Cell-penetrating peptides with intracellular actin-remodeling activity in malignant fibroblasts.

Cell-penetrating peptides can cross cell membranes and are commonly seen as biologically inert molecules. However, we found that some cell-penetrating peptides could remodel actin cytoskeleton in oncogene-transformed NIH3T3/EWS-Fli cells. These cells have profound actin disorganization related to their tumoral transformation. These arginine- and/or tryptophan-rich peptides could cross cell membrane and induce stress fiber formation in these malignant cells, whereas they had no perceptible effect in non-tumoral fibroblasts. In addition, motility (migration speed, random motility coefficient, wound healing) of the tumor cells could be decreased by the cell-permeant peptides. Although the peptides differently influenced actin polymerization in vitro, they could directly bind monomeric actin as determined by NMR and calorimetry studies. Therefore, cell-penetrating peptides might interact with intracellular protein partners, such as actin. In addition, the fact that they could reverse the tumoral phenotype is of interest for therapeutic purposes.