DNA-based vaccines for the treatment of cancer--an experimental model.

Antigenic differences between normal and malignant cells form the basis of clinical immunotherapy protocols. Because the antigenic phenotype varies widely among different cells within the same tumor mass, immunization with a vaccine that stimulates immunity to a broad array of tumor antigens expressed by the entire population of malignant cells is likely to be more efficacious than immunization with a vaccine for a single antigen. One strategy is to prepare a vaccine by transfer of DNA from the patient's tumor into a highly immunogenic cell line. Weak tumor antigens, characteristic of malignant cells, become strongly antigenic if they are expressed by immunogenic cells. In animal models of melanoma and breast cancer, immunization with a DNA-based vaccine is sufficient to deter tumor growth and to prolong the lives of tumor-bearing mice.