Infiltration of tumor-reactive transforming growth factor-beta insensitive CD8+ T cells into the tumor parenchyma is associated with apoptosis and rejection of tumor cells.
ABSTRACT TGF-beta is a potent immunosuppressant. High levels of TGF-beta produced by cancer cells have a negative inhibition effect on surrounding host immune cells and leads to evasion of the host immune surveillance and tumor progression. In the present study, we report a distinct ability of tumor reactive, TGF-beta-insensitive CD8+ T cells to infiltrate into established tumors, secrete relevant cytokines, and induce apoptosis of tumor cells.
CD8+ T cells were isolated from the spleens of C57BL/6 mice, which were primed with irradiated mouse prostate cancer cells, the TRAMP-C2 cells. After ex vivo expansion, these tumor reactive CD8+ cells were rendered TGF-beta-insensitive by infection with a retroviral (MSCV)-mediated dominant negative TGF-beta type II receptor (TbetaRIIDN). Control CD8+ cells consist of those transfected with the GFP-only empty vector and naïve CD8+ T cells. Recipient mice were challenged with a single injection of TRAMP-C2 cells 21 days before adoptive transfer of CD8+ T cells was performed. Forty days after the adoptive transfer, all animals were sacrificed. The presence of pulmonary metastases was evaluated pathologically. Serial slides of malignant tissues were used for immunofluorescent staining for different kinds of immune cell infiltration, cytokines, and apoptosis analysis.
Pulmonary metastases were either eliminated or significantly reduced in the group receiving adoptive transfer of tumor-reactive TGF-beta-insensitive CD8+ T cells (3 out of 12) when compared to GFP controls (9 out of 12), and naïve CD8+ T cells (12 out of 12). Results of immunofluorescent studies demonstrated that only tumor-reactive TGF-beta-insensitive CD8+ T cells were able to infiltrate into the tumor and mediate apoptosis when compared to CD4+ T cells, NK cells, and B cells. A large amount of cytokines such as perforin, nitric oxide, IFN-gamma, IL-2, TNF-alpha were secreted in tumor tissue treated with tumor-reactive TGF-beta-insensitive CD8+ T cells. No immune cells infiltration and cytokine secretion were detected in tumor tissues treated with naïve T cells and GFP controls.
Our results demonstrate the mechanism of anti-tumor effect of tumor-reactive TGF-beta-insensitive CD8+ T cells that adoptive transfer of these CD8+ T cells resulted in infiltration of these immune cells into the tumor parenchyma, secretion of relevant cytokines, and induction of apoptosis in tumor cells. These results support the concept that tumor-reactive TGF-beta-insensitive CD8+ T cells may prove beneficial in the treatment of advanced cancer patients.
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ABSTRACT: Natural killer (NK) cells hold great potential for improving the immunotherapy of cancer. However, existing data indicate that tumor cells can effectively escape NK cell-mediated apoptosis through immunosuppressive effect in the tumor microenvironment. Transforming growth factor-β (TGF-β) is a potent immunosuppressant. The present study was intended to develop a treatment strategy through adoptive transfer of TGF-β insensitive NK-92 cells. To block TGF-β signaling pathway, NK-92 cells were genetically modified with dominant negative TGF-β type II receptor (DNTβRII) by optimizing electroporation using the Amaxa Nucleofector system. These genetically modified NK-92 cells were insensitive to TGF-β and able to resist the suppressive effect of TGF-β on Calu-6 lung cancer cells in vitro. To determine the antitumor activity in vivo, recipient mice were challenged with a single subcutaneous injection of Calu-6 cells. Adoptive transfer of TGF-β insensitive NK-92 cells decreased tumor proliferation, reduced lung metastasis, produced more IFN-γ, and increased the survival rate of nude mice bearing established Calu-6 cells. Hence, we have demonstrated that blocking transforming growth factor-β signaling pathway in NK cells provides a novel therapeutic strategy and warrants further investigation.International immunopharmacology 06/2013; · 2.21 Impact Factor
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ABSTRACT: Adoptive T cell therapy (ACT) for the treatment of established cancers is actively being pursued in clinical trials. However, poor in vivo persistence and maintenance of antitumor activity of transferred T cells remain major problems. TGF-β is a potent immunosuppressive cytokine that is often expressed at high levels within the tumor microenvironment, potentially limiting T cell-mediated antitumor activity. In this study, we used a model of autochthonous murine prostate cancer to evaluate the effect of cell-intrinsic abrogation of TGF-β signaling in self/tumor-specific CD8 T cells used in ACT to target the tumor in situ. We found that persistence and antitumor activity of adoptively transferred effector T cells deficient in TGF-β signaling were significantly improved in the cancerous prostate. However, over time, despite persistence in peripheral lymphoid organs, the numbers of transferred cells in the prostate decreased and the residual prostate-infiltrating T cells were no longer functional. These findings reveal that TGF-β negatively regulates the accumulation and effector function of transferred self/tumor-specific CD8 T cells and highlight that, when targeting a tumor Ag that is also expressed as a self-protein, additional substantive obstacles are operative within the tumor microenvironment, potentially hampering the success of ACT for solid tumors.The Journal of Immunology 09/2012; 189(8):3936-46. · 5.52 Impact Factor
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ABSTRACT: Although TGF-β and IL-6 would turn CD8 T cells to differentiate into non-cytotoxic state, these treated cells were converted to cytolytic phenotypes after re-exposure to their antigenic epitope in vitro. Here, using spleen cells from TCR transgenic mice expressing TCRαβ genes of clone RT1 recognizing an epitope peptide (P18-I10: RGPGRAFVTI) of HIV-1 gp160, we generated CD8 cytotoxic T lymphocytes (CTLs) activated by re-exposure to P18-I10 after primarily cultured with TGF-β and IL-6 in vitro to examine their effector function. The CTLs, having strong cytotoxic activity in vitro, were not only resistant to Fas-FasL mediated apoptosis, but also insensitive to the suppression of their cytotoxicity by re-exposure to TGF-β in vitro. Moreover, adoptive transfer experiments indicated that the CTLs are capable of eliminating recombinant vaccinia virus expressing HIV-1 gp160 in vivo. Taken together, our data suggest that TGF-β and IL-6 may play pivotal roles in inducing apoptosis-resistant and TGF-β-insensitive CTLs in vitro.Cellular Immunology 12/2012; 280(2):138-47. · 1.74 Impact Factor