Carcinogenesis of Intraductal Papillary Mucinous Neoplasm of the Pancreas: Loss of MicroRNA-101 Promotes Overexpression of Histone Methyltransferase EZH2

Background. The mechanisms of IPMN carcinogenesis are as yet unclear. This study aimed to determine whether expression of EZH2 promotes neoplastic progression of IPMN and PDCA, and to elucidate regulation of EZH2 expression by miR-101. Methods. EZH2 mRNA and protein expression were investigated in 8 human pancreatic cancer cell lines by PCR and western blotting. Pre-miR-101 and anti-miR-101 were transfected into pancreatic cancer cells to elucidate EZH2 regulation by miR-101. To evaluate whether EZH2 modulates malignant progression of IPMN, EZH2 expression in IPMN was examined by immunohistochemistry. Next, we collected malignant and benign cells from FFPE samples of IPMNs using laser capture microdissection and extracted the RNA. miR-101 expression in IPMN was assessed using real-time PCR. Results. All pancreatic cancer cell lines expressed EZH2 mRNA and protein. The induction of miR-101 by transfection of pre-miR-101 in MIA PaCa-2 was closely related to a reduction in EZH2 protein production compared with control, whereas there was little difference in the expression of EZH2 mRNA. Anti-miR-101 transfected pancreatic cancer cells showed an increase in EZH2 protein, while the level of EZH2 mRNA was not elevated. Immunohistochemistry revealed that the expression of EZH2 was significantly higher in malignant than benign IPMN. Expression of miR-101 was significantly lower in malignant IPMN than benign IPMN. Conclusions. MiR-101 targets EZH2 at the posttranscriptional level, and loss of miR-101 could be a trigger for the adenomacarcinoma sequence of IPMN by upregulation of EZH2. This study suggests miR-101-EZH2 blockade as a potential therapeutic target in IPMN carcinogenesis.