The choice of treatment for breast cancer is based on a number of clinical markers. Despite the relative success in classifying tumors and assigning therapy, there is a need for improved markers for the disease. One approach to generating those markers is to analyze the protein content of the cancer; the presence of abnormal proteins or the absence of vital proteins could be indicators of the stage of the disease and could be used to guide therapy. Unfortunately, the present technology for protein analysis of tumors is not ideal. A relatively large biopsy is required for protein analysis. Tumors are complex mixtures of malignant cells, blood vessels, connective tissues, and normal tissues. The non-cancerous material will contribute to the protein signature, and may swamp the fingerprint from rare, but dangerous, cells in the tumor. Also, current protein analysis technology requires a fairly large amount of sample that can only be obtained from surgical biopsy; obtaining those biopsies entails trauma for the patient and cost to the healthcare system. We have developed novel technology that provides a million-fold increase in sensitivity for protein analysis, and we are now able to generate a protein fingerprint from a single cancer cell. Our long-term goal is to use this technology to generate a fingerprint from individual cells obtained by a fine needle biopsy. The fingerprint consists of hundreds of markers, some of which may improve the prognosis accuracy. Our technology is in its infancy, and it is premature to apply it to clinical samples. Instead, this Exploration Award grant will investigate the potential of this technology to generate protein fingerprints from cultured breast cancer cells. We will determine the changes in protein content of the cell as they prepare to divide. This information will allow us to determine the range of fingerprints of a specific cell type. Once this project is complete, we will have the experience necessary to begin study of clinical samples, and we will have optimized our protein fingerprint for breast cancer cells.