Methodological considerations in estrogen assays of breast fluid and breast tissue

Estradiol (E2) in nipple aspirate fluid (NAF), ductal lavage fluid (DLF), and random fine needle aspirates (rFNA) are compared. Quantification was by immunoassay or tandem MS. The percent of women yielding NAF varied between 24% and 48% and for DLF was 86.3%. Variation between ducts within a breast was not less than variation between breasts within women but variation between breasts and within women over time was significantly less than variation between women. Serum E2 was highly significantly different among phases of the menstrual cycle but NAF E2 was not different. The correlation between serum and breast fluid E2 concentrations in premenopausal women had coefficients of determination of less than 15%. The correlation between serum and NAF in studies of postmenopausal women varied greatly and may depend on patient selection. The difference between NAF E2 between pre- and postmenopausal women was only 22%; for rFNA it was non-significantly 44% lower in a similar group of postmenopausal women. Progesterone was 96% and 98% lower in postmenopausal NAF and rFNA samples, respectively. Measurements of E2 in breast fluid or breast tissue appears to provide similar estimates of E2 exposure. E2 levels in breast fluid do not reflect the rapid changes that occur in serum and, thus, serum availability of E2 is only one factor determining its levels in the breast. The similarity of levels between breasts and between ducts suggests that estimates of estrogen exposure does not require multiple samples, however, unavailability of fluid may require rFNA in some cases.

Resolving breast cancer heterogeneity by searching reliable protein cancer biomarkers in the breast fluid secretome

BACKGROUND

One of the major goals in cancer research is to find and evaluate the early presence of biomarkers in human fluids and tissues. To resolve the complex cell heterogeneity of a tumor mass, it will be useful to characterize the intricate biomolecular composition of tumor microenvironment (the so called cancer secretome), validating secreted proteins as early biomarkers of cancer initiation and progression. This approach is not broadly applicable because of the paucity of well validated and FDA-approved biomarkers and because most of the candidate biomarkers are mainly organ-specific rather than tumor-specific. For these reasons, there is an urgent need to identify and validate a panel of biomarker combinations for early detection of human tumors. This is especially important for breast cancer, the cancer spread most worldwide among women. It is well known that patients with early diagnosed breast cancer live longer, require less extensive treatment and fare better than patients with more aggressive and/or advanced disease.

RESULTS

In the frame of searching breast cancer biomarkers (especially using nipple aspirate fluid mirroring breast microenvironment), studies have highlighted an optimal combination of well-known biomarkers: uPA + PAI-1 + TF. When individually investigated they did not show perfect accuracy in predicting the presence of breast cancer, whereas the triple combination has been demonstrated to be highly predictive of pre-cancer and/or cancerous conditions, approaching 97-100% accuracy.

CONCLUSION

Despite the heterogeneous composition of breast cancer and the difficulties to find specific breast cancer biomolecules, the noninvasive analysis of the nipple aspirate fluid secretome may significantly improve the discovery of promising biomarkers, helping also the differentiation among benign and invasive breast diseases, opening new frontiers in early oncoproteomics.

High levels of DJ-1 protein in nipple fluid of patients with breast cancer

As we have previously demonstrated that some breast cancer cell lines secrete DJ-1 protein, we examined here whether breast cancer cells secrete DJ-1 protein in vivo. To this end, the levels of DJ-1 protein present in 136 specimens of nipple fluid was examined by enzyme-linked immunosorbent assay (ELISA). The average concentration of DJ-1 protein detected in diluted samples from 47 patients with invasive ductal carcinoma (IDC) was 22.4 ng/mL, while it was 18.6 ng/mL in 26 patients with ductal carcinoma in situ (DCIS). In contrast, the average DJ-1 concentration in samples from 63 women with benign lesions was 2.7 ng/mL, demonstrating that higher DJ-1 protein levels were detected in nipple fluid in the presence of cancer cells than in the presence of benign lesions (P < 0.0001). When a cut-off level of 3.0 ng/mL was applied, the higher level of DJ-1 was shown to be of significant clinical value for predicting the presence of breast cancer (85.9% specificity, 75% sensitivity; P < 0.0001). Multivariate logistic analysis that included established factors such as nipple discharge cytology, ductoscopic cytology, and carcinoembryonic antigen level further showed that the level of DJ-1 protein alone is of significant value for predicting the presence of breast cancer. Immunohistochemistry and in situ hybridization also showed that the low expression of DJ-1 protein, despite high mRNA expression, was significantly correlated with high DJ-1 protein levels in the nipple fluid. These data indicate that breast cancer cells secrete DJ-1 protein in vivo, and that its level is a potential indicator of breast cancer in patients with nipple discharge.