title: Breast Cancer Proteomics - Differences in Protein Expression between Estrogen Receptor-Positive and -Negative Tumors Identified by Tandem Mass Tag Technology.
abstract: BACKGROUND: Proteomic analysis has become an effective tool in breast cancer research. In this study, we applied the new gel-free tandem mass tag (TMT) reference method for the first time in breast cancer.  MATERIALS AND METHODS: Proteomic analysis was used to compare 10 estrogen receptor (ER)-positive and 10 ER-negative samples. The results of the proteomic approach were validated by Western blot, immunohistochemistry and gene expression analysis.  RESULTS: 17 proteins with significant differences in expression were identified. 13 proteins were overexpressed in ER-negative tumors and 4 were overexpressed in ER-positive samples. All these proteins were characterized by relatively high cellular abundance.  CONCLUSIONS: Our results demonstrate that the gel-free TMT approach allows the quantification of differences in protein expression levels. Further improvement of the sensitivity by subfractionation of the tissue should allow also the identification of low-abundance proteins and might lead to the use of this method in breast cancer research.
authors.affiliation: Department of Obstetrics and Gynecology, Goethe University Frankfurt, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Ruckhäberle
authors.forename: Thomas
authors.initials: T
authors.lastname: Karn
authors.forename: Lars
authors.initials: L
authors.lastname: Hanker
authors.forename: Josef
authors.initials: J
authors.lastname: Schwarz
authors.forename: Peter
authors.initials: P
authors.lastname: Schulz-Knappe
authors.forename: Karsten
authors.initials: K
authors.lastname: Kuhn
authors.forename: Gitte
authors.initials: G
authors.lastname: Böhm
authors.forename: Stefan
authors.initials: S
authors.lastname: Selzer
authors.forename: Neukum
authors.initials: N
authors.lastname: Erhard
authors.forename: Knut
authors.initials: K
authors.lastname: Engels
authors.forename: Uwe
authors.initials: U
authors.lastname: Holtrich
authors.forename: Manfred
authors.initials: M
authors.lastname: Kaufmann
authors.forename: Achim
authors.initials: A
authors.lastname: Rody