title: FOXP1, an estrogen-inducible transcription factor, modulates cell proliferation in breast cancer cells and 5-year recurrence-free survival of patients with tamoxifen-treated breast cancer.
abstract: Breast cancer is primarily a hormone-dependent tumor that can be regulated by the status of steroid hormones, including estrogen and progesterone. Forkhead box P1 (FOXP1) is a member of the forkhead box transcription factor family and has been reported to be associated with various types of tumors. In the present study, we investigated the expression of FOXP1 in 133 human invasive breast cancers, obtained by core biopsy, by immunohistochemical analysis. Nuclear immunoreactivity of FOXP1 was detected in 89 cases (67%) and correlated positively with tumor grade and hormone receptor status, including estrogen receptor alpha (ERα) and progesterone receptor, and negatively with pathological tumor size. In ERα-positive MCF-7 breast cancer cells, we demonstrated that FOXP1 mRNA was upregulated by estrogen and increased ERα recruitment to ER binding sites identified by ChIP-on-chip analysis within the FOXP1 gene region. We also demonstrated that proliferation of MCF-7 cells was increased by exogenously transfected FOXP1 and decreased by FOXP1-specific siRNA. Furthermore, FOXP1 enhanced estrogen response element-driven transcription in MCF-7 cells. Finally, FOXP1 immunoreactivity was significantly elevated in relapse-free breast cancer patients treated with tamoxifen. These results suggest that FOXP1 plays an important role in proliferation of breast cancer cells by modulating estrogen signaling and that FOXP1 immunoreactivity could be associated with the estrogen dependency of clinical breast cancers, which may predict favorable prognosis in the patients treated with tamoxifen.
authors: Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Japan.
authors: Takashi
authors: T
authors: Shigekawa
authors: Nobuhiro
authors: N
authors: Ijichi
authors: Kazuhiro
authors: K
authors: Ikeda
authors: Kuniko
authors: K
authors: Horie-Inoue
authors: Chikako
authors: C
authors: Shimizu
authors: Shigehira
authors: S
authors: Saji
authors: Kenjiro
authors: K
authors: Aogi
authors: Hitoshi
authors: H
authors: Tsuda
authors: Akihiko
authors: A
authors: Osaki
authors: Toshiaki
authors: T
authors: Saeki
authors: Satoshi
authors: S
authors: Inoue
mesh_terms: D000328:Adult; D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D002277:Carcinoma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D016022:Case-Control Studies; D049109:Cell Proliferation; D018572:Disease-Free Survival; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D012008:Recurrence; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013629:Tamoxifen / Q000627:therapeutic use*; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004967:Estrogens; C486626:FOXP1 protein, human; D051858:Forkhead Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D013629:Tamoxifen