13 April 2015
ByAppeared in BioNews 797
A new type of cancer vaccine that enriches the immune system with tailor-made anti-tumour cells has shown early signs of promise.
The small-scale trial was conducted at the Washington University School of Medicine in St Louis, USA and published in the journal Science. Three patients with advanced melanoma - a type of skin cancer - received the experimental treatment almost two years ago. Since then, one has been in remission, the second remained stable throughout the treatment and the third showed a temporary improvement.
Melanoma is caused by the sun's ultraviolet radiation damaging the DNA of skin cells, leading to mutations that vary from person to person. Some of these mutations result in small unique proteins, or neoantigens, that end up on the surface of tumour cells. These can be ideal targets for bespoke anti-cancer vaccines.
The researchers sequenced the complete genome of each patient, and they then compared the DNA of the tumour cells with the DNA in that person's healthy tissues. This process helped them identify every possible unique neoantigen for each patient. They narrowed down the search using a computer algorithm to determine the best candidates for developing a vaccine. To increase the chances of success, seven neoantigens were selected for each patient.
The neoantigens were mixed with specialised immune cells, known as dendritic cells, from each patient. When these cells were re-introduced into the patients' blood stream, they instructed their immune T cells to find and attack the tumour cells that bore the selected neoantigens.
Dr Gerald Linette, who led the trial, said: 'Many researchers have hypothesised that it would be possible to use neoantigens to broadly activate the human immune system, but we didn't know that for sure until now.'
A series of blood tests from the patients showed that in each case they had produced a substantial immune response against their individual melanomas. Dr Linette noted: 'Our team is very encouraged by the quality of the immune response directed against the melanoma neoantigens in all three patients. Our results are preliminary, but we think the vaccines have therapeutic potential.'
However, the team acknowledges that it's too early to judge the effectiveness of the treatment. The melanoma participants had received surgery and chemotherapy prior to the tailored vaccination. Further trials with more patients will follow later this year.
Dr Alan Worsley, of Cancer Research UK, said: 'At the moment it's not clear how effective this immunotherapy would be at killing cancer cells in the body and improving survival, but this promising study sets the stage for creating vaccines that are designed to target each patient's individual tumour in the future.'
Personalised vaccines might also be developed against other types of cancer with high mutation rates, including lung, bladder and certain colorectal, breast and ovarian cancers.