Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin.
The ability of the transcription factor NF-kappaB to upregulate anti-apoptotic proteins has been linked to the chemoresistance of solid tumors to standard chemotherapy. In contrast, recent studies have proposed that, in response to doxorubicin, NF-kappaB can be pro-apoptotic through repression of an...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2009-09-01
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| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC2734988?pdf=render |
| _version_ | 1819066974362140672 |
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| author | Brian K Bednarski Albert S Baldwin Hong Jin Kim |
| author_facet | Brian K Bednarski Albert S Baldwin Hong Jin Kim |
| author_sort | Brian K Bednarski |
| collection | DOAJ |
| description | The ability of the transcription factor NF-kappaB to upregulate anti-apoptotic proteins has been linked to the chemoresistance of solid tumors to standard chemotherapy. In contrast, recent studies have proposed that, in response to doxorubicin, NF-kappaB can be pro-apoptotic through repression of anti-apoptotic target genes. However, there is little evidence analyzing the outcome of NF-kappaB inhibition on the cytotoxicity of doxorubicin in studies describing pro-apoptotic NF-kappaB activity. In this study, we further characterize the activation of NF-kappaB in response to doxorubicin and evaluate its role in chemotherapy-induced cell death in sarcoma cells where NF-kappaB is reported to be pro-apoptotic. Doxorubicin treatment in U2OS cells induced canonical NF-kappaB activity as evidenced by increased nuclear accumulation of phosphorylated p65 at serine 536 and increased DNA-binding activity. Co-treatment with a small molecule IKKbeta inhibitor, Compound A, abrogated this response. RT-PCR evaluation of anti-apoptotic gene expression revealed that doxorubicin-induced transcription of cIAP2 was inhibited by Compound A, while doxorubicin-induced repression of other anti-apoptotic genes was unaffected by Compound A or siRNA to p65. Furthermore, the combination of doxorubicin and canonical NF-kappaB inhibition with Compound A or siRNA to p65 resulted in decreased cell viability measured by trypan blue staining and MTS assay and increased apoptosis measured by cleaved poly (ADP-ribose) polymerase and cleaved caspase 3 when compared to doxorubicin alone. Our results demonstrate that doxorubicin-induced canonical NF-kappaB activity associated with phosphorylated p65 is anti-apoptotic in its function and that doxorubicin-induced repression of anti-apoptotic genes occurs independent of p65. Therefore, combination therapies incorporating NF-kappaB inhibitors together with standard chemotherapies remains a viable method to improve the clinical outcomes in patients with advanced stage malignancies. |
| first_indexed | 2024-12-21T16:10:53Z |
| format | Article |
| id | doaj.art-b1523cccecaa4b44b06cd20e6b0e296d |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-12-21T16:10:53Z |
| publishDate | 2009-09-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-b1523cccecaa4b44b06cd20e6b0e296d2022-12-21T18:57:48ZengPublic Library of Science (PLoS)PLoS ONE1932-62032009-09-0149e699210.1371/journal.pone.0006992Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin.Brian K BednarskiAlbert S BaldwinHong Jin KimThe ability of the transcription factor NF-kappaB to upregulate anti-apoptotic proteins has been linked to the chemoresistance of solid tumors to standard chemotherapy. In contrast, recent studies have proposed that, in response to doxorubicin, NF-kappaB can be pro-apoptotic through repression of anti-apoptotic target genes. However, there is little evidence analyzing the outcome of NF-kappaB inhibition on the cytotoxicity of doxorubicin in studies describing pro-apoptotic NF-kappaB activity. In this study, we further characterize the activation of NF-kappaB in response to doxorubicin and evaluate its role in chemotherapy-induced cell death in sarcoma cells where NF-kappaB is reported to be pro-apoptotic. Doxorubicin treatment in U2OS cells induced canonical NF-kappaB activity as evidenced by increased nuclear accumulation of phosphorylated p65 at serine 536 and increased DNA-binding activity. Co-treatment with a small molecule IKKbeta inhibitor, Compound A, abrogated this response. RT-PCR evaluation of anti-apoptotic gene expression revealed that doxorubicin-induced transcription of cIAP2 was inhibited by Compound A, while doxorubicin-induced repression of other anti-apoptotic genes was unaffected by Compound A or siRNA to p65. Furthermore, the combination of doxorubicin and canonical NF-kappaB inhibition with Compound A or siRNA to p65 resulted in decreased cell viability measured by trypan blue staining and MTS assay and increased apoptosis measured by cleaved poly (ADP-ribose) polymerase and cleaved caspase 3 when compared to doxorubicin alone. Our results demonstrate that doxorubicin-induced canonical NF-kappaB activity associated with phosphorylated p65 is anti-apoptotic in its function and that doxorubicin-induced repression of anti-apoptotic genes occurs independent of p65. Therefore, combination therapies incorporating NF-kappaB inhibitors together with standard chemotherapies remains a viable method to improve the clinical outcomes in patients with advanced stage malignancies.http://europepmc.org/articles/PMC2734988?pdf=render |
| spellingShingle | Brian K Bednarski Albert S Baldwin Hong Jin Kim Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. PLoS ONE |
| title | Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. |
| title_full | Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. |
| title_fullStr | Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. |
| title_full_unstemmed | Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. |
| title_short | Addressing reported pro-apoptotic functions of NF-kappaB: targeted inhibition of canonical NF-kappaB enhances the apoptotic effects of doxorubicin. |
| title_sort | addressing reported pro apoptotic functions of nf kappab targeted inhibition of canonical nf kappab enhances the apoptotic effects of doxorubicin |
| url | http://europepmc.org/articles/PMC2734988?pdf=render |
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