TITLE:
Increased Cellular Invasion and Proliferation via Estrogen Receptor after 17-β-Estradiol Treatment in Breast Cancer Cells Using Stable Isotopic Labeling with Amino Acids in Cell Culture (SILAC)
AUTHORS:
Alimatou M. Tchafa, Zhijiu Zhong, Rong Meng, Judy N. Quong, Andrew A. Quong
KEYWORDS:
17-β-Estradiol; Breast Cancer; Estrogen Receptor; Mass Spectrometry; SILAC
JOURNAL NAME:
Advances in Breast Cancer Research,
Vol.2 No.2,
April
29,
2013
ABSTRACT: 17-β-estradiol
(estrogen) is a steroid hormone important to human development; however, high
levels of this molecule are associated with increased risk of breast cancer
primarily due to estrogen’s ability to bind and activate the estrogen receptor
(ER) and initiate gene transcription. Currently, estrogen mechanisms of action
are classified as genomic and non-genomic and occur in an ER-dependent and
ER-independent manner. In this study, we examine estrogen signaling pathways,
by measuring changes in protein expression as a function of time of exposure to
estrogen in both ER-positive (MCF-7) and ER-negative (MDA-MB-231) cell lines.
Using a robust experimental design utilizing isotopic labeling, two-dimensional
LC-MS, and bioinformatics analysis, we report genomic and non-genomic ER
regulated estrogen responsive proteins. We find a little over 200 proteins
differentially expressed after estrogen treatment. Cell proliferation,
transcription, actin filament capping and cell to cell signaling are
significantly enriched in the MCF-7 cell line alone. Translational elongation
and proteolysis are enriched in both cell lines. Subsets of the proteins
presented in this study are for the first time directly associated with
estrogen signaling in mammary carcinoma cells. We find that estrogen affected
the expression of proteins involved in numerous processes that are related to
tumorigenesis such as increased cellular division and invasion in an
ER-dependent manner. Moreover, we identified negative regulation of apoptosis
as a non-genomic process of estrogen. This study complements gene expression
studies and highlights the need for both genomic and proteomic analyses in
unraveling the complex mechanisms by which estrogen affects progression of
breast cancer.