Microorganisms and Cancer

It is well established that defined microorganisms may cause cancer. Basic, molecular mechanisms are known and might contribute to innovative prophylaxis or treatment strategies, e.g. vaccination. The ability of defined attenuated microorganisms to cause tumour regression is well known, however, the mode of action mostly remained unknown. It is generally believed that e.g. bacteria (or their products, components; probiotics) activate the immune system and that the activated immune system is responsible for cancer regression. However, experiments with Toxoplasma gondii have shown that the inhibition of angiogenesis may also contribute to cancer regression, at least in the case of T. gondii. Furthermore, the proliferation of anaerobic bacteria in the core of tumours is well established. However, there is a lack of knowledge whether local anti-tumourous anaerobic bacteria secrete soluble factors that could induce cancer cell death. Administration of bacterial probiotics in defined stages of malignant disease and its treatment is a promising option in complementary oncology and was shown to restore immune functions and to decrease amount and severity of side effects of tumour destructive standard treatments.