Tests spawn giant mutant fly

Scientists have created giant fruitflies while uncovering a cell growth gene that may prove significant in the fight against cancer.

The inflated size of insects with a mutant version of the PTEN gene is thought to be linked to the kind of genetic disasters connected with tumour growth.

While other teams have found growth genes that can be altered to produce dwarves containing small cells, Clive Wilson, Deborah Goberdhan and colleagues at the University of Kent at Canterbury are the first to find one that increases both cell number and cell size in the living organism.

In the latest issue of the journal Genes and Development the scientists report that mutating this gene caused tissues to grow to several times their normal size.

The fact that PTEN is also found in humans and is known to be a tumour suppressor raises the prospect of the discovery contributing to the scientific effort to tackle cancer.

"By mutating this gene you can get uncontrolled growth. Under the right conditions, the entire fly grows more than 20 per cent bigger than normal - this is the only gene found so far that does this," said Dr Wilson.

PTEN plays a vital role in the body's response to the hormone insulin. This hormone appears to be linked to growth before birth and with metabolism in adults.

It is now clear that when PTEN is defective, cells become too sensitive to insulin and this can be linked to cancer formation.

Cancers are caused by a combination of malfunctions in three growth-related factors - excess cell division, excessive cell growth and lack of cell death.

Hence the discovery of PTEN in flies is an important achievement in the quest to understand how genes control growth.