epstein-Barr virus (EBV) associated malignancies. The EBV latent membrane protein 1 (LMP1) is a 66-KD integral membrane protein encoded by EBV that consists of transmembrane-spanning loops. Previously, we have identified a functional signal chain variable fragment (scFv) that specifically recognizes LMP1 through phage library screening. Here, we constructed a LMP1 specific chimeric antigen receptor containing anti-LMP1 scFv, the CD28 signalling domain, and the CD3ζ chain (HELA/CAR). We tested its functional ability to target LMP1 positive nasopharyngeal carcinoma cells. HELA/CAR cells were efficiently generated using lentivirus vector encoding the LMP1-specific chimeric antigen receptor to infect activated human CD3+ T cells. The HELA/CAR T cells displayed LMP1 specific cytolytic action and produced IFN-γ and IL-2 in response to nasopharyngeal carcinoma cells overexpressing LMP1. To demonstrate in vivo anti-tumor activity, we tested the HELA/CAR T cells in a xenograft model using an LMP1 overexpressing tumor. Intratumoral injection of anti-LMP1 HELA/CAR-T cells significantly reduced tumor growth in vivo. These results show that targeting LMP1 using HELA/CAR cells could represent an alternative therapeutic approach for patients with EBV-positive cancers.

Enhanced frequency and potential mechanism of B regulatory cells in patients with lung cancer

BACKGROUND

Regulatory T cells (Tregs) and B cells (Bregs) play an important role in the development of lung cancer. The present study aimed to investigate the phenotype of circulating Tregs and Bregs in patients with lung cancer and explore potential mechanism by which lung cancer cells act on the development of both.

METHODS

Patients with lung cancer (n = 268) and healthy donors (n = 65) were enrolled in the study. Frequencies of Tregs and Bregs were measured by flow cytometry with antibodies against CD4, CD25, CD127, CD45RA, CD19, CD24, CD27 and IL-10 before and after co-cultures. qRT-PCR was performed to evaluate the mRNA levels of RANTES, MIP-1α, TGF-β, IFN-γ and IL-4.

RESULTS

We found a lower frequency of Tregs and a higher frequency of Bregs in patients with lung cancer compared to healthy donors. Co-culture of lung cancer cells with peripheral blood mononuclear cells could polarize the lymphocyte phenotype in the similar pattern. Lipopolysaccharide (LPS)-stimulated lung cancer cells significantly modulated regulatory cell number and function in an in vitro model.

CONCLUSION

We provide initial evidence that frequencies of peripheral Tregs decreased or Bregs increased in patients with lung cancer, which may be modulated directly by lung cancer cells. It seems cancer cells per se plays a crucial role in the development of tumor immunity.

Proliferation-linked apoptosis of adoptively transferred T cells after IL-15 administration in macaques

The adoptive transfer of antigen-specific effector T cells is being used to treat human infections and malignancy. T cell persistence is a prerequisite for therapeutic efficacy, but reliably establishing a high-level and durable T cell response by transferring cultured CD8⁺ T cells remains challenging. Thus, strategies that promote a transferred high-level T cell response may improve the efficacy of T cell therapy. Lymphodepletion enhances persistence of transferred T cells in mice in part by reducing competition for IL-15, a common γ-chain cytokine that promotes T cell memory, but lymphodepleting regimens have toxicity. IL-15 can be safely administered and has minimal effects on CD4⁺ regulatory T cells at low doses, making it an attractive adjunct in adoptive T cell therapy. Here, we show in lymphoreplete macaca nemestrina, that proliferation of adoptively transferred central memory-derived CD8⁺ effector T (T_CM/E) cells is enhanced in vivo by administering IL-15. T_CM/E cells migrated to memory niches, persisted, and acquired both central memory and effector memory phenotypes regardless of the cytokine treatment. Unexpectedly, despite maintaining T cell proliferation, IL-15 did not augment the magnitude of the transferred T cell response in blood, bone marrow, or lymph nodes. T cells induced to proliferate by IL-15 displayed increased apoptosis demonstrating that enhanced cycling was balanced by cell death. These results suggest that homeostatic mechanisms that regulate T cell numbers may interfere with strategies to augment a high-level T cell response by adoptive transfer of CD8⁺ T_CM/E cells in lymphoreplete hosts.

