Abstract 1939: Identification of microRNAs related to chemosensitivity in ovarian cancer using Next Generation Sequencing.
Authors: Tsuruga Tetsushi , Au Yeung Chi Lam , Leung Cecilia S. , Yeung Tsz-Lun , Wong Kwong K. , Schmandt Rosemarie , Co Ngai Na , Lu Karen H. , Mok Samuel 
Published: August 2014

Abstract
Ovarian cancer is the most common cause of gynecologic malignancy related mortality in women. The combination of tumor reductive surgery and chemotherapy is the main therapeutic strategy for ovarian cancer. However, especially in the most of advanced cases, complete site reduction is impossible to achieve. In those cases, the sensitivity to chemotherapy strongly affects their prognoses. MicroRNAs (miRNAs), which are approximately 22-nucleotide non-coding RNAs, regulate protein expression by translational inhibition and degradation of their target mRNAs. The expression of miRNAs is dysregulated in various types of cancers, suggesting that miRNAs are involved in carcinogenesis and cancer progression. The purpose of present work was to identify miRNAs which are related to chemo-sensitivity in ovarian cancer.
Using Next Generation Sequencing (NGS), miRNA profiling was performed in 38 advanced high-grade serous ovarian cancers (HGSOCs). RNAs including miRNAs were procured from the epithelial component of the laser microdissected tumor tissue removed from patients undergoing primary surgery without neo-adjuvant chemotherapy. A total of 1935 miRNAs and miRNA variants were detected by NGS and normalized expression data of each miRNAs and miRNA variants were used for further analyses. Comparing the copy numbers of each miRNAs between chemo-refractory group (patients with disease progression in the period of first line chemotherapy, n=7) and chemo-sensitive group (patients with disease progression in more than 6 months after completion of first line chemotherapy, n=13) by Mann-Whitney U test, 77 miRNAs and miRNA variants were found to be dysregulated with significant differences (p&lt;0.05). The 10 most significant miRs identified by NGS were selected for further validation studies by real-time reverse transcription PCR (RT-PCR) analysis on the same sample set. To determine whether miRNAs could be used as a prognostic marker HGSOC, expression levels of those 10 miRNAs were quantified by RT-PCR using 95 HGSOC samples including the 38 samples used in the discovery set. The results showed that mir-625-3p expression levels were significantly reduced in the chemo-refractory group compared with the chemo-sensitive group as indicated by the NGS data (n=20, p=0.029), and by the RT-PCR data (n=63, p=0.004). Furthermore, Kaplan-Meier survival analysis with log-rank test indicated that low expression of mir-625-3p (less than mean expression) was significantly associated with shorter progression-free survival (n=95, p=0.007) and shorter over-all survival (n=95, p&lt;0.001) as compared with the high expression group (more than mean expression).
Our results strongly suggest that mir-625-3p might be a prognostic marker that can be used to predict chemo-sensitivity in patients with HGSOC. Further characterization of mir-625-3p as a therapeutic target for HGSOC is in progress.
Citation Format: Tetsushi Tsuruga, Chi Lam Au Yeung, Cecilia S. Leung, Tsz-Lun Yeung, Kwong K. Wong, Rosemarie Schmandt, Ngai Na Co, Karen H. Lu, Samuel Mok. Identification of microRNAs related to chemosensitivity in ovarian cancer using Next Generation Sequencing. [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 1939. doi:10.1158/1538-7445.AM2013-1939