Nevertheless, poorly differentiated carcinoma was observed in Slc26a9fl/fl/Atp4b-Cre mice at 18 months (Fig. 3, c), which was accompanied by loss of MUC5AC and Claudin 18.2 expression compared with that in Slc26a9fl/fl littermates (Fig. 3, d). This evidence concerns the gene MUC5AC and carcinoma.