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IκB kinases increase Myc protein stability and enhance progression of breast cancer cells.

Yeh PY, Lu YS, Ou DL, Cheng AL - Mol. Cancer (2011)

Bottom Line: Consequently, these treatments decrease the tumorigenic and invasive ability of breast cancer cells.Inhibition of IKKs prevents these doxorubicin-induced effects.Our study indicates that IKKs tightly regulate Myc expression through prolonging protein stability, and suggests that IKKs are potentially therapeutic targets and that suppression of IKKs may be used following chemotherapy to reduce the risk of treatment-induced tumor progression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oncology, National Taiwan University Hospital, No, 7, Chung-Shan South Road, Taipei, 100, Taiwan.

ABSTRACT

Background: Both IκB kinase (IKK) complex and oncgenic protein Myc play important roles in cancer progression, including cancer cell invasiveness and metastasis. The levels of Myc is regulated by the phosphorylation of Myc at Thr58 and Ser62.

Results: In this study, we show that the expression of Myc is associated with IKKα and IKKβ in breast cancers and that Myc is an IKKs substrate. Suppression of IKK activity by either chemical inhibitor or transfection of kinase-dead mutants decreases the phosphorylation of Myc at Ser62 and enhances the degradation of Myc. Consequently, these treatments decrease the tumorigenic and invasive ability of breast cancer cells. Furthermore, doxorubicin, a frequently used anticancer drug in breast cancer, activates IKKs and Myc, thereby increasing invasiveness and tumorigenesis of breast carcinoma MCF7 cells. Inhibition of IKKs prevents these doxorubicin-induced effects.

Conclusions: Our study indicates that IKKs tightly regulate Myc expression through prolonging protein stability, and suggests that IKKs are potentially therapeutic targets and that suppression of IKKs may be used following chemotherapy to reduce the risk of treatment-induced tumor progression.

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Related in: MedlinePlus

IKKα and IKKβ increase Myc protein level. (A). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours and then were further treated with 20 ng/ml TNF-α for 30 minutes. The cytoplasmic and nuclear extracts were subjected to Western blot analysis of NF-κB p65 subcellular distribution. Stains of tubulin were used to represent the clearance of cellular fractionation and stains of actin were used as loading control. (B). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours, and then the whole cell lysates, the cytoplasmic and nuclear extracts were prepared. Equal amount of proteins (15 μg/lane) were subjected to Western blotting analysis. (C). MCF7 cells were transfected with IKKα and IKKβ (both wild-type and kinase-dead mutant). The transfected cells were analyzed by Western blotting of IKKα and IKKβ.(D). The whole cell lysates prepared from indicated cells were subjected to Western blot analysis.
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Figure 2: IKKα and IKKβ increase Myc protein level. (A). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours and then were further treated with 20 ng/ml TNF-α for 30 minutes. The cytoplasmic and nuclear extracts were subjected to Western blot analysis of NF-κB p65 subcellular distribution. Stains of tubulin were used to represent the clearance of cellular fractionation and stains of actin were used as loading control. (B). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours, and then the whole cell lysates, the cytoplasmic and nuclear extracts were prepared. Equal amount of proteins (15 μg/lane) were subjected to Western blotting analysis. (C). MCF7 cells were transfected with IKKα and IKKβ (both wild-type and kinase-dead mutant). The transfected cells were analyzed by Western blotting of IKKα and IKKβ.(D). The whole cell lysates prepared from indicated cells were subjected to Western blot analysis.

Mentions: To explore the effects of the IKKs on Myc expression, an IKK inhibitor Bay11-7082 [31,32] was used to treat breast carcinoma MCF7 cells. Bay11-0782 blocked TNFα-induced NF-κB p65 nuclear translocation (Figure 2A), whereas it did not alter the basal level of cytoplasmic or nuclear NF-κB p65 or p50, suggesting that Bay11-7082 did not influence basal activity of NF-κB. Bay11-7082 markedly decreased the level of phosphorylated and total Myc protein. The Myc-binding partner, Max, was not affected by Bay11-7082 (Figure 2B).


IκB kinases increase Myc protein stability and enhance progression of breast cancer cells.

