Noninvasive methods are needed to study the kinetic properties of viruses in living organisms. Oncolytic viruses are used increasingly for cancer therapy but there is currently no satisfactory way to measure efficiency of tumor transduction, changing levels of viral gene expression or the timing of virus elimination. We therefore generated trackable oncolytic measles viruses expressing inert (nonimmunogenic, nonfunctional and accurately measurable) soluble marker peptides. The marker peptides did not compromise virus replication. Ex vivo and in vivo kinetics of the trackable viruses could be easily followed by measuring the concentrations of virally encoded marker peptides in culture supernatant or in serum. When mice bearing human tumor xenografts were challenged with the trackable viruses, distinct kinetic profiles of marker-gene expression could be correlated with distinct therapeutic outcomes. Oncolytic viruses expressing inert soluble marker polypeptides should greatly facilitate the rational development of effective, individually tailored cancer virotherapy.

Experimental evidence suggests that blocking the interactions between endothelial cells and extracellular matrix (ECM) components may provide a potent and general strategy to inhibit tumor neovascularization. Based on these considerations, we have focused our efforts on laminin, component of the vascular basement membrane of every tumor-associated vessel, which serves an essential role in tube formation. We screened anti-laminin single-chain antibody fragments (scFv) derived from a human phage-display library and identified one that blocks the formation of capillary-like structures in vitro. This scFv inhibits angiogenesis in vivo in the chick embryo chorioallantoic membrane assay and prevents the establishment and growth of subcutaneous tumors in mice, either when administered as bolus protein therapy or when produced locally by gene-modified tumor cells. Our work represents the first demonstration of a direct in vivo therapeutic effect of a single-chain antibody secreted by gene-modified mammalian cells. These results open the way for a new antibody-based gene therapy strategy of cancer.