Impacts of glycosylation and mitochondrial mutations on prostate cancer cells

Prostate cancer is the most common non-cutaneous cancer in men in Europe and the USA. It is significantly age-associated and we have previously found that metabolism is altered and mutations accumulate in mitochondria. In the course of the last year we have identified a protein which regulates the growth potential of prostate cancer cells and is regulated in its expression and stability by the androgen receptor and by glycosylation. We have shown that drug combinations targeting these properties can have a significant cell death-inducing effect on prostate cancer cells. We have also identified additional druggable targets that are glycosylated and are associated with changes to DNA structure. This enables is to test additional treatment combinations and we are now working on the function of these targets in prostate cancer cells. We have also been able to characterise the properties of prostate cancer cells that are depleted of mitochondria and have been able to introduce mitochondria carrying disease causing mutations into these cells. We have found that many of the aforementioned drug combinations are not effective in the mitochondrially depleted cells and that the mutation carrying cells have higher levels of oxidative stress. This reinforces the importance of mitochondrial function in determining treatment response and in prostate cancer development. Further study of these modified proteins and cell-line derivatives will provide further opportunities to reposition clinically approved drugs for cancer therapy and develop new biomarkers.

Achieved:- 1. We have identified a protein which mediates the cross-talk between c-Myc and p53 in prostate cancer cells. 2. We have identified functional co-dependencies between OGlcNAcylation and lipid/amino acid metabolism, CDKs and neddylation. 3. We have identified OGlcNAc-enriched proteins associated with RNA splicing, processing and chromatin-modifying complexes. 4. We have undertaken a characterisation of antibodies raised against OGlcNAc-modified sites in c-Myc and p53. 5. We have generated mitochondrially depleted and mutated prostate cancer cell-lines, characterising their responses to treatment. Potential:- 1. Biomarkers - We are evaluating a novel OGlcNAc/AR co-regulated factor as a biomarker for stratifying prostate cancer patients. 2. Treatments - We are using molecular co-dependencies to identify actionable therapeutic combinations. 3. New biological research - This will be build on our identification of novel novel OGlcNAc-enriched proteins.

The development of high-throughput massively parallel sequencing has allowed the comprehensive identification of these sites across the genome and the availability of matched gene expression data from the same samples allows regulatory associations betwee n sites and gene expression to be identified. Using this approach gene networks associated with metabolism and cell cycle regulation have been found to be controlled by the AR. Gene expression data from localized PC reveals that prior to progression it is possible to classify PC based on metabolic gene signatures and metabolite profiling in the absence of high rates of cell proliferation. Cell cycle dysregulation occurs during progression to metastatic disease. Sequencing has also allowed the systemat ic identification of somatic mutations in prostate cancers. Localised PC is defined by a much lower incidence of autosomal mutations in archetypal autosomal cancer genes such as TP53, a high-degree of mutational heterogeneity from cancer focus to cancer focus within the prostate and a high abundance of somatic mitochondrial mutations found in the cancer foci versus surrounding tissue or blood samples from the same patients. These observations collectively reinforce the hypothesis that metabolic changes may constitute and promote the early stages in the development of PC and provide the basis for this application. The application consists of two parts:- 1. Do changes in the expression of metabolic genes and metabolite levels affect chromatin expression and gene expression creating an interplay which enhances the activity of oncogenic transcription factors such as the AR? 2. Do the introduction of mitochondrial mutations and/or the differential expression of metabolic genes provide the basis for new mo dels of PC progression? This question is central to a point made earlier which is that it is not currently clear whether localized PC and CRPC are distinct or connected diseases.