Identifying microRNA-mRNA regulatory network in gemcitabine-resistant cells derived from human pancreatic cancer cells.

Pancreatic cancer is unresectable in over 80 % of patients owing to difficulty in early diagnosis. Chemotherapy is the most frequently adopted therapy for advanced pancreatic cancer. The development of drug resistance to gemcitabine (GEM), which is always used in standard chemotherapy, often results in therapeutic failure. However, the molecular mechanisms underlying the gemcitabine resistance remain unclear. Therefore, we sought to explore the microRNA-mRNA network that is associated with the development of gemcitabine resistance and to identify molecular targets for overcoming the gemcitabine resistance. By exposing SW1990 pancreatic cancer cells to long-term gemcitabine with increasing concentrations, we established a gemcitabine-resistant cell line (SW1990/GEM) with a high IC50 (the concentration needed for 50 % growth inhibition, 847.23 μM). The mRNA and microRNA expression profiles of SW1990 cells and SW1990/GEM cells were determined using RNA-seq analysis. By comparing the results in control SW1990 cells, 507 upregulated genes and 550 downregulated genes in SW1990/GEM cells were identified as differentially expressed genes correlated with gemcitabine sensitivity. Gene ontology (GO) analysis showed that the differentially expressed genes were related to diverse biological processes. The upregulated genes were mainly associated with drug response and apoptosis, and the downregulated genes were correlated with cell cycle progression and RNA splicing. Concurrently, the differentially expressed microRNAs, which are the important player in drug resistance development, were also examined in SW1990/GEM cells, and 56 differential microRNAs were identified. Additionally, the expression profiles of selected genes and microRNAs were confirmed by using Q-PCR assays. Furthermore, combining the differentially expressed microRNAs and mRNAs as well as the predicted targets for these microRNAs, a core microRNA-mRNA regulatory network was constructed, which included hub microRNAs, such as hsa-miR-643, hsa-miR-4644, hsa-miR-4650-5p, hsa-miR-4455, hsa-miR-1261, and hsa-miR-3676. The predicted targets of these hub microRNAs in the microRNA-mRNA network were also observed in the identified differential genes. As a result, a differential gene and microRNA expression pattern was constructed in gemcitabine-resistant pancreatic cancer cells. Therefore, these data may be useful for the detection and treatment of drug resistance in pancreatic cancer patients, and the microRNA-mRNA network-based analysis is expected to be more effective and provides deep insights into the molecular mechanism of drug resistance.