Abstract
Due to the poor prognosis of pancreatic cancer, novel diagnostic modalities for early diagnosis and new therapeutic strategy are urgently needed. Recently, microRNA-21 (miR-21) was reported to be strongly overexpressed in pancreatic cancer as well as in other solid cancers. We investigated the functional roles of miR-21, which have not been fully elucidated in pancreatic cancer. miR-21 expression was assessed in pancreatic cancer cell lines (14 cancer cell lines, primary cultures of normal pancreatic epithelial cells and fibroblasts, and a human normal pancreatic ductal epithelial cell line) and pancreatic tissue samples (25 cancer tissues and 25 normal tissues) by quantitative real-time reverse transcription-PCR amplification. Moreover, we investigated the proliferation, invasion, and chemoresistance of pancreatic cancer cells transfected with miR-21 precursor or inhibitor. miR-21 was markedly overexpressed in pancreatic cancer cells compared with nonmalignant cells, and miR-21 in cancer tissues was much higher than in nonmalignant tissues. The cancer cells transfected with the miR-21 precursor showed significantly increased proliferation, Matrigel invasion, and chemoresistance for gemcitabine compared with the control cells. In contrast, inhibition of miR-21 decreased proliferation, Matrigel invasion, and chemoresistance for gemcitabine. Moreover, miR-21 positively correlated with the mRNA expression of invasion-related genes, matrix metalloproteinase-2 and -9, and vascular endothelial growth factor. These data suggest that miR-21 expression is increased in pancreatic cancer cells and that miR-21 contributes to the cell proliferation, invasion, and chemoresistance of pancreatic cancer.
Highlights
Pancreatic cancer is the fifth leading cause of cancer deaths in Japan and the fourth leading cause of cancer-related deaths in the United States
Primary cultures of human normal pancreatic epithelial cells were obtained from Cell Systems and maintained in CS-C medium containing 10% fetal bovine serum according to the supplier's instructions
We measured the expression of miR-21 in 14 pancreatic cancer cell lines, HPDE cells, and primary cultures of normal pancreatic epithelial cells and pancreatic fibroblasts by Quantitative real-time reverse transcriptionPCR (qRT-PCR) (Fig. 1A)
Summary
Pancreatic cancer is the fifth leading cause of cancer deaths in Japan and the fourth leading cause of cancer-related deaths in the United States. Over the past few years, microRNAs (miRNA) have emerged as a prominent class of gene regulators. MiRNAs were reported to have diverse functions, including the regulation of cellular differentiation, proliferation, and apoptosis [5]. A growing number of direct and indirect lines of evidence suggest relationships between altered miRNA expression levels and cancer, including alterations of miR-15a and miR-16-1 in chronic lymphocytic leukemia [6, 7], miR-143 and miR-145 in colorectal cancer [8], let-7 in lung cancer [9, 10], and miR-155 in diffuse large B-cell lymphoma [11]. Expression profiling has identified several miRNAs that are differentially expressed in other cancers, such as breast cancer [12], glioblastoma [13], and papillary thyroid cancer [14]
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