The neu gene is known to encode a PTK-activity-bearing phosphoprotein which is one of the homologous proteins of epidermal growth factor receptor (EGFR). Amplification and (or) overexpression of neu gene have been found in various human cancers recently. Some protein factors and chemical agents can suppress neu gene transcription or reduce the PTK activity of p185^neu, resulting in the inhibition of metastasis and proliferation of cancer cells with neu overexpression.