Physical activity and exercise can induce beneficial molecular and biological
regulations that have been associated with an incidence of various diseases,
including breast cancer. Recent studies demonstrated that the potential links
between physical activity-induced circulating microRNAs (miRNAs) and cancer risk
and progression. Here, we investigated whether altered miRNAs by exercise could
influence breast cancer progression. After primary searching in PubMed and
reviewing the full-text papers, candidate miRNAs altered by exercise in breast
cancer were identified. Analysis of expression profiles and clinical outcomes of
altered miRNAs using The Cancer Genome Atlas datasets showed altered miRNAs
expressions were significantly associated with the patient's prognosis,
whereas prognostic values of each miRNA varied in different stages and subtypes.
In addition, altered miRNAs profiles regulated various target genes and key
signaling pathways in tumorigenesis, including pathways in cancer and the
PI3K-Akt signaling pathway; however, miRNAs regulated the expression of target
genes differently according to tumor stages and subtypes. These results indicate
that circulating miRNAs are promising noninvasive stable biomarkers for early
detection, diagnosis, prognosis, and monitoring the response to clinical
therapies of breast cancer. Moreover, stages and subtype-stratified approaches
for breast cancer progression would be needed to evaluate the prognostic value
of miRNAs for biomarkers and therapeutic targets.