Abstract 1403: HOTAIR functions through NF-κB pathway in regulating ovarian cancer stem cells
Authors: Weini Wang, Fang Fang, Ali R. Özeş, Kenneth P. Nephew
Journal: Cancer Research (2020)

Abstract Ovarian cancer (OC) is the fifth leading cause of cancer-related death among American women. Persistence of OC stem cells (OCSCs) is believed to contribute to resistance to platinum-based chemotherapy and disease relapse. Long non-coding RNA HOXC transcript antisense RNA (HOTAIR) has been shown to be associated with chemoresistance and overexpressed in many types of cancers, including high-grade serous OC (HGSOC). Previously published work has demonstrated that NF-κB was activated by HOTAIR through I-κB inhibition via trimethylation of histone H3 lysine K27, which contributes to chemoresistance in HGSOC. NF-κB-medicated signaling pathways involved in maintaining characteristics of CSCs, such as targeting stem cell markers, CD44, CD133, and ALDH1 has been demonstrated but not well defined in OC. The goals of this study are to understand the mechanism of HOTAIR-mediated NF-κB signaling pathway in regulating OCSCs and develop novel strategies to target OCSCs and overcome OC recurrence and drug resistance. Quantitative RT-PCR analysis revealed that HOTAIR was overexpressed in OCSCs compared to non-OCSCs. In order to produce loss-of-function phenotypes of HOTAIR and investigate the function of this gene, we utilized the paired CRISPR guide RNA design to delete the functional sites of HOTAIR without affecting nearby protein-coding gene. Knockout of HOTAIR re-sensitized OC cells to platinum treatment and significantly decreased (P&amp;lt;0.001) OCSC population and stemness-related phenotypes, including spheroid formation and colony formation ability. ALDH1A1 and expression of other stemness-related genes, including Notch3, PROM1 were significantly decreased by HOTAIR knockout. Overexpression of HOTAIR in OC cells significantly increased (P&amp;lt;0.05) these stem-like characteristics. Furthermore, we showed NF-κB nuclear accumulation and activation in OCSCs compared to non-OCSCs. Knockout of HOTAIR decreased (P&amp;lt;0.01) nuclear localization of NF-κB in OCSCs. Inhibiting NF-κB in using a commercially available pharmacological approach as well as NF-κB knockout both significantly decreased OCSC population and stemness-related phenotypes, as well as ALDH1 protein expression (P&amp;lt; 0.01). However, inhibition of NF-κB has no effect on OCSC characteristics in HOTAIR knockout cells, indicating that HOTAIR may function through constitutively activated NF-κB in regulating OCSCs. We suggest a better understanding of HOTAIR- NF-κB axis in regulating OCSCs will facilitate identifying the key therapeutic target to eliminate residual tumor cells after conventional chemotherapy and prevent OC recurrence and drug resistance. Citation Format: Weini Wang, Fang Fang, Ali R. Özeş, Kenneth P. Nephew. HOTAIR functions through NF-κB pathway in regulating ovarian cancer stem cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1403.