Cell signalling clue to cancer

Cells are ordered to divide and die

A significant breakthrough in understanding the communication system within the body's cells could aid research into cancer.

Scientists have found that the chemical hydrogen peroxide - better known as a form of bleach - plays a central role in this communication process.

It appears to be one of the ways to tell cells when they should divide and when they die.

However, if the signalling system goes awry, then it may lead to cancer.

Hydrogen peroxide is a by-product of the energy-creating process in cells.

There is increasing evidence that some cancers have abnormal levels of peoxiredoxins

Nicola O'Connor

Usually it is toxic to cells and is broken down by an enzyme called peroxiredoxin.

But researchers from Oregon State University and Wake Forest University in the US found the enzyme is only effective when levels of hydrogen peroxide are low.

When levels of the chemical rise it appears to neutralise the enzyme which is then unable to break it down.

Special times

The evolution of this complex system suggests that at certain special times the body, rather than needing to get rid of hydrogen peroxide, actually requires the chemical to perform a specialised function.

The researchers believe these special times can include moments when a cell is ordered to divide, or when it is ordered to die - and that the sudden increase in hydrogen peroxide levels stimulates these processes.

Under normal circumstances, they believe, the enzyme keeps hydrogen peroxide levels in check so that no accidental signals are sent within the body's cells.

But when hydrogen peroxide is needed to stimulate the signalling process, the cells produce a sudden burst of the chemical, which overwhelms the enzyme, switching it off and permitting the signal.

The scientists believe cancer may be linked to the over-production of peroxiredoxin.

In this case there is so much of the enzyme that it is not switched off by a burst of hydrogen peroxide production.

Thus it is able to break down the chemical and prevent it from signalling to cells that they should commit suicide in the normal way.

Thus the cancer cells don't die off, but instead begin to divide in an controlled way.

Double action

Researcher Professor Andrew Karplus told BBC News Online: "What we have discovered is a remarkable and unexpected way that cells can protect themselves from the negative effects of hydrogen peroxide, yet still use it as a signalling molecule.

"Our work shows that the enzyme peroxiredoxin is the key to sorting out these two roles.

"Given that in many cases the peroxide signalling pathways have gone awry in diseases like cancer, this opens up novel possibilities for future medical applications."

Dr Zac Wood, who also worked on the study, said: "Hydrogen peroxide is an effective signalling molecule because it is rapidly produced, is reactive and is easily controlled by enzymes."

Nicola O'Connor, from the charity Cancer Research UK, told BBC News Online that the peroxiredoxins had been linked to wide range of biological activities that that implicate them in fundamental processes that control cell growth and death.

"There is increasing evidence that some cancers have abnormal levels of peoxiredoxins, suggesting that an imbalance of these enzymes could be involved in tumour development."

The research is published in the journal Science.