Brain metastases of breast cancer are thought to increasing in incidence, particuarly among metastatic patients with Her-2+ or triple negative tumors, and confer a dismal prognosis. Our goal is to understand the nature of the blood-tumor barrier (BTB), the endothelial-associated structure that results when the formation of a metastasis disturbs the normal blood-brain barrier (BBB). In initial studies the paracellular permeability of the BTB was tested in experimental brain metastasis model systems in mice, using dyes and drugs. Published collaborative research showed that experimental brain metastases of breast cancer were heterogeneous in their permeability, both within and between metastases in the same brain. While most metastases were permeable as compared to the normal BBB, only 10% exhibited sufficient permeability to enable a cytotoxic response to a systemic drug. Cellular and protein characterization of the BTB Quantitative immunofluorescence of the BTB in three model systems was performed. The relative expression of known BBB components was compared between normal (uninvolved) brain and brain metastases, and also between brain metastases that were either poorly or highly permeable to Texas red dextran. Many consistent alterations were observed between normal brain and the BTB, including endothelial cell size, neuro-inflammation, absence of astrycyte endfeet, increased VEGF, etc. In contrast, few differences were observed between poorly and highly permeable metastases. The relative expression of subpopulations of pericytes was the major difference observed. Highly permeable lesions exhibited an increase in Desmin+ pericytes and a decrease in CD13+ pericytes. This work presents the first description of the BTB. Desmin+ pericytes are one of the first markers of higher brain metastasis permeability. Current research aims to further characterize Desmin+ pericytes and determine their functional contribution to BTB permeability.These data are published in Clin. Cancer Res. 22: 5287-5299, 2016. Molecular characterization of BTB permeability A series of experiments identified molecular alterations correlated with BTB permeability using gene expression analysis. Permeable and impermeable brain metastases were laser capture microdissected from mouse brains and both human (tumor cell) and mouse (brain microenvironment) gene expression determined on microarrays. Most of the gene expression changes correlated with metastasis permeability were from the microenvironment, rather than the tumor cells. The sphingosine-1-phosphate receptor 3 (S1P3) was identified as overexpressed in more permeable metastases. This trend was confirmed at the protein level, and S1P3 expression was localized to astrocytes in the neuro-inflammatory response. Using a S1P3 antagonist and S1PR3 gene knockdown, in vitro TEER assays (modeling the BBB and BTB) have shown that reduced S1P3 expression and function causes altered BTB permeability. In vivo a S1P3 antagonist functionally modulated the permeability of the BTB. This research is published in Nature Comm. 9:2705, 2018. We published experimental brain metastasis data indicating that temozolomide, a first line treatment for primary brain tumors, was 100% effective at preventing brain metastases of 231-BR cells over a two log dose response (Clin. Cancer Res. 20: 2727-2739, 2014). This type of profound prevention has not been previously observed. Given later when brain metastases are already at least partially established, temozolomide was ineffective. Activity was dependent on methylguanine methyltransferase (MGMT). Staining of matched sets of primary breast cancers and resected brain metastases showed poor concordance, but 60% of the brain metastases were low in MGMT. A phase II trial has been developed in the WMB to test the effect of TMZ on preventing brain metastases in patients with 1-5 brain metastases from HER2+ metastatic breast cancer, having only local brain metastasis treatment (SRS or neurosurgery). Patients will be randomized to T-DM1 or T-DM1 + temozolomide, with a primary endpoint of one year freedom from a new brain metastasis ( Identifier: NCT03190967).

National Institute of Health (NIH)
National Cancer Institute (NCI)
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
Application #
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Basic Sciences
Zip Code
Samala, Ramakrishna; Thorsheim, Helen R; Goda, Satyanarayana et al. (2016) Vinorelbine Delivery and Efficacy in the MDA-MB-231BR Preclinical Model of Brain Metastases of Breast Cancer. Pharm Res 33:2904-2919
Lyle, L Tiffany; Lockman, Paul R; Adkins, Chris E et al. (2016) Alterations in Pericyte Subpopulations Are Associated with Elevated Blood-Tumor Barrier Permeability in Experimental Brain Metastasis of Breast Cancer. Clin Cancer Res 22:5287-5299
Steeg, Patricia S; Zimmer, Alexandra S; Gril, Brunilde (2016) Therapeutics for Brain Metastases, Version 3. Clin Cancer Res :
Sartorius, C A; Hanna, C T; Gril, B et al. (2016) Estrogen promotes the brain metastatic colonization of triple negative breast cancer cells via an astrocyte-mediated paracrine mechanism. Oncogene 35:2881-92
Duchnowska, Renata; Jassem, Jacek; Goswami, Chirayu Pankaj et al. (2015) Predicting early brain metastases based on clinicopathological factors and gene expression analysis in advanced HER2-positive breast cancer patients. J Neurooncol 122:205-16
Zhang, Lin; Zhang, Siyuan; Yao, Jun et al. (2015) Microenvironment-induced PTEN loss by exosomal microRNA primes brain metastasis outgrowth. Nature 527:100-104
Morikawa, Aki; Peereboom, David M; Thorsheim, Helen R et al. (2015) Capecitabine and lapatinib uptake in surgically resected brain metastases from metastatic breast cancer patients: a prospective study. Neuro Oncol 17:289-95
Moon, Y W; Rao, G; Kim, J J et al. (2015) LAMC2 enhances the metastatic potential of lung adenocarcinoma. Cell Death Differ 22:1341-52
Woditschka, Stephan; Evans, Lynda; Duchnowska, Renata et al. (2014) DNA double-strand break repair genes and oxidative damage in brain metastasis of breast cancer. J Natl Cancer Inst 106:
McMullin, Ryan P; Wittner, Ben S; Yang, Chuanwei et al. (2014) A BRCA1 deficient-like signature is enriched in breast cancer brain metastases and predicts DNA damage-induced poly (ADP-ribose) polymerase inhibitor sensitivity. Breast Cancer Res 16:R25

Showing the most recent 10 out of 38 publications