|Discovered population of immune cells in tumors is associated|
with less severe cancer outcomes in humans.
Molecules associated with these cells, newly identified by researchers, could be the focus of new immunotherapies that are more precisely targeted than current immunotherapies now in clinical trials. In fact, the researchers concluded that the presence of these cells may be the reason current immunotherapies aimed at boosting T lymphocyte responses have any effectiveness whatsoever.
The team depleted the population of these already rare cells in mice and demonstrated that the immune system was then unable to control tumors, even when the mice were given immunotherapeutic treatments.
Tumors are able to grow large and spread in part because they subvert the immune system. Cancers prevent the activation of T lymphocytes within the immune system that specifically target tumor molecules recognized as abnormal. Immune cells known as antigen-presenting cells need to activate T lymphocytes to trigger them to attack, but in cancer, cells called tumor-associated macrophages tell T lymphocytes to remain dormant, and also foster the development of blood vessels that feed the growing tumor.
However, the distinct, rare population of cells newly identified by the team persists in trying to activate tumor-targeting T lymphocytes, apparently with enough success despite their scarcity to make a difference in cancer outcomes. The researchers call the cells antigen-presenting CD103+ dendritic cells, and they make up fewer than 1 percent of all antigen-presenting cells.
The researchers found specific molecules on the cells that serve as a signature for their identification, and molecules that might be targeted to boost the cells' power to activate T lymphocytes.
Patients who have the signature of these cells live consistently longer than those with weak signatures.
These antigen-presenting CD103+ dendritic cells are an important but previously unrecognized ally in immunity to cancer, and it's believed that we can learn to manipulate their numbers for new cancer immunotherapies. The strength of the association between the CD103+ cell signature and cancer outcomes raises the prospect that researchers might even be able to detect cancer early via an immune response.