Abstract 5234: Serum microRNAs reflect microRNA expression in tumor tissues as well as systemic response to disease in HRAS-driven mouse models of HCC
Authors: Pavlicek Adam , Ratushna Vladyslava , Phillips Shirley , Heinlein Cynthia , Li Jian , Kaimal Vivek , Zabludoff Sonya , Chau Nelson 
Published: May 2015

Abstract
Circulating microRNAs are promising candidates as minimally-invasive biomarkers for tumor detection, disease monitoring, and patient stratification. Increases in serum concentrations have been reported for many microRNAs up-regulated in tumor cells. However, how well global changes in tumor microRNA expression are reflected in circulating microRNAs is less understood.
To answer this question, we performed experiments in a Tet-regulated mouse HRAS model of hepatocellular carcinoma (HCC). Male mice develop detectable HCC within a few weeks from activation of the oncogenic HRAS allele. Matched serum and liver tissues for microRNA profiling were collected at three timepoints: right before HRAS activation (normal liver), 3 weeks after activation (moderate tumor burden), and 6 weeks after activation (pervasive tumors). To emulate the effect of targeted treatment, we inactivated the HRAS allele in a group of animals 3 weeks after activation and collected serum and liver tissues at the 6 weeks timepoint (3 weeks HRAS on, 3 weeks off). Global liver and serum microRNA profiles were measured using the OpenArray TaqMan qPCR Platform.
The global microRNA profiling analysis revealed that the overall number of detected serum microRNAs as well as the overall serum expression increased with tumor progression and normalized after the HRAS withdrawal. In the liver, 3 weeks after the HRAS activation we observed small changes with just 7 differentially expressed microRNAs at FDR &lt; 20%. The changes became much more pronounced at 6 weeks with 89 microRNAs passing the FDR &lt; 20% threshold. Most of these changes reversed in the 3 weeks on/3 weeks off group and these samples resembled the normal liver controls. Many microRNAs differentially expressed in the liver were also altered in serum, albeit with smaller average fold changes in serum compared to liver. The fold changes were positively correlated between liver and serum samples (Pearson R = 0.25, p &lt; 0.01). We detected additional significant changes in serum microRNAs not reflected in liver tissues samples. The serum-specific alteration included microRNAs linked to immune response, liver injury and other systemic responses to the tumor burden. Similarly to liver, the serum changes were most pronounced in the 6 weeks HRAS group and partially reverted to normal-like profiles in the 3 weeks on/3 weeks off group.
In conclusion, using a mouse model of HCC we found that (1) deregulation of liver microRNA profiles increases with the tumor size and (2) that serum microRNA profiles reflect both changes in the tumor tissues and well systemic response to tumor burden. Importantly, most of the changes in both liver and serum are reversed upon inhibition of the driving oncogene. Thus circulating microRNAs are promising candidates for tumor detection, disease monitoring, and monitoring of treatment response.
Citation Format: Adam Pavlicek, Vladyslava Ratushna, Shirley Phillips, Cynthia Heinlein, Jian Li, Vivek Kaimal, Sonya Zabludoff, Nelson Chau. Serum microRNAs reflect microRNA expression in tumor tissues as well as systemic response to disease in HRAS-driven mouse models of HCC. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5234. doi:10.1158/1538-7445.AM2014-5234