Search

Inhibitor of IκB kinases (IKK) are key regulators of NF-κB signaling. Three IKK isoforms—α, β, and ϵ—have been linked to oncogenesis, yet the precise components of NF-κB signaling in ovarian cancer have not yet been dissected. We surveyed 120 ovarian cancer specimens for IKK-ϵ expression. Notably, cytoplasmic expression was elevated in metastatic lesions relative to primary tumors (P = 0.03). Therefore, we hypothesized that IKK-ϵ drives ovarian cancer metastasis. IKK-ϵ was identified previously as a breast cancer oncogene and was associated with poor clinical outcome in ovarian cancer. We now define an ovarian cancer–specific IKK-ϵ–regulated gene expression signature using stably expressed short hairpin RNA targeting IKK-ϵ. Pathway analysis of the signature indicated that IKK-ϵ regulates expression of genes involved in cell motility and inflammation. We further showed that IKK-ϵ depletion in metastatic ovarian cancer cell lines decreased growth, adhesion, and invasion. Consistently, human xenografts depleted of IKK-ϵ in mice showed decreased aggressiveness, whereas overexpression of IKK-ϵ in a less invasive ovarian cancer cell line increased metastasis in vivo. Taken together, these data provide evidence that IKK-ϵ is a key coordinator of invasion and metastasis programs in ovarian cancer. Inhibition of IKK-ϵ signaling thus emerges as a viable therapeutic strategy in women whose ovarian cancer shows aberrant activation of this pathway. Cancer Res; 72(21); 5494–504. ©2012 AACR.

Metastatic breast cancer carries a poor prognosis despite the success of newly targeted therapies and treatment options remain especially limited for the subtype of triple negative breast cancer (TNBC). Several signaling pathways, including NF-κB, are altered in TNBC. Given that ΙΚΚε behaves as an oncogene in breast cancer we hypothesized that IKKε regulates classical or alternative NF-κB signaling to control diverse oncogenic functions in TNBC. Vector expression and RNA interference were used to investigate the functional role of IKKε in triple-negative breast cancer cells. Viability, protein expression, NF-κB binding activity, invasion, anoikis, and spheroid formation were examined in cells expressing high or low levels of IKKε in conjunction with alternative NF-κB p52 RNA interference or MEK inhibition. Our data show that p52 protein levels and binding activity are inversely proportional to ΙΚΚε. Moreover, knockdown of IKKε leads to increased expression of p52 and the p52-regulated gene CXCL1. This interaction was confirmed by CHiP-PCR experiments showing increased binding of p52 in the CXCL1 promoter of cells with IKKε knockdown relative to control. We further found that IKKε and MEK were required for growth in anchorage supportive conditions whereas p52 was required in anchorage resistant conditions. Western blots confirm diminished IKKε expression and enhanced p52 processing in anchorage resistant conditions relative to anchorage supportive conditions. In this model, IKKε and MEK cooperate to support growth of cancer cells in the attached, anchored environment, whereas p52 is required for growth in unattached 3-D environment. These studies reveal novel information about the role of IKKε in TNBC and highlight the adaptability of NF-κB signaling in maintaining cancer cell survival under different growth conditions. Current studies are underway to clarify the mechanism of IKKε regulation of p52. A better understanding of the diversity of NF-κB signaling may ultimately improve the development of novel therapeutic regimens for TNBC. Citation Format: Carrie D. House, Valentina Grajales, Michelle Ozaki, Elizabeth Jordan, Helmae Wubneh, Danielle Kimble, Marianne Kim, Christina M. Annunziata. IKK-epsilon supports anchorage independent growth via alternative NF-kB signaling in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5470.

Metastatic breast cancer carries a poor prognosis despite the success of newly targeted therapies. Treatment options remain especially limited for the subtype of triple negative breast cancer (TNBC). Several signaling pathways, including NF-κB, are altered in TNBC, and the complexity of this disease implies multifaceted pathway interactions and compensatory signaling. We hypothesized that a subset of TNBCs expresses IKKϵ to promote a specific NF-κB signaling program that can enhance metastatic potential. Our data suggest that IKKϵ supports MEK activation and suppresses non-canonical signaling by the p52 NF-κB transcription factor. We found that NF-κB p52 expression is inversely proportional to activated MEK. We further demonstrate that IKKϵ and MEK cooperate to support viability and invasion potential under adherent conditions, whereas the p52 transcription factor supports viability under non-adherent conditions, underscoring the contrasting roles of these proteins. This study illustrates the diverse roles of NF-κB signaling components in TNBC, and highlights the adaptability of NF-κB in maintaining cancer cell survival under different microenvironments. A better understanding of the diversity of NF-κB signaling may ultimately improve the development of novel therapeutic regimens for TNBC. Citation Format: Carrie House, Valentina Grajales, Helmae Wubneh, Danielle Kimble, Marianne Kim, Christina Annunziata. IKKϵ maintains MEK activation and suppresses non-canonical NF-κB signaling in triple-negative breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1955. doi:10.1158/1538-7445.AM2015-1955