UMP functions as an endogenous regulator of NR4A1 to control gastric cancer progression [ChIP-Seq]

Nucleotide metabolism reprogramming drives tumor progression, yet how tumor cells sense nucleotide levels remain unclear. Here we identified UMP as an endogenous regulator of the orphan nuclear receptor NR4A1 in gastric cancer (GCa). Under UMP-sufficiency, UMP directly binds to NR4A1, inhibiting its tumor-suppressive function and promoting GCa progression. Conversely, UMP deficiency resulting from disrupted pyrimidine biosynthesis derepresses NR4A1, which suppresses GCa cell survival and progression by both increasing NR4A1 occupancy at super-enhancers to reprogram survival-gene expression and enhancing NR4A1's pro-apoptotic activity at the mitochondria. NR4A1 loss was sufficient to rescue the effects of pyrimidine nucleotide stress on GCa cells in vitro and in vivo. NR4A1 agonists suppressed the pyrimidine salvage pathway triggered by de novo pyrimidine biosynthesis (DNPB) inhibition. Co-targeting DNPB and NR4A1 induced synergistic tumor lethality in GCa xenograft models. Together, our results establish UMP as an endogenous regulator of NR4A1 and provide an effective therapeutic strategy for GCa. Overall design: AGS cells were treated with vehicle, BAY (5 nM) or BAY (5 nM) plus Uridine (100 µM) for 24 h before harvested. Cell preparation, crosslinking, nuclei preparation and chromatin shearing was following truChIP® Chromatin Shearing Kit (Covaris), according to the manufacturer's instruction. Chromatin fragments were precipitated by using specific antibodies and Protein G beads, washed, and treated with Proteinase K and RNAse A. Purified ChIP DNA was then used for library generation. Libraries were quantified with the Bioanalyzer 2100 (Agilent) and sequenced in single-end 50-bp mode on the MGISEQ2000 (BGI, Wuhan, China). Antibodies used were against H3K27ac (Abcam; ab4729).