Proteomic screen reveals a role for CD155 in tumor cell invasion. (a) Mice were inoculated with fixed HT1080 cells. A phage display library was generated from immunoglobulin genes (VH and VL) to generate recombinant scFvs (107 phage). Phage were immunopanned against HT1080 cells, and 2,760 binders were isolated. 595 of the resulting scFvs were further selected as HT1080 surface binders. These surface binders were conjugated to FITC and used to inactivate their protein targets by fluorophore-assisted light inactivation (FALI). The invasiveness of FALI- and control-treated cells was then compared using a high-throughput transwell assay in which cells were challenged to invade through a matrigel-coated 8βM filter towards a serum chemoattactant. Protein targets of candidate scFvs were identified by immunoprecipitation and mass spectrometry. (b) 338 scFvs were screened in triplicate in two independent experiments using the FALI-invasion assay. 6 scFvs caused a significant reduction of HT1080 invasion compared to non-FALI controls (p < 0.01, unpaired t-test and an amplitude change of greater than twice the average standard deviation).