Zombie cancer cells survive by eating themselves

A new study has found that cancer cells don't die when faced with 'stressful' chemotherapies because they "eat" parts of themselves.

According to a University of Colorado Cancer Center study, autophagy, from the Greek "to eat oneself", is a process of cellular recycling in which cell organelles, called autophagosomes, encapsulate extra or dangerous material and transport it to the cell's lysosomes for disposable.

Like tearing apart a Lego kit, autophagy breaks down unneeded cellular components into building blocks of energy or proteins for use in surviving times of low energy or staying safe from poisons and pathogens (among other uses).

Andrew Thorburn, deputy director of the CU Cancer Center, said that the study shows that if this mechanism doesn't work right, for example if autophagy is too high or if the target regulated by autophagy isn't around, cancer cells may be able to rescue themselves from death caused by chemotherapies.

A movie that accompanies the study online shows a cancer cell dying. In the first few frames, mitochondrial cell walls break down and the cell's mitochondria can be seen releasing proteins in a process abbreviated as MOMP, which is considered a common marker of cell death.

But then high autophagy allows the cell to encapsulate and "digest" these released proteins before MOMP can keep the cell well and truly dead. Later in the movie, the cancer cell recovers and goes on to divide.

"The implication here is that if you inhibit autophagy you'd make this less likely to happen, i.e. when you kill cancer cells they would stay dead," Thorburn said.

The finding has important implications. First, it demonstrates a mechanism whereby autophagy controls cell death. And second, the study further reinforces the clinical potential of inhibiting autophagy to sensitize cancer cells to chemotherapy.

The study is published in the journal Cell Reports.