Generation of CD19-chimeric antigen receptor modified CD8+ T cells derived from virus-specific central memory T cells

The adoptive transfer of donor T cells that have been genetically modified to recognize leukemia could prevent or treat leukemia relapse after allogeneic HSCT (allo-HSCT). However, adoptive therapy after allo-HSCT should be performed with T cells that have a defined endogenous TCR specificity to avoid GVHD. Ideally, T cells selected for genetic modification would also have the capacity to persist in vivo to ensure leukemia eradication. Here, we provide a strategy for deriving virus-specific T cells from CD45RA(-)CD62L(+)CD8(+) central memory T (T(CM)) cells purified from donor blood with clinical grade reagents, and redirect their specificity to the B-cell lineage marker CD19 through lentiviral transfer of a gene encoding a CD19-chimeric Ag receptor (CAR). Virus-specific T(CM) were selectively transduced by exposure to the CD19 CAR lentivirus after peptide stimulation, and bi-specific cells were subsequently enriched to high purity using MHC streptamers. Activation of bi-specific T cells through the CAR or the virus-specific TCR elicited phosphorylation of downstream signaling molecules with similar kinetics, and induced comparable cytokine secretion, proliferation, and lytic activity. These studies identify a strategy for tumor-specific therapy with CAR-modified T cells after allo-HSCT, and for comparative studies of CAR and TCR signaling.

Induction of tumor immunity following allogeneic stem cell transplantation

The curative potential of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for many hematologic malignancies derives in large part from reconstitution of normal donor immunity and the development of a potent graft-versus-leukemia (GVL) immune response capable of rejecting tumor cell in vivo. Elucidation of the mechanisms of GVL by studies of animal models and analysis of clinical data has yielded important insights into how clinically effective tumor immunity is generated following allo-HSCT. These studies have identified NK cells and B cells as well as T cells as important mediators of the GVL response. A variety of antigenic targets of the GVL response have also been identified, and include tumor-associated antigens as well as minor histocompatibility antigens. The principles of effective GVL can now be applied to the development of novel therapies that enhance the therapeutic benefit of allogeneic HSCT while minimizing the toxicities associated with treatment. Moreover, many components of this approach that result in elimination of tumor cells following allogeneic HSCT can potentially be adapted to enhance the effectiveness of tumor immunity in the autologous setting.

Memory T cells in cancer immunotherapy: which CD8 T-cell population provides the best protection against tumours?

Cancer immunotherapy strategies often fail because of immunosuppressive mechanisms present in the tumour-bearing host. Adoptive T-cell transfer therapy circumvents this problem by activating tumour-specific CD8(+) T cells in vitro and transferring them back into the patient. Classically, effector T cells have been used in these studies because of their potent anti-tumour activity. However, it is becoming apparent that highly activated effector cells may become terminally differentiated, display impaired proliferation and survival in vivo, and mediate short-term anti-tumour effects. In contrast to effector cells, memory cells have enhanced proliferative potential and survival, and the potential to provide more robust and enduring protection against tumours. Here, we discuss key studies in the field of adoptive T-cell transfer, along with some of our own results relating to this area. Based on the body of existing research, it is clear that CD8(+) T cells with memory potential are superior to terminally differentiated effectors in mediating successful tumour clearance. Opinions remain divided as to whether the central memory or effector memory T-cell subset is capable of providing the best protection against tumours. We propose that as these cell types have different but complementary benefits for the anti-tumour immune response, the ideal cell population to use for adoptive T-cell transfer should consist of a heterogeneous mixture of memory cells.

Gene-modified bone marrow cell therapy for prostate cancer

There is a critical need to develop new and effective cancer therapies that target bone, the primary metastatic site for prostate cancer and other malignancies. Among the various therapeutic approaches being considered for this application, gene-modified cell-based therapies may have specific advantages. Gene-modified cell therapy uses gene transfer and cell-based technologies in a complementary fashion to chaperone appropriate gene expression cassettes to active sites of tumor growth. In this paper, we briefly review potential cell vehicles for this approach and discuss relevant gene therapy strategies for prostate cancer. We further discuss selected studies that led to the conceptual development and preclinical testing of IL-12 gene-modified bone marrow cell therapy for prostate cancer. Finally, we discuss future directions in the development of gene-modified cell therapy for metastatic prostate cancer, including the need to identify and test novel therapeutic genes such as GLIPR1.

