T cell based immunotherapies in oncology; new approaches and improved strategies

Abstract

Various strategies for improving and broadening the efficacy of T cell therapies are currently being investigated. With the use of tumour-reactive γδ TCRs, a broad range of tumours can be targeted. However, the molecular mechanisms required in the malignant cell for recognition by these γδ TCRs remain partially opaque. Next to the identification of targetable mechanisms in tumour cells, T cell behaviour and activity in the tumour microenvironment (TME) provide additional roadblocks for optimal therapy efficacy. Within this thesis, we show how new strategies for improving the efficacy of γδT cell therapies can be identified and tested. In Chapter 3 we investigate which processes in healthy cells induce a malignant phenotype recognised during the immune surveillance of Vγ9Vδ2T cells. We demonstrated that single oncogenic mutations in tumor cells lead to increased PI3K activity induced surface expression of BTN2A1, allowing the binding of Vγ9Vδ2TCR. Furthermore, we identified PHLDB2, SYNJ2 and CARMIL1 as vital players in controlling surface dynamics of BTN2A1 and 3A1. Identification of these processes in early malignant cells highlights the potential of γδ TCR-based therapies in the treatment of malignancies. In Chapter 4 we combine two genome-wide CRISPR screening approaches to identify what pathways in the tumour cell regulate BTN3A cell surface expression, Vγ9Vδ2 TCRs binding and T cell killing. These screens identified that stimulation of the AMPK pathway in tumour cells increased the expression of the BTN2A1–BTN3A complex and enhanced Vγ9Vδ2 T cell receptor-mediated killing, highlighting the potential this approach to enhance the anticancer activity of Vγ9Vδ2 T cells. In Chapter 5, we identify a novel, tumour–reactive Vγ5Vδ1 TCR which shows an allogeneic, HLA-A*24:02-restricted tumour recognition pattern. Here we describe a TCR with a molecular interface at the HLA-A*24:02 peptide binding groove which binds malignant cells independent of the peptide presented. Identification of these Vδ2- TCRs shows the potential of these irregular γδ TCRs in cellular therapies in the context of targeting cancer. In Chapter 6 we describe a method to increase the infiltration of adoptive cellular therapies such as TEGs or CARs, within the tumour micro-environment. In this study, T cell infiltration patterns were investigated in 3 dimensional in vitro TME models which identified the pivotal role of the chemokine CCL4 in inducing T cell infiltration. We show that overexpression of the CCR5 chemokine receptor in T cell products improves infiltration towards the TME and increases the killing of multiple tumor types. In Chapter 7 we focus on the role of the mesenchymal stromal cells (MSCs) in modulating T cell responses within the malignant bone marrow niche. Using malignant bone marrow models, we found that the genetic makeup of MSCs, which is determined by donor origin, define the outcome of adoptive T cell therapies. These results indicate that we can use in vitro tumor models to identify novel targets for modifying T cell therapies to enhance clinical efficacy. Chapter 8 summarises the results of the previous chapters and discuss how these findings fit within the broader field of γδ, αβ and CAR T cell therapies.