Abstract 1623: CITED2 modulates metastatic ability through effects on IKK-alpha in breast cancer cells

Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain-2 (CITED2) is a member of the CITED family of non-DNA binding transcriptional co-activators. Previously, we identified CITED2 as a novel facilitator of bone metastasis in murine mammary cancer. Extending these initial studies to human breast cancer, CITED2 mRNA expression was significantly elevated in patient samples of metastatic breast cancer relative to primary tumors, with highest levels in bone metastasis. To explore the functional impact of CITED2 in breast cancer metastasis, we stably reduced CITED2 expression in the human breast cancer cell lines MDA-MB-231 and MDA-MB-468 cells, which are metastatic in animal models. While CITED2 knockdown had no effect on cell proliferation, it significantly reduced tumor migration and invasion in vitro and metastasis following intra-cardiac administration in athymic nude mice in vivo. To explore the mechanism responsible for these effects, we examined the impact of CITED2 knockdown on gene expression in MDA-MB-231 cells by microarray analysis. As confirmed at the mRNA and protein levels in both MDA-MB-231 and MDA-MB-468 cells, expression of the NF-κB regulator IKKα was significantly reduced along with several downstream targets of the NF-κB pathway (OPN, MMP9, uPA, SPARC, IL11 and IL-1β). In line with the reduced expression of IKKα, both canonical and non-canonical NF-κB signaling was inhibited following CITED2 knockdown. By ChIP assay, CITED2 was recruited to the promoters of IKKα, as well as the NF-κB targets OPN, MMP9, and SPARC. Finally, restoration of IKKα expression in MDA-MB-231 and MDA-MB-468 cells following CITED2 knockdown rescued their invasive ability. Collectively, these results suggest that CITED2 exerts its pro-metastatic effects in breast cancer cells via regulating IKKα. Citation Format: Swaathi Jayaraman, Michele Doucet, Wen M. Lau, Scott L. Kominsky. CITED2 modulates metastatic ability through effects on IKK-alpha in breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1623.