LONDON, March 4 (UPI) -- Researchers in England identified antigens on the surface of tumor cells that should attract immune cells to attack, but are turned off by the genetic mutations that drive the growth of cancer, according to a new study.
Cataloging different types of antigens, which are not necessarily present in all cells within a tumor, could help the development of better immunotherapy drugs and a clearer idea of which patients will respond the best to each treatment.
According to the study, published in the journal Science, researchers said the new understanding explains why some patients with the same cancer respond differently to the drugs, and others respond greatly but later have significant relapses.
Immunotherapy targets proteins on the surface of cancer cells, encouraging and enhancing the immune system's ability to see cancer cells as a foreign invader and attack as with any other infection. The most well-known is Keytruda, which former President Jimmy Carter was successfully treated with in 2015 for melanoma on the brain.
"For many years, we have studied how the immune response to cancer is regulated without a clear understanding of what it is that immune cells recognize on cancerous cells," Dr. Sergio Quezada, a researcher at the University College London, said in a press release. "Based on these new findings, we will be able to tell the immune system how to specifically recognize and attack tumors."
The researchers analyzed medical records for 139 lung cancer patients, looking at the relationship between T cell reaction to clonal neoantigens on the surface of cancer cells and patients' survival. They found that patients with higher levels of the antigens saw greater benefit from immunotherapy treatment.
Cancers that survive and grow larger tend to have fewer antigens, so the immune system does not recognize them. Getting the immune system to recognize antigens is also tricky because cancer cells continue to mutate and evolve as the tumors grow, so antigens present on one side of a tumor may not be on the other side.
"This opens up a way to look at individual patients' tumors and profile all the antigen variations to figure out the best ways for immunotherapy treatments to work, prioritizing antigens present in every tumor cell and identifying the body's immune T cells that recognize them," said Dr. Charles Swanton, a scientist at the Francis Crick Institute. "This is really fascinating, and takes personalized medicine to its absolute limit where each patient would have a unique, bespoke treatment."