[Show abstract][Hide abstract] ABSTRACT: The transcription factor Foxp3 represents the most specific functional marker of CD4+ regulatory T cells (TRegs). However, previous reports have described Foxp3 expression in other cell types including some subsets of macrophages, although there are conflicting reports and Foxp3 expression in cells other than Treg is not well characterized. We performed detailed investigations into Foxp3 expression in macrophages in the normal tissue and tumor settings. We detected Foxp3 protein in macrophages infiltrating mouse renal cancer tumors injected subcutaneously or in the kidney. Expression was demonstrated using flow cytometry and Western blot with two individual monoclonal antibodies. Further analyses confirmed Foxp3 expression in macrophages by RT PCR, and studies using ribonucleic acid-sequencing (RNAseq) demonstrated a previously unknown Foxp3 messenger (m)RNA transcript in tumor-associated macrophages. In addition, depletion of Foxp3+ cells using diphtheria toxin in Foxp3DTR mice reduced the frequency of type-2 macrophages (M2) in kidney tumors. Collectively, these results indicate that tumor-associated macrophages could express Foxp3.
PLoS ONE 01/2014; 9(9):e108670. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genetic modification of primary mouse T cells with chimeric antigen receptors (CAR) has emerged as an important tool for optimizing adoptive T cell immunotherapy strategies. However, limitations in current protocols for generating highly pure and sufficient numbers of enriched effector and helper CAR(+) T cell subsets remain problematic. Here, we describe a new retroviral transduction protocol for successfully generating transduced CD8(+) and CD4(+) T lymphocytes for in vitro and in vivo characterization.
[Show abstract][Hide abstract] ABSTRACT: The presence of an immunosuppressive microenvironment can limit the full potential of adoptive T cell immunotherapy. However, specific blockade of the PD-1 immunosuppressive pathway can significantly enhance the function of gene-modified T cells expressing a chimeric antigen receptor (CAR) leading to enhanced tumor eradication.
[Show abstract][Hide abstract] ABSTRACT: The tumor microenvironment can promote tumor growth and reduce treatment efficacy. Tumors can occur in many sites in the body, but how surrounding normal tissues at different anatomical sites affect tumor microenvironments and their subsequent response to therapy is not known.We demonstrated that tumors from renal, colon or prostate cell lines, in orthotopic locations responded much less than the same tumor type located subcutaneously to immunotherapy consisting of three agonist antibodies, Trimab. A tissue-specific response to Trimab was confirmed by ex vivo separation of subcutaneous or orthotopic tumor cells from stromal cells, followed by re-injection of tumor cells into the opposite site. Compared to subcutaneous tumors, orthotopic tumors had a microenvironment associated with a type 2 immune response, related to immunosuppression, and an involvement of alternatively-activated macrophages in the kidney model. Orthotopic kidney tumors were more highly vascularized than subcutaneous tumors. Neutralizing the macrophage- and Th2-associated molecules CCL2 or interleukin-13 led to a significantly improved therapeutic effect. This study highlights for the first time the importance of the tissue of implantation in sculpting the tumor microenvironment. These are important fundamental issues in tumor biology and crucial factors to consider in the design of experimental models and treatment strategiesMolecular Therapy (2013); doi:10.1038/mt.2013.219.
[Show abstract][Hide abstract] ABSTRACT: The tumor microenvironment is a complex assortment of cells that includes a variety of leukocytes. The overall effect of the microenvironment is to support the growth of tumors and suppress immune responses. Immunotherapy is a highly promising form of cancer treatment, but its efficacy can be severely compromised by an immunosuppressive tumor microenvironment. Chemotherapy and radiation treatment can mediate tumor reduction through cytotoxic effects, but it is becoming increasingly clear that these forms of treatment can be used to modify the tumor microenvironment to liberate tumor antigens and decrease immunosuppression. Chemotherapy and radiotherapy can be used to modulate the tumor microenvironment to enhance immunotherapy.
[Show abstract][Hide abstract] ABSTRACT: CD73 inhibits antitumor immunity through the activation of adenosine receptors expressed on multiple immune subsets. CD73 also enhances tumor metastasis, although the nature of the immune subsets and adenosine receptor subtypes involved in this process are largely unknown. In this study, we revealed that A2A/A2B receptor antagonists were effective in reducing the metastasis of tumors expressing CD73 endogenously (4T1.2 breast tumors) and when CD73 was ectopically expressed (B16F10 melanoma). A2A(-/-) mice were strongly protected against tumor metastasis, indicating that host A2A receptors enhanced tumor metastasis. A2A blockade enhanced natural killer (NK) cell maturation and cytotoxic function in vitro, reduced metastasis in a perforin-dependent manner, and enhanced NK cell expression of granzyme B in vivo, strongly suggesting that the antimetastatic effect of A2A blockade was due to enhanced NK cell function. Interestingly, A2B blockade had no effect on NK cell cytotoxicity, indicating that an NK cell-independent mechanism also contributed to the increased metastasis of CD73(+) tumors. Our results thus revealed that CD73 promotes tumor metastasis through multiple mechanisms, including suppression of NK cell function. Furthermore, our data strongly suggest that A2A or A2B antagonists may be useful for the treatment of metastatic disease. Overall, our study has potential therapeutic implications given that A2A/A2B receptor antagonists have already entered clinical trials in other therapeutic settings.
