Abstract 4680: Intracranial breast cancer brain metastases (BCBM) models - stereotactic vs. intracarotid inoculation
Authors: Cold Sigrid , Braig Moritz , Engel Trine Bjoernbo , Alfsen Maria Zeiler , Kristiansen Maria Nikoline , Kristensen Lotte Kellemann , Kjaer Andreas , Nielsen Carsten Haagen 
Published: April 2023

Abstract
Breast cancer is the most prevalent cancer in women worldwide. 30% of breast cancer patients develops metastases at distant organs, with 10-20% of these patients developing brain metastases. The median survival time for patients with brain metastases is only 7.2 months and there is an urgent need for effective therapies. Development of novel therapies relies on good translational animal models. Subcutaneous tumors are technically easy and highly reproducible but lacks the natural tumor environment and the impact of the blood brain barrier. Breast cancer brain metastasis (BCBM) models are most often established by stereotactic intracranial inoculation. However, this leads to formation of single tumors and does not take the extravasation and seeding part of the metastatic cascade into account and resembles primary tumors to a larger extend. Intracarotid inoculation incorporates extravasation and seeding of micro metastases making it a better suited translational animal model for BCBM. A panel of intracranial BCBM was established through stereotactic and intracarotid inoculation of breast cancer cell lines with high survival and take rates (&gt;85%). The panel included the ST941 PDX model, an estrogen receptor positive model harbouring the ESR1-Y537S mutation and exhibiting resistance to fulvestrant. The panel also included the triple negative breast cancer cell line MDA-MB-231 as well as HER2+ models. Tumor establishment and progression were evaluated using bioluminescence and magnetic resonance imaging (MRI). Whole brain and tumors were isolated, and paraffin embedded for histological evaluation of tumor establishment, invasiveness, and infiltration. Intracranial tumor establishment was evident early after inoculation using bioluminescence imaging and tumor growth was later confirmed by MRI. Tumor growth rate were dependent on inoculation method with rapid tumor growth observed with stereotactic inoculation. While stereotactic inoculation led to single tumor establishment with defined tumor borders, intracarotid inoculation led to micro seeding with multiple foci established throughout the brain. At early timepoints, the metastases consisted of &lt;150 cells per metastases, but at later timepoints larger metastases were formed. Tumor infiltration was more diffused in brains with multiple metastases and the blood brain barrier integrity was different when comparing the models and inoculation methods. A panel of BCBM was successfully established using both stereotactic and intracarotid inoculation. While bioluminescence allowed the earliest tumor imaging, MRI provided additional information on tumor establishment such as location, numbers, and blood brain barrier permeability. The models showed varying tumor establishment, infiltration, and marker expression. The established panel can be used as a platform for testing novel anti-cancer therapies targeting BCBM.
Citation Format: Sigrid Cold, Moritz Braig, Trine Bjoernbo Engel, Maria Zeiler Alfsen, Maria Nikoline Kristiansen, Lotte Kellemann Kristensen, Andreas Kjaer, Carsten Haagen Nielsen. Intracranial breast cancer brain metastases (BCBM) models - stereotactic vs. intracarotid inoculation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4680.