Spontaneous mammary tumors differ widely in their inherent sensitivity to adoptively transferred T cells

Immunotherapy of cancer can lead to the selection of antigen loss variants, which provides strong rationale to target oncogenes that are essential for tumor growth or viability. To investigate this concept, we tagged the HER2/neu oncogene with epitopes from ovalbumin to confer recognition by T-cell receptor transgenic CD8(+) (OT-I) and CD4(+) (OT-II) T cells. Transgenic mice expressing neu(OT-I/OT-II) developed mammary adenocarcinomas at 6 to 10 months of age. Adoptively transferred naive OT-I cells (with or without OT-II cells) proliferated vigorously on encountering neu(OT-I/OT-II)-expressing tumors. This was followed by the complete regression of 37% of tumors, whereas others showed partial/stable responses (40%) or progressive disease (23%). Those tumors undergoing complete regression never recurred. In mice with multiple primary tumors, simultaneous regressions and nonregressions were often seen, indicating that immune evasion occurred at a local rather than systemic level. The majority of nonregressing tumors expressed Neu(OT-I/OT-II) and MHC class I, and many avoided rejection through a profound block to T-cell infiltration. Thus, T cells directed against an essential oncogene can permanently eradicate a subset of spontaneous, established mammary tumors. However, in other tumors, local barriers severely limit the therapeutic response. To maximize the efficacy of immunotherapy against spontaneous cancers, predictive strategies that take into account the heterogeneity of the tumor microenvironment will be required.

The cytotoxic T cell response to peptide analogs of the HLA-A*0201-restricted MUC1 signal sequence epitope, M1.2

The mucin MUC1 molecule is overexpressed on a variety of adenocarcinomas and is thus, a potential target for immunotherapy. Of the MUC1 peptides that bind to HLA-A*0201(A2), M1.2 (LLLLTVLTV) from the signal sequence appears to be the most immunogenic in humans. Here we have shown that large numbers (10(9)) of tetramer-binding M1.2-specific cytotoxic T lymphocytes (CTL) can be generated ex vivo from circulating precursors, derived from healthy adults. However, there was significant interpersonal variation in the level of co-stimulatory signal required. Tetramer-binding cells also required maturation in culture to become proficient killers of the HLA-A2(+) MUC1(+) MCF7 cell line, known to express a low number of endogenously processed M1.2. The functional avidity of M1.2-specific CTL, however, was low as compared to CTL specific for an HIV-1 epitope. Despite the low avidity, M1.2-specific CTL were polyfunctional, secreting multiple cytokines upon degranulation with antigen recognition. To identify potential agonist peptides that may be superior immunogens, an M1.2-specific CTL culture was used to scan a large nonameric combinatorial peptide library. Of 54 predicted peptides, 4 were "consensus" agonists because they were recognized by CTL from two other donors. Two agonists, p29 (LLPWTVLTV) and p15 (VLLWTVLTV), were equally stimulatory when loaded onto C1R target cells transfected with wild-type HLA-A2. Both agonists induced IL-2, TNF-alpha, IFN-gamma, and degranulation with M1.2-specific CTL. In contrast, production of these cytokines, which are tightly regulated by specific activation through the T cell receptor, was restricted when the CTL were stimulated with peptides loaded onto C1R cells that were transfected with an HLA-A2 molecule bearing a mutation that abrogates binding to the CD8 co-receptor. Thus, activation by both M1.2 and its agonists was dependent upon CD8, showing that compensation by the co-receptor was necessary for the human T cell response to M1.2.

Interleukin-10-secreting type 1 regulatory T cells in rodents and humans

Interleukin-10 (IL-10)-secreting T regulatory type 1 (Tr1) cells are defined by their specific cytokine production profile, which includes the secretion of high levels of IL-10 and transforming growth factor-beta(TGF-beta), and by their ability to suppress antigen-specific effector T-cell responses via a cytokine-dependent mechanism. In contrast to the naturally occurring CD4+ CD25+ T regulatory cells (Tregs) that emerge directly from the thymus, Tr1 cells are induced by antigen stimulation via an IL-10-dependent process in vitro and in vivo. Specialized IL-10-producing dendritic cells, such as those in an immature state or those modulated by tolerogenic stimuli, play a key role in this process. We propose to use the term Tr1 cells for all IL-10-producing T-cell populations that are induced by IL-10 and have regulatory activity. The full biological characterization of Tr1 cells has been hampered by the difficulty in generating these cells in vitro and by the lack of specific marker molecules. However, it is clear that Tr1 cells play a key role in regulating adaptive immune responses both in mice and in humans. Further work to delineate the specific molecular signature of Tr1 cells, to determine their relationship with CD4+ CD25+ Tregs, and to elucidate their respective role in maintaining peripheral tolerance is crucial to advance our knowledge on this Treg subset. Furthermore, results from clinical protocols using Tr1 cells to modulate immune responses in vivo in autoimmunity, transplantation, and chronic inflammatory diseases will undoubtedly prove the biological relevance of these cells in immunotolerance.

