Nuclear ACAT1 orchestrates natural killer cell dependent antitumor immunity in colorectal cancer

Natural killer (NK) cells play pivotal roles in antitumor immunity, yet their connection to tumor metabolism remains unclear. Our systematic analysis of multiomics data and survival data from colorectal cancer (CRC) patients uncovered a novel association between mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1) and NK cell infiltration that influences disease progression. ACAT1, a metabolic enzyme involved in reversible conversion of acetoacetyl-CoA to two molecules of acetyl-CoA, exhibits nuclear protein acetylation activity through its translocation. Under immune stimulation, mitochondrial ACAT1 can be phosphorylated at serine 60 (S60) and enters the nucleus; however, this process is hindered in nutrient-poor tumor microenvironments. Nuclear ACAT1 directly acetylates lysine 146 of p50 (NFKB1), attenuating its DNA binding and transcriptional repression activity and thereby increasing the expression of immune-related factors, which in turn promotes NK cell recruitment and activation to suppress colorectal cancer growth. Furthermore, significant associations were found among low nuclear ACAT1 levels, decreased S60 phosphorylation, and reduced NK cell infiltration, as well as poor prognosis in CRC. Our findings reveal an unexpected function of ACAT1 as a nuclear acetyltransferase and elucidate its role in NK cell-dependent antitumor immunity through p50 acetylation. To isolate tumor-infiltrating NK cells from mice, tumors were dissected from ceca were cut into small pieces and subjected to enzymatic digestion. The digestion solution was filtered with 70 μm strainer and centrifuged at 500 g for 5 min. Cells were resuspended in MACS buffer and were Fc-blocked for 10 min. And then, cells were stained with Zombie UV™ Fixable Viability Kit following the manufacturer’s instruction and incubated with primary antibodies as follows: APC-CD45, FITC-CD3 with PE/Cyanine7-NKp46 for 30 min at 4°C. NK cells (CD3- NKp46+) were sorted by fluorescence-activated cell sorting (FACS) using MoFlo Astrios (BECKMAN). The purity (>98%) of sorted cells was checked on BECKMAN COULTER CytoFLEX LX cell analyzer.