Integrated bioinformatics identifies RRM2 as a lipid remodeling- and gemcitabine response-related gene in pancreatic cancer

Gemcitabine resistance remains a major obstacle to effective treatment of pancreatic ductal adenocarcinoma (PDAC). Ribonucleotide reductase regulatory subunit M2 (RRM2) maintains deoxyribonucleotide availability and DNA replication, but whether RRM2 coordinates lipid metabolic adaptation with gemcitabine resistance in PDAC remains unclear. This study investigated the clinical significance and functional role of RRM2 in linking nucleotide metabolism, lipid remodeling, and gemcitabine response. Bulk transcriptomic, clinical, single-cell RNA-sequencing, and tissue-level protein data were integrated to characterize RRM2 expression, cellular distribution, prognostic relevance, and associated biological programs in PDAC. Co-expression, functional enrichment, pathway activity, virtual perturbation, and pharmacogenomic analyses were performed. PANC-1 and SW1990 cells were exposed to palmitate-induced lipid stress and gemcitabine. Gemcitabine dose-response assays, RRM2 knockdown and re-expression, reciprocal RRM2/SREBF1 intervention, SREBF1 rescue, BODIPY 493/503 staining, TUNEL analysis, immunofluorescence, quantitative real-time PCR, and western blotting of total and nuclear SREBP1 were used to evaluate drug sensitivity, lipid accumulation, DNA damage, apoptosis, and lipogenic regulation. An HFD-associated xenograft model was used for supportive in vivo validation. RRM2 was upregulated in PDAC and associated with unfavorable clinical characteristics and shorter overall survival. RRM2 expression correlated with proliferative, hypoxic, epithelial-mesenchymal transition, and fatty-acid-metabolism-related programs, including FASN, ACSL4, PLIN2, and SCD. Palmitate exposure increased gemcitabine IC50 values and induced lipid-droplet accumulation together with an RRM2-high, TYMS-high, DCK-low, FASN-high, ACSL4-high, and PCNA-high phenotype. RRM2 depletion reduced the gemcitabine IC50, suppressed lipid accumulation and proliferative markers, restored DCK expression, and increased γ-H2AX accumulation, apoptosis, and gemcitabine-induced cytotoxicity. Re-expression of RRM2 partially reversed these effects. SREBF1 re-expression in RRM2-depleted cells partially restored lipid accumulation, FASN expression, nuclear SREBP1, and gemcitabine tolerance, supporting a functional contribution of SREBP1/FASN-associated lipogenic remodeling. In vivo, HFD attenuated the antitumor activity of gemcitabine, while addition of siRRM2 to HFD plus gemcitabine further reduced xenograft growth, FASN, TYMS, and Ki-67 expression and increased tumor necrosis and γ-H2AX accumulation. RRM2 is functionally associated with gemcitabine response in PDAC through coordinated changes in nucleotide metabolism and SREBP1/FASN-associated lipid remodeling. SREBF1 rescue experiments support a functional contribution of the lipogenic component to the RRM2-associated gemcitabine-tolerant phenotype. RRM2 depletion enhances chemotherapy-induced DNA damage and apoptosis in vitro, while the in vivo combination data provide supportive, but not definitive, evidence for therapeutic benefit under HFD conditions.