Tyrosine phosphorylation of maspin in normal mammary epithelia and breast cancer cells

Valerie A. Odero-Marah, Zhila Khalkhali-Ellis, Galen B. Schneider, Elisabeth A. Seftor, Richard E.B. Seftor, John G. Koland, Mary J.C. Hendrix

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Maspin is a 42 kDa tumor suppressor protein that belongs to the serine protease inhibitor (serpin) family. It inhibits cell motility and invasion in vitro, and tumor growth and metastasis in nude mice; however, maspin's molecular mechanism of action has remained elusive. Maspin contains several tyrosine residues and we hypothesized that phosphorylation of maspin could play a role in its biological function. Our study reveals that maspin is phosphorylated on tyrosine moiety(ies) in normal mammary epithelial cells endogenously expressing maspin. In addition, transfection of the maspin gene, using either a stable or inducible system into maspin-deficient breast cancer cell lines, yields a protein product that is phosphorylated on tyrosine residue(s). Furthermore, recombinant maspin protein can be tyrosine-phosphorylated by the kinase domain from the epidermal growth factor receptor in vitro. These novel observations suggest that maspin, which deviates from the classical serpin, may be an important signal transduction molecule in its phosphorylated form.

Original languageEnglish (US)
Pages (from-to)800-805
Number of pages6
JournalBiochemical and Biophysical Research Communications
Issue number4
StatePublished - 2002


  • Breast cancer
  • EGF receptor kinase
  • Ecdysone-inducible system
  • Maspin
  • Tyrosine phosphorylation

ASJC Scopus subject areas

  • Molecular Biology
  • Biophysics
  • Biochemistry
  • Cell Biology


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