Arginine starvation elicits chromatin leakage and cGAS-STING activation via epigenetic silencing of metabolic and DNA-repair genes [ChIP-seq]
One of the most common metabolic defects of cancer cells is the deficiency in arginine synthesis due to suppressed expression of argininosuccinate synthetase 1 (ASS1) which renders cancer cells auxotrophic to external arginine supply. Arginine deprivation has been effectively used as a treatment for leukemias, with several clinical trials on solid tumors underway.  We previously showed that in prostate cancer arginine depletion induced mitochondrial dysfunction and excessive ROS production resulting in chromatin autophagy, nuclear DNA leakage, and cellular death, but the detailed mechanism of arginine starvation-induced cell death remains unclear. In this study, we demonstrated that arginine deprivation coordinately suppressed metabolic genes, including those responsible for mitochondrial oxidative phosphorylation (OXPHOS), nucleotide metabolism, and DNA repair. The consequent ROS production and impaired DNA damage response resulted in nuclear DNA leakage and cGAS-STING activation which is accompanied by upregulation of type I interferon response. We also showed that coordinated silencing of OXPHOS and DNA repair genes is caused in part by the depletion of a-ketoglutarate (aKG) and inactivation of histone demethylases. Supplementing cell-permeable dimethyl a-ketoglutarate (DMKG) both reduced repressive histone methylations and partially restored OXPHOS gene expressions, mitochondrial functions, and mitigated nuclear DNA leakage. Using our dietary arginine-restriction model, we demonstrate that arginine starvation slows prostate cancer growth with evidence of enhanced interferon responses and recruitment of immune cells. Our data suggests arginine starvation induces cell killing of ASS1-low cancer cells by metabolic depletion and epigenetic silencing of metabolic genes, leading to DNA damage and leakage. Resulting cGAS-STING activation may further enhance these killing effects. Overall design: CWR22Rv1 cells were treated with ADI-PEG20 for 48 h, and H3K9me3 and H3K27me3 occupancy on the promoter regions was determined by ChIP-seq