Cascade‐Amplifying Synergistic Therapy for Intracranial Glioma via Endogenous Reactive Oxygen Species‐Triggered “All‐in‐One” Nanoplatform

Abstract

Targeted delivery of drug-loaded nanoparticles to brain tumors is exceptionally difficult due to the blood-brain barrier (BBB). In addition, several chemotherapeutic drugs induce autophagy, which protects the cells from apoptosis and mitigates the therapeutic effect. A novel "all-in-one" nanoparticles (AMPTL) consisting of endogenous reactive oxygen species-cleavable thioketal linkers conjugated to paclitaxel (PTX) and autophagy inhibitor 3-methyladenine, and angiopep-2 peptide-modified DSPE-PEG 2K is developed. AMPTL inhibits autophagy in the C6 glioma cells, as indicated by fewer autophagic vesicles, lower LC3-II expression and accumulation of SQSTM1/ P62, and significantly upregulates p53 and the pro-apoptotic Bax and cleaved caspase-3 proteins. In addition, AMPTL treatment induces cell cycle arrest at the G2/M phase. Thus, inhibition of autophagy in the AMPTL-treated glioma cells sensitizes them to PTX-induced cell cycle arrest and apoptosis. Furthermore, focused pulse ultrasound and microbubbles enhances the delivery of AMPTL to intracranial glioma tissues by reversibly opening the BBB, which significantly inhibits xenograft growth and markedly improves survival rates of the tumor-bearing mice. Taken together, combining non-invasive BBB opening with autophagy inhibitors and chemotherapeutic drugs can achieve cascade-amplifying synergistic therapeutic effects against glioma.

Low-Intensity Focused Ultrasound Technique in Glioblastoma Multiforme Treatment

“…With the use of optimal parameters, these procedures have been shown to be well tolerated in various experiments using both mice and rat models bearing glioblastoma, with no toxicity ( 53 , 59 , 63 , 66 , 70 ). There was no evidence of hematological toxicity, spleen damage, liver, renal, and myocardial dysfunction where major blood components (RBC, WBC, and platelets) stayed within normal ranges ( 38 , 62 , 69 ). Results were similar both in the short term (4 h) and long term (14 days) ( 66 ).…”

“…This can happen due to various mechanisms on the molecular level proposed by diverse preclinical studies such as disruption of TJs, increase in trans-endothelial fenestrations, and increased formation of caveolae ( 8 , 19 , 37 ). Application of LIFU+MBs has been shown to regulate several TJ integrated adhesion molecules such as claudin-1, claudin-5, occludin, and ZO-1 ( 31 , 38 ). Another possible explanation is that substances, such as α2-macroglobulin, are released by the NVU after LIFU+MBs to protect its integrity whereby BBB/BTB is further disrupted ( 39 ).…”

“…Besides, there is also a decrease in JAM-A, which is noted after LIFU+MBs mediated BBB/BTB disruption ( 30 ). These changes can be observed as early as 10-15 min following the procedure which increases as time passes by ( 47 , 59 , 77 , 93 ) showing a prolonged exposure ( 77 ), as well as retention and diffusion in targeted areas ( 38 , 54 , 71 , 74 ), which is independent of the drug concentration ( 77 ). This elevated level of drug in sonicated tumors could still be seen later, even when the drug concentration in plasma has decreased ( 47 ).…”

“…Motor coordination and cerebellar functions were unaffected as well ( 53 , 66 ) with normal behavior post-treatment ( 68 , 94 ). On histologic analysis, if the acoustic pressure was not too high (i.e., optimum), sonicated brain and non-sonicated brain, and glioblastoma tissue appears to be similar ( 47 , 59 , 74 ) showing no signs of pathological changes ( 30 , 63 , 69 , 70 , 92 , 94 ), including parenchymal injury, necrosis, or micro hemorrhage ( 38 , 53 ). There was no damage in brain tissue regardless of high or low doses of therapeutics delivered compared to controls ( 38 ).…”

“…Similar results (40% increase in survival) were observed after the delivery of liposomes containing PTX and anti-PD-1 antibody, which initiated ROS generation by ultrasound irradiation at glioblastoma sites ( 94 ). Delivery of AMPTL (NPs containing ROS and PTX with an autophagy inhibitor modified with angiopep-2 peptide) with LIFU+MBs showed significant inhibition of tumor growth and extended survival from 28 days to 50 days compared with controls with the slowest weight loss ( 38 ). After the delivery of Cabazitaxel with LIFU+MBs, tumor growth was significantly slowed, where its size was about one-third compared to the controls after 3 weeks ( 65 ).…”