Proteomics

The synthesis, activity and degradation of proteins, the functional products of genes, are regulated by the modification of the proteins’ amino acid sequences. Thus changes in gene expression, signal transduction and, ultimately, deregulation of cell processes in cancer, are reflected in changes in protein content and composition.

Introduction

2D-DIGE

Part of a two-dimensional differential gel electrophoresis (2D-DIGE) image indicating differential protein expression in two cell samples.

LICR scientists are using protein expression profiling to comprehensively analyze thousands of proteins in tissue samples and/or cell types. Protein expression profiling identifies gene activation and repression by indicating the presence and absence (and relative amount) of the protein product. It also identifies changes in protein modification that signifies activation or repression of signal transduction pathways required for cell processes such as growth, division and migration.

Protein differences are analyzed primarily through the use of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) that separate proteins based on their size and ‘isoelectric point’ (electric charge), which are determined by amino acid sequences. Proteins found to be differentially expressed in cancer cells and normal cells, are typically identified through the use of mass spectrometry, in which the protein is fragmented and the atomic and molecular mass of the resultant fragments then related to the known masses of amino acids and their modifications.

Identifying protein expression and modification is helping to further our understanding of how and why cancer occurs, allowing the development of better screening techniques for the diagnosis, prognosis and treatment of cancer, and identifying targets for future therapy strategies.

LICR investigators are applying proteomics technologies to analyze:

  • The Effects of ErbB-2 Over-expression in Breast Cancer — at the London Branch, investigators have used two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry to analyze protein expression during the cell cycle changes in a breast cancer cell model that over-expresses the ErbB-2/HER-2 receptor tyrosine kinase. Overexpression of this receptor is found in 25-30% of breast cancers.
  • Dynamic Changes in Protein-Protein Interactions — at the LICR San Diego Branch, investigators have devised a new technique for quantitatively analyzing the composition and phosphorylation of protein complexes. Areas of biological interest include the identification of protein complexes involved in halting the cell cycle when DNA damage occurs and thus preventing damaged normal cells becoming cancer cells.
  • Joint ProteomicS Laboratory (JPSL) — the JPSL at the LICR Melbourne Branch is a joint initiative between LICR and the Walter and Eliza Hall Institute (WEHI, Melbourne, Australia). The JPSL is involved in the development of new proteomics systems, and software and instrumentation for mass spectrometry, which increase the flexibility, speed, and sensitivity of protein identification and analysis. Areas of biological interest include the identification of specific and sensitive markers of colon cancer, and structure/function relationships in the interleukin-6/gp130 system.

Key Publications

Centers Involved in this Research