BIRC6 mediates imatinib resistance independently of Mcl-1.
Baculoviral IAP repeat containing 6 (BIRC6) is a member of the inhibitors of apoptosis proteins (IAPs), a family of functionally and structurally related proteins that inhibit apoptosis. BIRC6 has been implicated in drug resistance in several different human cancers, however mechanisms regulating BI...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Public Library of Science (PLoS)
2017-01-01
|
| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC5433768?pdf=render |
| _version_ | 1818258687823708160 |
|---|---|
| author | Denis O Okumu Michael P East Merlin Levine Laura E Herring Raymond Zhang Thomas S K Gilbert David W Litchfield Yanping Zhang Lee M Graves |
| author_facet | Denis O Okumu Michael P East Merlin Levine Laura E Herring Raymond Zhang Thomas S K Gilbert David W Litchfield Yanping Zhang Lee M Graves |
| author_sort | Denis O Okumu |
| collection | DOAJ |
| description | Baculoviral IAP repeat containing 6 (BIRC6) is a member of the inhibitors of apoptosis proteins (IAPs), a family of functionally and structurally related proteins that inhibit apoptosis. BIRC6 has been implicated in drug resistance in several different human cancers, however mechanisms regulating BIRC6 have not been extensively explored. Our phosphoproteomic analysis of an imatinib-resistant chronic myelogenous leukemia (CML) cell line (MYL-R) identified increased amounts of a BIRC6 peptide phosphorylated at S480, S482, and S486 compared to imatinib-sensitive CML cells (MYL). Thus we investigated the role of BIRC6 in mediating imatinib resistance and compared it to the well-characterized anti-apoptotic protein, Mcl-1. Both BIRC6 and Mcl-1 were elevated in MYL-R compared to MYL cells. Lentiviral shRNA knockdown of BIRC6 in MYL-R cells increased imatinib-stimulated caspase activation and resulted in a ~20-25-fold increase in imatinib sensitivity, without affecting Mcl-1. Treating MYL-R cells with CDK9 inhibitors decreased BIRC6 mRNA, but not BIRC6 protein levels. By contrast, while CDK9 inhibitors reduced Mcl-1 mRNA and protein, they did not affect imatinib sensitivity. Since the Src family kinase Lyn is highly expressed and active in MYL-R cells, we tested the effects of Lyn inhibition on BIRC6 and Mcl-1. RNAi-mediated knockdown or inhibition of Lyn (dasatinib/ponatinib) reduced BIRC6 protein stability and increased caspase activation. Inhibition of Lyn also increased formation of an N-terminal BIRC6 fragment in parallel with reduced amount of the BIRC6 phosphopeptide, suggesting that Lyn may regulate BIRC6 phosphorylation and stability. In summary, our data show that BIRC6 stability is dependent on Lyn, and that BIRC6 mediates imatinib sensitivity independently of Mcl-1 or CDK9. Hence, BIRC6 may be a novel target for the treatment of drug-resistant CML where Mcl-1 or CDK9 inhibitors have failed. |
| first_indexed | 2024-12-12T18:03:31Z |
| format | Article |
| id | doaj.art-6e9e1d2a1f244c7991f978e4459d5e18 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-12-12T18:03:31Z |
| publishDate | 2017-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-6e9e1d2a1f244c7991f978e4459d5e182022-12-22T00:16:34ZengPublic Library of Science (PLoS)PLoS ONE1932-62032017-01-01125e017787110.1371/journal.pone.0177871BIRC6 mediates imatinib resistance independently of Mcl-1.Denis O OkumuMichael P EastMerlin LevineLaura E HerringRaymond ZhangThomas S K GilbertDavid W LitchfieldYanping ZhangLee M GravesBaculoviral IAP repeat containing 6 (BIRC6) is a member of the inhibitors of apoptosis proteins (IAPs), a family of functionally and structurally related proteins that inhibit apoptosis. BIRC6 has been implicated in drug resistance in several different human cancers, however mechanisms regulating BIRC6 have not been extensively explored. Our phosphoproteomic analysis of an imatinib-resistant chronic myelogenous leukemia (CML) cell line (MYL-R) identified increased amounts of a BIRC6 peptide phosphorylated at S480, S482, and S486 compared to imatinib-sensitive CML cells (MYL). Thus we investigated the role of BIRC6 in mediating imatinib resistance and compared it to the well-characterized anti-apoptotic protein, Mcl-1. Both BIRC6 and Mcl-1 were elevated in MYL-R compared to MYL cells. Lentiviral shRNA knockdown of BIRC6 in MYL-R cells increased imatinib-stimulated caspase activation and resulted in a ~20-25-fold increase in imatinib sensitivity, without affecting Mcl-1. Treating MYL-R cells with CDK9 inhibitors decreased BIRC6 mRNA, but not BIRC6 protein levels. By contrast, while CDK9 inhibitors reduced Mcl-1 mRNA and protein, they did not affect imatinib sensitivity. Since the Src family kinase Lyn is highly expressed and active in MYL-R cells, we tested the effects of Lyn inhibition on BIRC6 and Mcl-1. RNAi-mediated knockdown or inhibition of Lyn (dasatinib/ponatinib) reduced BIRC6 protein stability and increased caspase activation. Inhibition of Lyn also increased formation of an N-terminal BIRC6 fragment in parallel with reduced amount of the BIRC6 phosphopeptide, suggesting that Lyn may regulate BIRC6 phosphorylation and stability. In summary, our data show that BIRC6 stability is dependent on Lyn, and that BIRC6 mediates imatinib sensitivity independently of Mcl-1 or CDK9. Hence, BIRC6 may be a novel target for the treatment of drug-resistant CML where Mcl-1 or CDK9 inhibitors have failed.http://europepmc.org/articles/PMC5433768?pdf=render |
| spellingShingle | Denis O Okumu Michael P East Merlin Levine Laura E Herring Raymond Zhang Thomas S K Gilbert David W Litchfield Yanping Zhang Lee M Graves BIRC6 mediates imatinib resistance independently of Mcl-1. PLoS ONE |
| title | BIRC6 mediates imatinib resistance independently of Mcl-1. |
| title_full | BIRC6 mediates imatinib resistance independently of Mcl-1. |
| title_fullStr | BIRC6 mediates imatinib resistance independently of Mcl-1. |
| title_full_unstemmed | BIRC6 mediates imatinib resistance independently of Mcl-1. |
| title_short | BIRC6 mediates imatinib resistance independently of Mcl-1. |
| title_sort | birc6 mediates imatinib resistance independently of mcl 1 |
| url | http://europepmc.org/articles/PMC5433768?pdf=render |
| work_keys_str_mv | AT denisookumu birc6mediatesimatinibresistanceindependentlyofmcl1 AT michaelpeast birc6mediatesimatinibresistanceindependentlyofmcl1 AT merlinlevine birc6mediatesimatinibresistanceindependentlyofmcl1 AT lauraeherring birc6mediatesimatinibresistanceindependentlyofmcl1 AT raymondzhang birc6mediatesimatinibresistanceindependentlyofmcl1 AT thomasskgilbert birc6mediatesimatinibresistanceindependentlyofmcl1 AT davidwlitchfield birc6mediatesimatinibresistanceindependentlyofmcl1 AT yanpingzhang birc6mediatesimatinibresistanceindependentlyofmcl1 AT leemgraves birc6mediatesimatinibresistanceindependentlyofmcl1 |