An uncleavable form of pro–scatter factor suppresses tumor growth and dissemination in mice
Massimiliano Mazzone, … , Paolo M. Comoglio, Paolo Michieli
Massimiliano Mazzone, … , Paolo M. Comoglio, Paolo Michieli
Published November 15, 2004
Citation Information: J Clin Invest. 2004;114(10):1418-1432. https://doi.org/10.1172/JCI22235.
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Article Oncology

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

Abstract

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.

Authors

Massimiliano Mazzone, Cristina Basilico, Silvia Cavassa, Selma Pennacchietti, Mauro Risio, Luigi Naldini, Paolo M. Comoglio, Paolo Michieli

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Uncleavable SF inhibits both SF-induced Met activation and protease-medi...
Uncleavable SF inhibits both SF-induced Met activation and protease-mediated pro-SF conversion. (A) Met activation assay. A549 cells were stimulated with active SF, pro-SF, or uncleavable SF, and the extent of Met phosphorylation was assessed using anti-phosphotyrosine (anti-pY). The 2 receptor bands correspond to unprocessed Met (p170, in the Golgi) and mature Met (p145, on the cell membrane). The p170/p145 ratio varies depending on the cell line. IP, immunoprecipitation; WB, Western blot. (B) Inhibition of Met phosphorylation. Cells were stimulated with a fixed amount of active SF plus increasing concentrations of pro-SF (left panel) or uncleavable SF (right panel). CTRL, control (unstimulated cells). (C) Inhibition of pro-SF conversion. Myc-tagged pro-SF was incubated with a fixed amount of uPA (upper panel) or FBS (lower panel), plus increasing concentrations of uncleavable SF (above lanes). Pro-SF conversion was assessed by Western blot with anti-Myc. (D) Uncleavable SF forms stable complexes with Met and uPA. A549 cells were exposed to 125I-labeled uncleavable SF (125I-U) in the presence of a cross-linking agent and then were lysed. Protein extracts were immunoprecipitated using anti-Met or anti-uPA, resolved by SDS-PAGE in nonreducing conditions, and visualized by autoradiography.