Vaccine Tf, Tn Now Testing on Prostate Cancer Patients at MSK
November 22, '98 A new vaccine for prostate cancer, created by chemists at the Sloan-Kettering Institute for Cancer Research, is being given to patients who have undergone prostate cancer surgery. The aim is to ward off a recurrence.
     Now in early trials with patients, this is the first synthetic vaccine to target what the researchers describe as "abundant, but elusive, carbohydrates on the surface of tumor cells."
     Using vaccines to stimulate an immune response against cancer typically focuses on proteins. These are relatively easy to make but often lodged within cells and not easy for antibodies to reach. Most of the good targets, or antigens, on a cancer cell's surface are not proteins, however. Instead they are small carbohydrates. But these small carbohydrates are hard to make, and their role in giving rise to an immune response is not well-understood.
     "Normally the carbohydrates are much more complex in normal cells. In cancer cells they're often very different," says Sloan-Kettering chemist Scott D. Kuduk, Ph.D. The difference may enable scientists to target cancer.
     Kuduk's team synthesized two key tumor carbohydrate antigens — called TF and Tn. They then clustered the antigens as they occur naturally and attached them to proteins which help produce an immune response.
     "Through chemistry, we were able to make substantial quantities of the material that allowed us to then do the testing," adds Kuduk. In mice, the Tn-protein complex was especially effective at triggering antibody production.
     "It's a wonderful antigen for prostate cancer because Tn is one of the main antigens on prostate cancer cells," says immunologist and co-author Philip O. Livingston, M.D., who calls the advance "more promising than other approaches."
    Although the vaccine is already being given to patients, the researchers say it is too early to know whether a series of vaccinations will provide an adequate defense against recurrence. Patients are definitely producing antibodies against Tn, Livingstone says.
    Scientists hope the vaccines will specifically attack prostate cancer cells, permanently curbing the cancer without side effects.

An article on this vaccine appeared on November 25, 1998 in The Journal of the American Chemical Society, a peer-reviewed journal published by the American Chemical Society, the world's largest scientific society.