Prevention of apoptosis by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the MCF-10A cell line: correlation with increased transforming growth factor alpha production.
We have recently reported that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) inhibits epidermal growth factor (EGF) withdrawal-induced apoptosis in the human mammary epithelial cell line MCF-10A. We hypothesized that TCDD-mediated inhibition of apoptosis was due to its ability to stimulate the EGF receptor (EGFR) pathway. Indeed, in the present studies, the EGFR inhibitor AG1478 was able to prevent TCDD-, EGF-, and transforming growth factor alpha (TGF-alpha)-dependent cell recovery and inhibition of apoptosis. These effects were specific for an EGFR-mediated pathway because cotreatment with AG825, an erbB2 inhibitor, had little effect on apoptosis. In addition, TCDD was able to mimic the EGF and TGF-alpha signaling as demonstrated by increasing Akt and extracellular signal-regulated kinase 1,2 phosphorylation. These effects were dependent on EGFR activity because AG1478, but not AG825, was able to prevent EGF-, TGF-alpha, or TCDD-mediated Akt and extracellular signal-regulated kinase 1,2 phosphorylation. The ability of TCDD to stimulate the EGFR pathway and inhibit apoptosis may be due to the ability of TCDD to increase expression of TGF-alpha, a ligand for EGFR. Treatment with 10 nM TCDD increased TGF-alpha mRNA at 2 h and TGF-alpha protein at 6 h. These data suggest a mechanism whereby TCDD is able to inhibit apoptosis in human mammary epithelial cells by stimulating TGF-alpha production, resulting in an autocrine effect.
Davis
J W
JW
Toxicology Program, The University of New Mexico College of Pharmacy, Albuquerque, NM 87131, USA.
Lauer
F T
FT
Burdick
A D
AD
Hudson
L G
LG
Burchiel
S W
SW
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D052160:Benzothiazoles; D001940:Breast / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002452:Cell Count; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000502:physiology; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis* / Q000235:genetics; D020032:Tyrphostins / Q000494:pharmacology
D052160:Benzothiazoles; D004791:Enzyme Inhibitors; D000072317:Polychlorinated Dibenzodioxins; D011518:Proto-Oncogene Proteins; D011799:Quinazolines; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D020032:Tyrphostins; C098214:tyrphostin AG825; C101044:RTKI cpd; D066246:ErbB Receptors; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases