title: NFκB signaling is important for growth of antiestrogen resistant breast cancer cells.
abstract: Resistance to endocrine therapy is a major clinical challenge in current treatment of estrogen receptor-positive breast cancer. The molecular mechanisms underlying resistance are yet not fully clarified. In this study, we investigated whether NFκB signaling is causally involved in antiestrogen resistant cell growth and a potential target for re-sensitizing resistant cells to endocrine therapy. We used an MCF-7-derived cell model for antiestrogen resistant breast cancer to investigate dependence on NFκB signaling for antiestrogen resistant cell growth. We found that targeting NFκB preferentially inhibited resistant cell growth. Antiestrogen resistant cells expressed increased p50 and RelB, and displayed increased phosphorylation of p65 at Ser529 and Ser536. Moreover, transcriptional activity of NFκB after stimulation with tumor necrosis factor α was enhanced in antiestrogen resistant cell lines compared to the parental cell line. Inhibition of NFκB signaling sensitized tamoxifen resistant cells to the growth inhibitory effects of tamoxifen but was not sufficient to fully restore sensitivity of fulvestrant resistant cells to fulvestrant. In support of this, depletion of p65 with siRNA in tamoxifen resistant cells increased sensitivity to tamoxifen treatment. Our data provide evidence that NFκB signaling is enhanced in antiestrogen resistant breast cancer cells and plays an important role for antiestrogen resistant cell growth and for sensitivity to tamoxifen treatment in resistant cells. Our results imply that targeting NFκB might serve as a potential novel treatment strategy for breast cancer patients with resistance toward antiestrogen.
authors.affiliation: Breast Cancer Group, Cell Death and Metabolism, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen Ø, Denmark. cwy@cancer.dk
authors.forename: Christina W
authors.initials: CW
authors.lastname: Yde
authors.forename: Kristina B
authors.initials: KB
authors.lastname: Emdal
authors.forename: Barbara
authors.initials: B
authors.lastname: Guerra
authors.forename: Anne E
authors.initials: AE
authors.lastname: Lykkesfeldt
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology / Q000627:therapeutic use; D004965:Estrogen Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D061986:MCF-7 Cells; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000096:biosynthesis; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction; D013629:Tamoxifen / Q000494:pharmacology / Q000627:therapeutic use; D051996:Transcription Factor RelA / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D051841:Transcription Factor RelB / Q000096:biosynthesis
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004965:Estrogen Antagonists; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C498143:RELA protein, human; C497593:RELB protein, human; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; D013629:Tamoxifen; D051841:Transcription Factor RelB; D000077267:Fulvestrant; D004958:Estradiol; D019869:Phosphatidylinositol 3-Kinases