Lin et al (2000) also showed that nuclear and/or cytoplasmic staining of β-catenin correlated with elevated cyclin D1, which is one of the known targets of β-catenin/TCF transcription. However, mutation of APC, CTNNB1 or AXIN is rare in breast cancer, and thus the mechanism of Wnt signal activation in this disease is not fully understood. The gene discussed is HNF4A; the disease is breast cancer.