APC and breast cancer: 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.