Tensin regulation of tumour cell movement: a link between metabolism and motility

Cancer cells generate their energy mostly through a process known as glycolysis. In normal cells this only usually occurs when oxygen supply is limited, but cancer cells use this pathway preferentially, even when oxygen is present (aerobic glycolysis). There is some debate as to the advantage this confers to tumour cells, since it is an inefficient pathway for generating energy, but it is thought that it provides tumour cells with a growth advantage by generating molecules required for cell division. The potential for cancer cell metabolism to impact on patient management has been shown through the use of positron emission tomography (PET) for the detection of tumours. However, it is becoming clear that rather than being simply a marker for detection, a tumour cell's glycolytic nature may alter cell function. Recently we have found that aerobic glycolysis in cancer cells promotes cell invasion, and this may link altered tumour metabolism with tumour spread.

Motility in cancer cells in particular has great significance, as it is required for cancer cells to spread either into local tissues (invasion) or other parts of the body (metastasis). Movement through tissues requires cancer cells to interact with the extracellular matrix (ECM), and this is regulated through specialised integrin receptors on the cell surface. We are interested in a molecule called Tensin, which serves to link integrins to scaffolding (structural) proteins inside the cell. Far from acting solely as a structural support, we have found that Tensins play a role in cancer cell movement, and that expression of these molecules can be regulated by cell metabolism; aerobic glycolysis in cancer cells results in the activation of a metabolic sensor (CtBP2 protein), which controls the level of Tensin. In turn, this affects the way in which cancer cells adhere and/or move on the ECM and provides a novel link between metabolism and motility.

Through our work exploring the relationship between tumour metabolism, Tensins and extracellular matrix interactions, we hope to identify key targets in the metabolic sensing and signalling pathways, furthering our understanding of the mechanisms regulating tumour cell invasion and metastasis, and possibly enabling the identification of new diagnostic and therapeutic targets.

I am a 3rd year otolaryngology (ENT)/head & neck surgical trainee, with a strong desire to use molecular biology techniques to revolutionise our approach to cancer. This research is being performed in a UK centre of excellence at the University of Southampton, and involves the combined research expertise of two Internationally recognised leading groups in these disciplines. The methods and techniques that I will master during this research include a variety of cell-based assays and will be key not only for my future academic career, but will also enable the development of key research skills within the surgical community. I am passionate to drive this collaboration between science and surgery forward.

Background: Cell metabolism is likely to influence many cellular processes, and we have recently identified a novel relationship between a metabolic sensor (CtBP2) and Tensin-4, a structural adaptor protein. Our preliminary data show that increased glycolysis modulates CtBP2-dependent expression of Tensin-4. Tensin-3 and -4 have a key role in regulating integrin-dependent interactions with the extracellular matrix, including adhesion, motility and also modulating TGF-beta activation.
Objectives/Methodology: 1) What are the functional roles of the Tensin isoforms in vitro? We will utilise gene knockdown of the Tensins in integrin-dependent functional assays.
2) How does the metabolic sensor CtBP2 regulate Tensin-4 to control a cell's motile/invasive phenotype? We will initially perform time course experiments with the temporal analysis of PTEN/Talin/Tensin-4 mRNA levels after CtBP knockdown, then further dissect these through specific signallling pathway inhibitor studies. To address whether CtBP2 is directly recruited to the Tensin-4 promoter, a chromatin immunoprecipitation (ChIP) analysis will be performed.
3) Do Tensin-3 and -4 contribute to a signaling complex regulating TGF-B 1 activation? We will use TGF-B1 activation assays utilising gene knockdown and specific inhibitors.
4) What is the expression of Tensin isoforms in human tumours? Tissue microarrays of multiple tumour types will undergo immunhistochemisty analysis.
5) Do Tensins promote tumour progression in vivo?
Scientific/Medical Opportunities: We will explore how metabolism regulates cell-ECM interactions, which may uncover new targets of diagnostic and therapeutic importance. Importantly, the project will determine the role of Tensins in cancer and determine how cell metabolism may be regulating a tumour's invasive phenotype. Long-term the simultaneous inhibition of both Tensin-4 and CtBP may lead to potent effects, especially in the realm of inhibiting cancer cell invasion and metastasis.

This proposal is for a novel basic science research project, in an area which is generating much scientific interest currently with direct translational relevance. The project plan and associated deliverables have been carefully designed to maximise the achievability, success and potential impact of the work.
Who might benefit from this research?
1. Basic Science: Cell motility/Metabolism cross-discipline researchers.
2. Clinical Academia: Head & Neck/Thyroid research teams.
3. General public: patients with head & neck/thyroid disease.
4. Health and Pharmaceutical industry.
5. University of Portsmouth.

How might they benefit from this research?
1. Many of the academic beneficiaries have already been outlined in the relevant section. However, there are a few specific benefits to academia with potential change of practice/research development and economic implications.

As a nascent academic surgeon, I have a passion for bridging the gap between laboratory-based research and clinical practice, and understand the importance of developing basic research findings in order to bring real benefits to patients. I also recognise the opportunity I have to encourage surgical interest in basic science research, and will use every opportunity to present at surgical meetings e.g. Royal Society of Medicine specialty meetings, to engage clinical leaders and enthuse early career researchers. The scientific impact of this work, with direct clinical and translational relevance, will help attract R&D investment from clinical and disease-specific funds into our specialty of otolaryngology.

In addition, utilising the expertise of our group in 3-dimensional tumour modelling, I have started to develop a novel organotypic model for the study of thyroid cancer invasion. As far as I am aware, no such model currently exists. With further optimisation, this new assay technique will directly benefit worldwide thyroid research teams, allowing detailed study of thyroid cancer cells in vitro, in a more physiologically relevant invasion model.

2. This project has long-term potential to identify important novel targets for developing new anti-tumour strategies. However, we anticipate possible short-term findings that may be of clinical importance.

To highlight one KEY early finding, we have identified a significant potential health benefit to patients with thyroid nodules. We have discovered that the presence of a specific protein called Tensin-3 appears to differentiate benign thyroid follicular adenomas from malignant follicular cancers. Currently this diagnosis can only be made post-operatively with histological analysis, meaning 70-80% thyroid surgeries are for benign disease. Mr Dae Kim, a co-supervisor on this application holds the position of Royal College of Surgeons National Speciality lead for Research for Endocrine Surgery. Therefore, as a project team we are perfectly placed to engage the specialty leaders and develop further biomarker trials, in the hope of developing a new national policy for thyroid nodule management with significant benefits to patients. In addition this has the potential to save millions of pounds to the NHS from unnecessary surgery.

3. Long-term may result in strategies to manipulate tumour cell metabolism. If our hypothesis is correct, suppressing aerobic glycolysis of tumour cells, or interfering with the signalling pathways activated through this process, may be of use in inhibiting cancer cell invasion and metastasis. Our research therefore may have real potential for identifying new potential therapeutic targets of interest for pharmaceutical development.

4. As outlined in our collaborations, we have developed a mutually beneficial relationship with Dr. Sassan Hafizi's group at the University of Portsmouth. The joint sharing of assay techniques and scientific expertise between our groups will offer great potential for future cross specialty projects and knowledge exchange.