Down-regulation and growth inhibitory role of C/EBPalpha in breast cancer.
OBJECTIVE
CCAAT/enhancer binding proteins (C/EBP) are a family of transcription factors that regulate proliferation and differentiation in a variety of tissues. The purpose of this study was to explore the possibility that C/EBPalpha is involved in breast cancer.


METHODS
We quantified C/EBPalpha mRNA expression levels in 24 primary breast tumors, 16 normal breast samples, and 8 breast cancer cell lines using quantitative real-time reverse transcription-PCR assay. C/EBPalpha protein levels were further determined by immunohistochemical analysis. To examine the consequence of C/EPBalpha expression in breast cancer, we stably transfected an inducible C/EPBalpha expression vector into three breast cancer cell lines.


RESULTS
Low expression of C/EBPalpha mRNA was found in 83% of primary breast cancer samples. Immunohistochemical study further showed either a markedly reduced or undetectable expression of C/EBPalpha protein in 30% of breast cancer specimens. The other 70% of breast cancers had C/EBPalpha expression in both the cytoplasm and nucleus; in control, C/EBPalpha was localized to the nucleus in the normal ductal cells. C/EBPalpha expression was associated with estrogen- and progesterone receptor-negative status. Induction of C/EBPalpha expression in these cell lines resulted in growth inhibition accompanied by G0-G1 cell cycle arrest and reduced anchorage-independent cell growth. C/EBPalpha expression was associated with down-regulation of c-myc and up-regulation of p21, PPARgamma, and the breast epithelial differentiation marker, maspin.


CONCLUSIONS
These results suggest that reduced expression of C/EBPalpha may play a role in the development and/or progression of breast cancer.
Gery
Sigal
S
Division of Hematology/Oncology, Cedars-Sinai Medical Center, University of California at Los Angeles School of Medicine, USA. gerys@cshs.org
Tanosaki
Sakae
S
Bose
Shikha
S
Bose
Namrata
N
Vadgama
Jay
J
Koeffler
H Phillip
HP
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006801:Humans; D007150:Immunohistochemistry; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
D022763:CCAAT-Enhancer-Binding Protein-alpha; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C489427:MYC protein, human; D047495:PPAR gamma; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; C085344:SERPIN-B5; D015843:Serpins