RO1 was met by completion of work package (WP)1. Briefly, the fellow consulted with the supervisor to identify a number of hypoxia-induced metabolites to screen for potential effects on T cell function. All three screened metabolites (lactate, succinate and urea) were found to alter T cell function, with succinate and lactate found to suppress expression of the anti-tumour T cell cytokine, interferon-gamma and lactate found to have opposing stimulatory vs suppressive effects under normixa vs hypoxia respectively. The fellow decided to further interrogate the effects of succinate on T cell function, since this was the most novel finding and has substantial therapeutic potential in certain tumours (e.g. Succinate Dehydrogenase (SDH)-deficient tumours). Comprehensive immunological assays identified which precisely which aspects of T cell function were impacted by succinate. Alongside this, analysis of patient transcriptional data identified evidence of this suppressive axis in vivo. RO2 was met by completion of WP2. Briefly, in-depth metabolic tracing analyses, combined with assays of key protein expression and activity (e.g. SUCNR1, HIF1-α) identified the mechanism by which succinate impairs T cell function. This appeared not to involve the succinate receptor, SUCNR1 or modulation of HIF1-α expression. Rather, we observed significantly altered glucose metabolism in T cells exposed to succinate, associated with impaired activity of a specific enzyme. RO3 was met by completion of WP3. In brief, having identified that succinate impairs T cell function via inhibition of glucose metabolism, we tested whether reversing this metabolic defect could rescue T cell function, which indeed proved to be the case. These results thereby prove that T cell function can be rescued and normalised in succinate-rich tumour envionments. These primary research data are now being prepared for publication. In addition the fellow has written several review articles during the fellowship.
