Insulin-like growth factor 1 attenuates antiestrogen- and antiprogestin-induced apoptosis in ER+ breast cancer cells by MEK1 regulation of the BH3-only pro-apoptotic protein Bim

Hdl Handle:
http://hdl.handle.net/10675.2/827
Title:
Insulin-like growth factor 1 attenuates antiestrogen- and antiprogestin-induced apoptosis in ER+ breast cancer cells by MEK1 regulation of the BH3-only pro-apoptotic protein Bim
Authors:
Periyasamy-Thandavan, Sudharsan; Takhar, Suchreet; Singer, Adam; Dohn, Michael Robert; Jackson, William Hutch; Welborn, April Eve; LeRoith, Derek; Marrero, Mario; Thangaraju, Muthusamy; Huang, Shuang; Schoenlein, Patricia Veronica
Abstract:
Introduction: In this pre-clinical in vitro study conducted in estrogen receptor positive (ER+) breast cancer cells, we have characterized the effects of insulin-like growth factor I (IGF-1) on the cytostatic and cytotoxic action of antiestrogen treatment when used as a single agent or in combination with the antiprogestin mifepristone (MIF). Our goal was to identify new molecular targets to improve the efficacy of hormonal therapy in breast cancer patients that have a poor response to hormonal therapy, in part, due to high circulating levels of unbound insulinIGF-1.; Methods: IGF-1-mediated effects on cytostasis and apoptotic cell death were determined with cell counts conducted in the presence and absence of trypan blue; enzyme-linked immunosorbent assays to determine the intracellular levels of cleaved cytokeratin 18, a marker of epithelial cancer cell apoptosis; and immunoblot analysis to determine the levels of cleaved poly-ADP ribose polymerase (PARP) and lamin A that result from caspase-dependent apoptosis. Cytotoxicity was further characterized by determination of the levels of reactive oxygen species (ROS) and the percent of mitochondrial membrane depolarization in cell populations treated with the different hormones in the presence and absence of IGF-1. Small molecule inhibitors of the dual-specificity protein kinase MEK1, MEK1 siRNA, Bim siRNA, and vectors overexpressing MEK1 wild type and mutant, dominant negative cDNA were used to identify key IGF-1 downstream prosurvival effectors.; Results: IGF-1, at physiologically relevant levels, blocked the cytotoxic action(s) of the antiestrogens 4-hydroxytamoxifen (4-OHT) and tamoxifen (TAM) when used as single agents or in combination with the antiprogestin MIF. The antiapoptotic action of IGF-1 was mediated primarily through the action of MEK1. MEK1 expression reduced the levels of ROS and mitochondrial membrane depolarization induced by the hormonal treatments via a mechanism that involved the phosphorylation and proteasomal turnover of the proapoptotic BH3-only Bcl-2 family member Bim. Importantly, small-molecule inhibitors of MEK1 circumvented the prosurvival action of IGF-1 by restoring Bim to levels that more effectively mediated apoptosis in ER+ breast cancer cells.; Conclusion: his study provides strong support for the use of MEK1 inhibitors in combination with hormonal therapy to effectively affect cytostasis and activate a Bim-dependent apoptotic pathway in ER+ breast cancer cells. We discuss that MEK1 blockade may be a particularly effective treatment for women with high circulating levels of IGF-1, which have been correlated to a poor prognosis.
Citation:
Breast Cancer Res. 2012 Mar 19; 14(2):R52
Issue Date:
19-Mar-2012
URI:
http://hdl.handle.net/10675.2/827
DOI:
10.1186/bcr3153
PubMed ID:
22429491
PubMed Central ID:
PMC3446386
Type:
Article
ISSN:
1465-542X
Appears in Collections:
Department of Cellular Biology and Anatomy: Faculty Research and Presentations

