A gene that is a modulator of tumor growth and metastasis in certain cancer types is provided. SCC-112 (about 150 kDa) and/or a mutant form of SCC-112 (about 65 kDa) is a tumor suppressor molecule. This gene and corresponding polypeptide have diagnostic and therapeutic application for detecting and treating cancers that involve expression of SCC-112 such as breast and kidney cancers.