Uveal Melanoma: Genetic and Epigenetic Characterisation

Uveal melanoma (UM) is the most common primary intraocular tumour and has a high propensity for liver metastasis. The mechanisms that drive metastatic spread and drug resistance are largely unknown. The doctoral thesis consists of three separate papers investigating basic mechanisms in UM, thus outlining future potential treatment strategies. The first paper sheds light on potential adaptive mechanisms in UM during cancer dissemination by exploring the effect of cell culture conditions (biopsies vs adherent cultures vs tumoursphere cultures) on gene expression. The tumoursphere cultures displayed traits associated with anoikis resistance, a shift towards a lipogenic profile and an upregulation of synovial sarcoma X breakpoint proteins (SSXs), known targets for immunotherapy in several cancers. The second paper investigated differential DNA methylation in archived formalin-fixed paraffin-embedded UM specimens. DNA methylation profiling showed differential clustering of samples according to chromosome 3 status. Integrated differential DNA methylation and gene expression of two subsets of samples identified genes associated with early metastasis and poor prognosis. The third paper investigated the expression of Connexin 43 (Cx43) in UM vs uveal melanocyte controls, and explored the effect of an Enhancer of Zeste homolog 2 (EZH2)-inhibitor on Cx43 expression. UM displayed decreased expression of Cx43. Furthermore, reduced membrane staining and diffuse cytoplasmic localisation of Cx43 in UM were observed. Inhibition of EZH2 in UM cell lines did not alter Cx43 expression, though a reduction of the histone modification H3K27me3 regardless of BRCA1- Associated Protein 1 (BAP1) status was evident