Cells come and go throughout our lifetime. Some live a long time (like brain cells), while others constantly grow, divide and die. Cell death is a process that must be carefully managed – too many cells dying in the brain leads to neurodegenerative diseases like Alzheimer’s, while not enough cell death allows tumors to form. But not all cell death is the same. Apoptosis, often called “programmed cell death”, is neat and clean – seppuku-style cell suicide. Necrosis, on the other hand, is the messy, unplanned version of cell death – the kind that might cause pain and swelling.

Apoptosis begins by activating enzymes known as caspases, setting the cell on the path towards death – a good thing if they are cancer cells or cells infected with a virus. One caspase, known as caspase-8, is a double agent of apoptosis – depending on the conditions, it can promote either cell death or cell survival. What makes caspases-8 choose a side? A new study led by Dr. Douglas Green at St. Jude Children’s Research Hospital and Sanford-Burnham’s Dr. Guy Salvesen points the finger at a protein called FLIP_L. Their study was published online March 2 in the journal Nature.

“We’ve known for some time that caspase-8 can play this dual role, but we didn’t know the molecular basis for the opposing functions. Knowing the mechanism may allow us to design therapies to defeat a cancer cell’s quest for immortality,” says Dr. Salvesen, director of the Apoptosis and Cell Death Research Program and dean of the Graduate School of Biomedical Sciences at Sanford-Burnham.

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