Mapping the Cellular and Spatial Landscape of Metastatic Melanoma

Abstract

Novel treatment strategies for metastatic melanoma have significantly improved patient outcomes in the last decade. To increase the number of patients that respond to available therapies and do not develop resistance, researchers must uncover the biological mechanisms involved in response. This study aimed to address this by profiling the cellular composition of metastatic melanoma and identifying novel features involved in tumour progression and response to therapy. First, we examine the immune infiltrate of metastatic melanoma tumours using high-parameter cytometry and identify two novel myeloid populations that are enriched in tumours of patients that responded to PD-1 immunotherapy when compared to non-responders. Secondly, we employ high-parameter imaging techniques to examine the spatial landscape of metastatic melanoma in treatment naïve lymph-node associated samples from 100 patients with metastatic melanoma that were enrolled in clinical trial ANZMTG 01.02/TROG 02.01. We identify many different cell types in high-tumour regions of metastatic melanoma, including immune, stromal and tumour cells. We find that patients with more activated, proliferating and functional immune cells within tumour regions were more likely not to relapse and to survive longer. Throughout these studies, we compare the accuracy, efficiency and value of the various computational methods employed to analyse high-parameter proteomic and transcriptomic data. We also establish a true multi-omics experiment by successfully performing sequential in situ hybridisation (transcriptomics), high-dimensional protein staining (proteomics) and histochemical staining. This thesis presents a comprehensive overview of the TME in metastatic melanoma and contributes to a better understanding of how cells co-operate within tumours, highlighting possible avenues for clinical treatment strategies and progresses the implementation of spatial omics in tumour immunology.