Potential of Using Cell-Free DNA and miRNA in Breast Milk to Screen Early Breast Cancer

The Role of Breast Milk Cell-Free DNA in the Regulation of the Neonatal Immune Response

The neonatal period is a critical phase for the development of the intestinal immune system, marked by rapid adaptation to the external environment and unique nutritional demands. Breast milk plays a pivotal role in this transition, yet the mechanisms by which it influences neonatal mucosal immunity remain unclear. This review examines the potential mechanisms by which cell-free DNA (cfDNA) in breast milk may impact neonatal immune development, particularly through Toll-like receptor 9 (TLR9) signalling and gut microbiota interactions. We propose that cfDNA in breast milk interacts with TLR9 on the apical surface of neonatal intestinal epithelial cells, potentially serving as an initial anti-inflammatory stimulus before the establishment of commensal bacteria. This hypothesis is supported by the high concentration and stability of cfDNA in breast milk, as well as the known activation of TLR9 by mitochondrial DNA in breast milk. The review emphasises the need for further empirical research to validate these interactions and their implications for neonatal health, suggesting that understanding these dynamics could lead to improved strategies for neonatal care and disease prevention.

Liquid Biopsies in Breast Milk for the Early Detection of Breast Cancer

SUMMARY

Cell-free tumor DNA has previously been detected in nonblood sources, including urine, saliva, stool, cerebrospinal fluid, and pleural fluid. In this issue, Saura and colleagues present a novel proof-of-concept study demonstrating that detection of tumor DNA in breast milk is feasible and may be a potential future strategy to screen for postpartum breast cancer. See related article by Saura et al., p. 2180 (14).

Potential utility of miRNAs for liquid biopsy in breast cancer

Breast cancer (BC) remains the most prevalent malignancy due to its incidence rate, recurrence, and metastasis in women. Conventional strategies of cancer detection– mammography and tissue biopsy lack the capacity to detect the complete cancer genomic landscape. Besides, they often give false- positive or negative results. The presence of this and other disadvantages such as invasiveness, high-cost, and side effects necessitates developing new strategies to overcome the BC burden. Liquid biopsy (LB) has been brought to the fore owing to its early detection, screening, prognosis, simplicity of the technique, and efficient monitoring. Remarkably, microRNAs (miRNAs)– gene expression regulators seem to play a major role as biomarkers detected in the samples of LB. Particularly, miR-21 and miR-155 among other possible candidates seem to serve as favorable biomarkers in the diagnosis and prognosis of BC. Hence, this review will assess the potential utility of miRNAs as biomarkers and will highlight certain promising candidates for the LB approach in the diagnosis and management of BC that may optimize the patient outcome.

Technical and Methodological Aspects of Cell-Free Nucleic Acids Analyzes

Analyzes of cell-free nucleic acids (cfNAs) have shown huge potential in many biomedical applications, gradually entering several fields of research and everyday clinical care. Many biological properties of cfNAs can be informative to gain deeper insights into the function of the organism, such as their different types (DNA, RNAs) and subtypes (gDNA, mtDNA, bacterial DNA, miRNAs, etc.), forms (naked or vesicle bound NAs), fragmentation profiles, sequence composition, epigenetic modifications, and many others. On the other hand, the workflows of their analyzes comprise many important steps, from sample collection, storage and transportation, through extraction and laboratory analysis, up to bioinformatic analyzes and statistical evaluations, where each of these steps has the potential to affect the outcome and informational value of the performed analyzes. There are, however, no universal or standard protocols on how to exactly proceed when analyzing different cfNAs for different applications, at least according to our best knowledge. We decided therefore to prepare an overview of the available literature and products commercialized for cfNAs processing, in an attempt to summarize the benefits and limitations of the currently available approaches, devices, consumables, and protocols, together with various factors influencing the workflow, its processes, and outcomes.