Cancer cells essentially get integrated into the brain's neural network and flourish with the help of structures that neurons use to communicate with one another
Scientists have a startling discovery that cancer cells can infiltrate into the brain's nerves and feed on them, making cancer difficult to treat, the Nature Reported.
The tumor cells' ability reinforces the significant role of the nervous system in the growth of cancers and open avenues for treating some aggressive tumors.
It was discovered in brain cancers called glioma and in some breast cancers that spread to the brain, according to a trio of studies published in the scientific journal on September 18, 2019. A glioma is a type of tumor that occurs in the brain and spinal cord.
Michelle Monje, a pediatric neuro-oncologist at Stanford University in California and a lead author of one of the studies, said.
The phenomenon was first discovered by Frank Winkler, a neurologist at Heidelberg University in Germany in 2014 while studying communication networks established by cells in some brain tumors.
He and his team discovered synapses – structures that neurons use to communicate with one another – in the dark.
While it was originally assumed to be a random occurrence, in the latest study, researchers found synapses in glioma samples taken from cancer cells, human glioma tumors transplanted into mice and glioma samples taken from there adults.
Simultaneously, Monje and her team discovered synapses between neurons and cells in pediatric gliomas. Both studies confirmed that tumor synapses help cancer cells to flourish.
According to Monje, with the help of tumor synapses, cancer cells tend to weave through the brain, making them hard to remove, rather than forming the usual hard and compact mass.
It also explains why patients typically show few symptoms: Because being reliant upon the brain circuits, the tumor cells do not disrupt them, but essentially get integrated into the brain's neural network, Monje explained.
Besides brain tumors, breast cancer cells in the brain that act like neurons also share the same ability, according to a third paper by Douglas Hanahan, a cancer scientist at the Swiss Institute for Experimental Cancer Research in Lausanne.
Hanahan's team found deadly breast cancers called triple-negative tumors activate genes that are involved in signaling between neurons. These breast cancers are known for spreading to the brain and, once there, are very difficult to treat, the researchers said.
After infiltrating the brain, the breast cancer cells form a specialized type of synapse that absorbs a chemical called glutamate – the most abundant neurotransmitter in the brain. Glutamate also helps boost tumor growth.
While the brain is in an extremely hostile environment for cancer cells, they "Somehow manage to really adopt and co-opt the machinery out there," according to Lisa Sevenich, from the University of Frankfurt in Germany.
The teams hope their findings will help in the development of new methods to treat cancer.
Winkler and Monje's teams have shown that an epilepsy drug can delay the spread of gliomas in mice, but it's yet to be determined in humans. Interrupting the connection between tumor cells and neurons could be the key to stopping cancer growth, they noted.
But it is a must target only Neuron-cancer cell hybrids without damaging normal connections between brain cells, Sevenich said.
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