THE latest cancer vaccine has an unusual target. It attacks tumours by killing growing blood vessels, starving the cancers of blood.
Because it targets normal, healthy cells, cancers can鈥檛 evade its effects by mutating. And the same vaccine could be given to everyone, instead of having to be tailored to specific cancers. It might provide long-term protection from many cancers.
Trials of drugs that block the growth of the blood vessels that feed tumours have been disappointing. So Ralph Reisfeld and Andreas Niethammer of the Scripps Research Institute in La Jolla, California, created a vaccine to make the immune system attack new blood vessels.
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Their team added the gene for a protein called FLK-1, found on cells in new blood vessels, to Salmonella bacteria. Then they fed the bacteria to mice. When the animals were injected with skin and lung cancer cells, the resulting tumours grew only a quarter as large as those in unvaccinated mice. 鈥淲e saw tumours vanish or we could not detect them any more, and we saw tumours that took longer to grow,鈥� says Niethammer.
The team also gave the vaccine to mice with colon cancer that had already spread to the lungs. All treated mice survived, with some lung damage, while untreated ones died (Nature Medicine, DOI: 10.1038/nm794).
Tumours often evade anti-cancer drugs if they are sheltered by scar tissue or the blood-brain barrier. But Reisfeld says the immune system鈥檚 killer T cells, which are activated by the vaccine, can reach growing blood vessels wherever the tumour is.
The vaccine also gives long-term protection. It was just as effective in mice injected with cancer cells 10 months after immunisation. 鈥淭he beautiful thing about T cells is that they have a memory,鈥� says Reisfeld.
The only side effect the researchers detected was that wounds took longer to heal. But careful safety studies will be needed before the vaccine is given to people.