Systems Analysis of the Response of Human Mammary Epithelial Cells to Epidermal Growth Factor Stimulation

Brian Thrall, Pacific Northwest National Laboratory

Understanding the underlying dynamics of a signaling network structure ultimately requires the global integration of quantitative data encompassing many levels of biological hierarchy, yet such comprehensive datasets are rare. We are developing a comprehensive inventory of the genes and proteins expressed in synchronized human mammary epithelial cells (HMEC) during the G1-S transition initiated by epidermal growth factor (EGF). Our approach integrates heterogeneous sets of time-course data obtained from whole genome microarray, global proteomic analysis using Fourier transform ion cyclotron resonance mass spectrometry coupled with isotopic labeling, and parallel Western blot analysis using more than 1000 antibodies.

The G1-S phase transition initiated by EGF receptor (EGFR) activation is associated with dynamic changes in abundance for more than 1300 mRNAs and 511 proteins, as well as 18 detected changes in protein phosphorylation status. Pathway analysis using these combined heterogeneous datasets reveals that during the initial hours following EGFR stimulation, signaling networks regulating cell motility, cell cycle, and differentiation predominate. However, as the cells progress toward mitosis, the primary response pathways evolve toward processes that build and modify the extracellular matrix, including coordinated induction of the plasminogen activator receptor and matrix metalloproteinase cascades. Our results suggest that the cellular decision to proliferate in response to EGF involves the induction of autocrine cascades, which are further modulated in a context-dependent manner by proteolytic remodeling of the local microenvironment.