Circulating muscle- and inflammation-related microRNAs in breast cancer survivorship: associations with subtype, 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 in circulating microRNAs (miRNAs). In this study, we measured levels of selected muscle- (miR-1, miR-133, miR-208, miR-486, and miR-499) and inflammation-related (miR-21, miR-126, miR-146, and miR-155) miRNAs in breast cancer patients and aimed to explore, using stratified analyses, how their levels relate to cancer subtype, treatment modality, treatment timing, and age. METHODS: We collected 77 plasma samples from pretreatment and post-treatment breast cancer patients and healthy controls. Circulating miRNA levels were measured using quantitative reverse transcription polymerase chain reaction. We compared miRNA levels across different breast cancer subtypes, treatment modalities, treatment timing, and age groups. RESULTS: Pretreatment patients with breast cancer did not show significant changes in the selected miRNAs compared with healthy controls. However, different breast cancer subtypes showed distinct patterns: Luminal A predominantly affected muscle-related miRNAs, and Luminal B affected inflammation-related miRNAs. Cancer treatment, especially surgery and chemotherapy, led to significant changes in miR-21 and miR-486, primarily within the first 91 days after cancer diagnosis. Increases in miR-133 and miR-486 after treatment were mostly seen in patients over 50 years old. CONCLUSION: 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.