Yeh PY, Lu YS, Ou DL, Cheng AL - Mol. Cancer (2011)

IKKα and IKKβ increase Myc protein level. (A). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours and then were further treated with 20 ng/ml TNF-α for 30 minutes. The cytoplasmic and nuclear extracts were subjected to Western blot analysis of NF-κB p65 subcellular distribution. Stains of tubulin were used to represent the clearance of cellular fractionation and stains of actin were used as loading control. (B). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours, and then the whole cell lysates, the cytoplasmic and nuclear extracts were prepared. Equal amount of proteins (15 μg/lane) were subjected to Western blotting analysis. (C). MCF7 cells were transfected with IKKα and IKKβ (both wild-type and kinase-dead mutant). The transfected cells were analyzed by Western blotting of IKKα and IKKβ.(D). The whole cell lysates prepared from indicated cells were subjected to Western blot analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104363&req=5

Figure 2: IKKα and IKKβ increase Myc protein level. (A). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours and then were further treated with 20 ng/ml TNF-α for 30 minutes. The cytoplasmic and nuclear extracts were subjected to Western blot analysis of NF-κB p65 subcellular distribution. Stains of tubulin were used to represent the clearance of cellular fractionation and stains of actin were used as loading control. (B). MCF7 cells were treated with 10 μM Bay11-0782 for 12 hours, and then the whole cell lysates, the cytoplasmic and nuclear extracts were prepared. Equal amount of proteins (15 μg/lane) were subjected to Western blotting analysis. (C). MCF7 cells were transfected with IKKα and IKKβ (both wild-type and kinase-dead mutant). The transfected cells were analyzed by Western blotting of IKKα and IKKβ.(D). The whole cell lysates prepared from indicated cells were subjected to Western blot analysis.
Mentions: To explore the effects of the IKKs on Myc expression, an IKK inhibitor Bay11-7082 [31,32] was used to treat breast carcinoma MCF7 cells. Bay11-0782 blocked TNFα-induced NF-κB p65 nuclear translocation (Figure 2A), whereas it did not alter the basal level of cytoplasmic or nuclear NF-κB p65 or p50, suggesting that Bay11-7082 did not influence basal activity of NF-κB. Bay11-7082 markedly decreased the level of phosphorylated and total Myc protein. The Myc-binding partner, Max, was not affected by Bay11-7082 (Figure 2B).

Bottom Line: Consequently, these treatments decrease the tumorigenic and invasive ability of breast cancer cells.Inhibition of IKKs prevents these doxorubicin-induced effects.Our study indicates that IKKs tightly regulate Myc expression through prolonging protein stability, and suggests that IKKs are potentially therapeutic targets and that suppression of IKKs may be used following chemotherapy to reduce the risk of treatment-induced tumor progression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oncology, National Taiwan University Hospital, No, 7, Chung-Shan South Road, Taipei, 100, Taiwan.

ABSTRACT

Background: Both IκB kinase (IKK) complex and oncgenic protein Myc play important roles in cancer progression, including cancer cell invasiveness and metastasis. The levels of Myc is regulated by the phosphorylation of Myc at Thr58 and Ser62.

Results: In this study, we show that the expression of Myc is associated with IKKα and IKKβ in breast cancers and that Myc is an IKKs substrate. Suppression of IKK activity by either chemical inhibitor or transfection of kinase-dead mutants decreases the phosphorylation of Myc at Ser62 and enhances the degradation of Myc. Consequently, these treatments decrease the tumorigenic and invasive ability of breast cancer cells. Furthermore, doxorubicin, a frequently used anticancer drug in breast cancer, activates IKKs and Myc, thereby increasing invasiveness and tumorigenesis of breast carcinoma MCF7 cells. Inhibition of IKKs prevents these doxorubicin-induced effects.

Conclusions: Our study indicates that IKKs tightly regulate Myc expression through prolonging protein stability, and suggests that IKKs are potentially therapeutic targets and that suppression of IKKs may be used following chemotherapy to reduce the risk of treatment-induced tumor progression.

Show MeSH
Related in: MedlinePlus