Signal molecule holds possible key to tumour growth

Immunity to a cancer in chickens could shed light on ways to control certain human cancers according to scientists from the Institute for Animal Health (IAH). Their work on Marek’s disease (MD) in chickens has identified the first natural model for specific Hodgkin’s and non-Hodgkin’s lymphomas, and is published this week in PNAS (06-10 September 2004).

Marek’s disease virus (MDV) shares many biological properties with Epstein-Barr virus (EBV) – a major cause of Hodgkin’s disease. Infection with these herpesviruses can lead to lymphoma formation, which is closely linked with the over-production of a cell-surface molecule called CD30.

“For the first time we have detected the presence of specific antibodies against CD30 after MDV infection in MD-resistant chickens,” says lead researcher Dr Shane Burgess, now at Mississippi State University, USA. “The presence of CD30-specific antibodies suggests anti-tumour immunity may exist in Marek’s disease, and perhaps also in some Hodgkin’s and non-Hodgkin’s lymphoma patients.”

CD30 promotes the survival of normal lymphocytes – essential for immune responses – and can also influence cell death. However, over-expression of CD30 is associated with the survival of lymphoma cells.

“We have shown that the chicken CD30 gene resembles the ancestral form of the human CD30 gene structure, and we have developed a new understanding for how this model has evolved in mammals, including humans” says Dr Fred Davison, Head of Avian Immunology at IAH. “CD30 over-expression is evolutionarily conserved, and we think that this molecule is part of a critical cell signalling pathway that is disturbed during the formation of many different lymphomas.”