Differential Expression of Cancer-Associated Proteins in Breastmilk

Abstract

Breast cancer that develops during or shortly after pregnancy is frequently more aggressive than cancer diagnosed at other times in a woman's life. To better understand the patterns of cancer-related protein expression in the breasts of lactating women, we determined the differences in total and individual protein expression in milk based on (a) three time points during lactation (early, mid, and late), (b) length of lactation, and (c) parity. Breastmilk was collected from 72 healthy lactating women within 10 days of starting lactation (transitional [T]), 2 months after lactation started, and during breast weaning (W). Sixteen proteins whose expression is altered in breast cancer (11 kallikreins [KLKs], basic fibroblast growth factor [bFGF], YKL-40, neutrophil gelatinase-associated lipocalin, and transforming growth factor [TGF] β1 and β2) were evaluated. The concentration of total milk protein decreased over time (p<0.01 at 2 months and W compared with T). After we controlled for total protein, KLK6 and TGFβ2 significantly increased, and bFGF decreased from T to W. Neither length of nursing nor parity significantly influenced individual protein expression at the W time point. On the other hand, length of nursing did influence the difference in KLK6, -7, and -8 expression between the W and T time points. Total milk protein concentration is lower in the mid and late phases of nursing. Biomarker differences between T and W milk samples in KLK6, TGFβ2, and bFGF are consistent with a protective effect of nursing.

Temporal Trends in the Inflammatory Cytokine Profile of Human Breastmilk

“…Cytokines constitute one class of proteins expressed in breastmilk, and Qin et al 17 previously suggested that cytokine analyses in breastmilk should account for total milk protein through statistical adjustment or normalization of expression values to protein concentration. We identified eight cytokines (ENA-78, granulocyte-macrophage colony-stimulating factor, IGFBP-1, IL-16, IL-8, MCP-1, MCP-4, and TIMP-2) that were significantly associated with total protein (Supplementary Table S3), although no q values were significant.…”

“…Their study did not extend beyond 2 months and thus was not informative regarding trends later in lactation. Qin et al 17 also reported strongly decreased total milk protein concentrations at 2 months compared with baseline (within 10 days postpartum) and observed a nonsignificant increase in total protein content at the time of weaning (an average of 40 weeks postpartum). Similarly, Bauer and Gerss 24 observed a significant decline in total protein levels over the first 2 months postpartum in the milk from mothers of term and preterm infants.…”

“…[8][9][10][11] Although some research has investigated the expression of cytokines and other proteins in human breastmilk, 12-23 methods have been diverse, and there is little consensus regarding the cytokine profile of human milk and how it changes over time. In fact, most studies of breastmilk cytokines have focused on exploring cytokines that impact infant nutrition and health, [12][13][14][15][16] identifying known cancer-associated cytokines in milk, [17][18][19] or investigating cytokines in conjunction with breast inflammatory diseases and noncancerous maternal conditions. 20,21 Few studies have attempted to simultaneously characterize the coordinated expression of multiple cytokines in milk, 22 expression throughout lactation and involution are rare and have had inconsistent results.…”

“…20,21 Few studies have attempted to simultaneously characterize the coordinated expression of multiple cytokines in milk, 22 expression throughout lactation and involution are rare and have had inconsistent results. 12,17,18 The present study investigated temporal trends in the expression of 80 cytokines in the breastmilk of healthy women throughout the first 3 months of lactation. Information on total milk protein concentration was also collected.…”

A-FABP Decreases in the Wean Milk of Nursing Women with a Family History of Breast Cancer

“…We report that A-FABP levels in breast milk are lower at 2 months compared to transitional milk for all women, both those with and without a FH. We previously reported that total protein expression is significantly lower at 2 months than either T or W milk [8], which likely explains this difference. On the other hand we observed that T and W total milk protein expression is similar, but observed that A-FABP expression was lower in W than T milk only among women with a FH.…”