Fig. 5. Tryptase is taken up into human melanoma cells as cargo of melanoma cell-derived exosomes.

a Human tryptase was incubated with heparin, cDNA or purified melanoma-derived exosomes as indicated, followed by assessment of enzymatic activity using a chromogenic substrate (S-2288). Note that the symbols representing samples without tryptase (Heparin, cDNA, exosomes) are superimposed and show no detectable activity against S-2288. b Purified melanoma cell-derived exosomes (~4 × 10⁷ exosomes) were either non-treated or digested with DNAse and then incubated with or without tryptase (as indicated), followed by washing and detection of bound tryptase by Western blot analysis. Purified tryptase was included as positive control (left lane). c Purified melanoma cell-derived exosomes (~2.5 × 10⁷ exosomes) were labeled with WGA, incubated with purified tryptase, washed and then incubated with human melanoma cells for 6 h, followed by confocal microscopy analysis. Note the presence of tryptase:WGA double-positive exosomes in the nucleus and cytoplasm of the melanoma cells