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

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  • Periyasamy-Thandavan, Sudharsan
    • Other Affiliation: Department of Cellular Biology and Anatomy, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • Takhar, Suchreet
    • Other Affiliation: Department of Cellular Biology and Anatomy, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • Singer, Adam
    • Other Affiliation: Department of Cellular Biology and Anatomy, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • Dohn, Michael Robert
    • Other Affiliation: Department of Cancer Biology, Vanderbilt University, 2220 Pierce Ave., Nashville, TN 37232, USA
  • Jackson, William Hutch
    • Other Affiliation: Department of Cellular Biology and Anatomy, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • Welborn, April
    • Other Affiliation: Department of Cellular Biology and Anatomy, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • LeRoith, Derek
    • Other Affiliation: Division of Endocrinology, Diabetes and Bone Diseases, Mount Sinai School of Medicine, 1428 Madison Ave, New York, NY 10029, USA
  • Marrero, Mario
    • Other Affiliation: Institute of Vascular Biology, Georgia Health Sciences University, 1459 Laney Walker Blvd., Augusta, GA 30912, USA
  • Thangaraju, Muthusamy
    • Other Affiliation: Department of Biochemistry; Medical College of Georgia Cancer Center, Georgia Health Sciences University, 1410 Laney Walker Blvd., Augusta, GA 30912, USA
  • Huang, Shuang
    • Other Affiliation: Department of Biochemistry; Medical College of Georgia Cancer Center, Georgia Health Sciences University, 1410 Laney Walker Blvd., Augusta, GA 30912, USA
  • Schoenlein, Patricia
    • Other Affiliation: Department of Cellular Biology and Anatomy; Medical College of Georgia Cancer Center, Georgia Health Sciences University, 1410 Laney Walker Blvd., Augusta, GA 30912, USA
Abstract
  • 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.
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  • Article
Rights statement
  • In Copyright
Rights holder
  • Sudharsan Periyasamy-Thandavan et al.; licensee BioMed Central Ltd.
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Journal title
  • Breast Cancer Research
Journal volume
  • 14
Journal issue
  • 2
Page start
  • R52
Language
  • English
Is the article or chapter peer-reviewed?
  • Yes
ISSN
  • 1465-5411
Bibliographic citation
  • Breast Cancer Research. 2012 Mar 19;14(2):R52
Publisher
  • BioMed Central Ltd
Access right
  • Open Access
Date uploaded
  • January 20, 2017

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