miRNA signatures underly chemoresistance in the gemcitabine-resistant pancreatic ductal adenocarcinoma cell line MIA PaCa-2 GR

Chemotherapy resistance is a major clinical issue for pancreatic adenocarcinoma (PDAC). MicroRNAs (miRNAs) play an important role in cancer progression and chemoresistance. In this study, we addressed the association between miRNA expression profiles and gemcitabine (Gem) resistance. A Gem sensitive (GS) PDAC cancer cell line, MIA PaCa-2, and its Gem resistant (GR) progeny MIA PaCa-2 GR, was used to determine miRNA expression changes by resistance to Gemcitabine. miRNA-seq was used to determine the miRNA expression profiles in these cell lines. Ingenuity Pathway Analysis (IPA) was performed to determine the biological functions of differentially expressed miRNAs. In total, 1867 miRNAs were detected in the two cell lines. We found that the miRNA expression profiles were different between the GR and its sensitive isogenic parental GS cell line, and certain differentially expressed miRNAs were only detected in one or the other of these PDAC cell lines. A total of 97 (5.2%) miRNAs were significantly differentially expressed between GR and the GS cell lines, of which 65 (3.5%) miRNAs were upregulated and 32 (1.7%) miRNAs were downregulated. The miRNAs with the most significant differential expression in the GR cell line as compared with GS were primarily involved in the following biological processes: cell proliferation, cell migration & invasion, chemo-sensitization, alternative splicing, apoptosis, and angiogenesis. These miRNAs from cell lines were further refined to a subset and were analyzed in patient samples where expression was used to identify patients with recurrent tumors. Taken together, the results suggest that these miRNAs may play important roles in Gem resistance in PDAC. This study’s findings provides a basis for further research in the diagnosis and treatment selection for PDACs with gemcitabine resistance. To investigate miRNA changes between sensitive parental cells (Mp2) and adapted resistant cells (Mp2GR), Mp2 cells were treated with IC50 concentration of Gem until growth continued. We incrementally increased the concentration of Gem until 500nm concentration was achieved. Cells were maintained in 500nm Gem until RNA harvest.