Tcf1−/− mice developing lymphomas show enhanced Wnt activity in the developmental stages in which the tumor cells are blocked (MFI of 1,425 and 1,225 for Wnt-reporter signal in DP and ISP for tumor 1 and 2,123, 2,374, and 1,203 in DP, ISP, and DN3 for tumor 2). The gene discussed is TCF7; the disease is neoplasm.