Various molecules involved in iron homeostasis and tumorigenesis have been detected in the tissue and gut metagenomes of breast cancer patients, including signal activator of transcription 5 (STAT5), STAT3, bone morphogenetic protein 6 (BMP6), cluster of differentiation 74 (CD74), TFR, inhibin alpha (INHA), iron exporter ferroportin (FPN), ferritin heavy chain (FHC) and ferritin light chain (FTL).121. Here, BMP6 is linked to breast cancer.