Carcinogenesis Advance Access published online on June 13, 2006
Carcinogenesis, doi:10.1093/carcin/bgl083
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 The University of New Mexico College of Pharmacy Toxicology Program, 1 University of New Mexico, Albuquerque, NM, USA; Current Address: The Pennsylvania State University, Center for Molecular Toxicology and Carcinogenesis, University Park, PA, 16802, USA
* To whom correspondence should be addressed. Polycyclic aromatic hydrocarbons, such as benzo[a]pyrene (BaP), are known mammary carcinogens in rodents and may be involved in human breast cancer. The carcinogenicity of BaP has been partially attributed to the formation of the BaP diol epoxide (BPDE) which has been shown to stably bind DNA and act as an initiator. BaP is a complete carcinogen, but the mechanisms for tumor promotion are less well characterized. Previous studies have demonstrated that BPDE enhanced anti-apoptotic signaling through Akt; however, mechanisms for Akt activation by BPDE are not well defined. In the current studies, we found that BPDE increased intracellular Ca2+ concentration in the human mammary epithelial cell line MCF-10A. A peak in Ca2+ concentration at 20 min was followed by increased phosphorylation of Pyk2 at Tyr881 and increased total tyrosine phosphorylation of the epidermal growth factor receptor (EGFR). Consistent with activation of the EGFR, Akt and ERK1/2 phosphorylation was detected in MCF-10A cells treated with BPDE. Pharmacological methods to prevent Ca2+ elevation and EGFR activity, and small-interfering RNA against Pyk2, prevented Akt phosphorylation by BPDE, which suggested that Ca2+, Pyk2 and EGFR activation lied upstream of Akt. In addition, we found that BPDE increased p53 activity and apoptosis in MCF-10A; however, transient transfection of constitutively active Akt attenuated both BPDE-dependent apoptosis and p53 activity. In contrast, apoptosis was enhanced by inhibitors of phosphatidyl inositol 3-kinase (PI3-K). This work demonstrates a novel mechanism for Akt activation by BPDE that occurs through increased Ca2+ concentration, and implicates Ca2+, Pyk2, EGFR, and Akt as a potential pathway by which BPDE can inhibit apoptosis and act as a promoter of carcinogenesis.
Received December 19, 2005
Revised April 14, 2006
Accepted May 17, 2006
CARCINOGENESIS
Pyk2 mediates anti-apoptotic Akt signaling in response to benzo[a]pyrene diol epoxide (BPDE) in mammary epithelial cells*
Andrew D. Burdick 1,
Irena D. Ivnitski-Steele 2,
Fredine T. Lauer 2,
and
Scott W. Burchiel 2 *
2 The University of New Mexico College of Pharmacy Toxicology Program, 1 University of New Mexico, Albuquerque, NM, USA
Scott W. Burchiel, E-mail: sburchiel{at}salud.unm.edu
Abstract
* Grant Support: NIEHS R01 ES07259 (to S.W.B.) and U.S. Army Medical Research and Materiel Command Grant DAMD17-02-1-0512 (to A.D.B.). This work was sponsored in part by the NM NIEHS Center, P30 ES-012072 with UNM Cancer Research and Treatment Center Facilities.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Fedida-Metula, S. Elhyany, S. Tsory, S. Segal, M. Hershfinkel, I. Sekler, and D. Fishman Targeting lipid rafts inhibits protein kinase B by disrupting calcium homeostasis and attenuates malignant properties of melanoma cells Carcinogenesis, August 1, 2008; 29(8): 1546 - 1554. [Abstract] [Full Text] [PDF]
|
|