Clinically relevant orthotopic pancreatic cancer models for adoptive T cell therapy

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor. Prognosis is poor and survival is low in patients diagnosed with this disease; ∼12% at 5 years. Immunotherapy, including adoptive T cell transfer therapy, has not impacted outcomes in PDAC patients, due in part to the hostile tumor microenvironment (TME) which limits T cell trafficking and persistence. We posit that murine models serve as useful tools to study the fate of T cell therapy. Currently, genetically engineered mouse models (GEMM) for PDAC are considered a “gold-standard” as they recapitulate many aspects of human disease. However, these models have limitations, including marked tumor variability across individual mice and cost of colony maintenance. We characterized the immunologic features and trafficking patterns of adoptively transferred T cells in orthotopic PDAC models using two mouse cell lines, KPC-Luc and MT-5, isolated from KPC-GEMM mouse models (KrasLSL-G12D/+p53-/- and KrasLSL-G12D/+p53LSL-R172H/+, respectively). The MT-5 orthotopic model best recapitulates the cellular and stromal features of the TME in the PDAC GEMM. In contrast, far more host immune cells infiltrate KPC-Luc tumors, which have less stroma. Albeit CD4+ T cells were similarly detected in MT-5 tumors compared to KPC-GEMM in mice. Interestingly, we found that CAR T cells redirected to recognize mesothelin on these tumors that signal via CD3σ and 41BB (Meso-41BBσ-CAR T cells) post antigen recognition infiltrated the tumors of mice bearing stroma-devoid KPC-Luc orthotopic tumors, but not MT-5 tumors. Our data establish for the first time a reproducible and realistic clinical system useful for modeling stroma-rich and stroma-devoid PDAC tumors. These models shall serve in-depth study of how to overcome barriers that limit anti-tumor activity of adoptively transferred T cells. ### Competing Interest Statement The authors have declared no competing interest. * ACT : adoptive cell therapy ASI : activated stroma index ɑSMA : alpha smooth muscle actin CAF : cancer associated fibroblast CAR : chimeric antigen receptor DAB : 3,3’-diaminobenzidine ECM : extracellular matrix GEMM : genetically engineered mouse models IHC : immunohistochemistry KPC : Krax, p53, cre LOF : loss of function LUAD : lung adenocarcinoma Luc : luciferase LUSC : lung squamous cell carcinoma mesoCAR : chimeric antigen receptor expressing T cells directed against mesothelin PDAC : pancreatic adenocarcinoma TBI : total body irradiation TGCA : the cancer genome atlas program TIL : tumor infiltrating lymphocytes TME : tumor microenvironment