Targeting the tumor and its microenvironment by a dual-function decoy Met receptor.

Met, the receptor for hepatocyte growth factor (HGF), is activated in human cancer by both ligand-dependent and -independent mechanisms. We engineered a soluble Met receptor (decoy Met) that interferes with both HGF binding to Met and Met homodimerization. By lentiviral vector technology, we achieved local or systemic delivery of decoy Met in mice. We provide evidence that in vivo expression of decoy Met (1) inhibits tumor cell proliferation and survival in a variety of human xenografts, (2) impairs tumor angiogenesis by preventing host vessel arborization, (3) suppresses or prevents the formation of spontaneous metastases, and (4) synergizes with radiotherapy in inducing tumor regression, without (5) affecting housekeeping physiological functions in the adult animal.

An uncleavable form of pro-scatter factor suppresses tumor growth and dissemination in mice.

Scatter factor (SF), also known as hepatocyte growth factor, is ubiquitously present in the extracellular matrix of tissues in the form of an inactive precursor (pro-SF). In order to acquire biological activity, pro-SF must be cleaved by specific proteases present on the cell surface. The mature form of SF controls invasive cues in both physiological and pathological processes through activation of its receptor, the Met tyrosine kinase. By substituting a single amino acid in the proteolytic site, we engineered an unprocessable form of pro-SF (uncleavable SF). Using lentivirus vector technology, we achieved local or systemic delivery of uncleavable SF in mice. We provide evidence that (a) uncleavable SF inhibits both protease-mediated pro-SF conversion and active SF-induced Met activation; (b) local expression of uncleavable SF in tumors suppresses tumor growth, impairs tumor angiogenesis, and prevents metastatic dissemination; and (c) systemic expression of uncleavable SF dramatically inhibits the growth of transplanted tumors and abolishes the formation of spontaneous metastases without perturbing vital physiological functions. These data show that proteolytic activation of pro-SF is a limiting step in tumor progression, thus suggesting a new strategy for the treatment or prevention of the malignant conversion of neoplastic lesions.

An HGF-MSP chimera disassociates the trophic properties of scatter factors from their pro-invasive activity.

Hepatocyte growth factor (HGF) and macrophage-stimulating protein (MSP) have an intrinsic dual nature: they are trophic cytokines preventing apoptosis on one side and scatter factors promoting invasion on the other. For therapeutic use, their anti-apoptotic activity must be separated from their pro-invasive activity. To this end, we engineered chimeric factors containing selected functional domains of HGF and/or MSP in different combinations, and tested their biological activity. Here we present a chimeric cytokine derived from the alpha-chains of HGF and MSP, named Metron factor 1 for its ability to concomitantly activate the HGF receptor (Met) and the MSP receptor (Ron). We provide evidence that Metron factor 1 prevents apoptosis and stimulates cell proliferation at nanomolar concentrations, but is devoid of any pro-invasive activity. In an in vivo murine model of drug-induced nephrotoxicity, intravenous injection of recombinant Metron factor 1 prevented renal damage and preserved tubular integrity.