In addition, around 4 in 10 UK cancer cases every year could be prevented, that’s more than 135,000 each year*. So understanding more about why people develop cancer and how it might progress can provide life-saving insights for patients.

Professor Chrissie Thirlwell is a leading expert in cancer genomics who joined Exeter Medical School as the Mireille Gillings Professor of Cancer Genomics in 2019. It is already known that there is an increased risk of developing certain cancers including bowel and uterine in individuals with type 2 diabetes and obesity. Chrissie’s research has been investigating the biological processes linking these conditions, with the ultimate goal of cancer prevention, earlier diagnosis, novel treatment strategies and improved outcomes.

Chrissie says: “By sequencing the genes in an individual patient’s cancers, we can gain life-saving insights into how their cancer might progress and, crucially, what drugs will be the most effective. This personalised approach to treatment has a huge impact because a drug that is life-saving for one patient might not work very well for another. Identifying new cancer-causing genetic mutations could also save lives in the future because some mutations are potential targets for new treatment. Alongside this we can also learn about how cancers develop and identify people who might be at higher risk of developing cancer.

“The human genome is a wonderful thing. We have three billion base pairs (DNA molecules) made up of the four letters of the DNA alphabet – A, C, G, T – which carry the instructions to make all living organisms. If you lay these three billion base pairs out it measures just over a metre and in every one of our cells there’s a tiny nucleus six microns across. Every time our cells divide this is unpacked, copied accurately, and then packed back up, so if you think that every time this happens you’re copying three billion letters, sometimes mistakes are going to be made and that’s essentially the basis of how most cancers develop.

“Cancer is often described as a disease of the genome because these mistakes can happen as cells divide but it’s also a disease of aging because of the number of times that our cells are dividing. We also know that some cancers arise due to inherited mutated genes from either or both of our parents, and that lifestyle and other environmental factors play an enormous part in cancer development.

“There are also strong links to other changes and modifications to our DNA called epigenetics. Over the last 10 years we’ve led integrated genomic analysis of some quite rare and really intriguing tumours and have seen there are different layers of control that turn our genes on and off. We’ve learned that neuroendocrine tumours actually have very few mutations in their DNA and it’s other mechanisms turning these genes on and off that are driving them. Some of these epigenetic changes reflect lifestyle and environmental impact – smoking, diet and other things such as body mass index.”

Chrissie’s research team has analysed hundreds of tumours to understand their biology and identified molecular subgroups which have led to differing outcomes. This process is now routine in the NHS to guide treatment but they have also been investigating at a much earlier pre-invasive stage to understand what drives cancer development before tumours appear.

Chrissie says: “This work has focused on lung cancer where smokers often have a bronchoscopy (a camera down the airway to check the lungs) and we often see an area in the lung that is clearly not normal but we’re not sure if the body will just get rid of it or if it will develop into cancer.

“We’ve performed comprehensive genomic analysis on tiny pieces of tissue and looked at these preinvasive lesions and from this we found molecular changes that could tell us if a pre-invasive lesion will go on to become a cancer. So from the first biopsy that is done we could have a readout that will tell you actually this is going to go away or this is going to become an invasive cancer.”

Trials are now underway to see if this work can be transformed into a screening programme for lung cancer and the team are also trying to learn how our body can overcome and remove cells which have mutations in them before the cells become cancerous. This knowledge could potentially be used in future to prevent cancer occurring in the first place.

Chrissie’s role at the University of Exeter was funded from a £10 million donation from the Dennis and Mireille Gillings Foundation. Three Mireille Gillings Professorial Fellows in Health Innovation provide opportunities for female leaders to develop the business acumen required to lead entrepreneurial activity that will have meaningful benefits for health worldwide.

* Cancer Research UK