The invention discloses LRP6 agonizing or antagonizing binding molecules (e.g., antibodies or a Fab fragments), and their use to facilitate or inhibit Wnt pathway signaling, respectively. Said LRP6 agonizing or antagonizing binding molecules can be used to e.g., diagnose, ameliorate the symptoms of, protect against, and treat Wnt signaling disorders associated with aberrantly low or aberrantly high levels of Wnt pathway signaling, respectively. Non-limiting examples of disorders which can be treated associated with aberrant upregulation of Wnt signaling is cancer (e.g., colon cancer). Non-limiting examples of disorders which can be diagnosed, protected against, and treated include cancers, bone disorders (e.g., osteoporosis and osteoarthritis), diabetes, neurodegenerative diseases such as Alzheimer's disease, and fibrotic disorders.
