Homeless cells find temporary lodging -- and th...( BOSTON Mass. (Nov. 29 2007)Sometimes...),Health

BOSTON, Mass. (Nov. 29, 2007)Sometimes healthy cells commit suicide. In the 1970s, scientists showed that a type of programmed cell death called apoptosis plays a key role in development, and the 2002 Nobel Prize in Physiology or Medicine recognized their work. As apoptotic cells degrade, they display standard characteristics, including irregular bulges in the membrane and nuclear fragmentation.

Now, Harvard Medical School researchers have uncovered a new type of death devoid of these features. In the Nov. 30 issue of Cell, they report a bizarre cell-in-cell invasion and death process, which they name entosis, after the Greek word for within.

We watched homeless cells, free of their normal attachments, bore into their neighbors and die inside compartments called vacuoles, says Michael Overholtzer, a postdoctoral researcher in Joan Brugges lab.

Were not sure if entosis evolved to play a particular role or if its simply an aberration of a normal process, adds Brugge, who is Chair of the Department of Cell Biology.

Overholtzer discovered entosis while working with human breast cells that normally form sheets of tissue. When these cells become detached from their protein-rich beds, they generally die through apoptosis. But Overholtzer noticed that they behave oddly long before displaying apoptotic features. In fact, many of these homeless cells actually nest inside their neighbors.

Further experimentation revealed that the cells actively invade neighboring cells. While some of the intruderswhich initially appear healthylater exit their hosts unharmed, most die inside vacuoles.

But Overholtzer didnt realize the implications of his initial observation until he crossed paths with Brigham and Womens Hospital pathologist Andrea Richardson. She informed him that the scientific literature is full of cell-in-cell references in the context of cancer.

Although these structures have been described by pathologists
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