Abstract 1712: MicroRNA signatures associated with EOC chemoresistance to platinum-based therapy
Authors: Wang Fengqiang , Difeo Analisa , Narla Goutham , Fishman David A. 
Published: June 2012

Abstract
Objectives: Despite innovative chemotherapeutics, the majority of women with epithelial ovarian cancer (EOC) relapse after primary therapy due to the development of chemoresistance. Effective biomarkers to predict an individual's response to a distinct therapy would significantly decrease the morbidity and mortality from this disease. In the present study, we examined carboplatin chemoresistant EOC associated microRNA (miRNA) signatures using a quantitative PCR based microRNA profiling platform.
Methods: The expression profile of 88 cancer-related miRNAs was determined using a 96-well plate cancer RT2 miRNA PCR array from SA Biosciences in an in vitro cell culture model composed of EOC cell line A2780 (sensitive) and its cisplatin resistant variants CP20 and CP70 (Fig 1A). Total RNA was extracted using the TRIzol reagent (Invitrogen) and reverse transcriped using the RT2 miRNA First Strand Kit from SA Biosciences, and the resultant cDNA was then diluted, mixed with 2× RT2 SYBR Green PCR Master Mix (SA Biosciences) and loaded into the wells of PCR array plate to allow real time PCR amplification and detection. Data analysis was performed using the web-based software for the miRNA PCR array system. Cell undergo apoptosis were measured by FACS upon carboplatin treatment to determine the apoptotic index.
Results: Among the 88 miRNAs profiled, 15 miRNAs were significantly over-expressed in CP70 cells and 7 miRNAs were down-regulated in CP70 cells as compared to A2780 (absolute fold change&gt;5, p &lt; 0.05). Hierarchical clustergram analysis was performed to show the cluster of those miRNAs (Figure 1B). Correlation analysis of those miRNAs’ expression with the apoptotic index of A2780, and its resistant variants, CP20 and CP70 revealed a panel of miRNAs associated with platin response. Of those miRNAs that are over-expressed in platin-resistant cell lines (CP20 and CP70) as compared to A2780, 7 miRNAs showed a positive linear correlation with cell resistance (Fig. 1C, R2 &gt; 0.9). Of the 7 miRNAs that were significantly down-regulated in CP70 cells, 5 miRNAs (miR-17, -18a, -19a, -20a and-125b) showed a negative linear correlation with chemoresistance (Fig. 1D, R2 &gt; 0.9), among which miR-17 displayed a perfect correlation (R2 = 0.9999).
Conclusions: Our analysis differs from previous models used to classify miRNA expression within two groups (sensitive vs. resistant or responsive vs. non-responsive) as we directly correlate the level of each miRNA expression with an apoptotic index that measures each of the cell lines’ sensitivity to cisplatin. Only miRNAs whose expression showed a linear correlation with cell sensitivity (R2 &gt; 0.9) in the three cell lines tested are deemed relevant for further validation. Our results suggest the complexity of miRNA regulation in chemoresistance and the miRNA panels identified in our preliminary study opens a new avenue for the study of miRNA biology and function evaluation in chemoresistance.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1712. doi:10.1158/1538-7445.AM2011-1712