Abstract 4528: Characterization of changes in passive permeability and drug uptake at the blood-tumor barrier in four preclinical models of brain metastases of breast cancer
Authors: Mohammad Afroz Shareef , Adkins Chris E. , Mittapalli Rajendar K. , Terrell-Hall Tori B. , Nounou Mohamed Ismail , Lockman Paul R. 
Published: August 2015

Background: Brain metastasis of breast cancer remain a challenging consequence of advanced breast cancer. To effectively treat brain metastases with anticancer agents, drugs must cross blood-brain barrier (BBB) and or blood-tumor barrier (BTB) sufficiently to provide adequate concentrations of drug. When metastasis develop, BBB anatomy changes that allows an increase in permeability of the vasculature in the tumor region. It has been shown that uptake and efficacy of chemotherapeutic agents significantly correlates to increased permeability in BTB vasculature. Therefore, it is critical to measure permeability changes when characterizing metastasis models. With the advent of multiple new preclinical models of brain metastases, where cells invade CNS from blood stream, we set out to characterize passive permeability alterations and survival in multiple preclinical models of brain metastases of breast cancer.

Methods: After intracardiac injection of different cells (JimT, 4T1, MDA-MB-231BR HER2+ and MDA-MB-231BR), metastases were allowed to develop until neurologic symptoms appeared (12-70 days). Animals were then injected with IV bolus dose of passive permeability markers 14C-AIB (104 Da) and 3kDa Texas Red dextran (TRD3k) 10 minutes prior to euthanasia. After euthanasia brain sample were harvested, sectioned and analyzed for quantification of radioactivity.

Results: Passive permeability changes in 4T1 metastatic lesions ranged from 1.25 fold to ∼13 fold over normal brain (mean was 3.59 + 1.9; SD) for 14C-AIB, and 1.0 to 7.6 fold (mean was 2.6 + 0.05; SD) for TRD3k. Permeability changes in JimT metastatic lesions ranged from 1 to ∼6 fold over normal brain (mean was 2.22 + 0.69; SD) for 14C-AIB and 1.0 to 7.6 fold (mean was 1.45 + 0.31; SD) for passive diffusion marker TRD3k. MDA-MB-231BR-HER2+ model had much higher permeability values for both 14C-AIB (1.5-34 fold; mean 7.10 + 6.2; SD) and for TRD3k (1.1-10 fold; mean 1.88 + 1.3; SD). For MDA-MB-231Br model permeability changes with 14C-AIB ranged 1.0 -∼19-fold above normal brain with a mean of 2.55 ± 2.0. The BTB permeability to TRD3k ranged from 0.8 to 4.0-fold with mean of 1.74 ± 1.2 (SD). Overall survival was shortest with 4T1 cell line (mean was 14 days) and longest was with MDA-MB-231Br (mean was 35.5 days).

Conclusions: Passive permeability is characterized in four novel breast cancer preclinical models which preferentially seed brain resulting in brain metastases. We have demonstrated that there are differences in passive permeability between each model and there are differences in overall survival and the size of lesions. Increased permeability of the vasculature of CNS tumors is critically important for both diagnosis and treatment.

Citation Format: Afroz Shareef Mohammad, Chris E. Adkins, Rajendar K. Mittapalli, Tori B. Terrell-Hall, Mohamed Ismail Nounou, Paul R. Lockman. Characterization of changes in passive permeability and drug uptake at the blood-tumor barrier in four preclinical models of brain metastases of breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4528. doi:10.1158/1538-7445.AM2015-4528