LAUSR

Chemotherapy is still a standard treatment of unresectable bladder cancer or distant metastases. The chemotherapy resistance always occurs after a period of treatment indicating poor prognosis. The current study aimed to explore the molecular mechanism of chemoresistance in bladder cancer cells. The gene expression profiles of GSE77883, including three untreated T24 cells samples and three gemcitabine‐resistant T24 cells samples, was downloaded from Gene Expression Omnibus database. The screening of differentially expressed genes (DEGs), gene function analysis, and interaction prediction between microRNAs (miRNAs) and DEGs were performed by R software. The protein‐protein interaction (PPI) and miRNA‐DEGs networks were constructed and visualized by Cytoscape software. Then, the small molecules, with potential synergistic or antagonistic effects to gemcitabine resistance, were identified using the Connectivity Map database. Finally, gemcitabine‐resistant T24 cell line was established and key genes were validated by quantitative real‐time polymerase chain reaction (qRT‐PCR). In total, 536 upregulated and 513 downregulated genes were screened and mainly enriched in oxidative stress response and signaling pathways related to extracellular matrix–receptor interaction and focal adhesion. PPI network showed interleukin 6, tumor necrosis factor, kinesin family member 11, and BUB1 mitotic checkpoint serine/threonine kinase B were key genes. The miRNA‐DEGs regulatory networks included 18 miRNAs and 185 DEGs, including miR‐182‐5p, miR‐590‐3p, miR‐320a and serum‐ and glucocorticoid‐regulated kinase 1 (SGK1). Then, the related key genes and miRNAs were confirmed by qRT‐PCR. Furthermore, 81 small molecules with antagonistic or synergistic effect to GEM were screened. We have investigated the molecular mechanisms driving GEM‐resistance in bladder cancer cells that would contribute to the development of chemotherapy for advanced bladder cancer.