Met, the high affinity receptor for Hepatocyte Growth Factor (HGF), is one of the most frequently activated tyrosine kinases in human cancer and a validated target for cancer therapy. We previously developed a mouse monoclonal antibody directed against the extracellular portion of Met (DN-30) that induces Met proteolytic cleavage (receptor "shedding") followed by proteasome-mediated receptor degradation. This translates into inhibition of HGF/Met-mediated biological activities. However, DN-30 binding to Met also results in partial activation of the Met kinase due to antibody-mediated receptor homo-dimerization. To safely harness the therapeutic potential of DN-30, its shedding activity must be disassociated from its agonistic activity. Here we show that the DN-30 Fab fragment (a) maintains high affinity Met binding, (b) elicits efficient receptor shedding and down-regulation, (c) without promoting kinase activation. In Met-addicted tumor cell lines, DN-30 Fab (d) displays potent cytostatic and cytotoxic activity in a dose-dependent fashion. DN-30 Fab also (e) inhibits anchorage-independent growth of several tumor cell lines. In mouse tumorigenesis assays using Met-addicted carcinoma cells, (f) intra-tumor administration of DN-30 Fab or systemic delivery of a chemically stabilized form of the same molecule results in reduction of Met phosphorylation and inhibition of tumor growth. These data provide proof-of-concept that monovalency unleashes the full therapeutic potential of the DN-30 antibody and point at DN-30 Fab as a promising tool for Met-targeted therapy.
Monovalency unleashes the full therapeutic potential of the DN-30 anti-Met antibody
PACCHIANA, Giovanni;STELLA, Maria Cristina;COMOGLIO, Paolo;MICHIELI, Paolo;VIGNA, Elisa
2010-01-01
Abstract
Met, the high affinity receptor for Hepatocyte Growth Factor (HGF), is one of the most frequently activated tyrosine kinases in human cancer and a validated target for cancer therapy. We previously developed a mouse monoclonal antibody directed against the extracellular portion of Met (DN-30) that induces Met proteolytic cleavage (receptor "shedding") followed by proteasome-mediated receptor degradation. This translates into inhibition of HGF/Met-mediated biological activities. However, DN-30 binding to Met also results in partial activation of the Met kinase due to antibody-mediated receptor homo-dimerization. To safely harness the therapeutic potential of DN-30, its shedding activity must be disassociated from its agonistic activity. Here we show that the DN-30 Fab fragment (a) maintains high affinity Met binding, (b) elicits efficient receptor shedding and down-regulation, (c) without promoting kinase activation. In Met-addicted tumor cell lines, DN-30 Fab (d) displays potent cytostatic and cytotoxic activity in a dose-dependent fashion. DN-30 Fab also (e) inhibits anchorage-independent growth of several tumor cell lines. In mouse tumorigenesis assays using Met-addicted carcinoma cells, (f) intra-tumor administration of DN-30 Fab or systemic delivery of a chemically stabilized form of the same molecule results in reduction of Met phosphorylation and inhibition of tumor growth. These data provide proof-of-concept that monovalency unleashes the full therapeutic potential of the DN-30 antibody and point at DN-30 Fab as a promising tool for Met-targeted therapy.
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