BLOCKADE OF TGF beta ENHANCES EFFICACY OF GENETICALLY MODIFIED HUMAN T CELLS TARGETED AGAINST PROSTATE SPECIFIC MEMBRANE ANTIGEN

You have accessJournal of UrologyProstate Cancer: Basic Research II1 Apr 2012317 BLOCKADE OF TGFβ ENHANCES EFFICACY OF GENETICALLY MODIFIED HUMAN T CELLS TARGETED AGAINST PROSTATE SPECIFIC MEMBRANE ANTIGEN Stephen Poon, Christopher Kloss, and Michel Sadelain Stephen PoonStephen Poon New York, NY More articles by this author , Christopher KlossChristopher Kloss New York, NY More articles by this author , and Michel SadelainMichel Sadelain New York, NY More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.377AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Phase I clinical trials utilizing adoptive transfer of genetically modified T cells for the treatment of metastatic prostate cancer are currently underway. We have created a second generation chimeric antigen receptor (CAR) called P28z, which contains the heavy and light chain domains of the antibody J591, allowing it to recognize prostate specific membrane antigen (PSMA). P28z+ T cells receive an activating CD3 ξ-chain signal and CD28 costimulatory signal when PSMA expressing tumors are encountered. However, solid tumors have adopted a number of mechanisms to evade the host immune response. Notably, prostate cancer is known to secrete high levels of TGFβ, which has a direct immunosuppressive effect. We hypothesized that blocking TGFβ signaling in P28z+ T cells would enhance T cell function. METHODS We created 3 γ-retroviral bicistronic vectors expressing the P28z CAR and either 1) a truncated TGFβ Receptor II (TBR2) dominant negative mutant (DNR), 2) a soluble TBR2 (sTBR2), or 3) a neutral control protein, low-affinity nerve growth factor (LNGFR). Human T cells from healthy donors were transduced with these viruses and cultured with or without the presence of TGFβ1. These 3 groups were compared. Cytotoxicity was evaluated by chromium release assay. In vitro proliferation and cytokine secretion were assessed during weekly stimulation with PSMA+ tumor cells. A metastatic xenograft prostate cancer model was established by tail vein injection of TGFβ1-secreting PSMA+ PC3 prostate cancer cells into immunodeficient mice. Mice were then treated with 1 of the 3 T cell groups, and in vivo anti-tumor activity was determined by bioluminescent imaging to assess tumor burden. RESULTS In vitro, DNR+ P28z+ and sTBR2+ P28z+ T cells showed less inhibition of cytotoxicity against PSMA+ target cells and secretion of effector cytokines in the presence of exogenously added TGFβ compared to P28z+ T cells expressing the control LNGFR protein. Elevated levels of TGFβ were detected in the serum of mice with PC3 metastases, and DNR+ P28z+ T cells were most effective in eradicating in vivo PC3 prostate cancer tumors. CONCLUSIONS TGFβ signaling blockade can successfully be incorporated into viral vectors. These modifications enhance the function of P28z+ T cells against TGFβ secreting prostate cancer tumors. Further research to investigate their integration into clinical trials is warranted. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e128-e129 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Stephen Poon New York, NY More articles by this author Christopher Kloss New York, NY More articles by this author Michel Sadelain New York, NY More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...