Scientists have discovered the two key processes that allow cancer cells to change the way they move in order to spread through the body.
The discovery has been made by Dr Victoria Sanz-Moreno in a research team led by Professor Chris Marshall at The Institute of Cancer Research.
Professor Marshall said: 'The spreading of cancer cells from one part of the body to another, called metastasis, is one of the biggest causes of death from cancer.
'The research has found the constant competition between two proteins called Rac and Rho is responsible for allowing the cancer cells to change shape and spread through the body.
'We have shown that cells from melanoma (an aggressive type of skin cancer) are able to rapidly alternate between two different forms of movement where cells have either a round shape or a more stretchy elongated shape.
'Together with Dr Erik Sahai and Dr Sophie Pinner at the Cancer Research UK London Research Institute, we have been able to see cells in live tumours carrying out these different forms of movement.
'These alternate shapes and ways of moving may enable tumour cells to deal with different situations during cancer spread.
'For example, tests indicated that a round-shaped tumour cell may have more durability to survive in our bloodstream than elongated-shaped tumour cells.' The Rac process involves a protein called NEDD9 (which was previously shown to be involved in melanoma metastasis) activating Rac through another protein called DOCK3.
This Rac activity encourages the cell to become elongated and suppresses the competing Rho activity.
When cells adopt the round form, a protein activated by Rho called ARHGAP22 switches off Rac activation.
Dr Victoria Sanz-Moreno says: 'Until now the conversion between different types of movement of individual cancer cells had been observed but the key players had not been identified.
'We are excited to discover that the amount and the activity of these proteins in the tumour cell regulates its shape and the mechanism for it to move and invade surrounding tissue.' Melanoma cells were being studied in this research and their behaviour is also expected to occur in many other types of cancer.
Melanomas are a major target for cancer therapies because although they are the least common, they are the most serious type of skin cancer.
There are about 160,000 new cases of melanoma worldwide each year, including the rarer types that affect the bowel or eye rather than the skin.
