BREAST cancer patients will be treated later this year with gene transplants after
considerable success with experiments on mice, scientists announced yesterday.
The successful use of the method on a strain of mouse that had been genetically
engineered to suffer human breast cancer was reported by a team from McMaster
University in Hamilton, Ontario, and the Californian Chiron Corporation.
A clinical trial of gene therapy to treat 20 breast and skin cancer patients will start this autumn in a Toronto Hospital, said Prof Frank Graham, who conducted the work with Ms Christina Addison, Mr Todd Braciak, Dr Robert Ralston, Prof William Muller, and
Prof Jack Gauldie.
In yesterday's issue of the Proceedings of the National Academy of Sciences, the team
reported suppression of tumour growth and in many cases complete tumour regression
by injecting into breast tumours a genetically altered virus.
Viruses are ideal for gene transplants because they have evolved over millions of years
efficiently to implant DNA in cells.
Viruses usually "pirate" the genetic machinery of cells but those used for this experiment were designed to be incapable of replicating in normal cells, so they are not able to run unchecked in the body.
The human gene for interleukin 2 - an intercellular messenger that stimulates the number and response of the body's protective immune cells - was delivered into the tumour cells by the virus. "We seem to be able to induce an immune response against the tumour," said Prof Graham.
The method boosts the body's protective immune response, which in itself is usually too weakly reactive against the tumour to be effective. "The tumour is recognised as non-self, and what one needs to do is to stimulate the immune response against the tumour cells. This is what the interleukin 2 does," said Prof Graham.
Normal cells that are infected with the virus are left unaffected, since the immune system does not perceive them as foreign.
The team also reported that mice with complete tumour regression remained tumour free and exhibited a protective immunity when challenged with the same tumour cells 12 weeks later.
This suggests possible protection against secondary tumour growths in the body or
