title: Phorbol ester-induced production of cytostatic factors by normal and oncogenic Ha-ras-transformed human breast cell lines.
abstract: The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on cell cycle progression were examined in the human breast cell line MCF10A-Neo and a derivative line which expresses a Ha-ras oncogene (MCF10A-NeoT cells). Exposure of MCF10A-Neo cultures to TPA induced a G(1) arrest that lasted approximately 16-24 h (IC(50) approximately 0.5 nM). TPA-treated cultures produced a cytostatic conditioned medium. Cytostatic activity was detectable within 1 h of TPA treatment, peaked 3-7 h later and disappeared between 16 and 24 h post-treatment. However, cytostatic conditioned medium could be quickly regenerated by re-feeding previously treated cultures with new medium. Removal of latent transforming growth factor beta (TGF beta) from the culture medium, supplementing the culture medium with anti-TGFbeta or soluble TGF beta(II) receptor, or pre-absorption of conditioned medium with anti-TGF beta all reduced the cytostatic effects of TPA or conditioned medium on MCF10A-Neo proliferation by approximately 50%. Co-treatment with the serine protease inhibitors aprotinin or plasminogen activator inhibitor-1 also suppressed the cytostatic activity of TPA approximately 50%. Conditioned medium isolated from TPA-treated MCF10A-Neo cultures was transiently cytostatic to MCF10A-NeoT cells. The proliferation of MCF10A-NeoT cultures, in contrast to MCF10A-Neo cells, was suppressed at least 72 h following TPA exposure. Conditioned medium isolated from TPA-treated MCF10A-NeoT cultures also suppressed MCF10A-NeoT proliferation for approximately 72 h, but suppressed MCF10A-Neo proliferation for <24 h. These studies suggest that TPA quickly activates proteolytic processes in MCF10A-Neo cells leading to the activation of latent TGF beta supplied by the serum in the culture medium. TPA also stimulates the production of an additional cytostatic factor(s) which signals via a mechanism not involving the TGF beta(II) receptor. Lastly, expression of an activated Ha-ras oncogene alters both the types of cytostatic factors produced following TPA treatment and responsiveness to these factors.
authors.affiliation: Institute of Chemical Toxicology, Wayne State University, 2727 Second Avenue, Room 4000, Detroit, MI 48201, USA.
authors.forename: M
authors.initials: M
authors.lastname: Guo
authors.forename: J J
authors.initials: JJ
authors.lastname: Reiners
mesh_terms: D000970:Antineoplastic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007611:Aprotinin / Q000494:pharmacology; D001940:Breast / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D017077:Culture Media, Conditioned; D004347:Drug Interactions; D011905:Genes, ras / Q000502:physiology*; D006801:Humans; D015689:Oncogene Protein p21(ras) / Q000096:biosynthesis / Q000502:physiology; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology; D017231:Proto-Oncogene Proteins c-mos / Q000096:biosynthesis*; D011960:Receptors, Estrogen / Q000502:physiology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014170:Transformation, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D017077:Culture Media, Conditioned; D017395:Plasminogen Activator Inhibitor 1; D011960:Receptors, Estrogen; D015842:Serine Proteinase Inhibitors; D016212:Transforming Growth Factor beta; D007611:Aprotinin; D017231:Proto-Oncogene Proteins c-mos; D015689:Oncogene Protein p21(ras); D013755:Tetradecanoylphorbol Acetate