Clinical DC vaccines. There are many alternative approaches for the preparation and use of DC vaccines to treat cancer. DCs may be prepared ex vivo following 3 general methods (lower left), each of which results in a different mixture of cells. DCs may be matured and loaded with antigens using a variety of techniques. Some of these techniques include the addition of DC survival factors, the use of substances that induce cross-presentation, or the use of stimulators of other innate immune cells such as NKT cells. DCs loaded with RNA or DNA can take advantage of sequences encoding cytokines, chemokines, or DC survival factors. Numerous variables such as antigen dose, cell dose, and route of administration also need to be optimized. In addition, less costly and labor-intensive approaches that stimulate and load DCs with antigen in situ are being explored. There are many unresolved issues regarding the monitoring of immune responses and in correlating these responses with clinical outcome. DC vaccines may prove most effective in the adjuvant setting or in combination with other treatments.