Epiregulin increases poFUT1 and O‐fucosylation expression through active transcription factor AP‐1. poFUT1 expression was detected by RT‐PCR and Western blot in (A) JAR and (B) HTR‐8/SVneo cells after treatment with epiregulin (0, 10, 50, 100 ng/mL) for 48 h. Immunofluorescence staining of poFUT1 in trophoblast cells (C, D). Green: poFUT1. Red: calnexin. Blue: DAPI. Analysis of levels of phosphorylated and non‐phosphorylated c‐Fos/c‐Jun and poFUT1 by Western blot (E, F) and immunofluorescence (G, H) in trophoblast cells treated with epiregulin (50 ng/mL) for 48 h, anti‐epiregulin antibody and erlotinib (EGFR inhibitor). Lectin blotting and lectin staining (I, J) were used to analyse the effect of poFUT1 on O‐fucosylation biosynthesis in trophoblasts by treatment with epiregulin (50 ng/mL) for 48 h, anti‐epiregulin antibody or erlotinib (EGFR inhibitor). Scale bars: 50 μm. The statistical analysis was shown: *P < .05; **P < .01; ***P < .001. poFUT1, protein O‐fucosyltransferase 1