That triggers EMT in a variety of solid tumours, including cervical cancer. It has been reported that the MedChemExpress 16960-16-0 tumours with high EGF receptor expression have poor clinical prognosis, and EGF-induced EMT may be one reason for this [3?5]. Thus, preventing EGF-induced EMT could be an appropriate method to inhibit invasion and metastasis. Recent studies have suggested that miRNAs play an important role in the regulation of EMT [6,7]. miRNAs are 18- to 25nucleotide-long noncoding RNAs that can regulate gene expression by accelerating the degradation and inhibiting the translation of target mRNAs. Among the miRNAs identified to date, Methionine enkephalin miR155 is associated with tumor proliferation and is overexpressed inmany human tumours [8]. One study illustrated that the abnormal expression of miR155 was an early event in pancreatic cancer and closely related to a low survival rate [9]. In endometrial cancer, the occurrence of EMT was accompanied by elevated miR155 expression levels [10]. It is not yet clear whether miR155 is involved with the occurrence of EMT in cervical cancer. In this study, using EGF as an EMT-inducing factor in human cervical cancer cells, we explored the regulatory roles of miR155 in the EMT process, cellular proliferation, cellular sensitivity to chemotherapeutic drugs, and evaluated the potential value of miR155 as a molecular target for the early prevention of cervical cancer invasion and metastasis.Materials and Methods Cell LinesCaski cells was purchased from the Cell Bank of China (Wuhan) and were cultured at 37uC in 5 CO2 in RPMI-1640 containing 10 foetal bovine serum (FBS), 100 mg/ml streptomycin, and 100 units/ml penicillin.RNA Isolation and miRNA DetectionRNA from the cultured cells was isolated with Trizol reagent (Invitrogen) and was then used to synthesise first strand cDNA. Detection of the matured miRNAs was performed with PCR using the SYBR Premix Ex Taq tm (TAKARA). U6 was used as an internal control. The primers used in this experiment are shown in Table S1.Up-regulated miR155 Function on EMTPlasmid Construction and Stable/transient Transfection of miRA human genomic DNA fragment of approximately 400 bp containing the miR155 sequence was cloned into the pcDNA3.1GFP vector. The resulting plasmid pcDNA3.1-GFP-miRNA-155 carries a recombinant DNA sequence for GFP and the miR155containing fragment. To generate a cell line that stably expresses miR155, Caski cells were transfected with pcDNA3.1-GFPmiR155 using Lipofectamine 2000 reagent (Invitrogen). Following selection with G418, the single clone that over-expressed miR155 was identified. For miR155 transient overexpression, miR155 mimics (RIBOBRO) were used to transfect the Caski cells.Flow CytometryCaski and Caski-miR155 cells were harvested in the logarithmic growth phase and fixed overnight with 80 ethanol. The cells were then washed with cold PBS, stained with propidium iodide (PI, 0.05 mg/ml) and RNase A (0.5 mg/ml). Flow cytometry analysis was used to determine the distribution of cells in cell cycle sub-phases and to measure the apoptosis peak induced by DDP (10 mmol/ml) for 24 hours.Statistical AnalysisAll data were presented as the mean 6 standard deviation (SD). Statistical analysis between groups was assessed by Student’s twotailed t-test and ANOVA. P-values less than 0.05 were regarded as statistically significant.In vitro Migration and Invasion AssaysA Matrigel-based transwell assay was used to assay cell migration and invasion in vitro as described previously.That triggers EMT in a variety of solid tumours, including cervical cancer. It has been reported that the tumours with high EGF receptor expression have poor clinical prognosis, and EGF-induced EMT may be one reason for this [3?5]. Thus, preventing EGF-induced EMT could be an appropriate method to inhibit invasion and metastasis. Recent studies have suggested that miRNAs play an important role in the regulation of EMT [6,7]. miRNAs are 18- to 25nucleotide-long noncoding RNAs that can regulate gene expression by accelerating the degradation and inhibiting the translation of target mRNAs. Among the miRNAs identified to date, miR155 is associated with tumor proliferation and is overexpressed inmany human tumours [8]. One study illustrated that the abnormal expression of miR155 was an early event in pancreatic cancer and closely related to a low survival rate [9]. In endometrial cancer, the occurrence of EMT was accompanied by elevated miR155 expression levels [10]. It is not yet clear whether miR155 is involved with the occurrence of EMT in cervical cancer. In this study, using EGF as an EMT-inducing factor in human cervical cancer cells, we explored the regulatory roles of miR155 in the EMT process, cellular proliferation, cellular sensitivity to chemotherapeutic drugs, and evaluated the potential value of miR155 as a molecular target for the early prevention of cervical cancer invasion and metastasis.Materials and Methods Cell LinesCaski cells was purchased from the Cell Bank of China (Wuhan) and were cultured at 37uC in 5 CO2 in RPMI-1640 containing 10 foetal bovine serum (FBS), 100 mg/ml streptomycin, and 100 units/ml penicillin.RNA Isolation and miRNA DetectionRNA from the cultured cells was isolated with Trizol reagent (Invitrogen) and was then used to synthesise first strand cDNA. Detection of the matured miRNAs was performed with PCR using the SYBR Premix Ex Taq tm (TAKARA). U6 was used as an internal control. The primers used in this experiment are shown in Table S1.Up-regulated miR155 Function on EMTPlasmid Construction and Stable/transient Transfection of miRA human genomic DNA fragment of approximately 400 bp containing the miR155 sequence was cloned into the pcDNA3.1GFP vector. The resulting plasmid pcDNA3.1-GFP-miRNA-155 carries a recombinant DNA sequence for GFP and the miR155containing fragment. To generate a cell line that stably expresses miR155, Caski cells were transfected with pcDNA3.1-GFPmiR155 using Lipofectamine 2000 reagent (Invitrogen). Following selection with G418, the single clone that over-expressed miR155 was identified. For miR155 transient overexpression, miR155 mimics (RIBOBRO) were used to transfect the Caski cells.Flow CytometryCaski and Caski-miR155 cells were harvested in the logarithmic growth phase and fixed overnight with 80 ethanol. The cells were then washed with cold PBS, stained with propidium iodide (PI, 0.05 mg/ml) and RNase A (0.5 mg/ml). Flow cytometry analysis was used to determine the distribution of cells in cell cycle sub-phases and to measure the apoptosis peak induced by DDP (10 mmol/ml) for 24 hours.Statistical AnalysisAll data were presented as the mean 6 standard deviation (SD). Statistical analysis between groups was assessed by Student’s twotailed t-test and ANOVA. P-values less than 0.05 were regarded as statistically significant.In vitro Migration and Invasion AssaysA Matrigel-based transwell assay was used to assay cell migration and invasion in vitro as described previously.