Background: Endometrial cancer (EC) is a hormone-related disease, showing highly diverse features of ER/PR/HER2 status-based molecular subtypes. Long noncoding RNA (lncRNA) HOX antisense intergenic RNA (HOTAIR) has recently emerged as a key molecule in many cancers, triggering epithelial-mesenchymal transition (EMT)-mediated cancer stem cell (CSC) formation, but little is known about its significance in EC. Thus, we aimed to investigate the clinical significance of HOTAIR itself in different molecular subtypes of EC and possible links between HOTAIR, EMT and CSC-related markers.
Methods: The study group included 156 consecutive, stage I-IV EC patients treated between 2000 and 2010. ER, PR and HER2 protein expression were examined by immunohistochemistry (IHC) on tissue microarrays. RT-qPCR was used to analyze the expression levels of HOTAIR, EMT-related genes - SNAIL and SLUG - and the CSCs marker CD133.
Results: Molecular subtypes, defined as ER/PR+HER2+, ER/PR+HER2-, ER-PR-HER2+ and ER-PR-HER2-, occurred in 40.2%, 52.3%, 4.7% and 1.9% of cases, respectively. The expression of HOTAIR did not differ between the subtypes, but high HOTAIR expression correlated with shorter overall survival (p = 0.04) in the entire group. The expression levels of HOTAIR, SNAIL, SLUG and CD133 were similar in defined EC molecular subtypes.
Conclusions: Our data do not confirm the role of HOTAIR in EMT-mediated CSC formation in EC. Neither does the diversity of EC molecular subtypes influence these processes. But HOTAIR expression could serve as an independent prognostic factor in EC. The clinical importance of the above discoveries requires further studies.