Abstract 5242: miR-10b functions as a novel tumor suppressor in uterine leiomyosarcoma by promoting overexpression of SDC1
Authors: Anderson Matthew L. , Kim Gyoung Eun , Mach Claire M. , Creighton Chad J. , Lev Dina 
Published: May 2015

MicroRNAs (miRNAs) are endogenous RNA transcripts that play a critical role in regulating pleuripotency and differentiation. Altered miRNA expression is a well-established feature of nearly all human cancers. However, the mechanisms by which dysregulated miRNA expression promote tumorigenesis remain poorly understood.To evaluate the role of miRNAs in uterine leiomyosarcoma (uLMS), we profiled patterns of small RNA expression in matched specimens of healthy myometrium (n=34), uterine leiomyomas (n=34) and uterine leiomyosarcoma (n=12) using Next Generation Sequencing (NGS). After quantile normalization, patterns of mature miRNA transcripts were compared. We found that 37 individual miRNAs were differentially expressed &gt;2-fold (p&lt;0.01) when uLMS were compared to myometrium and leiomyomas. Of these, miR-10a and miR-10b were the most robustly down-regulated miRNAs in uLMS (&gt;8-fold, p&lt;0.01). To determine whether a loss of miR-10b is critical for uLMS growth and metastasis, we examined the impact of enforced miR-10b expression in representative cell lines using standard MTA and Caspase assays (Promega) as well as flow cytometry and Boyden chamber assays. Overexpression of miR-10b resulted in a profound decrease in proliferation in all cell lines tested (SK-LMS, LEIO-505 and LEIO-285 LMS). Enforced miR-10b expression was also accompanied by G2-M cell cycle arrest, increased rates of apoptosis and decreased invasion and migration. Potential targets for miR-10b were identified by profiling the same panel of uLMS specimens using the Illumina gene chip (WG_v3). Genes overexpressed &gt;2-fold when uLMS were compared to myometrium (p&lt;0.01) were then screened using established miRNA target prediction algorithms (TargetScan, MiRanda). We discovered that levels of syndecan 1 (SDC1), a highly glycosylated cell surface proteoglycan implicated in maintaining pluripotent progenitor cells, is highly overexpressed in uLMS (2.71-fold, p&lt;0.001). Levels of SDC1, a predicted miR-10b target, were also dramatically reduced when uLMS cells lines transfected with miR-10b mimic were compared to controls (n=3). Lastly, we found that the number and size of tumor implants created when SK-LMS cells stably expressing miR-10b inoculated into the peritoneal cavity of immunodeficient mice were significantly reduced when compared to controls. The smaller size of miR-10b-expressing xenografts was accompanied by decreased rates of proliferation (as assessed by Ki-67 expression) and enhanced apoptosis (as assessed by TUNEL).Collectively, these results identify a novel sequence of events whereby the loss of miR-10b plays a key role in driving the growth and metastasis of uLMS by enhancing SDC1 expression. More fundamentally, the relationship between miR-10b and SDC1 in these aggressive cancers may also identify a critical link between the dysregulation of mesenchymal stem cells and sarcomagenesis.

Note: This abstract was not presented at the meeting.

Citation Format: Matthew L. Anderson, Gyoung Eun Kim, Claire M. Mach, Chad J. Creighton, Dina Lev. miR-10b functions as a novel tumor suppressor in uterine leiomyosarcoma by promoting overexpression of SDC1. [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 5242. doi:10.1158/1538-7445.AM2014-5242