Breast cancer is essentially incapable of taking a life as long as it stays in a person’s breasts and doesn’t spread to other areas of the body. When it metastasizes to important organs like the liver, lungs, bones, or brain, however, it can have disastrous consequences. Therefore, it’s important that breast cancer research emphasizes understanding the mechanisms behind metastasis and works to stop it.
For years, scientists have wondered how cancer cells manage to cross the blood-brain barrier and settle in the brain. Even after a patient has been treated and declared cancer-free, the disease sometimes returns in the brain, a complex issue research has been unable to fully understand. A new study, however, may shed some light on the subject.
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The study, conducted by City of Hope researchers and led by neurosurgeon Rahul Jandial, investigated how malignant breast cancer cells in the blood stream could cross over the blood-brain barrier and how they could survive in a foreign environment, where there are many proteins and chemicals that are specific to the brain and do not exist in the rest of the body.
The team believed that perhaps cancer cells exploit their new habitat by assuming similar properties to those of brain cells. As it turns out, they were right.
The researchers found that breast cancer cells are capable of using a “chameleon-like” technique to disguise themselves as neurons or neurotransmitters. This allows them to hide from the immune system and avoid getting killed off during treatment, but it also allows them to cross the blood-brain barrier unseen.
Once in the brain, these chameleon cells begin to form brain tumors, sometimes years after the individual’s initial diagnosis. Because they’re often hard to detect and hard to treat once detected, these tumors are often deadly.
Jandial and his team took samples from brain tumors that had resulted from breast cancer. They learned that the cells were using a chemical that is abundant in the brain, known as GABA, as an alternative fuel source.
GABA is a neurotransmitter that the brain uses for communication between neurons. Metastatic breast cancer cells, in contrast with non-metastatic breast cancer cells, expressed a receptor for GABA and also one for a protein that pulls the transmitter into cells.
Having these extra receptors allowed breast cancer cells to disguise themselves as neurons, acting as “cellular chameleons” in order to spread to the brain.
Further research may look at what enables breast cancer cells to disguise themselves in this way, as well as how to stop this chameleon process so that breast cancer cells will have a more difficult time spreading to the brain. But for now, this is an important step forward in understanding the mechanism behind this phenomenon.