Vertebrates have two orthologs of Pygo and Lgs: Pygo1 and Pygo2, and BCL9 and BCL9-2/B9L (referred to as B9L), which contribute to efficient β-catenin-dependent transcription in human colorectal cancer cell lines with high Wnt pathway activity.9,18–20 Overexpression of Pygo2, BCL9 and B9L has been reported for various human cancers,18,21–23 and BCL9 appears to have a role in promoting tumour progression.24 This evidence concerns the gene BCL9L and cancer.