title: Synthesis and secretion of transforming growth factor beta isoforms by primary cultures of human breast tumour fibroblasts in vitro and their modulation by tamoxifen.
abstract: 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.
authors.affiliation: Hartwell Laboratory, Section of Academic Surgery, Royal Marsden Hospital, London, UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Benson
authors.forename: L M
authors.initials: LM
authors.lastname: Wakefield
authors.forename: M
authors.initials: M
authors.lastname: Baum
authors.forename: A A
authors.initials: AA
authors.lastname: Colletta
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D011960:Receptors, Estrogen / Q000032:analysis; D013629:Tamoxifen / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D018931:Antineoplastic Agents, Hormonal; D011960:Receptors, Estrogen; D016212:Transforming Growth Factor beta; D013629:Tamoxifen