Full metadata record

DC FieldValue Language
dc.contributor.authorPeriyasamy-Thandavan, Sudharsanen_US
dc.contributor.authorTakhar, Suchreeten_US
dc.contributor.authorSinger, Adamen_US
dc.contributor.authorDohn, Michael Roberten_US
dc.contributor.authorJackson, William Hutchen_US
dc.contributor.authorWelborn, April Eveen_US
dc.contributor.authorLeRoith, Dereken_US
dc.contributor.authorMarrero, Marioen_US
dc.contributor.authorThangaraju, Muthusamyen_US
dc.contributor.authorHuang, Shuangen_US
dc.contributor.authorSchoenlein, Patricia Veronicaen_US
dc.date.accessioned2012-10-26T20:35:12Z-
dc.date.available2012-10-26T20:35:12Z-
dc.date.issued2012-03-19en_US
dc.identifier.citationBreast Cancer Res. 2012 Mar 19; 14(2):R52en_US
dc.identifier.issn1465-542Xen_US
dc.identifier.pmid22429491en_US
dc.identifier.doi10.1186/bcr3153en_US
dc.identifier.urihttp://hdl.handle.net/10675.2/827-
dc.description.abstractIntroduction: In this pre-clinical in vitro study conducted in estrogen receptor positive (ER+) breast cancer cells, we have characterized the effects of insulin-like growth factor I (IGF-1) on the cytostatic and cytotoxic action of antiestrogen treatment when used as a single agent or in combination with the antiprogestin mifepristone (MIF). Our goal was to identify new molecular targets to improve the efficacy of hormonal therapy in breast cancer patients that have a poor response to hormonal therapy, in part, due to high circulating levels of unbound insulinIGF-1.en_US
dc.description.abstractMethods: IGF-1-mediated effects on cytostasis and apoptotic cell death were determined with cell counts conducted in the presence and absence of trypan blue; enzyme-linked immunosorbent assays to determine the intracellular levels of cleaved cytokeratin 18, a marker of epithelial cancer cell apoptosis; and immunoblot analysis to determine the levels of cleaved poly-ADP ribose polymerase (PARP) and lamin A that result from caspase-dependent apoptosis. Cytotoxicity was further characterized by determination of the levels of reactive oxygen species (ROS) and the percent of mitochondrial membrane depolarization in cell populations treated with the different hormones in the presence and absence of IGF-1. Small molecule inhibitors of the dual-specificity protein kinase MEK1, MEK1 siRNA, Bim siRNA, and vectors overexpressing MEK1 wild type and mutant, dominant negative cDNA were used to identify key IGF-1 downstream prosurvival effectors.en_US
dc.description.abstractResults: IGF-1, at physiologically relevant levels, blocked the cytotoxic action(s) of the antiestrogens 4-hydroxytamoxifen (4-OHT) and tamoxifen (TAM) when used as single agents or in combination with the antiprogestin MIF. The antiapoptotic action of IGF-1 was mediated primarily through the action of MEK1. MEK1 expression reduced the levels of ROS and mitochondrial membrane depolarization induced by the hormonal treatments via a mechanism that involved the phosphorylation and proteasomal turnover of the proapoptotic BH3-only Bcl-2 family member Bim. Importantly, small-molecule inhibitors of MEK1 circumvented the prosurvival action of IGF-1 by restoring Bim to levels that more effectively mediated apoptosis in ER+ breast cancer cells.en_US
dc.description.abstractConclusion: his study provides strong support for the use of MEK1 inhibitors in combination with hormonal therapy to effectively affect cytostasis and activate a Bim-dependent apoptotic pathway in ER+ breast cancer cells. We discuss that MEK1 blockade may be a particularly effective treatment for women with high circulating levels of IGF-1, which have been correlated to a poor prognosis.en_US
dc.rightsCopyright ©2012 Schoenlein et al.; licensee BioMed Central Ltd.en_US
dc.subjectResearch Articleen_US
dc.titleInsulin-like growth factor 1 attenuates antiestrogen- and antiprogestin-induced apoptosis in ER+ breast cancer cells by MEK1 regulation of the BH3-only pro-apoptotic protein Bimen_US
dc.typeArticleen_US
dc.identifier.pmcidPMC3446386en_US
dc.contributor.corporatenameDepartment of Cellular Biology and Anatomy-
dc.contributor.corporatenameVascular Biology Center-
dc.contributor.corporatenameDepartment of Biochemistry and Molecular Biology-
dc.contributor.corporatenameGHSU Cancer Center-
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