Miess, H; (2015) Identification of metabolic genes essential for proliferation of clear cell Renal Cell Carcinoma (ccRCC) cells. Doctoral thesis , UCL (University College London).

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Abstract

Kidney cancer accounts for 2-3% of adult malignancies with clear cell renal cell carcinoma (ccRCC) being the most common histological subtype (70-80% of cases). Interestingly, ccRCCs show a highly distinct metabolic phenotype making this disease stand out amongst other cancer types. The underlying causes of the aberrant metabolism in ccRCC are not fully understood, but metabolic transformation could provide novel strategies for targeted therapies in this disease. The pVHL tumour suppressor is located on chromosome 3p21, which is frequently lost in ccRCC. pVHL is a negative regulator of the Hypoxia-inducible factor (HIF), which orchestrates the cellular response to oxygen deprivation and might contribute to the aberrant metabolic phenotype of ccRCC cells. In order to reveal metabolic weaknesses in ccRCC, a customised RNAi screen targeting 230 different metabolic enzymes, regulators and nutrient transporters was performed. The screen was performed in a panel of 5 ccRCC pVHL-null cell lines and included their counterparts with reconstituted pVHL, in order to also identify potential vulnerabilities that depend on VHL function. With this approach, several genes that are essential for ccRCC cell viability but dispensable for the survival of non-malignant renal epithelial cells were identified. It was found that ccRCC cell lines are highly sensitive to ablation of components of the glutathione-dependent reactive oxygen species (ROS) detoxification system. Silencing of enzymes of the glutathione biosynthesis pathway or different glutathione peroxidases (GPXs) severely impaired cell viability. One of the precursors of glutathione biosynthesis is glutamate, which is generated from glutamine by glutaminase (GLS). Interestingly, there is evidence that ccRCCs are highly dependent on the MYC oncogene, which induces many enzymes within the glutaminolysis pathway. Indeed, we found that glutamine starvation or chemical inhibition of GLS reduced proliferation and viability of ccRCC cells, confirming the importance of this pathway in ccRCC. In conclusion, the study reported in this thesis provides insight into the metabolic dependencies of ccRCC cells and emphasises the need for a solid anti-oxidant system for ccRCC cell survival and proliferation. Concomitantly, the reliance of ccRCC cells on glutamine and glutathione is a vulnerability that could potentially be exploited for diagnostic and/or therapeutical applications.

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