Poster Sessions

CANCER-29

Fabiola Cecchi

F. Cecchi, D. Pajalunga, D. Rabe, B. Peruzzi, A. Fowler, N. MacDonald, D. Blackman, S. Stahl, A. Byrd

A Hepatocyte Growth Factor Antagonist Engineered by Targeted Disruption of Heparan Sulfate Binding

Hepatocyte growth factor (HGF) signaling is critical from embryogenesis through adulthood but is subverted in many forms of cancer. HGF binds to the receptor tyrosine kinase Met and to cell-surface heparan sulfate (HS) proteoglycans via distinct domains within HGF. HGF/NK1 is a naturally occurring truncated HGF isoform consisting of the amino-terminal (N) and first kringle (K1) domains, and stimulates all major HGF-associated biological activities. Within NK1, the N domain binds HS, while K1 contains Met binding residues. We engineered opposite charge mutations at critical HS binding residues in the N domain of NK1 to define the role of HGF-HS interactions in HGF biological activities. Combined mutation at three sites (NK1/3M) severely disrupted HS binding and growth factor-stimulated cell motility and proliferation. Because these mutations did not affect Met binding, NK1/3M also antagonized biological activities driven by wild type NK1 or HGF. Indeed, when tumor cell lines with autocrine HGF-driven growth were transfected with plasmids encoding 3M and engrafted into mice, tumor growth rates were dramatically suppressed. Our results illustrate the importance of HS for HGF/Met signaling and reveal a strategy for competitive antagonist design that may be applicable to other HS binding growth fact