Abstract A01: Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) for the treatment of bladder cancer
Authors: Bunch Brittany L. , Morse Jennifer , Asby Sarah , Poch Michael , Pilon-Thomas Shari 
Published: August 2020

Abstract
Bladder cancer remains a leading cause of death and one of the most expensive cancers to treat in the United States. Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) is a personalized therapeutic approach that has the potential to treat bladder cancer at every stage of disease. We have previously demonstrated the ability to expand tumor reactive T cells from transurethral resection, radical cystectomy, and metastatic lymph node tumor specimens collected from bladder cancer patients. In this study, our goal is to investigate different delivery approaches of ACT in vivo to determine the best strategy to decrease tumor burden and advise clinical trial design. Experiments were performed using MB49 murine bladder cancer cells transfected to express ovalbumin (MB49OVA). MB49OVA cells are recognized by OVA-specific OT-I T cells as determined by IFN-gamma production in vitro. Our methods include both subcutaneous and orthotopic bladder tumor models. In vivo, we first tested systemic delivery of OT-I T cells (5.0 × 10e6) by tail vein injection after lymphodepletion with a regimen of cyclophosphamide followed by fludarabine in mice bearing subcutaneous MB49OVA tumors. ACT-treated mice experienced significant tumor regression (p=0.02), improved survival (median survival PBS=47 days, ACT=undefined, p=0.01), and increased tumor infiltration of CD3+, CD4+, and CD8+ T cells. OT-I T cells as well as endogenous OVA-specific CD8+ T cells were detectable in the spleens and tumors of treated mice. Next we tested the efficacy of intravesical delivery of OT-I T cells in mice bearing orthotopic MB49OVA tumors, without prior lymphodepletion. OT-I T cells (4.0 × 10e6) were delivered directly to the bladder via catherization and tumor growth was monitored weekly via ultrasound imaging. Infiltration of CellTrace Violet-labeled OT-I T cells into orthotopic tumors was detected after 3 hours of incubation by flow cytometry analysis of resected tumor. Orthotopic bladder tumor growth was significantly abrogated in ACT-treated mice compared with PBS control-treated mice (p=0.001) and improved survival was observed (median survival PBS=35 days, ACT=undefined). An increase in CD8+ T-cell infiltration was measured in tumors of mice at day 60 post treatment. In order to evaluate the efficacy of TIL transfer in these bladder tumor models, T cells infiltrating subcutaneous MB49OVA tumors were isolated and cultured in vitro in media containing IL-2. After 1 week, bladder TIL demonstrated reactivity against MB49OVA and MB49 parental cells as determined by IFN-gamma production. Future work will implement the adoptive transfer of MB49 TIL for the treatment of orthotopic bladder tumors alone or in combination with anti-PD-L1 therapy. Taken together, these data suggest that ACT using bladder tumor-specific T cells has the potential to reduce bladder tumor burden when given either systemically or intravesically directly into the bladder.
Citation Format: Brittany L. Bunch, Jennifer Morse, Sarah Asby, Michael Poch, Shari Pilon-Thomas. Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) for the treatment of bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2019 May 18-21; Denver, CO. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(15_Suppl):Abstract nr A01.