Circulating muscle- and inflammation-related microRNAs in breast cancer survivorship: associations with treatment, timing, and age

Purpose Cancer and its treatments often lead to inflammation, muscle problems, and ongoing loss of physical function, as reflected by alterations of circulating microRNAs. In this study, we measured levels of selected muscle- (miR-1, miR-133, miR-208, miR-486, miR-499) and inflammation-related (miR-21, miR-126, miR-146, miR-155) miRNAs in breast cancer patients, and aimed to explore, using a stratifies analysis, how their levels relate to cancer subtype, treatment type, treatment duration, and age. Methods We collected 77 plasma samples from pre-treated and post-treated breast cancer patients, and healthy controls. Circulating miRNA levels were measured using quantitative RT-PCR. We compared miRNA levels across different breast cancer subtypes, treatment types, treatment duration, and age groups. Results Pre-treated breast cancer patients did not show significant changes in the selected miRNAs compared to healthy controls. However, different breast cancer subtypes showed distinct patterns: Luminal A predominantly affected muscle-related miRNAs, and Luminal B inflammation-related miRNAs. Cancer treatment, especially surgery and chemotherapy, led to significant changes in miR-21 and miR-486, mainly within the first 91 days after diagnosis. Increases in miR-133 and miR-486 after treatment were mostly seen in patients over 50 years old. Conclusions Circulating muscle- and inflammation-related miRNAs display distinct expression patterns associated with breast cancer subtype and treatment. Specifically, miR-21, miR-133, and miR-486 demonstrate sensitivity to cancer treatment exposure, timing, and patient age. Implications for cancer survivors: Our findings support further investigation of these miRNAs as candidate biomarkers in prospective studies, including their potential use for monitoring physiological responses during exercise-based cancer rehabilitation.