PTK2 and laryngotracheoesophageal cleft: We previously reported that MUC5AC specifically induces phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 in LC cells [23]; however, in the current study, phosphorylation of FAK (Y397) was decreased as a result of ST6GalNAc‐I KO in the LC cells (Fig. 5B and S4A).