Scientists from Helmholtz Center for Infection Research are researching how salmonella kills tumors
In the scientific journal PLoS ONE, Sara Bartels and Siegfried Weiss of the Helmholtz Centre for Infection Research (HZI) in Braunschweig, Germany now show how the bacteria migrate into tumours. A messenger substance from the immune system is the door opener: It makes blood vessels in the cancerous tissue permeable; enabling the bacteria to conquer and destroy the tumour. Simultaneously, blood streams from the vessels into the cancerous tissue, a so-called necrosis develops - and the tumour dies. "This influx of blood was the starting point for our investigations," says Siegfried Weiss, Head of the Molecular Immunology group at the HZI. "There is an immunological messenger present during bacterial elicited inflammation that causes this kind of reaction. We searched for it - and found it." This messenger is named after its role in the immune system: tumour necrosis factor, TNF-alpha for short. Immune cells produce TNF-alpha when recognising salmonella, thus alarming other immune cells. This inflammatory reaction leads to an increased blood vessels permeability an action that also occurs in a tumour: TNF-alpha has an easy task here because the blood vessels in cancer differ fundamentally from healthy arteries or veins. They are irregularly built, porous, partially with dead ends. A small amount of TNF-alpha is subsequently enough to dissolve the walls of the blood vessels in the tumour and allow the blood to stream into the cancerous tissue.
The scientists hope to be able to modify salmonella so they can be used in tumour therapy. The aim is for the bacteria to migrate specifically into tumours and cause them to die. The attractiveness of this way of destroying tumours is the lifestyle of salmonella. They can live almost everywhere, including tissues, which are badly supplied with blood and thus have hardly any oxygen supply. And it is precisely these areas that are scarcely reachable in a cancerous ulcer using common cancer therapies: chemotherapeutics cannot be transported to an area where there is no blood flow. And even radiation therapy requires oxygen for its reactions in the tissue.