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'Cannibalistic' Cancer Cells Gobble Up Their Own Kind in Microscopic 'Horror Films'

Human breast cancer cells treated with a chemotherapy drug pull nearby tumor cells (red) into centers for digestion, called lysosomes (green).

(Image credit: Tonnessen-Murray et al., 2019)

Some cancer cells devour their own kind in an act of "cannibalism," and now, scientists have captured the grisly act on camera. 

New videos show human breast cancer cells in a lab dish being sucked into the belly of another cancer cell that had been treated with a chemotherapy drug. Compartments within the cannibalistic cell's structure, known as lysosomes,⁠⁠ break down the consumed cells with a fatal cocktail of digestive enzymes. 

In the footage, the engulfed cells shrink down into tiny nuggets before finally disappearing.   

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The researchers captured these microscopic horror films while attempting to learn how some tumor cells survive chemotherapy and promote cancer relapse down the line. 

Chemotherapy drugs take down cancer cells by wreaking damage to their DNA. But despite the onslaught, some breast cancer cells are resistant to chemotherapy because they retain a healthy copy of a gene called TP53. Rather than perishing, these resilient cells enter a dormant state where they no longer replicate but still produce chemical signals that ignite inflammation and drive later tumor growth. 

Scientists at the Tulane University School of Medicine aimed to learn more about how the sneaky cells survive. They treated human breast cancer cells grown in lab dishes with the chemotherapy drug doxorubicin and then mixed them with untreated cells. The treated cells entered a dormant state (they stopped replicating); even so, those dormant cells expanded the size of their lysosomes and activated genes normally used by white blood cells to gobble up invading pathogens. The newly equipped cells frequently ate untreated cells hanging out nearby, the researchers found, a ruthless behavior that may grant them the energy and materials to support later relapse. 

The researchers observed the cannibalistic behavior in cells grown in a mouse model of breast cancer, as well as human lung cancer and bone cancer cell lines grown in lab dishes. 

"We found that the doxorubicin-treated cells engulfed the untreated cells, but not vice versa, nor did untreated cells engulf untreated cells," study co-author James Jackson, a professor of biochemistry and molecular biology, told Live Science in an email. 

"Inhibiting this process [of cancer cell cannibalism] may provide new therapeutic opportunities," he added in a statement. For example, it's well known that breast cancer patients who have cancer cells with a normal TP53 gene suffer poor survival rates, he explained, but perhaps stopping those patients' tumor cells from eating each other might help improve their response to chemotherapy.  

The findings were published today (Sept. 17) in the Journal of Cell Biology.

 Originally published on Live Science.