Analysis of the Tumour Microenvironment in CLL
This thesis applies systems biology approaches to obtain a better understanding of complex cellular systems in Chronic Lymphocytic Leukaemia (CLL).CLL is a cancer of the blood which affects B cells. CLL cells accumulate quickly in the body but die rapidly by apoptosis when cultured in the lab, suggesting that CLL cell survival can be modulated by tumour cell interactions with the microenvironment in vivo. The first part of the thesis describes in vitro assays which demonstrated that CLL cell contact with endothelial cells in a co-culture system promotes CLL cell survival. The precise mechanisms involved remain unknown, however, they are thought to include both secreted factors and receptor:ligand interactions between CLL cells and the microenvironment. The second part of the thesis is based on gene expression profiling and investigates the transcriptional effects induced in CLL cells by co-culture. We identified genes that were statistically significantly up regulated >1.5 fold compared with liquid culture (q<0.001) and were common to two endothelial systems. The third part of the thesis focuses on cell surface proteins which allow CLL cells to communicate with other cells. In order to obtain a comprehensive analysis of the cell surface proteome of CLL cells, we developed a method utilising cell impermeable, cleavable sulfo-NHS-SS-biotin to enrich for cell surface proteins followed by high-content mass spectrometry (LC-MS/MS) for identification. Somewhat surprisingly, a number of proteins were identified which have traditionally been classified as intracellular. Some of these have been previously identified as specific binding partners for CLL B-cell receptor (BCR) stereotypes. It is possible that the BCR activation observed in CLL occurs as a consequence of binding to these aberrantly expressed autoantigens. This study provides insights into the mechanisms that underpin the cytoprotection afforded by CLL cell-endothelial cell co-culture and identifies potential new targets for disrupting these signals in vivo.
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