Researchers at the University of California, San Diego have identified a molecular mechanism that determines whether a malignant tumor will respond to immunotherapy. It turned out that some patients are refractory to treatment due to the fact that cancer cells have a specific protein on their surface. This was announced in a press release on MedicalXpress.
Usually, the immune system detects defective cells that can lead to cancer and destroys them with T cells. However, tumor cells can start synthesizing the PD-L1 protein in order to trick lymphocytes that have the PD-1 protein on their surface. Drugs that block the interaction of PD-L1 with PD-1 have been shown to be effective in fighting cancer, but they are not useful in some patients.
Scientists have found that some tumor cells have not only PD-L1, but also PD-1, as a result of which these proteins interact with each other. The deceptive protein is neutralized, which can no longer deactivate T-lymphocytes. Thus, patients with high PD-1 levels in malignant cells do not respond to PD-L1 blocking antibodies. According to the researchers, such tumors use as yet unknown mechanisms that allow them to avoid attack from the immune system.
Experts plan to continue research to identify other ways to deceive T-lymphocytes by cancer cells.