Embryonic Stem Cell Vaccines Effective in Mice

• PRAGUE, Czech Republic—Two embryonic stem cell vaccines proved 60% to 100% effective in preventing lung cancer in mice, John W. Eaton, PhD, reported at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics (abstract 29).

Dr. Eaton, of the University of Louisville James Graham Brown Cancer Center, said the antigenic similarities between tumor cells and embryos prompted him and his colleagues to test the concept that vaccination with embryonic stem cells (ESCs) would prevent tumorigenesis.

One vaccine consisted of live allogeneic ESCs, obtained from mouse blastocysts. The second contained live ESCs combined with cultured fibroblast cells producing GM-CSF. The team injected groups of C57B16 mice with the vaccines and gave booster shots 10 days later. Unvaccinated mice served as controls, and all of them developed lung tumors. In mice challenged with Lewis lung carcinomas, the ESC-only vaccine proved 80% effective; the combination vaccine was 100% effective. The two vaccines, respectively, showed 60% and 90% tumor-free effectiveness after 27 weeks in inoculated mice who were exposed to 3-methylcholanthrene followed by repetitive dosing with butylated hydroxytoluene, a carcinogenic combination that causes lung cancer. Moreover, lung tumors that did develop in the vaccinated mice were about 80% to 90% smaller than those in the controls. None of the more than 200 vaccinated mice developed autoimmune disease or showed a significant decline in adult pluripotent bone marrow stem cells.

"We think the results from the carcinogen-initiated cancers are probably the most important," Dr. Eaton said. "They are closer to the real-life model of the development of cancer than just implanting cancers cells in an animal."