To evaluate the mechanism of luteolin in inhibiting the proliferation of bladder cancer cells by means of network pharmacology and cell experiments.Methods:The targets of luteolin and bladder cancer were retrieved from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform(TCMSP)，SwissTarget Prediction，Pharmmapper，and GeneCards，and Venny2.1 was used to extract the common targets shared by luteolin and bladder cancer.The Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analyses were performed for the common targets，and the protein-protein interaction network was constructed via String.Cytoscape was used to build an active compound-pathway-target-disease network.The viability and colony formation ability of bladder cancer cells were examined by the Cell Counting Kit-8(CCK8) and colony formation assays，respectively.The expression levels of the proteins in the mitogen-activated protein kinase(MAPK) signaling pathway and proliferating cell nuclear antigen(PCNA) were determined by Western blotting.The 5-ethynyl-2'-deoxyuridine(EDU) assay was employed to detect the effect of luteolin on the proliferation of bladder cancer cells.Results:A total of 136 potential targets of luteolin and bladder cancer were screened out by network pharmacology.The GO analysis predicted 491，52，and 112 functional clusters involved in biological processes，cellular components，and molecular functions，respectively.A total of 151 pathways were obtained by the KEGG pathway enrichment analysis，including cancer pathway，phosphatidylinositol 3-kinase(PI3K)-protein kinase B(AKT) signaling pathway，and MAPK signaling pathway.The results of cell experiments showed that luteolin inhibited the proliferation of bladder cancer HT1376 cells through the MAPK signaling pathway.The results of the CCK8 assay showed that luteolin inhibited the viability of HT1376 cells.The results of the colony formation assay showed that luteolin inhibited the ability of bladder cancer cells to form colonies.Western blotting showed that luteolin significantly inhibited the expression of phospho-rapidly accelerated fibrosarcoma(P-RAF)，phospho-mitogen-activated extracellular signal-regulated kinase(P-MEK)，and phospho-extracellular regulated kinase 1/2(p-ERK1/2) in the MAPK pathway and down-regulated the expression of PCNA.The EDU assay showed that luteolin significantly inhibited the proliferation of HT1376 cells.Conclusion:Luteolin may inhibit the proliferation of bladder cancer HT1376 cells via the MAPK signaling pathway，as indicated by network pharmacology and cell experiments.