Abstract 2553: PSMA-specific, TGF-ß-insensitive CD8+T cells derived from metastatic castration resistant prostate cancer (mCRPC) patients induce apoptosis of PSMA positive prostate cancer (PCa)

Introduction: Manufacture of tumor specific CD8+ T cells has been an obstacle for developing immunotherapies for PCa, especially in patients with mCRPC. Here we report a new immunotherapeutic approach using adoptive transfer of patient-derived PSMA-specific, TGF-s-insensitive human CD8+ T cells to induce the apoptosis of PCa. Methods: Peripheral blood CD8+ T cells were collected from mCRPC patient by leukapheresis, and cultured in FDA approved Cell Processing Work Station with CD-3/CD28 beads. We developed a TsRIIDN-TK-IRES-PZ1 chimeric T cell receptor retroviral construct using an anti-PSMA IgTCR(ζ) gene (PZ1) and a dominant negative TGF-s type II receptor (TsRIIDN), that could induce CD8+ T cells to be PSMA reactive and insensitive to TGF-s. PC-3 cells (PSMA negative) or PSMA positive PC-3-PSMA cells were used for target cells for in vivo study. Subcutaneous injection of PC-3 and PC-3-PSMA cells (2x105 cells/each) into the left and right flank region respectively in each of 32 immunodeficient RAG-1 mice was performed. One week later, the animals were randomly assigned to one of three adoptive transfer groups (16 mice /each group, 2x106 CD8+ T cells/each mice): Group 1: PSMA-specific, TGF-s-insensitive CD8+ T cells infected with TsRIIDN-TK-IRES-PZ1 (71.1% positive); Group 2: Naive CD8+ T cells. The animals were provided 2 weekly adoptive transfer treatments and sacrificed after 3 weeks. The infiltration of CD8+ T cells and apoptosis of tumor tissue was evaluated by immunofluorescence staining and TUNEL assay. Results: In Group 1, the average tumor weight was significantly lower in the PC3-PSMA tumor (0.413g) compared to the PC3 tumor (2.75 g). There was no difference between the PC3 tumor (2.36g) compared to PC3-PSMA tumor (2.45g) in Group 2. HE 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2553.