Angulin-1/LSR inhibition transiently disrupts the blood-tumor barrier to enhance doxil permeability and impair malignant glioma progression

Abstract The blood-tumor barrier (BTB) prevents effective central nervous system (CNS) drug delivery, especially in malignant gliomas. Brain endothelium predominates the BTB and connects through bicellular and tricellular tight junctions (TJ). Angulin-1/LSR, is a highly expressed endothelial tricellular TJ. Our studies explore the role of Angubindin-1, an Angulin-1/LSR binder, to disrupt tricellular TJ integrity, increase drug entry and hamper glioma progression. Using rat brain endothelial cells (RBMVEC) we tracked Angulin-1/LSR localization and expression to the membrane; binding tightest to Angubindin-1 2-8 hours post-treatment (p < 0.05). Angubindin-1 dose-dependently reduced bicellular and tricellular TJs 1-4 hours post treatment (p < 0.05), returning to baseline by 24 hours (p < 0.05). In human and rat-derived glioma cells, Angubindin-1 transiently reduced Angulin-1/LSR expression between 2-8 hours (p < 0.05), with return to baseline by 24 hours (p < 0.001). Silenced Angulin-1/LSR expression on endothelium resulted in decreased mRNA levels of bicellular (occludin, claudin-5, ZO-1) and tricellular (tricellulin/MARVELD2, angulin-1/LSR) TJs compared to control (p < 0.01). Angubindin-1 treatment also inhibited efflux transporter P-gp in both RBMVECs and glioma cells with high P-gp expression only. Orthotopic rat glioma models were treated with Doxil (3 mg/kg), Angubindin-1 (10 mg/kg), or combination to evaluate BTB permeability/drug accumulation, and overall survival. Combination therapy enhanced Doxil tumor accumulation by 20% (p < 0.001), reduced tumor volume by day 14 (77.5% vs. 81.6%, p < 0.05), and significantly extended survival compared to Doxil alone (24 days vs. 18 days, p < 0.0001). These findings demonstrate the effects of tricellular tight junction inhibition on disrupting the BTB, enhancing CNS drug delivery, and improving rodent glioma survival. Significance This study demonstrates that Angubindin-1, a targeted modulator of tricellular tight junction protein Angulin-1/LSR, transiently disrupts BTB integrity to enhance chemotherapy delivery and prolong survival in glioma-bearing rats. Graphical AbstractAngubindin-1 targets both bicellular tight junctions and the tricellular tight junction protein, Angulin-1/LSR, in brain endothelial and glioma cells leading to transient disruption of the blood–tumor barrier (BTB) and inhibition of P-glycoprotein towards enhanced Doxil penetration and reduced tumor burden. Competing Interest Statement The authors have declared no competing interest. Footnotes The authors declare no potential conflicts of interest. Funding: This research was supported by the Intramural Research Program of the National Institutes of Health (NIH). The contributions of the NIH author(s) were made as part of their official duties as NIH federal employees, are in compliance with agency policy requirements, and are considered Works of the United States Government. However, the findings and conclusions presented in this paper are those of the author(s) and do not necessarily reflect the views of the NIH or the U.S. Department of Health and Human Services. This project has been funded in whole or in part with Federal funds from the National Cancer Institute, National Institute of Health, under Contract No. HHSN26120150003I. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.