Pharmacoproteomics investigation of the mechanisms of hormone therapy resistance in breast cancer

There is a need to establish a greater understanding of acquisition of drug resistance mechanisms in order to develop therapeutic strategies to counter them. A case in point is the use of Tamoxifen in the treatment of breast cancer. Tamoxifen, a selective estrogen receptor modulator, has proven effective in both early and advanced stages of breast cancer. In addition, depriving receptors of ligand using aromatase inhibitors and degrading receptors through pure nonsteroidal anti-estrogens has also proven effective. Unfortunately, after initial success, a large portion of these tumours will develop resistance.

Pharmacoproteomics is an emerging discipline that has the key strengths of allowing the monitoring of the expression of several proteins to allow comparison between subjects treated with drugs or placebo control, or the monitoring of expression changes over a treatment course. By combining proteomics data with bioinformatics tools it is possible to establish significant protein-protein interactions which may contribute to the progression of disease, response to treatment or acquisition of resistance. Whilst some work has been done using breast cancer cell lines in vitro and to a lesser extent using patient biopsies, little has been done to evaluating tumour in an experimental in vivo setting. This latter approach provides an opportunity to study the interaction between tumour cells and supporting cells (e.g. stromal cells, endothelial cells) which are essential to support tumour propagation and the effectiveness of anti-cancer drugs.

In this project we will use quantitative pharmacoproteomics techniques to study the response to tamoxifen and acquisition of resistance in human mammary tumour xenograft models in vivo, using the MCF-7 tumour cell line transplanted subcutaneously in mice. Initially, MCF-7 tamoxifen-resistant sub-lines will be established and the protein profiles of untreated wild type and resistant cell lines will be compared. Proteomic analysis of WT and tamoxifen-resistant xenografts will then be studied over a time course of drug treatment.
Identified proteins for which an intervention may reduce the potential for acquired resistance will be further investigated in vitro to confirm their role in the process of resistance. There will be scope within the project to create additional hormone therapy-resistance cell lines, explore their proteomic profiles for common mechanism of action and investigate the impact of drug administration on the proteomes of other vital organs in xenograft models.

The project will enable the PhD student to learn a diverse range of techniques including, cell culture protein preparation, proteomics techniques including (iTRAQ quantitation, nanoHPLC, mass spectrometry, bioinformatics), Western blotting and immunohistochemistry.