(A) Confocal microscopy of FITC-peptide uptake by MDA-MB-231 tumor cells. Images show uptake of peptides 2c, 10c and 14c. Nuclei are shown in blue (DAPI) while FITC-conjugated peptides are shown in green. Prior to addition of dye-conjugated peptides, cells were incubated with IgG, anti-RHAMM or anti-CD44 antibodies. Cells, which received no antibody treatment (no blocking) or cells treated with non-immune IgG served as controls. A reduction in fluorescence (FITC channel) was observed when cells are blocked with anti-RHAMM antibodies while no significant decrease in FITC signal was observed for cells treated with anti-CD44 antibodies. (B) Uptake in MDA-MB-231 tumor cells was quantified using ImageJ software, as described in Experimental Procedures. Values are mean fluorescence ± S.E.M., and data were analyzed using one-way ANOVA. Significant differences (p < 0.05) are marked by asterisks.