Lipid A in Cancer Therapy

Cancer remains a major challenge for modern society. Not only does cancer rank among the first three causes of mortality in most population groups but also the therapeutic options available for most tumor types are limited. The existing ones have limited efficacy, lack specificity and their administration carry major side effects. Hence the urgent need for novel cancer therapies. One of the most promising avenues in research is the use of specific immunotherapy.

The notion that the immune system may have important anti-tumor effects has been around for more than a century now. Every major progress in microbiology and immunology has been immediately followed by attempts to apply the new knowledge to the treatment of cancer. Progress has reached a point where it is well established that most cancer patients mount specific T cell responses against their tumors. The molecular identity of the antigens recognized by anti-tumor T cells has been elucidated and several hundredsof tumor-derived antigenic peptides have been discovered. Upon recognition of such peptides presented by self MHC molecules, both CD8 and CD4 T cells are activated, expand to high numbers and differentiate into effective anti-tumor agents. CD8 T cells directly destroy tumor cells and can cause even large tumors to completely regress in experimental mouse models. These observations have spurred intense research activity aimed at designing and testing cancer vaccines.

Over 100 years ago Coley successfully used intratumoral injection of killed bacteria to treat sarcomas. The important anti-tumor effects observed in a fraction of these patients fueled major research efforts. These led to major discoveries in the 80s and the 90s. It turns out that bacterial lipopolysaccharides stimulate the production of massive amounts of a cytokine still known today as tumor necrosis factor (TNF-a). They do so by engagement of a rather complex set of interactions culminating in the ligation of a Toll-like