Inhibitory effects of B cells on antitumor immunity

B-cell functions in antitumor immunity are not well understood. In this study, we evaluated the role of B cells in the development of antitumor immunity using Friend murine leukemia virus gag-expressing mouse EL-4 (EL-4 gag), D5 mouse melanoma, or MCA304 mouse sarcoma cells. To screen tumors for susceptibility to B-cell-deficient immune environments, spleen cells from naive C57BL/6 [wild-type (WT)] and B-cell knockout (BKO) mice were cultured with irradiated tumor cells in vitro. When cells were stimulated with EL-4 gag or D5 (but not MCA304 tumors), IFN-gamma production from CD8 T cells and natural killer cells was markedly decreased in WT compared with BKO cultures. IFN-gamma production was correlated with CD40 ligand expression on the tumor and inversely with interleukin-10 (IL-10) production by B cells. Sorted WT B cells produced more IL-10 than CD40 knockout (CD40KO) B cells when cocultured with EL-4 gag or D5 (but not MCA304). IFN-gamma production by BKO cells was reduced by the addition of sorted naive WT B cells (partially by CD40KO B cells) or recombinant mouse IL-10. In vivo tumor progression mirrored in vitro studies in that WT mice were unable to control tumor growth whereas EL-4 gag and D5 tumors (but not MCA304) were eliminated in BKO mice. Robust in vivo antitumor CTLs developed only in BKO tumor-challenged mice. Our studies provide the first mechanistic basis for the concept that B-cell depletion could therapeutically enhance antitumor immune responses to certain tumors by decreasing IL-10 production from B cells.

Generation of antitumor responses by genetic modification of primary human T cells with a chimeric NKG2D receptor

To create more effective T cells against human tumors, we have designed a strategy to allow T cells to recognize tumor cells using natural killer (NK) cell receptors but retain the effector responses of T lymphocytes. NKG2D is an activating cell surface receptor expressed on NK cells and on some T-cell subsets. Its ligands are primarily expressed on tumor cells. We have shown that by linking mouse NKG2D to the CD3zeta chain, it was possible to generate a chimeric NKG2D (chNKG2D) receptor that allowed activation of murine T cells on engagement with NKG2D ligand-positive tumor cells leading to antitumor responses in mice. In this study, a human version of the chNKG2D receptor was expressed on primary human T cells, and antitumor responses were determined. Human peripheral blood mononuclear cell-derived T cells were retrovirally transduced with a human chNKG2D receptor gene. These chNKG2D-bearing human T cells responded to NKG2D ligand-positive tumor cells by producing T-helper 1 cytokines, proinflammatory chemokines, and significant cellular cytotoxicity. This response could be blocked by anti-NKG2D antibodies, and it was dependent on NKG2D ligand expression on the target cells but not on expression of MHC molecules. In addition, the activity of chNKG2D-bearing T cells remained unimpaired after exposure to a soluble NKG2D ligand, soluble MICA, at concentrations as high as 1.5 mug/mL. These data indicate the feasibility of using chNKG2D receptors in primary human T cells and suggest that this approach may be a promising means for cancer immunotherapy.

Gene therapy for prostate cancer: current strategies and new cell-based approaches

Prostate cancer is the most commonly diagnosed cancer in adult males in the Western world. It accounts for one in ten cancer cases and is the second leading cause of cancer death in men, after lung cancer. A number of curative treatments are available for patients with localized prostate cancer such as radical prostatectomy, radiotherapy, or brachytherapy. However, a proportion of these men will develop progressive disease, and some will present de novo with advanced and metastatic prostate cancer, which is amenable to palliation only with androgen-withdrawal therapy. Most of these patients will eventually develop hormone refractory disease which is incurable, and for whom gene therapy, if feasible may develop as an alternative treatment option. In this review we discuss the gene therapy vectors and strategies that are currently in use, new cell-based approaches, discuss their advantages and disadvantages, and review the potential or proven pre-clinical and clinical efficacy in prostate cancer models/patients.

Stable, soluble, high-affinity, engineered T cell receptors: novel antibody-like proteins for specific targeting of peptide antigens

The recent development of T cell receptor phage display opens up the possibility of engineering human T cell receptors with antibody-like binding properties for cell-surface peptide antigens. In this review we briefly discuss recent developments in molecular targeting of peptide antigens. We then discuss potential clinical applications of engineered high-affinity T cell receptors in autoimmunity and cancer.