Negatively regulates the canonical Wnt signaling in breast cancer cells. Exerts an inhibitory effect on breast cancer growth by inhibiting CTNNB1 stabilization and nucleus translocation, which reduces the activity of Wnt targets (PubMed:29367600). Interacts with CTNNB1(PubMed:29367600). Expressed in normal breast tissues. Down-regulated in breast cancer cells (at protein level) (PubMed:29367600). Belongs to the TMEM170 family.