The local endocrine environment of the breast may have stronger relations to breast cancer risk than systemic hormones. Nipple aspiration fluid (NAF) provides a window into this milieu. We hypothesized that the correlations between proteins and steroid hormones in NAF are stronger, and specific relationships may reveal links to breast cancer risk. NAF and blood samples were obtained simultaneously from 54 healthy women and from the contralateral unaffected breast of 60 breast cancer patients. The abundance of five proteins, superoxide dismutase (SOD1), C-reactive protein (CRP), chitinase-3-like protein 1 (YKL40), cathepsin D (CatD), and basic fibroblast growth factor (bFGF) in NAF was measured using ELISA. The NAF and serum concentrations of estradiol, estrone, progesterone, androstenedione, testosterone, and dehydroepiandrostrerone (DHEA) were measured using ELISA or RIA. The correlations between proteins and hormones revealed that NAF proteins correlated with each other: SOD1 with CRP (R = 0.276, P = 0.033) and CatD (R = 0.340, P = 0.0036), and bFGF with CRP (R = 0.343, P = 0.0021). NAF proteins displayed significant correlations with NAF steroids, but not with serum steroids: SOD1 with DHEA (R = 0.333, P = 0.019), YKL40 with testosterone (R = 0.389, P = 0.0012), and bFGF negatively correlated with testosterone (R = -0.339, P = 0.015). The regulation of YKL40 and bFGF by testosterone was confirmed in breast cancer cell lines. In summary, NAF proteins were more strongly related to local hormone levels than to systematic hormone levels. Some proteins were specifically correlated with different NAF steroids, suggesting that these steroids may contribute to breast cancer risk through different mechanisms.

Background: Breast cancer risk is related to endogenous lifetime steroid hormone exposure. The local production of steroid hormones in the breast is a stable contributor to the hormonal environment. Several risk marker proteins have been identified in nipple aspirate fluid (NAF) in unaffected contralateral breast or in high-risk subjects as indicators of changes in breast on oxidative stress (superoxide dismutase), inflammation (C-reactive protein and YKL40), protease activity (cathepsin D) and growth factors (bFGF). However, it is not clear whether the alteration of protein markers is related to the local steroid hormone synthesis and metabolism in the breast. In the study, we studied the correlation between protein markers and both systematic (serum) and local (NAF) abundance of hormones. Methods: NAF and blood samples were obtained from normal breast of 54 healthy women and from unaffected breast of 60 breast cancer patients. The 114 subjects consisted of 48 women in premenopausal, 54 in postmenopausal and 12 in perimenopausal. The abundance of five protein markers (SOD1, CRP, YKL40, CatD and bFGF) was measured using ELISA. The NAF concentration of estradiol (E2), estrone (E1), progesterone (P4), andostenedione (A4), testosterone (T), dehydroepiandrostrerone (DHEA) and DHEA sulfate (DHEAS), and the serum concentration of E2, E1, P4, A4, T, DHEA and follicular-stimulating hormone (FSH) were measured using ELISA or RIA. The correlation between protein markers and hormones were examined using Spearman's rank correlation test with Bonferroni adjusted p < 0.05 as statistical significant. Results: The correlation among the protein markers showed that SOD1 was significantly correlated with CRP (r=0.276, p=0.033) and catD (r=0.340, p=0.0036). bFGF was significantly correlated with CRP (r=0.343, p=0.0021), indicating these proteins may be affected each other in the breast. The relationship between protein markers and hormones indicated that protein markers did not have much correlation with serum hormones, except bFGF was negatively correlated with serum T level (r=−0.339, p=0.017). In contrast, protein markers showed stronger correlation with multiple estradiol precursors in NAF. Specifically, SOD1 correlated with DHEA (r=0.333, P=0.019) and DHEAS (r=0.372, p=0.0030). YKL40 correlated with NAF T level (r=0.389, p=0.0012). CatD correlated with NAF DHEAS (r=0.400, p=0.0014). bFGF negatively correlated with NAF T (r=−0.339, p=0.015). CRP did not show significant correlation with any types of measured NAF hormones. Conclusions: NAF protein markers were more strongly related to local hormone levels in the breast, rather than systematic hormones in the blood. Protein markers were specifically correlated with different components of hormone hormones, suggesting that metabolic precursors may contribute to breast cancer risk through distinct mechanisms. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5756. doi:1538-7445.AM2012-5756