The use of mycobacterial adjuvant-based agents for immunotherapy of cancer.

A heat-killed preparation of Mycobacterium vaccae (SRL172) has been shown, in recent studies, to be effective in the treatment of adenocarcinoma of the lung and renal cell cancer. It is postulated that the mechanisms of this form of immunotherapy is, at least in part, due to immune regulation, reflected in the selective enhancement of Th1 and down-regulation of Th2 T cell activity. These beneficial effects are attributed to the ability of adjuvants in the bacterial cell walls to modify and optimise the response to antigens shared by the bacteria and stressed host tissues, resulting in the destruction of cancer cells by programmed cell death or apoptosis. The M. vaccae-induced apoptosis appears to be most effective against carcinomas, perhaps especially those of glandular tissue, in contrast to pyrexia-induced necrosis which is most effective against tumours of mesodermal origin. In view of the great range of adjuvants, especially in the genus Mycobacterium and related genera, it may prove possible to develop a range of immunotherapeutic agents with useful activity against a wide range of cancers.