These slides were examined by experienced pathologists to determine if the

benign tissues contained any pancreatic tumour cells. Benign tissues that contained residual tumour tissues were not included in the study. Complete clinicopathological follow-up data of the PDAC patients from which the specimens were collected were available. Validation of the most up-regulated or down-regulated miRNAs using qRT-PCR Total RNA was isolated from the frozen tissue sample with TRIzol (Invitrogen) according to the manufacturer’s instructions. First-strand complementary DNA (cDNA) was synthesised from 2 μg of the total RNA using an oligo-dT primer and superscript II reverse transcriptase (Invitrogen). Then, quantification BMN 673 ic50 of the most up-regulated or down-regulated miRNAs

was performed by qRT-PCR using SYBRR Premix Ex Taq (TakaRa). The U6 primers were obtained from TakaRa. PCR was performed in a real-time PCR system (Bio-Rad) as follows: 95°C for 3 min, followed by 35 cycles of 95°C for 5 sec, 60°C for 20 sec and 72°C for 30 sec, and then 94°C for 1 min and 60°C for 1 min, with an increase of 0.5°C per cycle. The expression LEE011 level values were normalised to those of the small AZD1080 mouse nuclear RNA U6 as a control. Relative fold-changes of miRNA expression were calculated using the △△CT method, and the values were expressed as 2-△△CT. The primer sequences were as follows: U6, 5′-CTCGCTTCGGCAGCACA-3′ (forward), 5′-AACGCTTCACGAATTTGCGT-3′ (reverse); miR-155, 5′-cgGCGGTTAATGCTAATCGTG-3′ (forward), 5′-GTGCAGGGTCCGAGGT-3′ (reverse); miR-100, 5′-GAATTCCCATACTGGTTGGCTCCCGC-3′

(forward), 5′-CTCGAGACGAATTCAATCGAAATATTC-3′ (reverse); miR-21, 5′-ACACTCCAGCTGGGTAGCTTATCAGACTGA-3′ (forward), 5′-TGGTGTCGTGGAGTCG-3′ (reverse); miR-221, 5′-CCCAGCATTTCTGACTGTTG-3′ (forward), 5′-TGTGAGACCATTTGGGTGAA-3′ (reverse); miR-31, 5′-ACGCGGCAAGATGCTGGCA-3′ (forward), 5′-CAGTGCTGGGTCCGAGTGA-3′ (reverse); miR-143, 5′-CCTGGCCTGAGATGAAGCAC-3′ (forward), 5′-CAGTGCTGGGTCCGAGTGA-3′ (reverse); of miR-23a, 5′-CTTGAACTCCTGGCCTGAAG-3′ (forward), 5′-GCCAAAGAAACACTCACAGCT-3′ (reverse); miR-217, 5′-GCGTACTGCATCAGGAACTGATTGGA-3′ (forward), 5′-GGGCACACAAAGGCAACTTTTGT-3′ (reverse); miR-148a, 5′-TCAGTGCACTACAGAACTTTGT-3′ (forward), 5′-GCTGTCAACGATACGCTACGT-3′ (reverse); miR-375, 5′-GAAGATCTTGAGGTACATCGCAGAGGCCAG-3′ (forward), 5′-CATGCCATGGGGGCCGGAGCGGAAGACCC-3′ (reverse). Statistical analysis Kaplan-Meier survival analysis was used to analyse the association between postoperative survival and the miRNA expression level measured by qRT-PCR, and the resulting curves were divided into two classes (high and low expression in comparison to the mean level of miRNA expression as the threshold). Survival analysis was performed for each clinical covariate to assess their influence on outcome using a log-rank test. A multivariate Cox regression model was used to adjust for competing risk factors, and the hazard ratio (HR) with a 95% confidence interval (CI) was reported as an estimate of overall survival risk.