Levels of total-, phosphorylated- (Ser552) and active β-catenin (i.e. unphosphorylated at Ser33/Ser37/Thr41) as well as the downstream target gene (c-MYC) were also reduced in RSPO4-expressing tumor cells compared with vector control cells (Fig. 3G and Fig. S3A). Here, RSPO4 is linked to neoplasm.