The chain of events that explains calcitonin receptor (CTR)-stimulated invasion and metastasis of prostate cancer cells was identified. The CTR-stimulated events depend on the interaction of CTR with the PDZ3 domain of ZO-1. Small peptides and small molecules were identified that inhibit this interaction. The small inhibitory peptides were synthesized and can be used to attenuate or inhibit metastasis in solid cancer tumors.