Discovery and initial characterization of therapeutic anti-hepatocyte growth factor aptamers

C34 Hepatocyte growth factor (HGF) is a pleotropic, heterodimeric protein that specifically recognizes and binds to the extracellular domain of Met, a receptor tyrosine kinase. HGF mediates signaling through the Met receptor which activates multiple cellular pathways resulting in mitogenesis, motogenesis, angiogenesis, and cytoprotection. The function of the HGF:Met axis is important during development, homeostasis, and tissue regeneration. Dysregulation of the HGF:Met pathway has been shown to play a critical role in tumorigenesis and promotes aggressive cellular invasiveness that is linked to tumor metastasis. Mouse and human cell lines that overexpress HGF and/or c-Met become tumorigenic and metastatic in nude mice. Additionally, a wide range of solid and hematological malignancies overexpress HGF and c-Met and their misexpression often correlates with poor prognosis thus interruption of the HGF:c-Met signaling axis represents an attractive target for the treatment of cancer.
 Aptamers are single stranded oligonucleotides with distinct three dimensional structures that bind protein targets with high affinity and specificity and modulate the target protein function. Anti-HGF aptamers were generated through the process of SELEX (Systematic Evolution of Ligands by Exponential enrichment) using nuclease resistant oligonucleotide pools. These aptamers and polyethylene glycol (PEG) conjugated derivatives bind human HGF with high affinity and are potent inhibitors of HGF-dependent signaling in vitro. These aptamers block HGF-mediated proliferation of endothelial and epithelial cells as well as HGF-mediated endothelial cell migration. These promising PEGylated anti-HGF aptamer leads are ready for in vivo pharmacokinetic and efficacy testing in murine xenograft models of human cancer.