scholarly journals Endogenous Bak inhibitors Mcl-1 and Bcl-xL: differential impact on TRAIL resistance in Bax-deficient carcinoma

2010 ◽  
Vol 188 (6) ◽  
pp. 851-862 ◽  
Author(s):  
Bernhard Gillissen ◽  
Jana Wendt ◽  
Antje Richter ◽  
Anja Richter ◽  
Annika Müer ◽  
...  
Keyword(s):  
Tumor Necrosis Factor ◽  
Tumor Cells ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Death Receptor ◽  
Apoptosis Pathway ◽  
Mitochondrial Apoptosis Pathway ◽  
Induced Apoptosis ◽  
Factor Α ◽  
Necrosis Factor

Tumor necrosis factor (α)–related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that preferentially kills tumor cells with limited cytotoxicity to nonmalignant cells. However, signaling from death receptors requires amplification via the mitochondrial apoptosis pathway (type II) in the majority of tumor cells. Thus, TRAIL-induced cell death entirely depends on the proapoptotic Bcl-2 family member Bax, which is often lost as a result of epigenetic inactivation or mutations. Consequently, Bax deficiency confers resistance against TRAIL-induced apoptosis. Despite expression of Bak, Bax-deficient cells are resistant to TRAIL-induced apoptosis. In this study, we show that the Bax dependency of TRAIL-induced apoptosis is determined by Mcl-1 but not Bcl-xL. Both are antiapoptotic Bcl-2 family proteins that keep Bak in check. Nevertheless, knockdown of Mcl-1 but not Bcl-xL overcame resistance to TRAIL, CD95/FasL and tumor necrosis factor (α) death receptor ligation in Bax-deficient cells, and enabled TRAIL to activate Bak, indicating that Mcl-1 rather than Bcl-xL is a major target for sensitization of Bax-deficient tumors for death receptor–induced apoptosis via the Bak pathway.

scholarly journals Estradiol Abrogates Apoptosis in Breast Cancer Cells through Inactivation of BAD: Ras-dependent Nongenomic Pathways Requiring Signaling through ERK and Akt

2004 ◽  
Vol 15 (7) ◽  
pp. 3266-3284 ◽  
Author(s):  
Romaine Ingrid Fernando ◽  
Jay Wimalasena
Keyword(s):  
Breast Cancer ◽  
Tumor Necrosis Factor ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Dominant Negative ◽  
Induced Apoptosis ◽  
Factor Α ◽  
Necrosis Factor

Estrogens such as 17-β estradiol (E2) 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 E2 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-α, H2O2, and serum starvation in causing apoptosis. Furthermore, the ability of E2 to prevent tumor necrosis factor-α-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 p90RSK1 and Akt, was not phosphorylated in response to E2 in vitro. E2 treatment rapidly activated phosphatidylinositol 3-kinase (PI-3K)/Akt and p90RSK1 to an extent similar to insulin-like growth factor-1 treatment. In agreement with p90RSK1 activation, E2 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 E2. Dominant negative Ras blocked E2-induced BAD phosphorylation and the Raf-activator RasV12T35S induced BAD phosphorylation as well as enhanced E2-induced phosphorylation at S112. Chemical inhibition of PI-3K and mitogen-activated protein kinase kinase 1 inhibited E2-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 E2 prevents apoptosis.

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