Cell that causes eye cancer identified

In collaboration with the Press Association

Researchers have identified the specific cell that causes retinoblastoma, a rare form of cancer that develops in the retina of the eye, usually in children under the age of five.

Scientists at St Jude Children's Research Hospital have discovered that retinoblastoma can arise from fully matured nerves in the retina called horizontal interneurons, despite the fact that these cells were previously believed to be incapable of multiplying.

The researchers bred mice which lacked one or more members of the Rb family of genes, a group of related genes required for immature cells to stop dividing and begin to differentiate into a specific kind of cell.

Publishing their findings in the journal Cell, they reveal that reduced Rb function allowed the horizontal neuron cells in the mouse retina to multiply.

Senior author Dr Michael Dyer, an associate member in the St Jude Department of Developmental Neurobiology, said: "For the past 100 years, it's been ingrained among scientists that differentiated mature nerves are so elaborate that they can't divide, and if they try to divide, they undergo apoptosis [programmed cell death].

"There was no exception to this rule until now. This is the first time that anyone has shown that under certain conditions, a fully mature and differentiated nerve can undergo cell division and multiply."

The researchers also found that if the cells were allowed to multiply unchecked, highly differentiated tumours were formed that were aggressive and spread rapidly.

This discovery showed that the established belief that cancer cells are most aggressive when they are undifferentiated does not hold true for retinoblastoma.

Dr Dyer said: "On the contrary, we showed that when certain genes are inactivated in the retina, horizontal neurons that are already differentiated and fully integrated into the brain can start multiplying rapidly and produce a very aggressive cancer.

"This opens an exciting new chapter in the study of neurons and brain tumours."

The expert said that the finding may also enable researchers to trigger genes to multiply temporarily, replacing nerve cells that have been lost as a result of neurodegenerative diseases such as Alzheimer's disease.

"However, there is still a lot of research required to determine if it is possible to control gene activity to make this approach practical," he added.