Abstract 896: miR-198 silencing is a mechanism of gemcitabine resistance in human pancreatic adenocarcinoma.

Abstract

Abstract Pancreatic adenocarcinoma (PAC) is a very aggressive disease with extremely high mortality rate. Chemotherapy with gemcitabine (G) is a standard of care for advanced disease, but chemotherapy resistance is commonly noted. Human PAC is characterized by overexpression of the proto-oncogene c-met. Increased activation of c-met has been reported in G-resistant PAC cells. Also, aberrant expression of microRNAs (miRNAs) has been linked to cancer progression. Furthermore, a recent study showed that miR-198 regulates c-met expression by binding to the 3′-untranslated region of c-met mRNA. However, the role of miR-198 in chemotherapy resistance in PAC has not previously been studied. Consequently, in this study we used the G-sensitive and G-resistant subclones of the L3.6pl human PAC cell line to examine the role of miR-198 in G-resistant PAC. We observed that the G-resistant subclone had increased expression of c-met (using qPCR and western blotting) and phosphorylated c-met (using western blotting), but not hepatocyte growth factor (HGF). Furthermore, using qPCR we observed significant silencing of miR-198 expression in the G-resistant subclone in comparison to the G-sensitive subclone (P < 0.01). To determine the functional significance of miR-198 silencing in G resistance, we silenced miR-198 expression in the G-sensitive subclone by transfection of a specific oligonucleotide inhibitor of miR-198. We observed that miR-198 silencing resulted in increased expression of c-met and phosphorylated c-met. Further, miR-198 silencing on its own increased total RNA concentration significantly by 146% (P < 0.05) and cell viability by 14.3% (P < 0.05; using MTT assay), both suggestive of a proliferative effect. However, significant effects on apoptosis were undetectable (using Hoechst nuclear staining). Furthermore, miR-198 silencing significantly abrogated G-induced apoptosis (P < 0.05) and G-induced reduction of cell viability (P < 0.05). We conclude that G-resistant human PAC cells have silencing of miR-198. Moreover, miR-198 silencing in PAC cells induces increased expression and phosphorylation of c-met, increased cell proliferation and abrogation of G-induced apoptosis and induction of proliferation. Therefore, miR-198 silencing is a mechanism of G-resistance in PAC. Furthermore, therapeutic strategies to enhance miR-198 expression may be beneficial in PAC. Citation Format: Olorunseun O. Ogunwobi, Jian Li, Xiangxuan Zhao, Jose Trevino, Thomas George, Chen Liu. miR-198 silencing is a mechanism of gemcitabine resistance in human pancreatic adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 896. doi:10.1158/1538-7445.AM2013-896