Breast cancer cells have lower activating protein 1 transcription factor activity than normal mammary epithelial cells

To determine whether normal breast cells have different levels of activating protein 1 (AP-1) expression and activation relative to breast cancer cells, we have compared the level of c-Jun and c-Fos expression and AP-1 activity in human mammary epithelial cells (HMECs) at different stages of transfo...

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Bibliographic Details
Published in:Cancer research (Chicago, Ill.) Ill.), 1997-07, Vol.57 (14), p.3046-3054
Main Authors: SMITH, L. M, BIRRER, M. J, STAMPFER, M. R, BROWN, P. H
Format: Article
Language:English
Subjects:
Biological and medical sciences
Breast - chemistry
Breast Neoplasms - chemistry
Breast Neoplasms - genetics
Cell Line
Epidermal Growth Factor - pharmacology
Epithelium - chemistry
Female
Genes, fos
Genes, jun
Gynecology. Andrology. Obstetrics
Humans
Mammary gland diseases
Medical sciences
Transcription Factor AP-1 - analysis
Transfection
Tumors
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Summary:To determine whether normal breast cells have different levels of activating protein 1 (AP-1) expression and activation relative to breast cancer cells, we have compared the level of c-Jun and c-Fos expression and AP-1 activity in human mammary epithelial cells (HMECs) at different stages of transformation (normal proliferating HMECs, immortal HMECs, oncogene-transformed HMECs, and breast cancer cell lines). These studies demonstrated that normal and immortal HMECs have a high basal level of expression of cJun and cFos and higher AP-1 DNA-binding and transcriptional activating activities than do oncogene-transformed HMECs or human breast cancer cells, with a gradual decrease in AP-1 transactivating activity as cells progress through the carcinogenesis pathway (normal > immortal > oncogene-transformed > cancer cell lines). The AP-1 activity in normal or immortal cells was not modulated by growth factor supplementation or oncogene overexpression, as it is in breast cancer cells. However, the addition of suramin, a nonspecific growth factor antagonist, did inhibit AP-1 in these HMECs, suggesting that this high level of AP-1 present in normal HMECs may be due to autocrine stimulation of growth factor pathways. The differences in AP-1 activity in normal and malignant breast cells may indicate that normal cells are more dependent on AP-1-mediated signals for their growth than are breast cancer cells.
ISSN:0008-5472
1538-7445