Aim: To determine the patterns of lactoferrin (LF) expression in breast cancer (BC) in relation to biologic properties of the neoplasms and clinical features of the disease course. Materials and Methods: Clinical specimens of 266 BC patients (115 patients with BC of stages I–II — retrospective study, and 151 BC patients — prospective study) were analyzed. Morphological, immunohistochemical and statistical methods were used. Results: The number of LF-positive tumors in retrospective and prospective groups was similar (52.1 and 52.8%, respectively). Among common clinical criteria for prognosis of the disease outcome in BC patients (patient’s age; stage of the disease; histological type, differentiation grade, receptor status; presence of metastases), a strong correlation was found only between expression indexes of LF and estrogen receptors (ER). In ER-positive tumors expression of LF was significantly higher than in ER-negative tumors (35 vs 18%). 5-Year survival rate of BC patients was higher in LF-positive group (70 vs 52% in LF-negative group). The presence of regional metastasis tended to correlate with an increased number of LF-positive tumors. In the patients with invasive ductal carcinoma, expression level of LF moderately correlated with occurrence of luminal A subtype (r = 0.43), while in the patients with invasive lobular carcinoma this index strongly correlated with occurrence of luminal B subtype (r = 0.71). LF expression correlated positively with low and moderate differentiation grade of luminal B or basal tumors, and negatively with luminal B or basal tumors of high differentiation grade (r = −0.57 and −0.63, respectively). Conclusion: It has been shown that LF expression in breast tumors correlated with life expectancy of BC patients and important physiologic and clinical features of the disease, while the character of such relation strongly depended on molecular phenotype of tumor, i.e. luminal A, luminal B or basal.

Aim: To assess the role of endogenous lactoferrin (LF) in the formation of the molecular phenotype of human breast cancer (BC) cell lines with varying degrees of malignancy, including cisplatin/doxorubicin resistant cell lines, and identify possible impact of exogenous LF. Materials and Methods: 5 breast cell lines of different origin — MCF-10 A, MCF-7, including doxorubicin/ cisplatin resistant ones, T47D, MDA-MB-231, and MDA-MB-468. Immunocytochemistry: e xpression of LF, Ki-67, adhesion molecules E- and N-cadherin, CD44, CD24 rating the invasive potential of cells. Results: Expression of LF in human BC cell lines varies. It is associated with the heterogeneity of molecular profiles of cell lines in terms of adhesion. A link has been established between the level of LF expression in the resistant cell line MCF-7/CP and MCF-7/Dox, features of their molecular profile and invasive properties. Exogenous LF was shown to be capable of modifying the molecular profile and invasive properties of all the studied cell lines including resistant ones (MCF-7/CP and MCF-7/Dox). Conclusions: The sensitivity of cytostatic-resistant cell lines (MCF-7/CP and MCF-7/Dox) tends to increase under the influence of exogenous LF. It is likely that this effect is due to LF-mediated inhibition of the expression of proteins associated with drug resistance.