Up-Regulation of microrna-125b Induced By 5-Fluorouracil (5-FU) Treatment Inhibits Cell Growth and Proliferation in Pancreatic Cancer Cells

Abstract

MicroRNAs (miRNAs) are a class of small non-coding RNAs that play regulatory roles in protein synthesis by repressing translation or cleaving RNA transcripts. Their aberrant expression has been shown to be involved in human diseases, including cancer. The functional importance of miRNAs is evidenced by many biological processes in which they are implicated, including developmental timing, cell proliferation, apoptosis, metabolism, cell differentiation and morphogenesis. However, little is known about the roles of miRNAs in 5-Fluorouracil (5-FU) resistance and metabolism pathway in pancreatic cancer cells. To address this enigma, miRNA profiles that correlate with 5-FU treatments are defined using miRNA microarray, and comparison of miRNA profiles reveals specific differences between untreated and 5-FU treated pancreatic cancer cells. A subset of miRNAs is being upregulated in 5-FU treated pancreatic cancer cells, with the most significantly upregulated miRNAs being miR-125b, miR-181a, miR-181b, miR181d, miR-27a, miR-222, miR-30a-5pre and miR-495. Transient transfection of the Pre-miRTM miRNA precursor molecules for miR-125b showed that it inhibited cell proliferation. Expression plasmids of miR-125b were constructed and transfected into human pancreatic cancer cell line PANC-1. PANC-1 miR-125b transfected stable clones showed decreased cell growth and proliferation. Our study suggested that miR-125b may act as a tumor suppressor and present a novel strategy for anticancer therapy.. IntroductionPancreatic cancer is one of the most frequently reported gastrointestinal tumors and has been reported to have a 5-year survival rate of < 5%. It is most commonly diagnosed at an advanced stage and the most frequently administered chemotherapeutic compound for patients with advanced disease has been 5-Fluorouracil (5-FU) [1]. 5-FU alone remains one of the standard treatments in advanced pancreatic cancer. The well-known mechanism of the anti-tumor effects of 5-FU is to inhibit DNA and RNA synthesis [1]. In addition, cell resistance to cytotoxic agents and radiation are two other factors contributing to the poor prognosis of pancreatic cancer [2].Recently it has been demonstrated that miRNAs may provide an additional post-transcriptional mechanism by which protein expression can be negatively regulated by either translational repression or mRNA degradation. MiRNAs are produced endogenously in mammalian cells approximately 60-nt long pre-miRNA hairpin intermediates. They are further processed to around 22-nt miRNA duplexes which regulate the stability or translational efficiency of target mRNAs by base-pairing to complementary sites on the targets [3]. The functional importance of miRNAs is evidenced by many biological processes in which they are involved, including developmental timing, cell proliferation, apoptosis, metabolism, cell differentiation and morphogenesis [4,5]. It has been shown that miRNAs are aberrantly expressed or mutated in cancer, suggesting that they may play a role as a novel class of oncogenes...