Construction and characterization of a fusion protein which mediates cytolysis of her2-overexpressing tumor cells by type i fc gamma receptor (fcjri)-expressing effector cells

J. Boldstein, R. F. Grazlano, K. Sundarapandiyan, R. Lupu, Y. Dbo

Research output: Contribution to journalArticle

Abstract

Heregulin (HRG) is a ligand for the HER3 and HER4 molecules. Both of these receptors may form heterodimers with HER2, a molecule which is overexpressed in some breast cancer cells. The affinity of HRG for HER3 and HER4 dramatically increases when these molecules form heterodimers with HER2. We have constructed by genetic means a bispeciflc reagent which binds to the HER3 and HER4 molecules and to the high affinity receptor for the Fc portion of IgG, FcrRI, which is a cytotoxic trigger molecule expressed by myeloid cells. For this construction, genomic DNA encoding the Fd fragment of humanized anti-FcrRI mAb, H22, which binds FcyRI at an epitope that is distinct from the Fc binding site, was fused to cDNA encoding the EGF domain of the β2 form of HRG. The resulting H22Fd-HRG expressing vector was transfected into a myeloma cell line which was previously transfected with a vector containing DNA encoding the H22 kappa light chain. The resultant fusion protein was expressed predominantly as H22Fab-HRG monomers, even though there exists a free Cys residue in the hinge region of the H22 Fab component. Using flow cytometry It was found that this molecule was able to bind to the HER2 overexpresslng tumor cell line, SKBR-3, as well as to FcrRI-expressIng cells. This H22-HRG fusion protein can inhibit the growth of SKBR-3 tumor cells and can mediate fusion protein dependent cytotoxicity of these cells in the presence of FoyRI-bearlng cytotoxic effector cells. These results suggest that this fusion protein could mediate anti-tumor cytotoxic activities under physiologic conditions, and that it may have therapeutic utility.

Original languageEnglish (US)
Pages (from-to)A1350
JournalFASEB Journal
Volume10
Issue number6
StatePublished - Dec 1 1996

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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