Our results showed that: (1) The expression of miR-139-5p is downregulated in gastric cancer tissues and cancer lines (Fig. 1); (2) miR-139-5p inhibits GC cell proliferation in vitro (Fig. 2); (3) PMP22 is a direct target of miR-139-5p in GC cells (Fig. 3); (4) Overexpression of PMP22 ablates the inhibitory effects of miR-139-5p in GC cells (Fig. 4); (5) MiR-139-5p represses PMP22 by inhibiting the NF-κB pathway (Fig. 5), and (6) miR-139-5p suppresses tumorigenicity in vivo in nude mice (Fig. 6). The gene discussed is NFKB1; the disease is gastric cancer.