Proceedings of the National Academy of Sciences 08/2013; · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is much promise in the use of immunotherapy for the treatment of cancer. Approaches such as those using antibodies or adoptive cell transfer can mediate complete tumor regression in a proportion of patients. However, the tumor microenvironment can inhibit immune responses leading to ineffective or suboptimal responses of tumors to immunotherapy in the majority of cases. As our knowledge of the tumor microenvironment increases, many strategies are emerging for changing the immunosuppressive nature of the tumor toward a microenvironment able to support immunity. These strategies aim to enhance the ability of immunotherapies to initiate effective immune responses able to destroy tumors. In this article, we review approaches that use immunomodulators specifically to modify the tumor microenvironment, and their use in combination with other immune-based strategies for cancer therapy.
[Show abstract][Hide abstract] ABSTRACT: To determine the antitumor efficacy and toxicity of a novel combination approach involving adoptive T cell immunotherapy utilizing chimeric antigen receptor (CAR) T cells with an immunomodulatory reagent for blocking immunosuppression.
We examined whether administration of a PD-1 blocking antibody could increase the therapeutic activity of CAR T cells against two different Her-2+ tumors. The use of a self-antigen mouse model enabled investigation into the efficacy, mechanism and toxicity of this combination approach.
In this study we first demonstrated a significant increase in the level of PD-1 expressed on transduced anti-Her-2 CD8+ T cells following antigen-specific stimulation with PD-L1+ tumor cells and that markers of activation and proliferation were increased in anti-Her-2 T cells in the presence of anti-PD-1 antibody. In adoptive transfer studies in Her-2 transgenic recipient mice, we demonstrated a significant improvement in growth inhibition of two different Her-2+ tumors treated with anti-Her-2 T cells in combination with anti-PD-1 antibody. The therapeutic effects observed correlated with increased function of anti-Her-2 T cells following PD-1 blockade. Strikingly a significant decrease in the percentage of Gr1+ CD11b+ myeloid derived suppressor cells (MDSC) was observed in the tumor microenvironment of mice treated with the combination therapy. Importantly, increased anti-tumor effects were not associated with any autoimmune pathology in normal tissue expressing Her-2 antigen.
This study demonstrates that specifically blocking PD-1 immunosuppression can potently enhance CAR T cell therapy that has significant implications for potentially improving therapeutic outcomes of this approach in cancer patients.
Clinical Cancer Research 07/2013; · 7.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aim: The aim of the current study was to fully elucidate the functions of T cells genetically modified with an erbB2-specific chimeric antigen receptor (CAR). Material & methods: In this study, key functional parameters of CAR T cells were examined following antigen-specific stimulation of the chimeric anti-erbB2 receptor. Results: Gene-modified T cells produced the cytokines IFN-γ, IL-2, IL-4, IL-10, TNF-α and IL-17, and the chemokine RANTES upon CAR ligation. A multifunctional capacity of these CAR T cells was also demonstrated, where 13.7% of cells were found to simultaneously express IFN-γ and CD107a, indicative of cytolytic granule release. In addition, the CAR T cells were able to respond to a greater degree on the second ligation of CAR, which has not been previously shown. IFN-γ secretion levels were significantly higher on second ligation than those secreted following initial ligation. CAR-expressing T cells were also demonstrated to lyze erbB2-expressing tumor cells in the absence of activity against bystander cells not expressing the erbB2 antigen, thereby demonstrating exquisite specificity. Conclusion: This study demonstrates the specificity of CAR gene-engineered T cells and their capacity to deliver a wide range of functions against tumor cells with an enhanced response capability after initial receptor engagement.
