HER-2/neu （erbB-2） encodes an 185-kDa orphan receptor tyrosine kinase that is constitutively active as a dimer and displays potent oncogenic activity when overexpressed. Herstatin， as the product of alternative HER-2 transcript， retains intron 8.
The herstatin mRNA is expressed in normal human fetal kidney and liver， but is at reduced levels relative to p185HER-2 mRNA in carcinoma cells that contain an amplified HER-2 gene. Herstatin appears to be an inhibitor of p185HER-2， because it disrupts dimers， reduces tyrosine phosphorylation of p185， and inhibits the anchorage-independent growth of transformed cells that overexpress HER-2.
