Navigation System Used by Cancer Discover By Scientists
of - Duke University
Durham, NC - 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
“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.
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
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.
Their time-lapse analyses reveal that when netrin production is blocked, netrin
receptors on the surface of the anchor cell periodically cluster, disperse and reassemble in a different region of
the cell membrane. The receptors cluster alongside patches of actin filaments -- thin flexible fibers that help
cells change shape and form invasive protrusions –- that pop up in each new spot.
“It’s kind of like a missile detection system,” Sherwood said.
Rather than the whole cell having to move around, its receptors move around on the
outside of the cell until they get a signal. Once the receptors locate the netrin signal, they stabilize in the
region of the cell membrane that is closest to the source of the signal.
The findings redefine decades-old ideas about how the cell’s navigation system
works. “Cells don’t just passively respond to the netrin signal -- they’re actively searching for it,” Sherwood
Given that netrin has been found to promote cell invasion in some of the most
lethal cancers, the findings could lead to new treatment strategies. Disrupting the cell’s netrin detection system,
for example, could prevent cancer cells from finding their way to the bloodstream or the lymphatic system and stop
them from metastasizing, or becoming invasive and spreading throughout the body.
“One of the things we’re gearing up to do next are drug screens with our
collaborators to see if we can block this detection system during invasion,” Sherwood said.
Scientists have also known for years that netrin plays a key role in wiring the
brain and nervous system by guiding developing nerve cells as they grow and form connections.
This means the results could also point to new ways of treating neurological
disorders like Parkinson's and ALS and recovering from spinal cord injuries.
inkering with the cell’s netrin detection machinery, for example, may make it
possible to encourage damaged cells in the central nervous system -- which normally have limited ability to
regenerate -- to regrow.
This work was supported by a Pew Scholars Award and by the National Institutes of
Health (Grant No. GM100083).
Sherwood’s co-authors on the study are Zheng Wang, Lara Linden, Kaleb Naegeli and
Qiuyi Chi of Duke, Joshua Ziel of New York University Medical Center, Elliott Hagedorn of Boston Children’s
Hospital and Natasha Savage of the University of Liverpool.
Article Source: http://today.duke.edu/2014/08/cellinvasion