Cellular Self-Eating Might Be Turned Against Tumors

By Rachel Tompa, UCSF Science Cafe | October 26, 2007

We all know that recycling can reduce the strain on global resources. But if we could see into the cellular world inside us, we might also notice that our cells are running a successful recycling campaign of their own.

Cells recycle and reuse their own contents through a process called autophagy, which means "self-eating."

That's not just a fun fact -- autophagy plays a role in disease too. With their growing understanding of autophagy, some medical researchers, including UCSF's Jayanta Debnath, MD, believe that cellular recycling might be manipulated to better treat cancer.

But first, he wants to find out whether autophagy helps or hurts cancer cells. A cell undergoing autophagy might eat itself to death -- which would be a good thing if it's a cancer cell. On the other hand, a cancer cell might undergo autophagy as a desperate tactic to recycle molecules for the extra fuel it needs in a hurry to respond to acute stress -- during chemotherapy, for instance. In that case, it would be better to shut down autophagy.

Desperate Times Call for Desperate Measures
On a small scale, autophagy is routine. When cellular components are old or damaged, the cell will destroy them. Without autophagy, these old or damaged parts could accumulate and cause problems for the cell.

Material within cells that needs to be recycled is packaged into microscopic trash containers and delivered to the cell's garbage disposals, called lysosomes, which break it down for reuse.

Cells also use autophagy to deal with starvation or other stresses. When nutrients in the environment are lacking, the cell turns to its own components for survival. Survival by self-consumption has to be kept under a tight rein, Debnath says.

"Too little autophagy is bad for a cell," Debnath says. "During a time of stress, if it no longer has this adaptive mechanism, it will die. But at the other extreme, if there is too much autophagy, the cell will literally eat itself to death."

Scientists originally thought that autophagy was a kind of cellular suicide. That's because it often appeared in dying cells. They compared it to a better understood and distinctly different type of programmed cell death -- called apoptosis -- that often is set in motion by cells in distress. But now researchers have learned that autophagy sometimes can be an alternative to suicide that permits some cells to stay alive in harsh conditions.

Read more at Rachel Tompa, UCSF Science Cafe