Experimental vaccine reduces bowel cancer spread in mice
US scientists have tested an experimental bowel cancer vaccine that they believe could lead to the development of an entirely new kind of cancer vaccine.
The vaccine was inspired by the knowledge that the intestines essentially have their own immune system that is distinct from the body's general immune system.
A significant hurdle to developing cancer vaccines is to find a 'normal' protein that is able to trigger the immune system to attack cells that carry it. Normally the body does not react against such 'self' proteins.
Bowel cancer arises from cells that line the intestine, known as mucosal cells.
Researchers at the Kimmel Cancer Centre at Thomas Jefferson University in Philadelphia realised that, due to being part of a separate immune system, normal mucosal cells could contain proteins that might not be recognised by the body's general immune system and could therefore be used as a basis for anti-cancer vaccines.
To test this idea, they injected mice with an intestinal protein called guanylyl cyclase C (GCC) - sensitising their immune systems to this protein. They then injected the mice with bowel cancer cells.
These mice developed fewer metastatic (advanced) tumours in their lungs and liver than a 'control' group of unimmunised mice, as the immune system attacked any cancer cells that spread from the bowel.
Vaccinated mice developed 90 per cent fewer tumours in the liver and 75 per cent fewer in the lungs. They also tended to survive for longer - 38 days on average compared with 29 days in control mice.
The discovery, which is detailed in the Journal of the National Cancer Institute, suggests that the technique could provide a way to block the spread of bowel cancer in people who already have the disease.
According to Dr Scott Waldman, professor and chair of pharmacology and experimental therapeutics at Jefferson, "Immunising an animal or person systemically with GCC will be recognised to some degree as foreign, and the body will mount an immune response in the systemic compartment. We think that the immune response will be effective against the cancer but it won't cross over into the intestines and cause autoimmune disease."
Dr Waldman suggested that, if shown to be safe and effective, the vaccine would most probably be aimed at patients who have had surgery and chemotherapy and have no evidence of remaining cancer, to prevent any stray cells from regrowing and spreading.