These anti-HER2 scFvs exosomes were further labeled with CFSE (5(6)-Carboxyfluorescein diacetate N-succinimidyl ester) and applied to monitor the targeting delivery ability to cancer cells with different HER2 expression levels, demonstrating that both high-affinity scFv and high receptor expression were parameters positively influencing the selective uptake [239]. This evidence concerns the gene ERBB2 and cancer.