Cells in groups may promote cancer’s spread

Study finds cellular gangs, not individuals, form distant tumors from breast malignancies

PHILADELPHIA — Some cancer cells rove as a gang instead of moving out on their own.

Researchers have previously thought that single rogue cancer cells broke away from tumors and migrated to other places in the body where they could later give rise to new tumors. But a study of mice shows that breast cancer cells decamp in groups, and the clumps of cells have a better chance of establishing a colony than loners do, Kevin Cheung of Johns Hopkins University reported December 7 at the annual meeting of the American Society for Cell Biology.

Understanding how cancer spreads may influence treatments for the disease, said Crislyn D’Souza-Schorey, a cell biologist at the University of Notre Dame. Chemotherapy aimed at killing single cells may not work as efficiently against bands of spreading tumor cells, she said.

Cheung and his colleagues genetically engineered mice to produce fluorescently tagged tumor cells. Within a tumor, some cells were red and some were green. The researchers watched through a microscope as cells spread from the original tumor. On average, about a third of cells that left the tumor migrated as bicolored clumps of cells. In some cases more than 60 percent of breakaway cells moved in groups, the team found.

Moving in clumps gives cancer cells a competitive advantage, the researchers found. Cheung and colleagues injected tumor cells into the tail veins of mice and then later assessed how many tumors sprouted. Cells injected in clumps were 100 times as efficient at taking hold and growing into a tumor than those forced to go it alone, the researchers found.

Cancer cells that move as groups may support each other’s growth, Cheung said. The results may “shift the focus from the Superman cell to teams of cells that work together,” he said.

The data that the breast cancer cells spread more successfully in clumps are compelling, D’Souza-Schorey said, but no one yet knows whether cells from other types of cancer also need help to migrate. 

Editor’s Note: This article was updated December 11, 2014, to correct how much more efficient cells in clumps were at growing into a tumorcompared with individual cells: 100 times, not 10 times.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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