Supplementary Material for: MicroRNA-296-5p Promotes Cell Invasion and Drug Resistance by Targeting Bcl2-Related Ovarian Killer, Leading to a Poor Prognosis in Pancreatic Cancer

<b><i>Background/Aims:</i></b> Pancreatic ductal adenocarcinoma (PDAC) is characterized by aggressive invasion, early metastasis, and resistance to chemotherapy, leading to a poor prognosis. To clarify the molecular mechanism of these malignant characteristics, we performed a genome-wide microRNA (miRNA) array analysis utilizing micro-cancer tissues from patients with unresectable PDAC (stage IV), obtained by endoscopic ultrasound-fine needle aspiration (EUS-FNA). <b><i>Methods:</i></b> The expression profiles of 2,042 miRNAs were determined using micro-cancer tissues from 13 patients with unresectable PDAC obtained by EUS-FNA. The relationship between individual miRNA levels and overall survival (OS) was analyzed. Possible target genes for miRNAs were bioinformatically analyzed using the online database miRDB. Pancreatic cancer cell lines PANC-1, MIA PaCa-2, and PK-8 were transfected with miRNA mimic or small interfering RNA, and cell invasion, epithelial-mesenchymal transition (EMT), and apoptosis markers were examined. miRNA and mRNA expressions were examined by quantitative polymerase chain reaction. <b><i>Results:</i></b> Of 2,042 miRNAs, the 10 that exhibited the lowest correlation coefficient (<i>p</i> ≤ 0.005) between miRNA expression level and OS among the patients were identified. The miRDB and expression analysis in cancer cell lines for the 10 miRNAs identified miR-296-5p and miR-1207-5p as biomarkers predictive of shorter survival (<i>p</i> &lt; 0.0005). Bioinformative target gene analysis and transfection experiments with miRNA mimics showed that <i>Bcl2-related</i> <i>ovarian</i> <i>killer</i> (<i>BOK</i>), a pro-apoptotic gene, is a target for miR296-5p in pancreatic cancer cells; transfection of miR-296-5p mimic into PANC-1, MIA PaCa-2, and PK-8 cells resulted in significant suppression of <i>BOK</i> mRNA and protein expression. These transfectants showed significantly higher invasion capability compared with control cells, and knock down of <i>BOK</i> in pancreatic cancer cells similarly enhanced invasion capability. Transfectants of miR-296-5p mimic also exhibited aberrant expression of EMT markers, including vimentin and N-cadherin. Moreover, these transfectants showed a significantly lower apoptosis rate in response to 5-fluorouracil and gemcitabine with a decrease of <i>BOK</i> expression, suggesting a role of miR-296-5p in drug resistance. <b><i>Conclusion:</i></b> These results suggest that miR-296-5p is a useful biomarker for a poor prognosis in patients with PDAC, and that the miR-296-5p/BOK signaling axis plays an important role in cell invasion, drug resistance, and EMT in PDACs.