Their efforts have been fueled by new insights into genetic changes, coupled with the recognition that because even a nascent one can suppress the immune system, vaccines should work better in healthy people who have never had cancer.
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Science advances with proven vaccines for cancer prevention. [Recuadro de Science]
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“Sounds like science fiction”
Some scientists thought that cancer vaccines might work better at preventing than treating the disease.
One advocate was the University of Pittsburgh immunologist, Olivera Finnwhose team discovered in 1989 the first tumor-associated antigen: a version of a protein (MUC1) whose altered version dots many types of cancer cells.
Finn developed a vaccine consisting of short stretches of MUC1. In the first study of a preventive vaccine in healthy people, tested security in 39 people who previously had precancerous colon polyps, putting them at increased risk of colon cancer.
In 2013, his team reported that 17 had a strong immune response, with much higher levels of antibodies against the tumor version of MUC1 than those previously observed in cancer patients who received the vaccine as treatment.
The other 22 people, who did not produce antibodies, had immunosuppressive cells in their blood, apparently lingering from the removed polyps.
The modest success of the trial led to a largest placebo-controlled trial to see if the vaccine prevented new polyps in people who had had them removed. This time, only 11 of the 53 participants who received the vaccine produced abundant antibodies, possibly because the patients’ immunosuppressive polyps had recently been removed.
But among the 11 responders, only three had polyp recurrence within 1 year of receiving the vaccine, compared with 31 of 47 participants in a placebo group, Finn’s team reported.
“When there is no recurrence in the responders, it is known that the vaccine is working”Finn said. His team now plans trials of the MUC1 vaccine for various precancerous conditions.
All prevention vaccines would face a long road to regulatory approval if researchers must wait for the tumor to appear to judge the vaccine’s efficacy.
Another defender of a universal vaccine is Johns Hopkins cancer geneticist Bert Vogelstein. The expert told Science that sequencing has shown that “a relatively small number of genes are involved in most cancers.”
such a vaccine “looks like science fiction”but “a concerted effort of many laboratories” could be successful, Vogelstein said.
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*Excerpts from an article published in Science.
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