Introduction and purpose of study: Uterine carcinosarcoma (UCS) is an aggressive and rare malignancy with poor prognosis and limited treatment options. These biphasic tumors, consisting of epithelial and mesenchymal components, are hypothesized to evolve from less aggressive endometrial adenocarcinomas (EACs) through epithelial-mesenchymal transition (EMT). EMT is a reversible process, and mesenchymal-epithelial transition (MET) has been shown to decrease tumor aggressiveness. Inducing MET has been suggested for treatment of cancers with a mesenchymal phenotype. In our studies, we investigated the importance of EMT in the evolution of UCS by depleting miR-200, a family of microRNAs critical for EMT, in EAC cell lines. We also explored the role of miR-200 overexpression as a driving force for MET in UCS with a focus on finding novel therapeutic approaches to the treatment of this aggressive disease.

Experimental procedures: To test whether UCSs evolve from EACs, we depleted miR-200b/c in EAC cell lines, Ishikawa and MFE-280. For the MET studies, we stably overexpressed miR-200c in UCS cell lines, SNU685 and JHUCS1. Gene expression was measured using TaqMan and whole transcriptome sequencing (RNA-seq) assays. Immunoblotting was performed on the EMT-relevant proteins. Cell adhesion and in vitro cell proliferation were measured using commercially available assays. In vivo tumor growth of JHUCS1 miR-200c-overexpressed cells was measured in xenografted mice.

Summary of the data: Compared to EAC cells, UCS cells had undetectable miR-200c expression. Depletion of miR-200b/c in EAC cells resulted in expected increased ZEB1 and decreased E-cadherin expression. The lack of increased N-cadherin, vimentin and morphologic changes, even in the presence of exogenous TGF-β suggests partial EMT induction. Overexpression of miR-200c in UCS cells resulted in full MET, with a decrease in ZEB1, ZEB2, N-cadherin and vimentin and an increase in E-cadherin. Increased cellular adhesion was observed along with typical MET morphologic changes. miR-200c overexpression led to inhibited UCS cell proliferation and metabolic activity. Overexpression of miR-200c in vivo resulted in substantially smaller tumors compared to mice bearing control UCS cells.

Conclusions: Our data suggest that mechanisms additional to, or other than EMT, are necessary for the evolution of UCS from EAC. UCS cell lines, however, readily undergo robust MET in the setting of increased miR-200c expression rendering them less aggressive. These findings suggest that miR200 overexpression through advanced microRNA therapeutics may lead to new options for the treatment of uterine carcinosarcomas.

Citation Format: Jill H. Tseng, Maria Bisogna, Lien N. Hoang, Narciso Olvera, Douglas A. Levine, Petar Jelinic. miR-200c-driven mesenchymal-to-epithelial transition as a therapeutic target in uterine carcinosarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3422. doi:10.1158/1538-7445.AM2017-3422