Cancer vaccine gets first test in patients
By Nathan Seppa
From Chicago, at a meeting of the American Society of Clinical Oncology
An experimental cancer vaccine given to 58 patients for whom all other treatments had failed induced an immune response in all of them, suggesting the vaccine can sensitize the body to the presence of tumor cells. This is the first human test of the vaccine.
One patient’s colon tumor shrank under the therapy, and cancers of the colon, stomach, pancreas, breast, and lung in 22 other people stopped growing, says John L. Marshall of Georgetown University, who conducted the test with several colleagues.
The investigators gave the patients six monthly injections of a vaccine called TRICOM, and then one shot every 3 months during the ongoing study, now into its third year. The vaccine uses a genetically engineered virus to carry genes for a protein called carcinoembryonic antigen (CEA) and three other proteins. When produced inside the patient, these proteins stimulate an immune response. Marshall says that CEA normally is displayed exclusively on the surface of tumor cells, making it a good target even though it’s usually overlooked by the immune system.
When introduced via a vaccine, CEA draws the attention of the immune system’s T cells. They then orchestrate an attack on all CEA-bearing cells.
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