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. This evidence concerns the gene SLC40A1 and breast cancer.