Stem cells could potentially be used to vaccinate people against colon cancer. This surprising conclusion was made by researchers from China and the US after laboratory mice immunised with human embryonic stem cells (ES) experienced a dramatic decline in tumour growth compared to control mice. The idea that embryonic material may generate an anti-tumour response is an old one, but one that has never been tested outside animal research, so to find such an effect with human stem cells is considered very novel and unexpected. The scientists, who published their work in the journal Stem Cells, believe that their findings will open up a whole new avenue for cancer research to follow.

The immune system creates antibodies to fight tumours when it recognises antigens such as proteins on the surface of tumour cells. Therefore most current cancer research is focused on these antigens. This study took the different approach of trying to trick the immune system into thinking that a cancer was present and triggering an immune response that way instead. ES cells are an ideal candidate to use in such a deception as they are very similar to cancer cells in many ways, particularly in how they form and replicate. So, the researchers vaccinated laboratory mice with human ES cells and discovered a consistent immune response against colon cancer cells and a dramatic decline in tumour growth amongst the immunised mice.

'This finding potentially opens up a new paradigm for cancer vaccine research,' said Dr Li, one of the leaders of the study, adding: 'Cancer and stem cells share many molecular and biological features. By immunizing the host with stem cells, we are able to fool the immune system to believe that cancer cells are present and thus to initiate a tumour-combating immune program.' Dr. Liu, another leader of the study also commented, saying that 'although we have only tested the protection against colon cancer, we believe that stem cells might be useful for generating an immune response against a broad spectrum of cancers, thus serving as a universal cancer vaccine.'

One potentially negative implication of this study is that the researchers only noticed the positive anti-tumour effects with natural human ES cells, and not with their artificial counterpart iPS (induced pluripotent stem) cells. This may be a significant drawback for iPS cells, which many recent studies have touted as an efficacious and ethically acceptable alternative to ES cells, whose use remains controversial.