Purpose: Loss of heterozygosity (LOH) and microsatellite instability (MSI) have been identified in a variety of human cancers. The purpose of this prospective study was to determine whether (a) DNA can be isolated from nipple aspirate fluid (NAF) and PCR amplified to large fragments, (b) LOH and MSI are detectable in NAF, and (c) LOH and MSI in tissue and NAF increase with disease progression from precursor lesions to cancer.
Experimental design: Forty-six matched samples from breast lesions, normal breast, and NAF were microdissected, and DNA was extracted. Eleven microsatellite markers from seven chromosomes that have a high frequency of LOH/MSI in breast cancer were designed and respectively amplified.
Results: LOH and/or MSI were identified in 22 of 46 (48%) breast lesions, including LOH in 8 of 36 (22%) proliferative/papilloma (P/Pap) and 7 of 10 (70%) cancer specimens, whereas MSI was found in 14 of 36 (39%) P/Pap and 6 of 10 (60%) cancer specimens. LOH/MSI loci in which alterations were detected in the 22 tissue specimens were PCR amplified using matched NAF DNA. LOH/MSI was detected in NAF from both P/Pap (5 of 15; 33%) and breast cancer (3 of 7; 43%) samples.
Conclusions: Our findings suggest that (a) DNA from NAF, a physiological fluid collected noninvasively, can be PCR amplified and used to screen for LOH and MSI alterations that are known to be linked to breast cancer, suggesting that this methodology might prove useful for breast cancer screening, and (b) similar to findings in breast tissue, LOH and MSI alterations increase in frequency with disease progression in NAF, which suggests that NAF is a surrogate for breast tissue which has important prognostic implications.