Synthesis and secretion of transforming growth factor beta isoforms by primary cultures of human breast tumour fibroblasts in vitro and their modulation by tamoxifen

• Published in: British journal of cancer Vol. 74; no. 3; pp. 352 - 358
• Main Authors: BENSON, J. R, WAKEFIELD, L. M, BAUM, M, COLLETTA, A. A
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing Group 01.08.1996
• Subjects: Antineoplastic agents; Antineoplastic Agents, Hormonal - pharmacology; Biological and medical sciences; Breast Neoplasms - metabolism; Cells, Cultured; Female; Fibroblasts - metabolism; Fluorescent Antibody Technique; General aspects; Humans; Medical sciences; Pharmacology. Drug treatments; Receptors, Estrogen - analysis; Tamoxifen - pharmacology; Transforming Growth Factor beta - analysis; Transforming Growth Factor beta - biosynthesis; Transforming Growth Factor beta - metabolism; Antineoplastic agent; Human; Cell culture; Molecular form; Transforming growth factor β; Cytokine; Antiestrogen; Biosynthesis; Antihormone; Malignant tumor; In vitro; Tamoxifene; Mammary gland diseases; Regulation(control); Primary culture; Paracrine secretion; Mammary gland; Fibroblast
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.1996.365

Tamoxifen may mediate its effect in early breast cancer in part via an oestrogen receptor (ER)-independent pathway by directly stimulating fibroblasts to produce the negative paracrine growth factor transforming growth factor (TGF)-beta. We have previously shown that secretion of this factor is induced 3-to 30-fold in human fetal fibroblasts in vitro, and by stromal fibroblasts in vivo following tamoxifen treatment of ER-positive and ER-negative breast cancer patients. Primary cultures of breast tumour fibroblasts have been exposed to tamoxifen for 48 h, and rates of secretion of TGF-beta 1 and TGF-beta 2 measured using a quantitative immunoassay. Fibroblast strains derived from malignant and benign tumours produced and secreted similar amounts of TGF-beta 1, but benign breast tumour fibroblasts secreted significantly higher levels of TGF-beta 2 compared with fibroblasts of malignant origin. Tamoxifen did not induce any consistent increase in TGF-beta secretion into the conditioned medium, but immunofluorescence analysis for the intracellular form of TGF-beta 1 revealed evidence of increased immunoreactive protein in tamoxifen-treated fibroblasts, which is localised to the nucleus. Therefore synthesis of TGF-beta 1 appears to be stimulated by tamoxifen, but increased secretion may be abrogated in vitro. Furthermore, using immunocytochemistry and transient transfection with an ER-responsive reporter construct, no ER was demonstrable in these fibroblasts supporting the proposed ER-independent paracrine pathway.