RNA as a tumor vaccine: a review of the literature.

Many approaches have been attempted to harness the host immune system to act against malignant tumors. These have included animal and clinical trials with agents to non-specifically boost immunity, factors to augment specific immunity, transfer of lymphokine-activated killer cells and transfer of expanded populations of tumor-infiltrating lymphocytes. Therapeutic vaccination strategies have been employed using tumor extracts, purified tumor antigens, recombinant peptide tumor antigens and specific DNA sequences coding for a tumor antigen (genetic vaccination) both through direct administration to the host and by administration of antigen presenting cells exposed to these materials ex vivo. Recently, the use of RNA has been proposed for use in tumor vaccination protocols. The use of RNA has several potential advantages. Since total cellular RNA or mRNA can be utilized, it is not necessary to know the molecular nature of the putative tumor antigen(s). RNA can be effectively amplified; thus, unlike tumor-extract vaccines, only a small amount of tumor is needed to prepare the material for vaccination. Also, unlike DNA-based vaccines, there is little danger of incorporation of RNA sequences into the host genome. The possible utility of RNA-based vaccines for tumor immunotherapy should be further explored to determine whether such approaches are clinically useful.