Development of a dendritic cell (DC)-based vaccine for patients with advanced colorectal cancer

An ability to induce a specific immune response to cancer would provide an important new dimension in its management. We report our initial work investigating the safety and efficacy of a dendritic cell vaccine in patients with colorectal cancer.

Fifteen (15) patients with advanced colorectal cancer had vaccines prepared from autologous dendritic cells pulsed with tumor RNA and keyhole limpet hemocyanin. Vaccines were administered intravenously and patients were observed in hospital for 2 days. Thereafter, consultations were at monthly intervals at which time booster doses were given to a total of 4. Patients were monitored with weekly blood tests, including carcinoembryonic antigen, and 3-monthly computed tomography scans.

Flow cytometry confirmed dendritic cell phenotype and in vitro function was confirmed by mixed lymphocyte reaction. No major adverse effects were observed. Eleven of 13 patients tested developed a positive keyhole limpet hemocyanin skin test and in 7 the carcinoembryonic antigen fell suggesting some in vivo anticancer effect. To date no dramatic clinical responses have been observed but follow-up is very short.

The therapy was well tolerated. Dendritic cells were verified by phenotype and in vitro function. The positive keyhole limpet hemocyanin skin test confirms in vivo function by effective vaccination to keyhole limpet hemocyanin. Demonstration of any anticancer efficacy will require further follow-up.