Selection of a brain‐seeking subline of breast cancer cells

Abstract

Our lab has shown that MDA‐MB‐231 human breast cancer cells can be isolated from the chick embryo brain after injection into the extra‐embryonic vasculature. Others have demonstrated with nude mice that re‐injection of these cells results in sublines with enhanced capability to metastasize to the brain. It remained unknown whether this was the result of cells specifically targeting the brain, or increased survival in the brain compared to other organs. We transfected MDA‐MB‐231 cells with neomycin resistance and lacZ genes to enable drug‐selection and visualization. This allowed us to quantitate cells which extravasated into the brain and grew as colonies after dissection, dissociation, and drug selection following injection. To determine the sensitivity of the chick embryo system for detecting brain metastases, cells were injected at high and low concentrations. Colonies were detected following injection of as few as 5,000 cells (average of 32.2 colonies/brain). Sublines of cells which had been through the brain up to five times were created. The number of colonies isolated from the brain and liver after re‐injection was compared to that of previously uninjected cells. Re‐injected cells produced a greater number of colonies, suggesting that these cells specifically target the brain. This project was supported by NIH grant 2 P20 RR016472‐07 under the INBRE Program of the National Center for Research Resources.