Notably, the β-catenin binding-deficient TCF7L1ΔN mutant increased tumor size similarly to full-length TCF7L1, whereas the Groucho/TLE corepressor binding-deficient TCF7L1ΔG did not significantly increase the tumor size (despite having a 100 fold stronger activity on WNT reporter in vitro). The gene discussed is TCF7L1; the disease is neoplasm.