Improving immunotherapy for melanoma: models, biomarkers and regulatory T cells

Abstract

While immune checkpoint blockade (ICB) (CTLA4/ PD1) therapy has resulted in durable responses in patients with advanced stage cutaneous melanoma, some patients do not benefit from this, due to resistance mechanisms. This thesis aims to improve response of a subset of melanoma patients to immunotherapy. Firstly, mouse melanoma tumor models are developed that closely resemble some of the resistance mechanisms occurring in patient tumors, which are useful for research. Thereafter, a prognostic biomarker is used to identify the subset of melanoma patients that are unlikely to benefit from ICB therapy. It is then evaluated whether this subset of patients would benefit from combining histone deacetylase inhibitor with ICB. Despite encouraging pre-clinical results showing enhanced anti-tumor immune responses using this combination, this did not result in improved responses in the clinic. Furthermore, this thesis focuses on an immune cell subset, namely regulatory T cells (Tregs), which are known to suppress anti-tumor immune responses. Thus, their presence in the tumor microenvironment (TME) is detrimental to tumor cell killing. This thesis provides an increased understanding of the metabolic adaptation of Tregs to conditions in the TME and propose that targeting these adaptations might overcome the suppression by Tregs and enhance responses to immunotherapy.