Scientists uncover navigation system used by cancer, nerve cells

Duke University researchers have found a "roving detection system" on the surface of cells that may point to new ways of treating diseases like cancer, Parkinson's disease and amyotrophic lateral sclerosis (ALS).

The cells, which were studied in nematode worms, are able to break through normal tissue boundaries and burrow into other tissues and organs - a crucial step in many normal developmental processes, ranging from embryonic development and wound-healing to the formation of new blood vessels.

But sometimes the process goes awry. Such is the case with metastatic cancer, in which cancer cells spread unchecked from where they originated and form tumors in other parts of the body.

"Cell invasion is one of the most clinically relevant yet least understood aspects of cancer progression," said David Sherwood, an associate professor of biology at Duke.

Sherwood is leading a team that is investigating the molecular mechanisms that control cell invasion in both normal development and cancer, using a one-millimeter worm known as C. elegans.

At one point in C. elegans development, a specialized cell called the anchor cell breaches the dense, sheet-like membrane that separate the worm's uterus from its vulva, opening up the worm's reproductive tract.

Anchor cells can't see, so they need some kind of signal to tell them where to break through. In a 2009 study, Sherwood and colleagues discovered that an extracellular cue called netrin orients the anchor cell so that it invades in the right direction.

In a new study appearing Aug. 25 in the Journal of Cell Biology, the team shows how receptors on the invasive cells essentially rove around the cell membrane "hunting" for the missing netrin signal that will guide the cell to the correct location.

The researchers used a video camera attached to a powerful microscope to take time-lapse movies of the slow movement of the C. elegans anchor cell during its invasion.

Cancer cells vs. normal cells: what's different?

To understand what cancer is, it is important to first understand how the body's cells normally work.

How does the body grow and maintain itself?

The body is made up of tiny cells - for example, skin cells, muscle cells, heart cells, nerve cells, and bone cells. When a baby grows, the number of cells increases very quickly. A cell becomes a bit larger, then divides into 2 "daughter" cells (Figure 1). After a period of time, each of these cells divides, and so on.

Normal cell division. A cell grows a bit larger then divides into 2 cells.

Once a child grows to adulthood, the size of the body no longer increases. However, our bodies go through a lot of wear and tear, both inside and outside. Worn-out cells constantly need to be replaced, so cell division still takes place, but more slowly. An obvious "outside" change is the tiny bits of dead skin flaking off as the skin constantly renews itself.