[Show abstract][Hide abstract] ABSTRACT: Genetic engineering of cellular function holds much promise for the treatment of a variety of diseases including gene deficiencies and cancer. However, engineering the full complement of cellular functions can be a daunting genetic exercise since many molecular triggers need to be activated to achieve complete function. In the case of T cells, genes encoding chimeric antigen receptors (CARs) covalently linking antibodies to cytoplasmic signaling domains can trigger some, but not all, cellular functions against cancer cells. To date, relatively few CAR formats have been investigated using a candidate molecule approach, in which rationally chosen molecules were trialed one by one. Therefore, to expedite this arduous process we developed an innovative screening method to screen many thousands of CAR formats to identify genes able to enhance the anticancer ability of T cells. We used a directional in-frame library of randomly assembled signaling domains in a CAR specific for the tumor associated antigen erbB2. Several new and original CARs were identified, one of which had an enhanced ability to lyse cancer cells and inhibit tumor growth in mice. This study highlights novel technology that could be used to screen a variety of molecules for their capacity to induce diverse functions in cells.
PLoS ONE 01/2013; 8(5):e63037. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Malignant cells are susceptible to viral infection and consequent cell death. Virus-induced cell death is endowed with features that are known to stimulate innate and adaptive immune responses. Thus danger signals emitted by cells succumbing to viral infection as well as viral nucleic acids are detected by specific receptors, and tumor cell antigens can be routed to professional antigen-presenting cells. The anticancer immune response triggered by viral infection is frequently insufficient to eradicate malignancy but may be further amplified. For this purpose, transgenes encoding cytokines as co-stimulatory molecules can be genetically engineered into viral vectors. Alternatively, or in addition, it is possible to use monoclonal antibodies that either block inhibitory receptors of immune effector cells, or act as agonists for co-stimulatory receptors. Combined strategies are based on the ignition of a local immune response at the malignant site plus systemic immune boosting. We have recently reported examples of this approach involving the Vaccinia virus or Semliki Forest virus, interleukin-12 and anti-CD137 monoclonal antibodies.
[Show abstract][Hide abstract] ABSTRACT: Oncolytic virotherapy using vaccinia virus (Vv) has shown some encouraging antitumor responses in mouse models and patients, but the breadth of efficacy in clinical trials has been somewhat limited. Given that antitumor effects have correlated with increased host immune responses, we hypothesized that improved therapeutic outcomes may be achieved by using oncolytic virus (OV) in combination with a potent immune agonist reagent. In this study, we carried out a preclinical evaluation of a genetically engineered strain of oncolytic vaccinia virus (Vvdd) for its capacity to induce antitumor responses when combined with an agonist antibody (Ab) specific for the costimulatory molecule 4-1BB (CD137). In immune-competent syngeneic mouse models of cancer, this combination therapy significantly reduced the growth of established subcutaneous tumors relative to either treatment alone. Importantly, the development of pulmonary metastatic lesions was also reduced. Tumor growth inhibition was associated with increased numbers of CD11b(+) and CD11c(+) myeloid cells in the tumor draining lymph nodes, greater infiltration of CD8(+) effector T and natural killer (NK) cells, and a more sustained presence of neutrophils at the tumor site. Depletion of T or NK cells or neutrophils reduced efficacy, confirming their contribution to an effective therapeutic response. We further extended this conclusion through results from IFNγ-deficient mice. In summary, our findings offered a proof-of-concept for a combinatorial approach to enhance the antitumor efficacy of an OV, suggesting a strategy to improve their use as an immunotherapeutic treatment for cancer.
Cancer Research 02/2012; 72(7):1651-60. · 9.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Toll-like receptor (TLR) agonists can trigger broad inflammatory responses that elicit rapid innate immunity and promote the activities of lymphocytes, which can potentially enhance adoptive immunotherapy in the tumor-bearing setting. In the present study, we found that Polyinosinic:Polycytidylic Acid [Poly(I:C)] and CpG oligodeoxynucleotide 1826 [CpG], agonists for TLR 3 and 9, respectively, potently activated adoptively transferred T cells against a murine model of established melanoma. Intratumoral injection of Poly(I:C) and CpG, combined with systemic transfer of activated pmel-1 T cells, specific for gp100(25-33), led to enhanced survival and eradication of 9-day established subcutaneous B16F10 melanomas in a proportion of mice. A series of survival studies in knockout mice supported a key mechanistic pathway, whereby TLR agonists acted via host cells to enhance IFN-γ production by adoptively transferred T cells. IFN-γ, in turn, enhanced the immunogenicity of the B16F10 melanoma line, leading to increased killing by adoptively transferred T cells. Thus, this combination approach counteracted tumor escape from immunotherapy via downregulation of immunogenicity. In conclusion, TLR agonists may represent advanced adjuvants within the setting of adoptive T-cell immunotherapy of cancer and hold promise as a safe means of enhancing this approach within the clinic.
Cancer Immunology and Immunotherapy 02/2011; 60(5):671-83. · 3.64 Impact Factor