Cyclin B1 Vaccine Prevents Cancer Development in Mouse Model

Cancer researchers have obtained promising results after vaccinating mice with a naturally occurring protein that appears transiently in normal cells but is consistently overexpressed in many tumors.

Investigators at the University of Pittsburgh School of Medicine (PA, USA) vaccinated a group of mice with purified cyclin B1, a protein expressed only transiently in the G2/M stage of the cell cycle in normal cells, but constitutively expressed at high levels in the cytoplasm of many tumor types, including breast, lung, and head and neck cancers. The choice of cyclin B1 was based on earlier findings that some normal individuals had antibodies against cyclin B1 despite never having had cancer.

Results published in the August 3, 2009, online edition of the journal Proceedings of the [U.S.] National Academy of Sciences (PNAS) revealed that the vaccinated mice were protected from developing cancer after having been injected with cells from a tumor cell line that had been established from a tumor arising in a p53−/− mouse (lacking the p53 tumor suppressor gene) that spontaneously overexpresses cyclin B1.

"Cyclin B1 is known to be produced in excess amounts in several kinds of cancer,” said senior author Dr. Olivera Finn, professor of immunology at the University of Pittsburgh School of Medicine. "While we were studying it, we noted that many healthy people already had an immune response, or antibodies, against the protein, even though they had never had cancer. Because cyclin B1 is a "self” protein, there have been concerns that boosting the immune response against it would produce autoimmunity and create new problems. But now that we know that perhaps 20 to 30% of people already recognize it as abnormal when made in excess, we can be more confident about the safety of a vaccine strategy to immunize high-risk groups against it.”

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