The expression of CCAAT/enhancer binding protein (C/EBP) in the human ovary in vivo: specific increase in C/EBPβ during epithelial tumour progression

Abstract

SummaryThe CCAAT/enhancer binding protein (C/EBP) family of transcription factors is involved in metabolism and differentiation of cells, especially in rodent liver cells and adipocytes. Their roles in vivo and in particular during pathophysiological conditions in humans are largely unknown. We have investigated the presence of C/EBPα, -β, -δ and -ζ in normal ovaries and in epithelial ovarian tumours of different stages. Immunohistochemical experiments demonstrated that C/EBPα and C/EBPβ were preferentially expressed in epithelial/tumour cells irrespective of stage or grade of the tumour. C/EBPβ was located in the nuclei of the cells, in contrast to C/EBPα, which was present only in the cytoplasm of these cells. The nuclear localization of C/EBPβ indicates an active role of this transcription factor in tumour cells, whereas the cytoplasmic distribution suggests a more passive function of C/EBPα. C/EBPδ and -ζ demonstrated a more diverse distribution with predominant localization to epithelial cells, but stromal distribution was also noted. The intracellular distribution was confined to both the nucleus and the cytoplasm for C/EBPδ and -ζ. Western blotting demonstrated that C/EBPα, -β, -δ and -ζ were present in a majority of the samples. The amount of C/EBPβ increased markedly with malignancy, i.e. with degree of dedifferentiation, while the other members of the C/EBP family displayed a more constant expression level. These results demonstrate an association between the expression of members of the C/EBP family and the formation of epithelial ovarian tumours, with C/EBPβ as a potential marker for these tumours. As C/EBPβ is known to be expressed during proliferation of cells in vitro, it may participate in the proliferative process of ovarian epithelial tumour cells in vivo and play a central role in tumour progression.

Wnt-signalling pathway in ovarian epithelial tumours: increased expression of β-catenin and GSK3β

“…Soluble tissue and cells were prepared by homogenisation in a PEbuffer with proteinase inhibitors, analysed for protein content by the method of Lowry and stored at À701C as previously described (Sundfeldt et al, 1999). Briefly, 35 mg of total protein was diluted in a sodium dodecyl suplhate (SDS)-sample buffer and heated before loading on a 1D SDS-polyacrylamide gel (8% Tris-Glycine) or NuPage gel (10%) (NOVEX, San Diego, CA, USA).…”

“…Fresh frozen tissues were cryosectioned and fixed in cold acetone for 10 min, air dried and stored at À201C as previously described (Sundfeldt et al, 1999). Briefly, slides were blocked with 5% nonfat milk (NFM) before the addition of primary antibodies to b-catenin (1 : 100), Lef-1 (1 : 100), Lef-1 antiserum (1 : 100), GSK3b (1 : 50), APC-COOH and APC-NH 2 -terminus (1 : 100) and incubated overnight.…”

Conditional ablation of C/EBPβ demonstrates its keratinocyte-specific requirement for cell survival and mouse skin tumorigenesis

“…Moreover, overexpression of C/EBPb-2 in a human mammary epithelial cell line lead to anchorage independence and invasive properties (Bundy and Sealy, 2003). C/EBPb is highly expressed in colorectal tumors (Rask et al, 2000) and is associated with ovarian tumor progression (Sundfeldt et al, 1999). Furthermore, C/EBPb can interact with cyclin D1 and appears to be important for the unique pattern of altered gene expression in human cancers that overexpress cyclin D1 (Lamb et al, 2003).…”

Increased expression of CCAAT/enhancer binding protein β correlates with prognosis in glioma patients

“…An increased expression of C/EBP ß is reported in breast cancer (24), ovarian cancer (25), colorectal cancer (26) and renal cell carcinoma (27). In contrast, downregulated expression has been reported in squamous cell carcinoma (28) and hepatocellular carcinoma (29).…”