Genetic Redirection of T Cells for the Treatment of Pancreatic Cancer

Abstract

Conventional treatments for pancreatic cancer are largely ineffective, and the prognosis for the vast majority of patients is poor. Clearly, new treatment options are desperately needed. Immunotherapy offers hope for the development of treatments for pancreatic cancer. A central requirement for the efficacy of this approach is the existence of cancer antigen-specific T cells, but these are often not present or difficult to isolate for most pancreatic tumors. Nevertheless, specific T cells can be generated using genetic modification to express chimeric antigen receptors (CAR), which can enable T cell responses against pancreatic tumor cells. CAR T cells can be produced ex vivo and expanded in vitro for infusion into patients. Remarkable responses have been documented using CAR T cells against several malignancies, including leukemias and lymphomas. Based on these successes, the extension of CAR T cell therapy for pancreatic cancer holds great promise. However, there are a number of challenges that limit the full potential of CAR T cell therapies for pancreatic cancer, including the highly immunosuppressive tumor microenvironment (TME). In this article, we will review the recent progress in using CAR T cells in pancreatic cancer preclinical and clinical settings, discuss hurdles for utilizing the full potential of CAR T cell therapy and propose research strategies and future perspectives. Research into the use of CAR T cell therapy in pancreatic cancer setting is rapidly gaining momentum and understanding strategies to overcome the current challenges in the pancreatic cancer setting will allow the development of effective CAR T cell therapies, either alone or in combination with other treatments to benefit pancreatic cancer patients.

Keywords: adoptive cell transfer; chimeric antigen receptor; immunotherapy; pancreatic cancer; pancreatic ductal adenocarcinoma; tumor microenvironment.

Figure 1

CAR T cell antigen-targeting strategies and pancreatic cancer TME. (A) The pancreatic TME consists of tumor cells as well as many immunosuppressive cells, such as CAFs, TAMs, MDSCs, PSCs, and Treg cells. (B) CAR T cells can be directed to the TAA expressed on pancreatic cancer cells and/or other antigens targeting the TME components, such as FAP on CAFs. (C) CARs are composed of extracellular, transmemebrane and endo-domains. The extracellular domain consists of an antibody variable heavy chain (VH) and a light chain (VL) domain, which are derived from an scFv from an antibody specific for a TAA. A flexible hinge region links the extracellular domain to a transmembrane and endodomain. The endodomain has cytoplasmic signaling regions derived from CD3ζ and costimulatory signaling domains. TAMs, tumor-associated macrophages; CAFs, cancer associated fibroblasts; MDSCs, myeloid-derived suppressor cells; Tregs, regulatory T cells; PSCs, pancreatic stellate cells; FAP, fibroblast activation protein; scFv, single chain variable fragment. TAA, tumor associated antigen; TME, tumor microenvironment.