Therapeutic Co-targeting of oxidative phosphorylation and pyrimidine synthesis restores gemcitabine response in pancreatic ductal adenocarcinoma.

Gemcitabine resistance remains a major barrier to effective therapy in pancreatic ductal adenocarcinoma (PDAC), and current combination regimens show potential to overcome this resistance. Here, we identify the mitochondrial ribosomal proteins MRPS22 and MRPL3 as key metabolic gatekeepers that maintain mitochondrial OXPHOS and pyrimidine metabolism, thereby promoting pancreatic cancer cell proliferation and chemoresistance. Across independent cohorts, high MRPS22/MRPL3 expression associates with poorer survival. Depletion of either gene in PDAC curtailed cell proliferation and xenograft growth, which might be due to an impaired mitochondria function, including destabilized respiratory super-complex assembly, diminished ATP production, and increased oxidative stress. Multi-omics profiling revealed a broad reduction of central-carbon intermediates and a pronounced blockade of de novo pyrimidine synthesis at the dihydroorotate dehydrogenase (DHODH) node. MRPS22 depletion hampered nucleotide-pool generation, and exogenous deoxynucleotides partially rescued PDAC cell growth when MRPs were knocked down. Pharmacologic OXPHOS inhibition increased gemcitabine sensitivity, whereas gemcitabine-resistant derivatives exhibited heightened OXPHOS activity and upregulated mitochondrial ribosomal programs. Co-targeting OXPHOS (antimycin A) or DHODH (brequinar) with gemcitabine produced Loewe synergy in vitro and suppressed growth of gemcitabine-resistant xenografts without affecting body weight. Collectively, these findings established MRPS22/MRPL3 as translation-level drivers of PDAC metabolic fitness and nominate OXPHOS/DHODH blockade as a rational combination strategy to overcome gemcitabine resistance.