[Metabolic signatures of niraparib-resistant ovarian cancer cells based on non-target metabolomics]

Objective: To establish a niraparib-resistant ovarian cancer cell line and preliminarily explore its biological characteristics and metabolic signatures. Methods: (1) Using ovarian adenocarcinoma cell line A2780 as parental cells, the niraparib-resistant cell line A2780-NiraR was established by the method of concentration gradient increased induction, and its morphological characteristics were observed using inverted phase-contrast microscope. The half-inhibitory concentration (IC₅₀) of niraparib was determined by cytotoxicity assay. (2) Cell proliferation was determined by cell count kit-8 (CCK-8) assay and direct cell counting assay, cell cycle distribution was analyzed by flow cytometry. (3) The differential metabolites between A2780 and A2780-NiraR cells were detected by non-target metabolomics based on ultra-high performance liquid chromatography-high resolution mass spectrometry (UPLC/HRMS). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was conducted on the above differential metabolites to explore related metabolic pathways. Results: (1) Compared with the parental A2780 cells, A2780-NiraR cells exhibited predominantly short-spindle or oval morphology with reduced cellular projections and indistinct cell borders. The IC₅₀ values of niraparib were 3.17 and 26.19 μmol/L against A2780 cells and A2780-NiraR cells, respectively (F=98.50, P<0.001). (2) A2780-NiraR cells had a slower proliferation rate compared with A2780 cells (F=146.80, P<0.001). The doubling time of A2780-NiraR cells [(37.5±1.9) hours] was significantly longer than that of A2780 cells [(14.5±1.0) hours; t=10.50, P<0.001]. Compared with the parental A2780 cells, A2780-NiraR cells had a significantly lower S phase fraction [(44.5±0.7)% in A2780 cells, (30.2±2.9)% in A2780-NiraR cells; t=4.78, P<0.001] and higher G₀/G₁ phase fraction [(35.4±1.2)% in A2780 cells, (52.2±3.1)% in A2780-NiraR cells; t=5.10, P<0.001]. (3) The metabolites of A2780 and A2780-NiraR cells were analyzed by non-target metabolomics. Forty-four differential metabolites between A2780 and A2780-NiraR cells were screened using the orthogonal partial least squares-discriminant analysis (OPLS-DA) model, the majority of which were significantly increased, such as pyrrolidone carboxylic acid, L-lysine and 1-pyrroline-4-hydroxy-2-carboxylate. Pathway enrichment analysis indicated that the arginine metabolism, purine metabolism, and pyrimidine metabolism were the most significantly enriched pathways. Conclusion: A2780-NiraR cells have acquired a stable niraparib resistance phenotype, and metabolic pathways including arginine metabolism may serve as potential therapeutic targets for enhancing niraparib efficacy in ovarian cancer.