Dual-specific Chimeric Antigen Receptor T Cells and an Indirect Vaccine against Pancreatic Cancer

Abstract

Pancreatic cancer is one of the most aggressive malignancies with an overall 5-year survival rate of <7%. Pancreatic cancer is highly resistant to radiotherapy and chemotherapy, and surgery is not feasible in most patients. In this thesis, I developed a new form of treatment for pancreatic cancer, based on immunotherapy. Adoptive cell transfer (ACT) is a promising form of cancer immunotherapy, which involves the isolation and reinfusion of tumour specific T lymphocytes into patients. While ACT can eliminate substantial burdens of some leukaemia, the ultimate challenge remains the eradication of large solid tumours and metastases for most cancers, including pancreatic cancer. In this thesis, an enhanced ACT treatment strategy for pancreatic cancer was developed, which was termed ‘ACTIV: Adoptive Cell Transfer Incorporating Vaccination’. This treatment included dual-specific T cells that expressed a chimeric antigen receptor (CAR) specific for the tumour antigen Her2, and a TCR specific for the melanocyte protein (pMEL, gp100). These dual specific T cells were termed ‘CARaMEL T cells’. CARaMEL T cells were administered together with an injection of a recombinant vaccinia virus vaccine expressing gp100 (VV-gp100). We hypothesized that adoptively transferred CARaMEL T cells would proliferate mediated by their gp100 TCR, in response to the VV-gp100 vaccine, and kill Her2+ tumours through their anti-Her2 CAR. Functional assays performed in vitro indicated that murine CARaMEL T cells mediated antigen-specific cytokine secretion and killing abilities against pancreatic cancer cells, and demonstrated potent proliferative ability in response to gp100 antigen, confirming our hypothesis. In addition, I found that ACTIV therapy inhibited tumour growth and prolonged the survival of mice bearing Her2+ subcutaneous murine pancreatic tumour. However, tumours usually relapsed after ACTIV therapy administration. Therefore, I directed my study to augment the anti-tumour activity of ACTIV therapy by the administration of either a histone deacetylase inhibitor (Panobinostat) or an immune agonist monoclonal antibody specific for CD40. Panobinostat significantly suppressed the growth of pancreatic cancer cells in vitro through apoptosis and cell cycle arrest. Also, Panobinostat significantly increased the growth suppression of pancreatic cancer cells mediated by CARaMEL T cells. In addition, I found that the combination of ACTIV therapy and Panobinostat significantly reduced the tumour growth and prolonged the survival of mice bearing Her2+ subcutaneous murine pancreatic tumours. In addition, administration of an agonist CD40 monoclonal antibody with ACTIV therapy significantly reduced the tumour growth and prolonged survival of mice bearing subcutaneous Her2+ pancreatic tumours through a T-cell-dependent immune mechanism. Finally, I explored the clinical translational potential for ACTIV therapy through the generation of human CARaMEL T cells expressing both a Her2-specific CAR and a gp100-TCR. In vitro functional assays indicated that human CARaMEL T cells mediated powerful and antigen-specific killing and cytokine secretion against Her2, together with a strong proliferative ability in response to gp100 antigen. In addition, I found that the administration of both human CARaMEL T cells and an adenovirus vaccine expressing gp100 led to potent anti-tumour activity against subcutaneous human Her2+ pancreatic tumours in immunodeficient mice.