Therapeutic cancer vaccines.

Therapeutic vaccination against cancer-associated antigens represents an attractive option for cancer therapy in view of the comparatively low toxicity and, so far, excellent safety profile of this treatment. Nevertheless, it is now recognized that the vaccination strategies used for prophylactic vaccinations against infectious diseases cannot necessarily be used for therapeutic cancer vaccination. Cancer patients are usually immunosuppressed, and most cancer-associated antigens are self antigens. Therefore, various immunostimulation techniques are under investigation in an effort to bolster immune systems and to overcome immune tolerance to self antigens. Various strategies to stimulate antigen presentation, T-cell reactivity and innate immune activity are under investigation. Similarly, strategies to produce an immunological 'danger signal' at the site of the tumor itself are under evaluation, as it is recognized that while tumor-specific T-cells can be activated at the site of vaccination, they require appropriate signals to be attracted to a tumor. The detection, evaluation and quantification of specific immune responses generated by vaccination with cancer-associated antigens is another important area of therapeutic cancer vaccine evaluation receiving much attention and novel strategies. Multiple clinical trials have been undertaken to evaluate therapeutic vaccines in patients. Aggressive protocols such as those combining specific stimulation of T-cells and chemotherapy or strategies to block immune regulation are having some success.