Targeting alpha-ketoglutarate starvation within the tumor-immune microenvironment rescues T cell effector function in cancer immunotherapy
Given its status as the leading cause of global cancer mortality, there is a critical need to enhance immunotherapy strategies for lung cancer to overcome widespread resistance to current treatments. Immunotherapy recruits the patient's immune system to attack and destroy cancer cells. While highly effective in a subset of patients, chronic exposure of immune cells to cancer cells leads to a progressive loss of effector T cell function and progression of T cell exhaustion; now considered two well-established hallmarks of immunotherapy resistance. The tumor-immune microenvironment (TIME)-driven differentiation into the exhausted T cell phenotype is marked by a loss of metabolic plasticity and epigenome-wide changes in distribution of repressive histone marks such as histone H3 subunit methylation at lysine 27 (H3K27me3). Here, we studied how these processes are connected to metabolite availability within the TIME. In vitro, chronic antigen stimulation and hypoxia led to rapid loss of effector function, associated with a suppression of alpha-ketoglutarate (aKG) intracellular concentrations in T cells. Supplementation of cell-permeable aKG led to a rescue of effector cytokine production and to improved cytotoxic capacity despite chronic antigen stimulation and hypoxia. Increased intracellular aKG levels restored the activity of H3K27 demethylases UTX and JMJD3, consistent with epigenome-wide decreased H3K27me3. In vivo, dietary supplementation with commercially available calcium-aKG (Ca-aKG) supplements led to an elevation of serum and intratumoral aKG levels associated with a significant increase of immunotherapy effectiveness in mouse models of NSCLC. Clinical samples from patients with NSCLC contained significantly decreased serum aKG levels in older NSCLC patients (>65 years of age). Analysis identified a novel association between serum aKG levels and poor immunotherapy response. Thus, our work demonstrates that intratumoral metabolite starvation can be therapeutically exploited to improve immunotherapy outcomes in non-small cell lung cancer (NSCLC).