# What does PD-L1 mean in cancer immunotherapy?

Source: https://oncologyistanbul.com/answers/what-does-pd-l1-mean-in-cancer-immunotherapy
Last updated: 2026-07-13

According to the U.S. National Cancer Institute (NCI), PD-L1 is a protein that acts as a kind of "brake" to keep the body's immune responses under control. NCI explains that it may be found on some normal cells and in higher-than-normal amounts on some cancer cells; when PD-L1 binds to PD-1, a protein on T cells, it keeps those T cells from killing the PD-L1-containing cells, including cancer cells. Drugs called immune checkpoint inhibitors bind to PD-L1 and block this, leaving the T cells free to kill cancer cells. PD-L1 is also a biomarker doctors may test to help guide immunotherapy decisions, though such tests do not always accurately predict response. This is general information, not personal medical advice.

## Verify at
- [NCI Dictionary of Cancer Terms — PD-L1](https://www.cancer.gov/publications/dictionaries/cancer-terms/def/pd-l1) — National Cancer Institute (NCI) (checked 2026-07-13)

Related: [Immunotherapy, in depth](https://oncologyistanbul.com/treatments/immunotherapy)