CLU and gastric adenocarcinoma: The neck_2 cluster expressed several genes associated with a type of gastric adenocarcinoma–associated metaplasia called spasmolytic polypeptide-expressing metaplasia (SPEM; refs. 21–23), including gastrokine Gkn3, the chloride channel Cftr, clusterin (Clu), Wfcd2 (HE4), the cell surface glycoprotein Cd44, and the water channel protein Aqp5, but had low expression of the SPEM markers Mal2 (a proteolipid family member) and the non-coding RNA Xist.