Estradiol abrogates apoptosis in breast cancer cells through inactivation of BAD: Ras-dependent nongenomic pathways requiring signaling through ERK and Akt.
Estrogens such as 17-beta estradiol (E(2)) play a critical role in sporadic breast cancer progression and decrease apoptosis in breast cancer cells. Our studies using estrogen receptor-positive MCF7 cells show that E(2) abrogates apoptosis possibly through phosphorylation/inactivation of the proapoptotic protein BAD, which was rapidly phosphorylated at S112 and S136. Inhibition of BAD protein expression with specific antisense oligonucleotides reduced the effectiveness of tumor necrosis factor-alpha, H(2)O(2), and serum starvation in causing apoptosis. Furthermore, the ability of E(2) to prevent tumor necrosis factor-alpha-induced apoptosis was blocked by overexpression of the BAD S112A/S136A mutant but not the wild-type BAD. BAD S112A/S136A, which lacks phosphorylation sites for p90(RSK1) and Akt, was not phosphorylated in response to E(2) in vitro(.) E(2) treatment rapidly activated phosphatidylinositol 3-kinase (PI-3K)/Akt and p90(RSK1) to an extent similar to insulin-like growth factor-1 treatment. In agreement with p90(RSK1) activation, E(2) also rapidly activated extracellular signal-regulated kinase, and this activity was down-regulated by chemical and biological inhibition of PI-3K suggestive of cross talk between signaling pathways responding to E(2). Dominant negative Ras blocked E(2)-induced BAD phosphorylation and the Raf-activator RasV12T35S induced BAD phosphorylation as well as enhanced E(2)-induced phosphorylation at S112. Chemical inhibition of PI-3K and mitogen-activated protein kinase kinase 1 inhibited E(2)-induced BAD phosphorylation at S112 and S136 and expression of dominant negative Ras-induced apoptosis in proliferating cells. Together, these data demonstrate a new nongenomic mechanism by which E(2) prevents apoptosis.
Fernando
Romaine Ingrid
RI
Department of Obstetrics and Gynecology, and the Comparative and Experimental Medicine Program, Graduate School of Medicine, University of Tennessee, Knoxville, Tennessee 37920, USA.
Wimalasena
Jay
J
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology* / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D051025:bcl-Associated Death Protein; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; D004958:Estradiol; D048049:Extracellular Signal-Regulated MAP Kinases; D006861:Hydrogen Peroxide; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D014409:Tumor Necrosis Factor-alpha; D025521:Tumor Suppressor Proteins; D051025:bcl-Associated Death Protein; D018631:ras Proteins; C494819:BAD protein, human; C494918:AKT1 protein, human; C494929:PTEN protein, human