PMP22 is a direct target of miR-139-5p in GC cells. (A) The putative miR-139-5p binding sites and mutant (Mut) 3'-untranslated region (3'-UTR) PMP22 sequences are shown. The replaced site is underlined. WT, wild type; MT, mutant type. (B-C) Relative luciferase activity was measured in 293T (B) or SGC7901(C) cells cotransfected with WT/MT-PMP22-3'UTR reporter plasmid and miR-139-5p mimic or miR-NC. (D-E) PMP22 mRNA and protein expression levels were measured in SGC7901 or BGC823 cells transfected with miR-NC, miR-139-5p mimic, and miR-139-5p-inhibitor. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as an internal control, **p < 0.01.