LEF1 and gastrointestinal stromal tumor: However, in GIST T1 and GIST882 cells, even though active and total β-catenin were decreased by ETV4 knockdown and increased by ETV4 overexpression (Figure 3D & 3E, Figure 4A & 4E), β-catenin and LEF1 mRNA were not altered (data not shown).