The invention encompasses polypeptides, polynucleotides, and antibodies, for Artemin and related ligands, including Persephin (PSPN). The invention also encompasses expression vectors and host cells for producing these polypeptides, polynucleotides, or antibodies. The invention further encompasses diagnostics and therapeutics, especially for cancer, and particularly breast cancer, colon cancer, prostate cancer, endometrial cancer, lung cancer, stomach cancer, liver cancer, and others, comprising one or more of the disclosed polypeptides, polynucleotides, antibodies, expression vectors, host cells, or compositions thereof. Particularly encompasses are inhibitors of Artemin and/or related ligands, and uses for these inhibitors.