Prof Eaton explained: "We needed a delivery vehicle for GM-CSF and chose STO fibroblasts because they are often used as a 'feeder layer' to maintain these particular mouse embryonic stem cells in their embryonic state. If we had used only ESCs expressing GM-CSF, they might have differentiated into non-embryonic cells, which, therefore, would not have worked as a vaccine."
He and his team injected mice with ESCs alone or ESCs + STO/GM-CSF. In mice that had Lewis lung carcinoma transplanted into them afterwards, ESCs were 80% effective in preventing tumour growth and ESCs + STO/GM-CSF were 100% effective. In mice subsequently exposed to a carcinogen that causes lung cancer (3-methylcholanthrene followed by repetitive dosing with butylated hydroxytoluene), ESCs resulted in 60% of mice remaining tumour free after 27 weeks and ESC + STO/GM-CSF resulted in 90% remaining tumour free. Importantly, tumours arising in vaccinated mice were, on average, about 80-90% smaller than tumours in unvaccinated mice. All the unvaccinated mice developed tumours. None of the vaccinated mice developed autoimmune disease or a showed a significant decline in adult pluripotent bone marrow stem cells ?both potential adverse responses to the vaccinations.
Prof Eaton said: "We think the results from the carcinogen-initiated cancers are probably the
Source:European Organisation for Research and Treatment of Cancer