**5.4 Potential role of plant miRNAs in breast cancer**

According to the potential function of plant miRNAs, the authors sought to clarify the influence of exogenous molecules on tissues outside the GI tract. By sequencing serum and tumor tissue samples from stage II and III breast cancer patients, plant miR159 was detected up to six times more frequently than plant miRNAs. The results showed a higher abundance of miRNA in healthy patients than in breast cancer (BC) patients and patients with metastasis. Therefore, it was proposed that miR159 might influence breast cancer progression. By transfecting cells containing miR159 isolated from patient serum, they had the ability to reduce proliferation in BC cells. To identify miR159 target genes they used three independent methods: computational prediction, RNA-induced silencing, and sequencing. All three methods identified three potential target genes: transcription factor 7 (TCF7), nuclear receptor coactivator 6 (NCOA6), and engrailed homeobox 2 (EN2). Of which the TCF7 gene belongs to a family of transcription factors of the Wnt signaling pathway, which is overexpressed in breast cancer. Finally, the authors report that mice fed with MIR159 showed a significant reduction of TCF7 and MYC expression in their tumors with decreased tumor cell proliferation, reduced tumor growth, and increased apoptosis, providing important information on kingdom interactions for the prevention and treatment of various human diseases [39].
