Since β-catenin is critical for tumor growth in the DMBA/TPA model of skin SCC, and both nuclear β-catenin and Tcf7l1 mRNA are upregulated in papillomas (Malanchi et al., 2008), it was thought that TCF7L1’s tumor-promoting role might depend on its binding to β-catenin in the canonical WNT signaling pathway. The gene discussed is TCF7L1; the disease is papilloma.