DNA promoter hypermethylation in nipple fluid: A potential tool for early breast cancer detection

Abstract

Introduction: Nipple fluid aspiration provides direct non-invasive sampling of fluid from the mammary ductal system, where the majority of breast cancer soriginate. DNA promoter hypermethylation ("methylation") occurs early and at high frequency in breast carcinogenesis, bearing the potential as a biomarker for cancerdetection at its earliest stages. We assessed methylation in nipple fluid from breastsof healthy women, of women with sporadic breast cancer and of their contralateral breasts. Our goal was to investigate whether nipple fluid can be used as a reliable methylation biomarker source. Methods: Methylation levels of 13 genes were analysed by quantitative multiplex methylation specific PCR (QM-MSP) in nipple fluid samples from breasts of healthy women, and from the affected and contralateral breasts of breast cancer patients. Results: Methylation analysis of the low-volume nipple fluid samples was feasible. Despite the generally low methylation levels, cancerous and healthy breasts nipple fluid could be discriminated with an area under the receiver operating characteristic curve (AUC) of 0.64 (p<0.01) based on a multivariate model including AKR1B1, ALX1, RASSF1A and TM6SF1. Within-patient differences between cancerous andcontralateral nipple fluid samples were less prominent. Conclusions: Cancerous nipple fluid contains increased levels of methylation oftumor suppressor genes that potentially could serve as a biomarker for early breast cancer detection.