title: C/EBPβ expression is an independent predictor of overall survival in breast cancer patients by MHCII/CD4-dependent mechanism of metastasis formation.
abstract: CCAAT-enhancer binding protein β (C/EBPβ) is a transcription factor that has a critical role in mammary gland development and breast cancer progression. Loss of C/EBPβ increases metastatic dissemination of mouse mammary tumor cells. However, the mechanism by which C/EBPβ expression affects metastasis formation remains unknown. This study aims at determining the relationship between C/EBPβ and survival of breast cancer patients, and elucidating C/EBPβ's link with metastasis formation. C/EBPβ expression was evaluated in 137 cases of human breast cancer, and the correlation with overall survival was estimated by Kaplan-Meier analysis. Additionally, the mouse 4T1 tumor model was used for in vivo studies. Decreased C/EBPβ expression was found to be associated with shorter overall survival of breast cancer patients. In the murine 4T1 model, loss of C/EBPβ affects tumor growth, morphology and promotes metastatic spread to the lungs. Immunohistochemical analyses showed that C/EBPβ inhibition leads to increased major histocompatibility complex II (MHCII) expression, followed by the accumulation of CD45-, CD3- and CD4-positive (CD4+) lymphocytes in the tumors. Inflammation involvement in C/EBPβ-mediated metastasis formation was confirmed by DNA microarray and by experiments on CD4+ cell-deprived nude mice. Additionally, anti-CD3 and anti-CD4 treatments of C/EBPβ-silenced tumor-bearing mice resulted in reverting the C/EBPβ effect on tumor growth and metastasis. Altogether, C/EBPβ is a predictor of overall survival in breast cancer patients, and affects tumor growth, morphology and lung metastasis formation in murine 4T1 model. The mechanism of metastasis formation involves immunologic response depending on C/EBPβ-mediated activation of MHCII and accumulation of CD4+ lymphocytes in the tumor.
authors.affiliation: 1] Department of Medicine, Centre for Molecular Medicine, Karolinska Institute, Stockholm, Sweden [2] Postgraduate School of Molecular Medicine, Department of Internal Medicine and Hypertension, Medical University of Warsaw, Warsaw, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Kurzejamska
authors.affiliation: Division of Vascular Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Johansson
authors.affiliation: Division of Pathology, Department of Clinical Sciences, Lund University, Skåne University Hospital, Lund, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Jirström
authors.affiliation: 1] Department of Medicine, Centre for Molecular Medicine, Karolinska Institute, Stockholm, Sweden [2] Postgraduate School of Molecular Medicine, Department of Internal Medicine and Hypertension, Medical University of Warsaw, Warsaw, Poland.
authors.forename: V
authors.initials: V
authors.lastname: Prakash
authors.affiliation: Department of Medicine, Centre for Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Ananthaseshan
authors.affiliation: Bioceros Holding BV, Utrecht, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Boon
authors.affiliation: Division of Vascular Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Fuxe
authors.affiliation: 1] Department of Medicine, Centre for Molecular Medicine, Karolinska Institute, Stockholm, Sweden [2] Postgraduate School of Molecular Medicine, Department of Internal Medicine and Hypertension, Medical University of Warsaw, Warsaw, Poland.
authors.forename: P
authors.initials: P
authors.lastname: Religa