Identification of distinct protein expression patterns in bilateral matched pair breast ductal fluid specimens from women with unilateral invasive breast carcinoma. High-throughput biomarker discovery

Background: Analysis of the biochemical and cellular contents of breast ductal fluid has recently gained attention as a potential noninvasive method for studying the local microenvironment associated with the development and progression of breast carcinoma.

Methods: Patients with unilateral primary invasive breast carcinoma were eligible for the current prospective pilot study. Nipple aspiration fluid (NAF) was obtained from the breast with cancer and the normal contralateral breast and subjected to two-dimensional electrophoresis. Computer-assisted image analysis was used to analyze NAF protein expression profiles.

Results: The number of separate protein spots detected in NAF samples ranged from 1280 to 1649. Substantial qualitative differences were identified between NAF protein expression patterns in the breast with cancer compared with the breast without cancer. Protein spots detected in the breast with cancer and not in the breast without cancer from the same patient varied from 30 to 202 different proteins. In addition, the number of protein spots detected in the breast without cancer and not in the breast with cancer of the same patient varied from 14 to 73 different proteins. Conversely, in an individual without breast carcinoma, only three protein spots were detected in the left breast but not the right breast, and only two were detected in the right breast but not the left breast.

Conclusions: The breast is a unique organ in that its microenvironment can be readily accessed and evaluated by aspiration of fluid from the nipple. Breast ductal fluid contains a large number of proteins. As breasts are paired organs, comparisons of ductal fluid from a breast with cancer and the same patient's normal contralateral breast may reveal significant differences in protein expression associated with breast carcinoma. Recent advances in image analysis, automated mass spectrometry, and bioinformatics have provided the tools necessary to use ductal fluids from breast carcinoma patients for high-throughput biomarker discovery.