Objective:Using gene expression data,we compared the genotype expression profile of different 5-fluorouracil(5-FU) resistance phenotypes of pancreatic cancer cells after in vitro selection. The aims of our study were to identify genes showing altered expression in resistant derivatives,as well as several central genes or important pathways that were associated with 5-FU resistance in pancreatic cancer cells. Methods:The 5-FU-resistant MIAPaCa-2 derivatives were developed through exposure to increasing concentrations of 5-FU with repeated subcultures until the cells became fully resistant to 5-FU. Gene array analysis was performed using a Uniset Human 20 K I Codelink Bioarray. Data were analyzed with CodeLink System Software. The expression profiling of selected genes was confirmed by real-time PCR assays. Results:We got successively two resistant derivatives:the low-resistance phenotype MIA-FU-2.4 and the high-resistance phenotype MIA-FU-10.0. Analysis of array data showed that the resistance of 5-FU in pancreatic cancer cell was related to widespread transcriptional activation. In MIA-FU-2.4 and MIA-FU-10.0,we identified respectively 1075 and 1628 differentially expressed genes. The biological functions of these genes included cell cycle,cell adhesion,signal transduction,DNA repair and apoptosis et al. Conclusions:Our data suggest that 5-FU resistance development in pancreatic cancer cell MIAPaCa-2 involves in many aspects of the biological functions and might be mainly attributed to apoptosis,DNA repair and cell cycle mechanisms and some signal transductions or some pivotal genes.