They are specialized white blood cells whose job it is to alert the immune system to the presence of invading cancers, bacteria or viruses so the invaders can be surrounded and destroyed. In the study performed at the U-M Comprehensive Cancer Center, blood was drawn from each of 13 children, ages 3 to 17. Among the 13 children, a variety of pediatric tumor types were treated including three neuroblastomas , four sarcomas , one osteosarcoma, one fibrosarcoma, two undifferentiated sarcomas, one renal sarcoma, and one Wilms' tumor . From each patient's blood, the U-M team isolated dendritic cells, enticed them to replicate, then sensitized them to the tumor before injecting them back into the patient. The dendritic cell presents these antigens to other white blood cells called T-lymphocytes until it finds those lymphocytes with receptors that fit the tumor antigen.
Cancer cells can hide from lymphocytes by becoming almost invisible.
Instead of displaying all their proteins on their surfaces, the cancer cells keep most of their proteins inside where the T-lymphocytes cannot find them. The lysates from each child's tumor were mixed with a protein and then added to the child's dendritic cells. The activated dendritic cells are then injected back into the patient once every two weeks, a total of three times. Additionally, we found that it is feasible to generate large quantities of functional dendritic cells from pediatric patients, even those with a large tumor burden. Five patients achieved stable disease including three that had minimal disease at the time of the vaccine therapy and their cancers did not progress for at least eight to 20 months.