Hoang, Tuyen

Abstract Patients with melanoma have a high risk of developing brain metastasis, which is associated with a dismal prognosis. During early stages of metastasis development, the blood–brain barrier (BBB) is likely intact, which inhibits sufficient drug delivery into the metastatic lesions. We investigated the ability of the peptide, K16ApoE, to permeabilize the BBB for improved treatment with targeted therapies preclinically. Dynamic contrast enhanced MRI (DCE-MRI) was carried out on NOD/SCID mice to study the therapeutic window of peptide-mediated BBB permeabilization. Further, both in vivo and in vitro assays were used to determine K16ApoE toxicity and to obtain mechanistic insight into its action on the BBB. The therapeutic impact of K16ApoE on metastases was evaluated combined with the mitogen-activated protein kinase pathway inhibitor dabrafenib, targeting BRAF mutated melanoma cells, which is otherwise known not to cross the intact BBB. Our results from the DCE-MRI experiments showed effective K16ApoE-mediated BBB permeabilization lasting for up to 1 hour. Mechanistic studies showed a dose-dependent effect of K16ApoE caused by induction of endocytosis. At concentrations above IC50, the peptide additionally showed nonspecific disturbances on plasma membranes. Combined treatment with K16ApoE and dabrafenib reduced the brain metastatic burden in mice and increased animal survival, and PET/CT showed that the peptide also facilitated the delivery of compounds with molecular weights as large as 150 kDa into the brain. To conclude, we demonstrate a transient permeabilization of the BBB, caused by K16ApoE, that facilitates enhanced drug delivery into the brain. This improves the efficacy of drugs that otherwise do not cross the intact BBB.

Abstract BACKGROUND: Melanoma patients have a high risk of developing brain metastases, which is associated with a poor prognosis. The blood-brain barrier (BBB) inhibits sufficient drug delivery into metastatic lesions. We investigated the ability of a synthetic peptide (K16ApoE) to permeabilize the BBB for more effective drug treatment. METHODS: DCE-MRI was performed to study the therapeutic window of BBB opening facilitated by K16ApoE. In vivoand in vitroassays were used to determine K16ApoE toxicity and also to obtain mechanistic insight into its action on the BBB. The therapeutic impact of K16ApoE on melanoma metastases was determined together with dabrafenib, which is otherwise known not to cross an intact BBB. RESULTS: DCE-MRI exhibited an effective K16ApoE-mediated BBB opening for up to 1h. Mechanistic studies displayed a dose-dependent effect of K16ApoE caused by induction of endocytosis. At higher concentrations, the peptide also showed unspecific disturbances on plasma membranes. Combined treatment with K16ApoE and dabrafenib reduced the brain metastatic burden in mice compared to dabrafenib. We also showed by PET/CT that the peptide facilitated the delivery of compounds up to 150 kDa into the brain. CONCLUSIONS: We demonstrate a transient opening of the BBB, caused by K16ApoE, that facilitates improved drug-delivery into the brain. This improves the efficacy of drugs that otherwise do not cross the intact BBB.