Cancer vaccines: dream, reality, or nightmare?

Over the past 30 years, a multidisciplinary approach combining surgery, chemotherapy, and radiation has led to a dramatic improvement in survival for patients affected by malignant diseases. Cellular therapies, such as stem cell transplantation, have also made a significant contribution. Nonetheless, many patients are still resistant to standard therapies, which also have high and often unacceptable acute and chronic organ toxicity, with an increased risk for secondary malignancies. Therefore new strategies are needed to improve overall survival and decrease treatment-associated morbidity. Immunotherapy represents one of the most appealing of these approaches, and active immunization in particular has proved to be amongst the most important of these new cellular strategies because of its ability to stimulate the immune system to actively recognize and kill the malignant cells. Identification of antigens expressed on tumor cells (Table 1), together with a better understanding of the molecular and cellular mechanisms involved in the immune response against cancer, have given investigators tools to manipulate the immune system to induce an efficient immune response in the tumor-bearing host [1-5]. The present review describes the approaches used in cancer vaccination that are intended not only to optimize antitumor immunity but also to overcome tumor immune escape. Examples of how these approaches are being applied clinically are also given.