Open Access Research

Comparative proteomic analysis implicates eEF2 as a novel target of PI3Kγ in the MDA-MB-231 metastatic breast cancer cell line

Meizhi Niu1, Manuela Klingler-Hoffmann1, Julie A Brazzatti13, Briony Forbes1, Chareeporn Akekawatchai12, Peter Hoffmann1 and Shaun R McColl1*

Author Affiliations

1 School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia

2 Current address: Department of Medical Technology, Thammasat University, Patumtani, 121212, Thailand

3 Current address: Immunology Group, Paterson Institute for cancer research, The University of Manchester, Manchester, M20 4BX, England

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Proteome Science 2013, 11:4  doi:10.1186/1477-5956-11-4

Published: 15 January 2013

Abstract

Background

Cancer cell migration is fundamentally required for breast tumour invasion and metastasis. The insulin-like growth factor 1 tyrosine kinase receptor (IGF-1R) and the chemokine G-protein coupled receptor, CXCR4 have been shown to play an important role in breast cancer metastasis. Our previous study has shown that IGF-1R can transactivate CXCR4 via a physical association in the human MDA-MB-231 metastatic breast cancer cell line and that this plays a key role in IGF-I-induced migration of these cells. In the present study we used pharmacological inhibition and RNAi to identify PI3Kγ as an important migration signalling molecule downstream of receptor transactivation in MDA-MB-231 cells. To identify PI3Kγ-regulated proteins upon transactivation of CXCR4 by IGF-I, we undertook a comparative proteomics approach using 2-D- Fluorescence Difference Gel Electrophoresis (DIGE) and identified the proteins by mass spectrometry.

Results

These experiments identified eukaryotic elongation factor 2 (eEF2) as a novel downstream target of PI3Kγ after activation of the IGF-1R-CXCR4 heterodimer by IGF-I. Further analysis demonstrated that eEF2 is phosphorylated in MDA-MB-231 cells in response to IGF-I and that this is dependent on PI3Kγ activity.

Conclusions

Our data imply a novel role for PI3Kγ in facilitating cell migration by regulating phosphorylation of eEF2.

Keywords:
Receptor transactivation; Cell migration; IGF-I; CXCR4; PI3Kγ; eEF2; 2D-DIGE