Proteomics Analysis of Human Breast Milk to Assess Breast Cancer Risk

Objective Detection of breast cancer (BC) in young women in the early stages is challenging for several reasons. First, mammography and imaging techniques are less effective because young women have dense breast tissue. Second, there is a possible relationship between pregnancy and BC risk. One of the potential options for detection of BC is biochemical monitoring of protein markers in different types of bodily fluids such as serum, nipple aspirate fluid and ductal lavage fluid, tear, urine, saliva and breast milk (BM). BM provides access to breast tissue in the form of exfoliated epithelial cells that are the origins of the most types of BCs. Analysis of BM is a noninvasive method that could be used for cancer diagnosis. Here we analyzed human BM by mass spectrometry (MS) based proteomics, to build biomarker signatures for early detection of BC, and for the prediction of the onset of BC. Methods Milk samples were from donors with BC and matched controls, some of which donated before being diagnosed by BC which used for risk assessment studies. In addition, samples with the same genotype were investigated: the donor with BC donated milk from the breast affected by BC and from the healthy breast, used as control. We analyze human BM as an appropriate cancer microenvironment for BC biomarkers discovery using different analytical approaches such as in‐gel (1D or 2D SDS‐PAGE) and in‐solution digestion of human BM samples coupled with nanoliquid chromatography tandem mass spectrometry (nanoLC‐MS/MS) followed by data processing, data base search and statistical analysis. Results We identified several alterations in protein expression; some of these proteins such as plasminogen, myeloperoxidase isoform CRA_b, tenascin C (hexabrachion) isoform CRA_a, alpha1‐antichymotrypsin, complement C4B precursor, apolipoprotein (J and A–I) and several other proteins were overexpressed (upregulated) in the BC samples and some of them such as different proteins from the casein family, lactoferrin, human bile salt, mannose receptor and several other proteins had a lower expression (downregulation) in the BC samples, as compared to healthy controls. These dysregulated proteins might be associated with BC risk. The upregulated and downregulated proteins that we found in human BM samples from BC suffering mothers, compared to controls, matched well with the current literature. Conclusion We completed a set of preliminary studies for identification of potential BC protein biomarkers and found some dysregulated (upregulated and/or downregulated) proteins and the outcome of our experiments was well matched with literature in terms of dysregulated proteins (same proteins, or similar proteins in the same family of proteins that we identified in our experiments) found by others, who worked on different bodily fluids or tumor tissues and cell lines either in BC or in different types of cancers. Working on BM as a local cancer microenvironment and a noninvasive method, we found the possible BC associated proteins to be dysregulated in human BM from women with BC compared to controls. Most of our dysregulated proteins found in BM were related to BC development. This could strongly introduce those protein as a potential biomarker for BC diagnosis and in some cases risk assessment of BC.