The human immune system is, in principle, capable of killing cancer cells all by itself, without need for any extra drugs or doses of radiation. But that supposes the immune system is able to distinguish cancer cells from healthy body cells, since it’s not a good thing when the immune system targets healthy cells.
Adult stem cells from mice converted to antigen-specific T cells — the immune cells that fight cancer tumor cells — show promise in cancer immunotherapy and may lead to a simpler, more efficient way to use the body’s immune system to fight cancer, according to Penn State College of Medicine researchers.
“Cancer immunotherapy is a promising method to treat cancer patients,” said Jianxsun Song, assistant professor of microbiology and immunology. “Tumors grow because patients lack the kind of antigen-specific T cells needed to kill the cancer. An approach called adoptive T cell immunotherapy generates the T cells outside the body, which are then used inside the body to target cancer cells.”
In order to target only cancer cells, the immune system needs to be able to recognize them by the presence of specific antigens – proteins that are found only on the surface of the cancer cells to be targeted. The conventional way to do this in cancer immunotherapy is to administer a vaccine containing antigens derived from a patient’s own cells. But it may be difficult and expensive to culture cells from a patient’s tumor.
The solution contemplated in this research is to create induced pluripotent stem cells (iPSCs) from the patient’s own normal adult cells. The cells would be genetically modified to have antigen-specific T-cell receptors. They would then be introduced back into the patient’s body and stimulated to differentiate into T cells. Since they were originally from the same patient, they should not be rejected by the patient’s immune system. Upon maturation, the cells should in principle be able to attack cancer cells expressing the antigen.
As a proof of concept, this procedure was performed with mice. In mice with tumors, 100% of the animals survived when treated with the modified cells, versus only 55% of mice in a control group.