Major study suggests 'squirting' as key to cancer's spread
Researchers may be a step closer to solving the mystery of how cancer cells can split away from a tumour and spread to other parts of the body, a report in the journal Science reveals.
Cancer cells are able to speedily shift key building materials to the outgrowing part of a cell, perhaps by squirting them from one part to another, scientists from Cancer Research UK and the Medical Research Council have discovered.
Researchers used a brand new technique, developed in their laboratories, to label individual molecules with two fluorescent dyes and track their relative movement within the cell. They found cancer cells can propel certain types of molecule at incredible speed to the parts of a cell growing forwards, giving them the momentum they need for rapid spread.
As cancer develops, cells often grow out from the main tumour into the surrounding tissues, as the first step towards entering the bloodstream or lymphatic system and spreading around the body.
When a cell grows outwards, one part of it sticks out in front, marking the direction that the cell is planning to move. Cells then creep forwards using molecules of a substance called actin, which add together, end on end, to form long flexible filaments that give a cell structure and mobility.
Scientists had previously thought the actin molecules reached the frontline by the passive process of diffusion, but this may not account for the rapid and aggressive way that some cancer cells spread out from a tumour.
Researchers used their new visualisation technique1 to measure the time it took actin molecules to move to the outgrowing parts of the cell. The molecules moved far faster than expected, indicating cells were actively moving them, rather than waiting for them to arrive.
Study author Dr Daniel Zicha, of the Cancer Research UK London Research Institute, says: "We found cancer cells can rapidly propel growth materials to the places they need them.
"Our discovery that the process is an active one is highly significant, because it means we might be able to find ways of stopping it from happening, potentially preventing cancer cells from growing and spreading."
Researchers believe the key to the process may be another important molecule called myosin II, one of the components of muscle, which can pull the walls of a cell together, squeezing it like a tube of toothpaste.
When they blocked the action of myosin II, they found that actin molecules moved much slower. So it seems cancer cells may be contracting themselves in certain areas, in order to squirt vital building materials from one place to another.
Sir Paul Nurse of Cancer Research UK is also currently involved in studying the way that cells change their shape during their growth and spread. Sir Paul comments: "Cancer cells often do most damage when they start splitting away from a tumour and spreading to other tissues and organs.
"They can do this because they find ways of changing their shape and becoming much more mobile than normal cells. Finding out how cancer cells gain their ability to move around is a vital part of cancer research and will open up new avenues for blocking the disease's ability to spread."
- Fluorescence localisation after photobleaching (FLAP)