An Indel Polymorphism within pre-miR3131 Confers Risk for Hepatocellular Carcinoma

Polymorphisms in pre-miRNAs may affect its expression, then having effect on its target mRNAs and be associated with cancer susceptibility. In the current study, we evaluated the association of a 3-base pair (3-bp) indel polymorphism (rs57408770) in pre-miR-3131 with hepatocellular carcinoma (HCC) susceptibility in a Chinese population. Logistic regression analysis showed that the insertion allele of rs57408770 was significantly associated with an increased risk for HCC occurrence in both case-control studies. To further investigated the molecular mechanism underlying the correlation between rs57408770 and the risk of HCC, overexpression of pre-miR-3131 in HCC cell line was performed. Human HCC cell lines Sk-Hep-1 was obtained from Shanghai Cell Bank of Chinese Academy of Sciences on 9 December 2013.The fragment of 366bp including the insert allele of rs57408770 in pre-miR-3131 was directly synthesized and cloned into BamHI and EcoRI sites of pEGFP-N1 yielding the wild-type vector (pEGFP-N1-miR3131-WT). The mutant-type vector (pEGFP-N1-miR3131-MT) including the delete allele of rs57408770 was generated using QuikChange Lightening Site-Directed Mutagenesis Kit. The resulting constructs were verified by direct sequencing. For overexpression experiments, cells were cultured in 6-well plates at a density of 200 000 cells per well the day before transfection. 2.5μg plasmids of empty vector pEGFP-N1, pEGFP-N1-miR3131-WT or pEGFP-N1-miR3131-MT were transfected into the growing cells (about 80%-90% confluent) using Lipofectamine2000. After 24 hours of the transfection, the cells were collected for subsequent experiments.And human genome-wide gene expression profile assay was used to screen the targets of miR-3131. For overexpression experiments, cells were cultured in 6-well plates at a density of 200 000 cells per well the day before transfection. 2.5μg plasmids of empty vector pEGFP-N1, pEGFP-N1-miR3131-WT or pEGFP-N1-miR3131-MT were transfected into the growing cells (about 80%-90% confluent) using Lipofectamine2000 (Invitrogen). After 24 hours of the transfection, the cells were collected for subsequent experiments. There are 3 samples in this experiment.