Assessing the Safety of Cytotoxic T Lymphocytes Transduced With a Dominant Negative Transforming Growth Factor-β Receptor

Abstract

Transforming growth factor (TGF)-beta, a pleiotropic cytokine that regulates cell growth, is secreted by many human tumors and markedly inhibits tumor-specific cellular immunity. It has previously been shown by our group that transduction of cytotoxic T lymphocytes (CTLs) with a retroviral vector expressing the dominant-negative TGFbeta type II receptor (DNR) overcomes this tumor evasion in a model of Epstein-Barr virus (EBV)-positive Hodgkin disease. TGFbeta is an important physiologic regulator of T-cell growth and survival, however, abrogation of this regulatory signal in genetically modified cells is potentially problematic. To ensure that unresponsiveness to TGFbeta did not lead to the unregulated growth of genetically modified CTLs, the characteristics of DNR-transduced CTLs in vivo were studied. Donor C57BL6 mice were vaccinated with human papillomavirus-E7 plasmid DNA to induce production of E7-specific CTLs. The E7-specific CTLs were genetically modified to express enhanced green fluorescent protein (GFP) or DNR and administered to syngeneic mice. All mice received monthly boosts with E7 DNA for 9 months, and during this time, transduced CTLs were detected in the peripheral blood of most of the mice using a quantitative real-time polymerase chain reaction. By 12 months, 3 months after cessation of vaccination, no DNR-transduced CTLs or GFP-transduced CTLs were detected in the peripheral blood. There were 4 cases of lymphoma (2 DNR-transduced mice and 2 control mice): all tumors were CD3-/CD8- and were also negative for the DNR transgene. Hence, mature antigen-specific cytotoxic T cells can be genetically modified to resist the antiproliferative effects of TGFbeta without undergoing spontaneous lymphoproliferation in vivo. They may be of value for treating human cancers, which use TGFbeta as a powerful immune evasion mechanism.

Improving Chimeric Antigen Receptor-Modified T Cell Function by Reversing the Immunosuppressive Tumor Microenvironment of Pancreatic Cancer

“…Other modifications include the transgenic expression of Th1 cytokines to promote autocrine growth 36,[39][40][41] or the incorporation of a dominant-negative TGF-b receptor, which sequesters this tumor-produced immunosuppressive cytokine. 42,43 Our approach extends upon the dominant-negative receptor concept by inverting a soluble immunosuppressive signal present in the tumor microenvironment into one that is immunostimulatory (4/7 ICR). 44 However, this strategy is not limited to soluble molecules as demonstrated by Jensen and colleagues who designed an inverted receptor to interact with PD-L1 on tumor cells and deliver co-stimulation to transgenic T cells.…”

Antitumor Activity of EBV-specific T Lymphocytes Transduced With a Dominant Negative TGF-β Receptor

“…Reassuringly, however, studies in an immunocompetent (nontumor) murine model have shown that DNRII-specific CTL do not spontaneously proliferate in the absence of antigenic stimulation. 19 A countermeasure, such as the one we have described, which is active against just one of many tumor immune evasion strategies, may be insufficient for clinical benefit. Indeed, the presence of other immune evasion mechanisms such as tumor-derived IL-10 20 may be one reason why tumor eradication in our study was incomplete.…”

Enhancing Antitumor Immunity: Combining IL-12 With TGFβ1 Antagonism

“…However, on the basis of other studies evaluating the long-term outcomes in mice treated with either dnTGFbRII cytotoxic T cells, or global TGFb neutralization strategies with either blocking antibodies or soluble antagonists, chronic TGFb blockade seems to cause minimal immunologic perturbations. 42,59,60 On the basis of the safety observed in murine studies, human clinical trials are underway assessing the efficacy of antiTGFb monoclonal antibodies or TGFb-resistant cytotoxic T cells for the treatment of melanoma, renal cell carcinoma, or relapsed Epstein-Barr virus-positive lymphoma.…”