Cellular Localization and Antiproliferative Effect of Peptides Discovered from a Functional Screen of a Retrovirally Delivered Random Peptide Library Original Research Article

We have generated a random peptide library fused to GFP in a retroviral vector system and used this library to screen for peptides inhibiting tumor cell growth. Four unique peptide sequences were isolated that exhibited antiproliferative effects and that specifically localized to the plasma membrane and cytoplasmic granular compartments. Mutational analysis revealed critical residues in each peptide sequence and demonstrated a correlation between peptide subcellular localization and antiproliferative activity. Synthetic analogs of the peptides with poly-lysine internalization sequences, but not loss-of-function mutant peptides, competed for subcellular localization of the parent GFP-fused peptides. The synthetic peptides exhibited dose-dependent antiproliferative effects in tumor cells, while mutant peptides had no effect. Our screening approach using retrovirally expressed intracellular peptides enables identification of unique sequences with a specific biological function and with potential as therapeutics.