To further study the relationship between STAT3 and miR-21-5p, and more specifically, to confirm the presence of the STAT3/miR-21-5p positive feedback loop mediated by the down-regulation of STAT3-inhibitor by miR-21-5p in BOS, we evaluated STAT3 mRNA levels in cultured LFs derived from BAL and A549 cells after miR-21-5p inhibition. The gene discussed is STAT3; the disease is Buschke-Ollendorff syndrome.