Most of the lives lost to cancer are due to secondary tumours,
when the cancer spreads from one part of the body to another.
Scientists have now discovered that cancer cells use different
mechanisms to move around the body depending on their environment.
This means that balanced combinations of different drugs, aimed at
stopping the different types of movement, are needed to prevent
cancer spreading.
The findings should help improve the efficiency of drug testing
by allowing early tests to be done using the computational models
developed by the team - which are faster and less expensive than
laboratory experiments.
The research was carried out by Erik Sahai, Paul Bates, Melda
Tozluoglu and their team at Cancer Research UK's London Research
Institute (now part of the Francis Crick
Institute).
Dr Tozluoglu explained: "For cancer to spread, cancer cells
actually need to move inside the body, from one point to another,
stop, and start a new tumour. Our work focuses on understanding how
the cancer cells move in the body, so that we can stop
them."
The researchers developed a computer model to mimic moving
cancer cells and predict how they would move under different
conditions. They started by measuring properties such as how much a
cancer cell extends forward while 'crawling', or how much it can
contract while 'squeezing'. They then created surroundings similar
to inside the mice and tested how fast the model cell moved in
these environments, as well as the effect of different drug
treatments on the cell's movement. Finally, the team tested their
results again in the laboratory, to prove the model was
correct.
They found that when cancer cells move on top of smooth
surfaces, they move most efficiently by 'crawling' on the surface.
They take hold of the surface, extend forward and become elongated,
and then detach themselves at the back, like moving in
steps.
On the other hand, while moving through a complex meshwork such
as structural connective tissue, cancer cells are more efficient if
they are rounder and squeeze through the meshwork. Here, they do
not need to stick to the rods of the meshwork but need contractile
proteins, which contract the cell and help it squeeze through small
gaps.
Dr Tozluoglu said: "Our study shows that cancer cells need
different molecular mechanisms to navigate in different modes, just
like you would need light running shoes to jog in the park but
strong boots to hike in hills in the rain.
"We also know that cancer cells have the ability to use all
different methods of movement, so stopping just one type will not
stop them spreading through the body. In other words, if we take
their hiking boots away, they will switch to running shoes and,
although they may not be as fast, they will keep moving.
"We need to use drugs to target these different mechanisms in
different environments - by eliminating sticking on a smooth
surface and eliminating contractility in a complex meshwork. We
need to apply balanced combinations of drugs to target both
machineries."
The paper, Matrix geometry determines optimal cancer cell migration strategy
and modulates response to interventions, is published
inNature Cell Biology.