Login to Access Video or Poster Abstract: MP83-04
Sources of Funding: 1.Walter S. and Lucienne Driskill Immunotherapy Research Program_x000D_ (320-5314000-30026197)_x000D_ 2.Matthews Center for regenerative medicine pilot grants 2014 _x000D_ 3.National Cancer Institute-SPORE in Prostate Cancer (P50 CA90386-01)_x000D_ 4. Developmental Therapeutics Program, FSM Division of Hematology Oncology

Introduction

It has previously been shown that tumor-derived TGF-β related potent immunosuppression and lack of tumor killing specificity promote CaP progression. Here we report a new immunotherapeutic approach using adoptive transfer of patient-derived PSMA-specific, TGF-β-insensitive human CD8+ T cells to inhibit solid xenograft CaP.

Methods

Peripheral blood CD8+ T cells were collected from metastatic castration resistant CaP patient by leukapheresis and cultured in the FDA approved Cell Processing Work Station (CPWS, Panasonic) with CD-3 Biotin/CD28/Anti-Biotin Beads (Bead: Cell 1:2) and IL-2 (100units/ml). We developed a TβRIIDN-TK-IRES-PZ1 chimeric T cell receptor retroviral construct using an anti-PSMA IgTCR(&[zeta]) gene (PZ1) and a dominant negative TGF-β type II receptor (TβRIIDN) that could induce CD8+ T cells to be PSMA reactive and insensitive to TGF-β. PC-3 cells (PSMA negative; ATCC) or PSMA positive PC-3-PSMA cells (Cleveland Clinic) were used for target cells. Subcutaneous injection of PC-3 and PC-3-PSMA cells (2x105 cells/each, infected with HSV1-tk-GFP-luciferase reporter) into the left and right flank region respectively in each of 48 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: CD8+ T cells infected with TβRIIDN-TK-IRES-PZ1 (71.1% positive); Group 2: Naive CD8+ T cells; Group 3: No treatment group. Tumor growth was monitored by IVIS luciferase imaging. The animals were provided 2 weekly adoptive transfer treatments and sacrificed after 3 weeks. The size and the weight of the tumor were recorded, and the infiltration of CD8+ T cells and apoptosis was evaluated by immunofluorescence staining and TUNEL.

Results

In Group 1, the average tumor weight and volume was significantly lower in the PC3-PSMA tumor (0.413g and 514.2mm3) compared to the PC3 tumor (2.75 g and 3165.2 mm3); (~3-6×, P<0.05). There was no difference between the PC3 tumor (2.36g and 2768.5mm3 ) compared to PC3-PSMA tumor (2.45g and 2411.99 mm3) in Group 2 or Group 3. H&E staining showed large amount of nuclear fusion, fragmentation and necrosis were found in PC3-PSMA tumors in Group 1 compared to Group 2 and 3. In Group 1, tumor apoptosis (72.5/1,000 µm2) and CD8+ T cell infiltration (45.5/1,000 µm2 ) in PC3-PSMA tumor parenchyma was significantly higher compared to PC3 tumor (6.7/1,000 µm2 and 3.1/1,000 µm2 respectively). There was no significant apoptosis or CD8+ T cells infiltration observed in either PC3 and PC3-PSMA tumor in Group 2 and Group 3.

Conclusions

Our approach combines TGF-β insensitive with PSMA selectivity that significantly enhance the specificity and tumor killing ability of patient CD8+ T cells, and simultaneously suppress the tumor derived TGF-βinduced immunosuppression. Therefore, this construct may offer a novel therapeutic intervention for both primary CaP treatment as well as for recurrence after prostatectomy.

Funding

1.Walter S. and Lucienne Driskill Immunotherapy Research Program_x000D_ (320-5314000-30026197)_x000D_ 2.Matthews Center for regenerative medicine pilot grants 2014 _x000D_ 3.National Cancer Institute-SPORE in Prostate Cancer (P50 CA90386-01)_x000D_ 4. Developmental Therapeutics Program, FSM Division of Hematology Oncology