Cancer cells rely on the healthy cells that surround them for sustenance. Tumors reroute blood vessels to nourish themselves, secrete chemicals that scramble immune responses, and, according to recent studies, even recruit and manipulate neurons for their own gain. This pattern holds true not just for brain cancers, but also for prostate cancer, skin cancer, pancreatic cancer, and stomach cancer. Stanford neuroscientists review how tumors exploit neuronal signals in Trends in Cancer.

"There is no part of the body that isn't well innervated," says Michelle Monje of the Stanford University School of Medicine, who co-authored the article with PhD candidate Humsa Venkatesh. "The nervous system is an extremely arborized tree that reaches every aspect of every tissue and contributes importantly to tissue development. Those growth signals are already there, so why shouldn't cancer cells co-opt them?"

Cancer treatments often target tumors by cutting off blood vessels and other nutrient supply routes, so Monje and others are interested to learn whether it may be possible to target nerves via analogous therapies or by simply blocking secreted neural growth factors. The challenge is that growth-promoting signals vary by neuron and cancer type. Furthermore, blocking neural activity can be dangerous.

"In the brain, modulating neuronal activity isn't a great option because we don't want to silence the brain. Brains need to be active and functioning," says Monje. "But we can interrupt the specific molecular pathways that are being co-opted by the tumor."
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Monje first became interested in neurons' role supporting tumors while working on childhood glioma, a cancer that strikes in the precursors to glial cells in the developing brain. In 2015, her lab published a paper in Cell (DOI: 10.1016/j.cell.2015.04.012) that found that both adult and pediatric glioma cells grew faster when adjacent to highly active neurons.

A team of investigators from Cedars-Sinai and UCLA is using a new blood-analysis technique and tiny experimental device to help physicians predict which cancers are likely to spread by identifying and characterizing tumor cells circulating through the blood.

The investigators are conducting "liquid biopsies" by running blood through a postage-stamp-sized chip with nanowires 1,000 times thinner than a human hair and coated with antibodies, or proteins, that recognize circulating tumor cells. The device, the NanoVelcro Chip, works by "grabbing" circulating tumor cells, which break away from tumors and travel through the bloodstream, looking for places in the body to spread.

Use of the chip in liquid biopsies could allow doctors to regularly and easily monitor cancer-related changes in patients, such as how well they're responding to treatment. The research earned the lead investigators a place on the U.S. Cancer Moonshot program, an initiative led by former Vice President Joe Biden to make available more therapies to more patients and to prevent cancer.

"It's far better to draw a tube of blood once a month to monitor cancer than to make patients undergo repeated surgical procedures," said Edwin Posadas, MD. "The power of this technology lies in its capacity to provide information that is equal to or even superior to traditional tumor sampling by invasive procedures."

Although some forms of prostate cancer are so slow-growing that they pose little risk to patients, other forms of the disease are lethal. Identifying which patients have which type of disease has become a crucial area of study because prostate cancer is one of the leading causes of cancer death among men in the U.S. Nearly 27,000 U.S. men are expected to die from the disease in 2017, according to the American Cancer Society.