Differential Phosphoprotein Profiling of Tamoxifen Response
Abstract
Advanced breast cancers that initially respond well to tamoxifen treatment eventually become refractory to this compound. Several mechanisms of acquired resistance have been hypothesized, including crosstalk between ER and growth factor receptor tyrosine kinase pathway. The cumulative data from clinical studies show that overexpression of HER-2 and/or EGFR, and high levels of phosphorylated Akt or ERK, contribute to tamoxifen resistance in some patients. HER-2, EGFR, Akt and ERK are all kinases and components of signaling pathways critical to cell growth and survival, highlighting the need for global phosphoproteome analysis. In this report I describe a method for comparison of global phosphoprotein profiles involving stable isotope labeling, a phosphoprotein affinity step, 1-D SDS-PAGE and LC-MS/MS. I applied this method, differential phosphoprotein profiling to compare phosphoprotein profiles in MCF-7 (tamoxifen sensitive) and MCF-7/HER2-18 (tamoxifen resistant) cells and to examine their regulation by tamoxifen. I found that FADD and other proteins involved in apoptosis were identified in the phosphoenriched fraction of MCF-7 cells but not MCF-7/HER2-18 cells. I also found several proteins regulated by tamoxifen. For example, phosphorylation of XRCC1 on XXX is decreased in MCF-7/HER2- 18 cells but not in MCF-7 cells. Both FADD and XRCC1 have previously been described as being involved in tamoxifen resistance showing that phosphoprotein profiling is a feasible method for identifying proteins relevant to tamoxifen resistance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2010
- Accession Number
- ADA549243
Entities
People
- Kolbrun Kristjansdottir
Organizations
- University of Chicago