In mammary gland tumorigenesis, tumorigenesis was enhanced in Apc1638NCtnnb1+/- mice relative to Apc1638NCtnnb1+/+ mice, perhaps because Ctnnb1 functions as a tumor suppressor gene in Apc1638N mammary gland tumors via β-catenin’s role in E-cadherin-dependent tumor suppression [14]. The gene discussed is CTNNB1; the disease is neoplasm.