Professor David Finlay

A new immunoregulatory axis has emerged in recent years demonstrating that cellular metabolism is crucial in controlling immune responses. This regulatory axis is acutely sensitive to nutrients that fuel metabolic pathways and support nutrient sensitive signalling pathways. My recent research demonstrates that nutrients are dynamically controlled and are not equally available to all immune cells. The data shows that activated T cells, clustered around a dendritic cell (DC), can consume the available nutrients, leaving the DC nutrient deprived in vitro. This local regulation of the DC nutrient microenvironment by neighbouring cells has profound effects on DC function and T cell responses. Nutrient deprived DC have altered signalling (decreased mTORC1 activity), increased pro-inflammatory functions (IL12 and costimulatory molecule expression) and induce enhanced T cell responses (proliferation, IFN production). However, proving this, particularly in vivo, is a major challenge as the tools to investigate nutrient dynamics within complex microenvironments have not yet been developed. This research programme will generate innovative new technologies to measure the local distribution of glucose, glutamine and leucine (all of which control mTORC1 signalling) to be visualised and quantified. These technologies will pioneer a new era of in vivo nutrient analysis. Nutrient deprivation of antigen presenting DC will then be investigated (using our new technologies) in response to various stimuli within the inflammatory lymph node and correlated to CD8 T cell responses. We will generate state-of-the-art transgenic mice to specifically knock-down nutrient transporters for glucose, glutamine, or leucine in DC to definitively prove that the availability of these nutrients to antigen presenting DC is a key mechanism for controlling CD8 T cells responses. This would be a paradigm shifting discovery that would open new horizons for the study of nutrient-regulated immune responses.

Effective anti-tumour immune responses rely upon key effector immune cells, such as Natural Killer (NK) cells, sustaining their anti-tumour activity within the inhospitable tumour microenvironment. Our initial data suggest that NK cell glucose metabolism is closely linked to key anti-tumour functions. Activated NK cells that cannot maintain elevated glycolysis do not sustain the expression of key anti-tumour molecules, IFNγ and granzyme B. This data provides a new perspective to explain defective NK cell function within the tumour microenvironment. We hypothesise that the tumour microenvironment represses NK cell anti-tumour functions by disrupting NK cell metabolism. This project will fully characterise the relationship between NK cell metabolism and function and investigate the mechanisms involved using state-of-the-art technologies including various transgenic mouse models. Central to this research will be the identification of novel metabolic biomarkers, using mass spectrometry-based proteomics, that accurately report on NK cell metabolism and thus NK cell anti-tumour functions. These analytical tools will allow the effect of the tumour microenvironment on NK metabolism and function to be accurately monitored in vivo, but will also have widespread applications in pathological diagnostics and prognostics that will ultimately lead to enhanced patient management.

Modulating immune responses by shifting the balance of effector versus regulatory/memory T cells has significant potential as a therapy for various autoimmune diseases and preventing organ transplant rejection. The mammalian Target Of Rapamycin Complex1 (mTORC1) has diverse effects in T cells and dictates T cell fate. mTORC1 inhibition provides potent immunosuppression but is associated with significant toxicity. Dissecting the mechanisms that account for the multiple mTORC1 effects on T cell differentiation would allow for the design of therapies that provide desirable immunomodulation with less toxicity. Recent data suggests mTORC1 integrates the control of T cell glucose metabolism and differentiation by controlling the HIF1 transcription factor complex. mTORC1 also regulates lipid metabolism through the control of Srebp1c, though this has not been investigated in T cells. Given that lipid metabolism has also been linked to the control of T cell fate, it seems crucial to comprehensively study the role of mTORC1/Srebp1c signalling in T cells. Preliminary data confirms mTORC1 dependent Srebp1c expression and activity in T cells. This project aims to study mTORC1/Srebp1c with respect to lipid metabolism, differentiation and function of T cells. This will be achieved using pharmacological and genetic approaches and using state of the art in vivo technologies.

Cancer immunotherapy is being heralded as the most important advances in cancer therapy since the discovery of the first chemotherapeutic agents. A growing number immunotherapeutic strategies demonstrate how the immune system can eradicate tumours once it is given appropriate instruction. It is well established that NK cells have important roles in the anti-tumour effect of immunotherapeutic strategies. It is therefore imperative to understand factors that might affect the ability of cancer patients NK cells to mount a robust anti-tumour response during the course of cancer immunotherapy. Dr Finlay's research has demonstrated the importance of NK cell metabolism in facilitating robust NK cell responses. NK cells that cannot up-regulate rates of glucose metabolism have reduced expression of key effector molecules. Furthermore, recent data argue that elevated levels of cholesterol and oxidised cholesterol derivatives (oxysterols) prevent the up-regulation cellular glucose metabolism in activated NK cells and the acquisition of normal NK cell effector function. Dr Finlay's research suggests that this effect of cholesterol/oxysterols is mediated by the ability of these sterol molecules to inhibit the action of the Srebp transcription factors. This preliminary data has lead us to the hypothesis that cholesterol/oxysterol mediated inhibition of Srebp transcription factors limits NK cell metabolism and represses the NK cell anti-tumour response. This project will robustly test this hypothesis using complementary pharmacological and mouse transgenics approaches and combined with detailed biochemical analyses and murine tumour models. The key findings will be validated in human NK cells isolated from PBMC of healthy donors. Through a collaboration with Dr Hogan at St Vincent's hospital, serum samples from patients with high levels of cholesterol will be collected. The effect of these serum samples on NK cell on metabolism and NK cell effector function will be investigated. Through these robust scientific approaches, we aim to establish the effect of cholesterol/oxysterols on NK cell anti-tumour responses. If validated, this novel mechanism to control NK cell responses has important implications for the treatment of cancer patients. The data would suggest that the management of patients cholesterol levels should precede the initiation of cancer immunotherapy. Altering patient management in this way could potentially lead to significant increases the efficacy of diverse cancer immunotherapeutic approaches.

Natural Killer (NK) cells are important in our bodies defence against cancer. They are lymphocytes with the ability to detect and directly kill tumour cells. However, in cancer patients NK cells are often found to be dysfunctional. Dr Finlay's lab has recently made the discovery that activated NK cells show dramatic changes in the way that they metabolise glucose that are essential for their functions including the ability to kill cancer cells. A key and highly novel finding was that the key regulator of this metabolic response is a factor called Sterol regulatory element binding protein, or Srebp. When Srebp is blocked, NK cells cannot undergo these metabolic changes and they fail to kill tumour cells in the lab and in a mouse model of melanoma (Assmann et al, Nat. Immunol. 2017). Srebp can be blocked by cholesterol and in particular by the cholesterol-like molecule called 25-hydroxysterol (25HC). This research has revealed a completely novel way to control anti-tumour NK cell functions through regulating the activity of Srebp. Cancer cells have been described to produce and secrete 25HC. Additionally, activated macrophages express high amounts of the enzyme that makes 25HC, and macrophage-derived 25HC is emerging as important in the regulation of inflammatory responses. In addition, 25HC levels are elevated in individuals with high blood cholesterol levels (hypercholesterolemia). This project will investigate the impact of 25HC produced by macrophages, tumour cells or due to a high cholesterol diet, on NK cell metabolic and functional responses. This will be achieved using various cutting-edge approaches including metabolic analyses and tumour cytotoxicity assays. NK cells functions will also be monitored in mice fed a high cholesterol diet. This project will increase our understanding of the control of NK cell anti-tumour functions and provide important insight into why NK cells are dysfunctional in cancer patients.