Background: Proteomic analysis of nipple aspiration fluid (NAF) is a noninvasive method for studying the local biologic microenvironment of the breast ducts where carcinoma originates.
Methods: NAF samples from each breast of 23 women with stage I or II unilateral invasive breast carcinoma were collected, and protein expression was analyzed comprehensively by using protein arrays and time-of-flight mass spectrometry. Blinded hierarchical clustering analysis was performed to identify potential associations between protein expression patterns and clinicopathologic factors.
Results: After analysis of all spectra, 463 distinct peaks in the mass range of 7 to 30 kD were identified in NAF samples. Blinded hierarchical clustering analysis of protein expression patterns demonstrated a conservation of these patterns between the breasts of individual patients (P=.0003 x 10(-12)). Hierarchical clustering revealed an association between protein expression patterns, and the presence and absolute number of axillary lymph nodes containing metastases (P=.038).
Conclusions: Protein expression patterns are highly conserved between cancerous and noncancerous breasts in women with unilateral invasive breast cancer; unique expression patterns may be associated with extent of disease. High-throughput proteomic methods may reveal biologically relevant proteins involved in carcinogenesis and progression of disease.