Abstract 1052: Synergy between inhibition of novel histone demethylase (LSD2) and DNA methyltransferase (DNMT) and histone deacetylase (HDAC) in modulating gene expression and inhibiting growth in human breast cancer cells
Authors: Katz Tiffany A. , Vasilatos Shauna N. , Oesterreich Steffi , Chandran Uma , Davidson Nancy E. , Huang Yi 
Published: August 2012

Abstract
Epigenetic gene silencing plays a critical role in breast tumor aggression. Our previous studies have shown that abnormal activities of histone lysine demethylases (KDMs) are associated with aberrant gene expression in breast cancer development. However, the precise molecular mechanisms underlying the activity of KDMs in chromatin remodeling and regulation of gene transcription in breast cancer are still elusive. Recently, a novel mammalian histone demethylase LSD2 (also known as KDM1B or AOF1) was identified. We have shown that LSD2 possesses the activity to demethylate H3K4 in breast cancer cells. This clearly suggests the existence of a more sophisticated FAD-dependent histone demethylase family whose members play a role in chromatin remodeling and transcription regulation in breast cancer. Here we demonstrated that inhibition of LSD2 mRNA expression by shRNA suppressed migratory behavior in human breast cancer MDA-MB-231 cells. RNAi -mediated LSD2 deficiency led to a significant re-expression of ERα mRNA, in ER negative breast cancer cells and upregulated ER-mediated transcription activity as evidenced by ERE luciferase assay. Microarray studies indicated a unique subset of genes whose expression was significantly changed by LSD2 KD in MDA-MB-231 cells. The genes identified are extensively involved in regulation of tumor cell proliferation, metastasis, cell signaling, transcription regulation, and chromatin remodeling. For example, a panel of the upregulated genes potentially plays a role in cell adhesion and cell death such as CLDN1 & 11, CDH11, CASP5 & 10, PDCD4, and NCR3. In addition, expression of several tumor suppressor genes such as ERBB2IP, MTSS1, and S100A2 were up-regulated by LSD2 KD in MDA-MB-231 cells. Moreover, treating LSD2 KD cells with the low doses of DNMT inhibitor, 5-aza-2-deoxycitidine (DAC) led to a robust reexpression of ERα and CASP5 mRNA in MDA-MB-231 cells. Treatment with the HDAC inhibitor vorinostat in LSD2 KD MDA-MB-231 cells also lead to the reexpression of ERα as well as other genes of interest such as CASP5, ESRRG, and MTSS1. Further simultaneous treatment of LSD2 KD cells with DAC and vorinostat produced a more robust transcriptional re-activation of ERα, CASP5, and MTSS1 mRNA expression. Finally, LSD2 KD MDA-MB-231 cells exhibited increased sensitivity to growth inhibition induced by combination therapy of vorinostat and DAC. Taken together, these data implicate an important role for LSD2 in mediating expression of epigenetically silenced genes in breast cancer cells and suggest that combined inhibition of LSD2 with other epigenetic targets could have the potential to improve the treatment of breast cancer.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1052. doi:1538-7445.AM2012-1052