Evidence for role of transforming growth factor-beta in RRR-alpha-tocopheryl succinate-induced apoptosis of human MDA-MB-435 breast cancer cells.
MDA-MB-435 human breast cancer cells treated with 10 micrograms/ml of RRR-alpha-tocopheryl succinate (vitamin E succinate, VES) for one, two, three, and four days exhibit 9%, 19%, 51%, and 73% apoptotic cells, respectively. Likewise, cells cultured for one, two, and three days with conditioned media (CM) obtained from MDA-MB-435 cells treated with VES exhibit 10%, 36%, and 74% apoptosis, respectively. A quantitative luciferase-based assay showed CM from VES-treated cells collected at 24 and 48 hours after treatment initiation to contain 75 and 32 pg of active transforming growth factor-beta (TGF-beta), respectively, per 10(6) cells. Although purified TGF-beta 1 is not an effective apoptotic agent for MDA-MD-435 cells, cotreatment of the cells for three days with suboptimal levels of VES (2.5 and 5 micrograms/ml) + 10 ng/ml of purified TGF-beta 1 enhanced apoptosis by 66% and 68%, respectively. Interference of the TGF-beta-signaling pathway by transient transfection of MDA-MB-435 cells with antisense oligomers to TGF-beta type II receptor (TGF-beta R-II) blocked VES-induced apoptosis. Likewise, addition of neutralizing antibodies to TGF-beta 1 or to all three mammalian isoforms of TGF-beta (TGF-beta 1, -beta 2, -beta 3) blocked VES- and CM-induced apoptosis. Furthermore, inhibitors of TGF-beta conversion from an inactive latent form to a biologically active form inhibited VES-induced apoptosis. In summary, the ability to reduce apoptosis by blocking TGF-beta or the TGF-beta receptor-signaling pathway with antisense oligomers or ligand-neutralizing antibodies or prevention of activation of TGF-beta indicates a role for TGF-beta signaling in VES-induced apoptosis.
Yu
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Division of Nutritional Sciences, University of Texas at Austin 78712-1097, USA.
Heim
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K
Qian
M
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Simmons-Menchaca
M
M
Sanders
B G
BG
Kline
K
K
D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D001943:Breast Neoplasms / Q000473:pathology*; D017077:Culture Media, Conditioned; D053938:DNA Fragmentation; D004357:Drug Synergism; D005341:Fibrinolysin / Q000037:antagonists & inhibitors; D006801:Humans; D008360:Mannosephosphates / Q000235:genetics / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000037:antagonists & inhibitors; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D015398:Signal Transduction; D024505:Tocopherols; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D014407:Tumor Cells, Cultured; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology
D000906:Antibodies; D017077:Culture Media, Conditioned; D008360:Mannosephosphates; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D014810:Vitamin E; C027693:mannose-6-phosphate; D005341:Fibrinolysin; D024505:Tocopherols