An Investigation of the role of the MDM2-NME interaction in cancer cells

MDM2 is a proto-oncogene well known for its role as a negative regulator of the p53 tumour suppressor. It has also been demonstrated that co-upregulation of MDM2 and wild-type p53 is linked with reduced disease specific survival in renal cell carcinoma (RCC). Moreover, MDM2 expression has been shown to promote cell motility and invasiveness in several cancer cell types including RCC cells in a p53- and RING-finger- independent manner, suggesting a role for protein-protein interactions in mediating this effect. The work presented in this thesis has aimed to study the role of MDM2 interaction with other proteins, in particular with members of the NME (Non-metastatic protein) family of metastasis suppressing genes, in order to decipher the mechanisms of action by which MDM2 may contribute to a more aggressive phenotype in cancer cells. To accomplish this we have used a range of methodologies including investigating the consequences of MDM2 expression using exon array analysis in an attempt to identify changes in gene expression induced by wild type MDM2 (Clone 9) and an MDM2 RINGmutant (RFM9) expressed stably in clonal derivatives of H1299 cells. In parallel studies in our research group, an interaction was identified between MDM2 and NME2. Since NME2 is a member of a family of genes that has been implicated in metastasis suppression, and since metastatic spread is a primary determinant of patient survival, we also focused on an analysis of this interaction. Thus the primary aim of this work became an examination of the mechanistic details and consequences of MDM2-NME interaction in cancer cells. The two most highly expressed forms of NME genes in most cell types are the highly related NME1 and NME2 genes which both encode nucleoside diphosphate kinase (NDPK) activity, essential for maintaining cellular pools of nucleoside triphosphates. They are also metastasis suppressor genes with an ability to suppress cellular motility. Since MDM2 possesses an E3 ubiquitin ligase activity, we have investigated whether MDM2 has ...